2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway^*

• Replace the “Practice Guidelines for Management of the Difficult Airway: A Report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway,” adopted by the American Society of Anesthesiologists in 2012 and published in 2013.¹ 

• Specifically address difficult airway management. The guidelines do not address education, training, or certification requirements for practitioners who provide anesthesia and airway management.

• Differ from previous guidelines in that they were developed by an international task force of anesthesiologists representing several anesthesiology, airway, and other medical organizations.

• Provide new evidence obtained from recent scientific literature along with findings from new surveys of expert consultants, American Society of Anesthesiologists members, and 10 participating organizations.

• Provide consideration for the development of a difficult airway management strategy including considerations for awake airway management.

• Update equipment for standard and advanced difficult airway management.

• Recommend supplemental oxygen administration before initiating and throughout difficult airway management, including the extubation process.

• Offer noninvasive and invasive alternatives for difficult airway management.

• Emphasize awareness of the passage of time and limiting the number of attempts of different devices and techniques during difficult airway management.

• Provide more robust recommendations for extubation of the difficult airway.

• Provide new algorithms and infographics for adult and pediatric difficult airway management.

For these practice guidelines, a difficult airway includes the clinical situation in which anticipated or unanticipated difficulty or failure is experienced by a physician trained in anesthesia care, including but not limited to one or more of the following: facemask ventilation, laryngoscopy, ventilation using a supraglottic airway, tracheal intubation, extubation, or invasive airway. These clinical situations are further defined as follows.

It is not possible to provide adequate ventilation (e.g., confirmed by end-tidal carbon dioxide detection), because of one or more of the following problems: inadequate mask seal, excessive gas leak, or excessive resistance to the ingress or egress of gas.

It is not possible to visualize any portion of the vocal cords after multiple attempts at laryngoscopy.

It is not possible to provide adequate ventilation because of one or more of the following problems: difficult supraglottic airway placement, supraglottic airway placement requiring multiple attempts, inadequate supraglottic airway seal, excessive gas leak, or excessive resistance to the ingress or egress of gas.

Tracheal intubation requires multiple attempts or tracheal intubation fails after multiple attempts.

The loss of airway patency and adequate ventilation after removal of a tracheal tube or supraglottic airway from a patient with a known or suspected difficult airway (i.e., an “at risk” extubation).

Anatomic features or abnormalities reducing or preventing the likelihood of successfully placing an airway into the trachea through the front of the neck.

Indicators of inadequate ventilation include absent or inadequate exhaled carbon dioxide, absent or inadequate chest movement, absent or inadequate breath sounds, auscultatory signs of severe obstruction, cyanosis, gastric air entry or dilatation, decreasing or inadequate oxygen saturation, absent or inadequate exhaled gas flow as measured by spirometry, anatomic lung abnormalities as detected by lung ultrasound, and hemodynamic changes associated with hypoxemia or hypercarbia (e.g., hypertension, tachycardia, bradycardia, arrhythmia). Additional clinical symptoms may include changed mental status or somnolence.

The purposes of these guidelines are to guide the management of patients with difficult airways, optimize first attempt success of airway management, improve patient safety during airway management, and minimize/avoid adverse events. The principal adverse outcomes associated with the difficult airway include (but are not limited to) death, brain injury, cardiopulmonary arrest, airway trauma, and damage to the teeth. The appropriate choice of medications and techniques for anesthesia care and airway management is dependent upon the experience, training, and preference of the individual practitioner, requirements or constraints imposed by associated medical issues of the patient, type of procedure, and environment in which airway management takes place. The choice of agents, techniques, and devices may be limited by federal, state, or municipal regulations or statutes.

These guidelines focus specifically on the management of the difficult airway encountered with mask ventilation, tracheal intubation, or supraglottic airway placement during procedures requiring general anesthesia, deep sedation, moderate sedation, or regional anesthesia or elective airway management without a procedure. Procedures include diagnostic, elective, and emergency procedures and invasive airway access. Airway management during cardiopulmonary resuscitation is not addressed by these guidelines. The guidelines are intended for adult and pediatric patients with either anticipated or unanticipated difficult airways, obstetric patients, intensive care (ICU) patients, and critically ill patients. The guidelines do not address patients at risk of aspiration without anatomically difficult airways, patients where difficult airways are not encountered, or physiologically difficult airways that are not anatomically difficult.^‡

These guidelines do not address education, training, or certification requirements for practitioners who provide anesthesia and airway management. Some aspects of the guidelines may be relevant in other clinical contexts. The guidelines do not represent an exhaustive consideration of all manifestations of the difficult airway or all possible approaches to airway management.

These guidelines are intended for use by anesthesiologists and all other individuals who perform anesthesia care or airway management. The guidelines are intended to apply to all airway management and anesthetic care delivered in inpatient (e.g., perioperative, nonoperating room, emergency department, and critical care settings) and ambulatory settings (e.g., ambulatory surgery centers and office-based surgery and procedure centers performing invasive airway procedures). Excluded are prehospital settings and individuals who do not deliver anesthetic care or perform airway management. These guidelines are also intended to serve as a resource for other physicians and patient care personnel who are involved in the care of difficult airway patients, including those involved in local policy development.

In 2019, the ASA Committee on Standards and Practice Parameters requested that these guidelines be updated. This update is a revision developed by an ASA-appointed task force of 15 members, including physician anesthesiologists in both private and academic practices from the United States, India, Ireland, Italy, and Switzerland; an independent consulting methodologist; and an ASA staff methodologist. Conflict-of-interest documentation regarding current or potential financial and other interests pertinent to the practice guideline were disclosed by all task force members and managed.^§

These updated guidelines were developed by means of a six-step process. First, consensus was reached on the criteria for evidence. Second, a comprehensive literature search was conducted by an independent librarian to identify citations relevant to the evidence criteria. Third, original published articles from peer-reviewed journals relevant to difficult airway management were evaluated and added to literature included in the previous update. Fourth, consultants who had expertise or interest in difficult airway management and who practiced or worked in various settings (e.g., private and academic practice) were asked to participate in opinion surveys addressing the appropriateness, completeness, and feasibility of implementation of the draft recommendations and to review and comment on a draft of the guidelines. Fifth, additional opinions were solicited from random samples of active members of the ASA and participating organizations. Sixth, all available information was used to build consensus to finalize the Guidelines. A summary of recommendations is provided in appendix 1. Preparation of these updated guidelines followed a rigorous methodologic process, described in more detail in appendix 2 and other related publications.^2–5 

Criteria for literature acceptance included randomized controlled trials, prospective nonrandomized comparative studies (e.g., quasiexperimental, cohort), retrospective comparative studies (e.g., case control), observational studies (e.g., correlational or descriptive statistics), and case reports or case series from peer-reviewed journals. Literature exclusion criteria included: (1) patients or practitioners described in the study who were specifically excluded or not identified by evidence criteria in the evidence model; (2) interventions not identified or specifically excluded in the evidence model; (3) studies with insufficient or no outcome data or reported outcomes not relevant to the evidence model; (4) articles with no original data, including review articles, descriptive letters, or editorials; (5) systematic reviews, secondary data, meta-analysis,^‖ or other articles with no original data; (6) abstracts, letters, or articles not published in a peer-reviewed journal; (7) studies outside of designated search dates; (8) duplicate data presented in a different reviewed article; or (9) retracted publications.

Within the text of these guidelines, literature classifications are reported for each intervention as follows: Category A, level 1, meta-analysis of randomized controlled trials; Category A, level 2, multiple randomized controlled trials; Category A, level 3, a single randomized controlled trial; Category B, level 1, nonrandomized studies with group comparisons; Category B, level 2, nonrandomized studies with associative findings; Category B, level 3, nonrandomized studies with descriptive findings; and Category B, level 4, case series or case reports. Statistically significant outcomes (P < 0.01) are designated as either beneficial (B) or harmful (H) to the patient; statistically nonsignificant findings are designated as equivocal (E).^# When available, Category A evidence is given precedence over Category B evidence for any particular outcome. The lack of sufficient scientific evidence in the literature is reported in the text of the guidelines as “insufficient evidence.”^** Opinions regarding the scientific quality of the studies or opinion ratings of the strength of recommendations are not reported in this document.

Survey findings from task force–appointed expert consultants and samples of the memberships of ASA and participating organizations^†† are reported in appendix 2. Survey responses for each recommendation are reported using a five-point scale based on median values from strongly agree to strongly disagree.

Airway evaluation topics include (1) risk assessment to predict a difficult airway or risk of aspiration, and (2) airway examination (bedside and advanced). Risk assessment includes evaluation of information obtained from a patient’s history or medical records, including demographic information, clinical conditions, diagnostic tests, and patient/family interviews or questionnaires. An airway examination is intended to identify the presence of upper airway pathologies or anatomical anomalies. Issues addressed in these guidelines include: (1) measurement of facial and jaw features, (2) anatomical measurements and landmarks, (3) imaging with ultrasound or virtual laryngoscopy/bronchoscopy, (4) three-dimensional printing, and (5) bedside endoscopy.

Patient demographic and personal characteristics evaluated for difficult airway risk prediction included age, sex, body mass index, weight, and height. Clinical characteristics assessed included a history of difficult intubation, distorted airway anatomy, snoring, obstructive sleep apnea, diabetes mellitus, or findings from diagnostic tests (e.g., radiography, computed tomography), patient interviews, and questionnaires. Measurement of facial and jaw features included mouth opening, the ability to prognath, head and neck mobility, prominent upper incisors, presence of a beard, and an upper lip bite test. Anatomical measures included Mallampati and modified Mallampati scores, thyromental distance, sternomental distance, interincisor distance, neck circumference, ratio of neck circumference to thyromental distance, ratio of height to thyromental distance, hyomental distance, and hyomental distance ratio. Measurements obtained from ultrasound included skin-to-hyoid distance, tongue volume, and distance from skin to epiglottis.

Observational studies reported comparative demographic findings for difficult versus nondifficult airway patients, as well as sensitivity, specificity, positive predictive, negative predictive, and accuracy values for difficult laryngoscopy, supraglottic airway use, and tracheal intubation. Findings for the above patient characteristics were shown to have very high predictive and comparative variability, with sensitivity, specificity, and significance values ranging from low to very high across all patient demographic measures (Category B2-E evidence).^6–70  No single characteristic was identified as consistently being more predictive than another, and multivariate measures intended to predict difficult airways were too few and diverse among the studies to determine a common set of predictors.

Case reports identified difficult laryngoscopy or difficult intubation occurring among patients with a variety of acquired or congenital disease states (e.g., ankylosing spondylitis, degenerative osteoarthritis, Treacher–Collins, Klippel–Feil, Down syndrome, mucopolysaccharidosis, and airway masses) (Category B4-H evidence).^71–122 

Observational studies reported comparative findings for facial and jaw features and anatomical measurement for difficult versus nondifficult airway patients as well as sensitivity, specificity, positive predictive, negative predictive, and accuracy values for difficult laryngoscopy and intubation. Findings for facial and jaw features,^{7–11,13,14,18,27,33,38–40,42,43,45–47,49,51–54,57,58,64,68,123–159}  anatomical measurements,^{7–11,13–15,18,22,23,27–30,33,35,37–40,45–47,49,51–54,57,58,60, 64,65,68,70,123–132,134–154,156,158–203}  and ultrasound anatomical measurements^{69,139,162,170,194,196,203–213}  were shown to have very high predictive and comparative variability, with sensitivity, specificity, and significance values ranging from low to very high across all patient measures (Category B2-E evidence). No single characteristic was identified as consistently being more predictive than another, and multivariate measures intended to predict difficult airways were too few and diverse among the studies to determine a common set of predictors.

A prospective cohort study reported improved laryngeal views (during tongue protrusion) when transnasal endoscopy was added to the preoperative bedside evaluation (Category B2-B evidence),²¹⁴  and an observational study utilizing preoperative endoscopic examination as an added airway assessment tool reported that airway management plans were revised in 26% of patients based on the results of this examination (Category B3-B evidence).²¹⁵  Observational studies and case reports indicated that radiography and computed tomography scans identified anatomical characteristics such as laryngeal deviations, cervical abnormalities, fractures, and abscesses that may suggest a potential difficult airway (Category B3-B and B4-B evidence).^90,216–219  Observational studies indicated that patient questionnaires may identify patients at risk of difficult ventilation and intubation (Category B3-B evidence).^163,220,221  The literature was insufficient to evaluate the predictive value of virtual laryngoscopy/bronchoscopy or three-dimensional printing.

The consultants and members of participating organizations strongly agree with recommendations to ensure that an airway risk assessment is performed by the person(s) responsible for airway management whenever feasible before the initiation of anesthetic care or airway management and with the recommendation to conduct an airway physical examination before the initiation of anesthetic care or airway management.

• •

  Before the initiation of anesthetic care or airway management, ensure that an airway risk assessment is performed by the person(s) responsible for airway management whenever feasible to identify patient, medical, surgical, environmental, and anesthetic factors (e.g., risk of aspiration) that may indicate the potential for a difficult airway.

  • ◦

    When available in the patient’s medical records, evaluate demographic information, clinical conditions, diagnostic test findings, patient/family interviews, and questionnaire responses.

  • ◦

    Assess multiple demographic and clinical characteristics to determine a patient’s potential for a difficult airway or aspiration.

• •

  Before the initiation of anesthetic care or airway management, conduct an airway physical examination to further identify physical characteristics that may indicate the potential for a difficult airway.

  • ◦

    The physical examination may include assessment of facial features^‡‡ and assessment of anatomical measurements and landmarks.^§§

  • ◦

    Additional evaluation to characterize the likelihood or nature of the anticipated airway difficulty may include bedside endoscopy, virtual laryngoscopy/bronchoscopy, or three-dimensional printing.^‖‖

• •

  Assess multiple airway features to determine a patient’s potential for a difficult airway or aspiration.

Topics related to interventions intended to prepare for difficult airway management include (1) the availability of equipment for airway management (e.g., items for anesthetizing locations, portable storage unit, cart, or trolley for difficult airway management); (2) informing the patient with a known or suspected difficult airway; (3) preoxygenation; (4) patient positioning; (5) sedative administration; (6) local anesthesia; (7) supplemental oxygen during difficult airway management; (8) patient monitoring; and (9) human factors.^##

Although the need for immediate access to difficult airway management equipment is a well accepted practice, the literature is insufficient to directly evaluate outcomes associated with the availability of such equipment. In addition, the literature is insufficient to evaluate the outcomes associated with informing the patient of a known or suspected difficult airway, preoxygenation, administration of sedatives or local anesthesia, or patient monitoring. One randomized controlled trial comparing the ramped with sniffing positions reported equivocal findings (P > 0.01) for laryngoscopic view and intubation success (Category A3-E evidence).²²²  A nonrandomized study comparing the sniffing position with head and neck raised beyond the sniffing position reported improved laryngeal views with the raised position (Category B-2 B evidence).²²³ 

The consultants and members of participating organizations strongly agree with recommendations to ensure that a skilled individual is present or immediately available to assist with airway management if a difficult airway is known or suspected; inform the patient or responsible person of the special risks and procedures pertaining to management of the difficult airway; and administer oxygen before initiating management of the difficult airway and to deliver supplemental oxygen throughout the process of difficult airway management, including extubation.

• •

  Ensure that airway management equipment is available in the room.^***

• •

  Ensure that a portable storage unit that contains specialized equipment for difficult airway management is immediately available.^†††

• •

  If a difficult airway is known or suspected:

  • ◦

    Ensure that a skilled individual is present or immediately available to assist with airway management when feasible.

  • ◦

    Inform the patient or responsible person of the special risks and procedures pertaining to management of the difficult airway.

  • ◦

    Properly position the patient, administer supplemental oxygen before initiating management of the difficult airway,^‡‡‡ and continue to deliver supplemental oxygen whenever feasible throughout the process of difficult airway management, including extubation.^§§§

• •

  Ensure that, at a minimum, monitoring according to the ASA Standards for Basic Anesthesia Monitoring are followed immediately before, during, and after airway management of all patients.^‖‖‖

Airway management of an anticipated difficult airway consists of interventions addressing awake tracheal intubation, anesthetized tracheal intubation, or both awake and anesthetized intubation.

Studies with observational findings reported successful awake intubation in 88 to 100% of anticipated difficult airway patients (Category B3-B evidence).^224–227  Case reports for awake intubation (e.g., blind tracheal intubation, intubation through supraglottic devices, optically guided intubation) also observed success with anticipated difficult airway patients (Category B4-B evidence).^228–230 

The literature is insufficient to evaluate the benefit or harm of the following interventions: use of cricoid pressure (i.e., Sellick maneuver), pressure-limited mask ventilation versus ablation of spontaneous ventilation, maintenance of spontaneous ventilation versus ablation of spontaneous ventilation, administration of neuromuscular blockade to improve mask ventilation, or rocuronium with sugammadex versus suxamethonium or succinylcholine for airway management of anticipated difficult airway patients.

Interventions addressed for anticipated difficult airway patients receiving either awake or anesthetized airway management include (1) airway maneuvers, (2) noninvasive airway management devices, (3) combination techniques, (4) invasive airway management interventions, and (5) extracorporeal membrane oxygenation (ECMO).

Two case reports indicated that use of a backward-upward-rightward pressure of the larynx maneuver resulted in successful intubation of difficult airway patients (Category B4-B evidence).^231,232  One case report observed successful intubation using external cricoid manipulation after failed direct intubation (Category B4-B evidence).²³³ 

Noninvasive devices for airway management of patients with anticipated difficult airways include rigid laryngoscopic blades of alternative design and size; adjuncts (e.g., introducers, bougies, stylets, and alternative tracheal tubes); videolaryngoscopes; flexible intubation scopes; supraglottic airway devices; lighted or optical stylets; and rigid bronchoscopes. The literature is insufficient to evaluate which devices are most effective when attempted first after failed intubation, nor is the literature sufficient to evaluate the most effective order of devices to be used for attempted intubation of an anticipated difficult airway.

A randomized controlled trial comparing levering laryngoscopes to standard laryngoscopes reported no differences in laryngoscopic view, but shorter times to intubation and fewer intubation maneuvers were needed for successful intubation with the levering laryngoscope (Category A3-B evidence).²³⁴  Case reports observed intubation success with levering laryngoscopic blades (Category B4-B evidence).^235,236  Case reports of mechanical failure and arytenoid dislocation have been noted with levering blades (Category B4-H evidence).^237–239 

Observational studies reported intubation success ranging from 87 to 100% of patients (Category B3-B evidence),^240–242  and case reports observed intubation success with bougies and stylets (Category B4-B evidence).^243–248 

Meta-analyses of randomized controlled trials comparing video-assisted laryngoscopy with direct laryngoscopy in patients with predicted difficult airways reported improved laryngeal views, a higher frequency of successful intubations, a higher frequency of first attempt intubations, and fewer intubation maneuvers with video-assisted laryngoscopy (Category A1-B evidence);^249–259  findings for time to intubation were equivocal (Category A1-E evidence).^{250,253–255,258–261 ###} Randomized controlled trials comparing video-assisted laryngoscopy with awake laryngoscopy with a flexible intubation scope reported equivocal findings for laryngeal view, visualization time, first attempt intubation success, and time to intubation (Category A2-E evidence).^262–265  Randomized controlled trials comparing channel-guided videolaryngoscopes with non–channel-guided videolaryngoscopes reported equivocal findings for laryngeal view, intubation success, first attempt intubation, time to intubation, and needed intubation maneuvers (Category A3-E evidence).^256,266  Randomized controlled trials reported equivocal findings for laryngoscopic view, intubation success, first attempt intubation success, and time to intubation when hyperangulated videolaryngoscopes were compared with nonangulated videolaryngoscopes for anticipated difficult airways (Category A2-E evidence).^257,259 

Observational studies indicated intubation success rates for videolaryngoscopes ranging from 85 to 100% of patients^267–275  and first attempt successful intubation rates ranging from 51 to 100%^{267,269,271–275} (Category B3-B evidence). Case reports observed videolaryngoscope intubation successes with a wide range of difficult airway conditions (Category B4-B evidence).^{160,276–297}  Adverse outcomes that may occur include sore throat, laryngospasm, lip, dental, or mucosal injuries (Category B4-H evidence).^278,298 

A nonrandomized comparative study comparing intubation with a flexible bronchoscope versus direct laryngoscopy reported equivocal findings for complicated intubations (Category B2-E evidence).²⁹⁹  Studies with observational findings for flexible intubation scopes indicated success rates ranging from 78 to 100% (Category B3-B evidence).^{224–227,300–303}  Case reports also observed successful intubation with flexible intubation scopes (Category B4-B evidence).^304–356 

Observational studies indicated successful supraglottic airway insertion and intubation ranging from 65 to 100% of anticipated difficult airway patients (Category B3-B evidence).^357–367  Three observational studies reported oxygen desaturation occurring in 1.8 to 3.3% of patients after supraglottic airway placement (Category B3-H evidence).^362,363,368  Case reports observed successful ventilation and intubation with various supraglottic airways (Category B4-B evidence).^369–413 

Randomized controlled trials comparing flexible intubation through supraglottic airways versus flexible intubation scopes alone reported a higher frequency of first attempt intubation success with the supraglottic airway (Category A2-B evidence)^414–417 ; findings were equivocal for overall successful intubation and time to intubation (Category A2-E evidence).^415–417  A randomized controlled trial comparing second generation supraglottic airways with first generation supraglottic airways reported faster times to intubation with second generation supraglottic airways (Category A2-B evidence).⁴¹⁸  Randomized controlled trials reported equivocal findings for overall successful intubation (Category A2-E evidence).^418,419 

A randomized controlled trial comparing intubation with a lightwand versus blind intubation for patients with anticipated difficult airways reported a significantly higher frequency of successful intubations and shorter intubation times for the lightwand (Category A3-B evidence).⁴²⁰  Two randomized controlled trials reported shorter intubation times when lighted stylets were compared with direct laryngoscopy (Category A2-B evidence); findings were equivocal for successful intubation and first attempt success (Category A2-E evidence).^255,421  Randomized controlled trials comparing lighted stylets with flexible bronchoscopes reported shorter intubation times with lighted stylets (Category A3-B evidence).^422,423 

Observational studies reported successful intubation ranging from 84.9 to 100% of anticipated difficult airway patients when lighted stylets were used (Category B3-B evidence).^424–428  Case reports observed successful intubations with lighted and optical stylets (Category B4-B evidence).^429–437 

The literature is insufficient to evaluate the benefit or harm of the rigid bronchoscope for patients with anticipated difficult airways.

Examples of combination techniques include: (1) direct or video laryngoscopy combined with either optical/video stylet, flexible intubation scope, airway exchange catheter, retrograde-placed guide wire, or supraglottic airway placement and (2) supraglottic airway combined with either optical/video stylet or flexible intubation scope (with or without hollow guide catheter). A randomized controlled trial comparing a lightwand combined with direct laryngoscopy versus a lightwand alone for intubation reported equivocal findings for successful intubation, first attempt success, time to intubation, and number of intubation attempts (Category A3-E evidence).⁴³⁸  A randomized controlled trial comparing a videolaryngoscope combined with a flexible bronchoscope reported a greater first attempt success rate with the combination technique than with a videolaryngoscope alone (Category A3-B evidence).⁴³⁹ 

Observational studies indicated successful intubation with combination techniques ranging from 80 to 90%^440–445  and first attempt success rates ranging from 50 to 100% of anticipated difficult airway patients^{440–442,446} (Category B3-B evidence). Case reports also observed successful intubation occurring with various combinations of techniques (Category B4-B evidence).^447–468 

Invasive Interventions Invasive airway management interventions for anticipated difficult airway management include retrograde wire–guided intubation, front-of-neck percutaneous or surgical cricothyrotomy/tracheostomy, awake cricothyrotomy/tracheostomy, and ECMO. Case reports observed successful intubations when retrograde wire–graded intubation was performed for patients with anticipated difficult airways (Category B4-B evidence).^469–473  A case report observes successful percutaneous tracheostomy for an anticipated difficult airway patient as an alternative after unsuccessful surgical tracheostomy (Category B3-B evidence).⁴⁷⁴  The literature is insufficient to evaluate awake cricothyrotomy/tracheostomy and ECMO for anticipated difficult airway patients.

The consultants and members of participating organizations strongly agree with the recommendation to identify a strategy for (1) awake intubation, (2) the patient who can be adequately ventilated but is difficult to intubate, (3) the patient who cannot be ventilated or intubated, and (4) alternative approaches to airway management failure. The consultants strongly agree and members of participating organizations agree or strongly agree with recommendations to perform awake intubation, when appropriate, if the patient is suspected to be a difficult intubation and difficult ventilation (face mask/supraglottic airway) is anticipated; perform awake intubation, when appropriate, if the patient is suspected to be a difficult intubation and increased risk of aspiration is anticipated; and perform awake intubation, when appropriate, if the patient is suspected to be a difficult intubation and the patient is likely incapable of tolerating a brief apneic episode. The consultants and members of participating organizations strongly agree with the recommendation to perform awake intubation, when appropriate, if the patient is suspected to be a difficult intubation and difficulty with emergency invasive airway rescue is anticipated.

The consultants and members of participating organizations strongly agree with the recommendation to identify a preferred sequence of noninvasive devices to use for airway management if a noninvasive approach is selected. The consultants strongly agree and members of participating organizations agree or strongly agree that if difficulty is encountered with individual techniques, combination techniques may be performed. The consultants and members of participating organizations strongly agree with the recommendation to be aware of the passage of time the number of attempts and oxygen saturation. The consultants strongly agree and members of participating organizations agree or strongly agree with the recommendation to provide and test mask ventilation between attempts. The consultants and members of participating organizations strongly agree with recommendations to limit the number of attempts at tracheal intubation or supraglottic airway placement to avoid potential injury and complications; identify a preferred intervention if an elective invasive approach to the airway is selected; ensure that an invasive airway is performed by an individual trained in invasive airway techniques whenever possible; and identify an alternative invasive intervention if the selected invasive approach fails or is not feasible.

• •

  Have a preformulated strategy for management of the anticipated difficult airway.

  • ◦

    This strategy will depend, in part, on the anticipated surgery, the condition of the patient, patient cooperation/consent, the age of the patient, and the skills and preferences of the anesthesiologist.

  • ◦

    Identify a strategy for: (1) awake intubation, (2) the patient who can be adequately ventilated but is difficult to intubate, (3) the patient who cannot be ventilated or intubated, and (4) difficulty with emergency invasive airway rescue.

  • ◦

    When appropriate, perform awake intubation if the patient is suspected to be a difficult intubation and one or more of the following apply: (1) difficult ventilation (face mask/supraglottic airway), (2) increased risk of aspiration, (3) the patient is likely incapable of tolerating a brief apneic episode, or (4) there is expected difficulty with emergency invasive airway rescue.^****

  • ◦

    The uncooperative or pediatric patient may restrict the options for difficult airway management, particularly options that involve awake intubation. Airway management in the uncooperative or pediatric patient may require an approach (e.g., intubation attempts after induction of general anesthesia) that might not be regarded as a primary approach in a cooperative patient.

  • ◦

    Proceed with airway management after induction of general anesthesia when the benefits are judged to outweigh the risks.

  • ◦

    For either awake or anesthetized intubation, airway maneuver(s) may be attempted to facilitate intubation.

  • ◦

    Before attempting intubation of the anticipated difficult airway, determine the benefit of a noninvasive versus invasive approach to airway management.

    • ▪

      If a noninvasive approach is selected, identify a preferred sequence of noninvasive devices to use for airway management.^††††

• •

  If difficulty is encountered with individual techniques, combination techniques may be performed.^‡‡‡‡

• •

  Be aware of the passage of time, the number of attempts, and oxygen saturation.

• •

  Provide and test mask ventilation after each attempt, when feasible.

• •

  Limit the number of attempts at tracheal intubation or supraglottic airway placement to avoid potential injury and complications.

  • ▪

    If an elective invasive approach to the airway is selected, identify a preferred intervention.^§§§§

• •

  Ensure that an invasive airway is performed by an individual trained in invasive airway techniques, whenever possible.

• •

  If the selected approach fails or is not feasible, identify an alternative invasive intervention.

  • ◦

    Initiate ECMO when/if appropriate and available.

Airway management of an unanticipated or emergency difficult airway consists of interventions addressing (1) calling for help, (2) optimization of oxygenation, (3) use of a cognitive aid, (4) noninvasive airway management devices, (5) combination techniques, (6) invasive airway management interventions, and (7) ECMO.

The literature is insufficient to evaluate patient outcomes associated with the immediate access to airway management support equipment or calling for help, although the necessity of these interventions is obvious. The literature is also insufficient to evaluate difficult airway patient outcomes associated with the use of a visual aid, cognitive aid, or algorithm for unanticipated or emergency difficult airways.

Case reports have observed successful emergency ventilation via tube exchangers using expiratory ventilation assistance after multiple failed intubation attempts (Category B4-B evidence).^475,476  Devices for noninvasive airway management of patients with unanticipated or emergency difficult airways include rigid laryngoscopic blades of alternative designs and sizes; adjuncts (e.g., introducers, bougies, stylets, and alternative tracheal tubes), videolaryngoscopes; flexible intubation scopes; supraglottic airway devices (supraglottic airways); lighted or optical stylets; and rigid bronchoscopes.

The literature is insufficient to evaluate patient outcomes associated with rigid laryngoscopic blades of alternative designs and sizes for patients with unanticipated or emergency difficult airways. Observational findings from a randomized trial reported a first attempt intubation success rate for difficult airways of 96% with bougies and 82% with stylets and tracheal tubes in an emergency department (Category B3-B evidence).⁴⁷⁷  Case reports observed intubation successes with bougies, introducers, and stylets for patients with unanticipated or emergency difficult airways (Category B4-B evidence).^{114,478–485} 

Nonrandomized studies comparing videolaryngoscopes with direct laryngoscopy reported equivocal findings for intubation success with difficult airways in emergency departments (Category B1-E evidence).^6,486,487  Observational studies indicated successful videolaryngoscope-guided intubation rates after failed intubation ranging from 92 to 100% for unanticipated and emergency difficult airways (Category B4-B evidence).^488–491  Case reports also observed successful intubation with videolaryngoscopes in unanticipated and emergency difficult airways (Category B4-B evidence).^{160,492–496}  A retrospective observational study reported a flexible bronchoscopy success rate of 78% for intubation rescue after failed direct laryngoscopy (Category B3-B evidence).⁴⁸⁸  Case reports of flexible bronchoscopy or fiberoptic nasotracheal intubation observed successful rescue intubations for unanticipated and emergency difficult airways (Category B4-B evidence).^497–503 

A retrospective observational study reported a 78% successful rescue intubation rate, and another observational study reported 94.1% successful rescue ventilation with supraglottic airway placement (Category B3-B evidence).^488,504  Case reports also observed successful rescue ventilation and intubation using supraglottic airways for unanticipated and emergency difficult airways (Category B4-B evidence).^505–521 

A retrospective observational study reported a success rate with a lighted stylet of 77% for intubation rescue after failed direct laryngoscopy (Category B3-B evidence).⁴⁸⁸  Case reports observed successful intubations with lighted stylets after failed direct laryngoscopies for emergency airways (Category B4-B evidence).^522,523  A case report observed successful intubation with a rigid bronchoscope in an emergency airway obstruction case (Category B4-B evidence).⁵²⁴ 

An observational study reported successful intubation in 97.7%, first attempt success in 86.4%, and successful ventilation in 100% of unanticipated difficult airway patients using a combination of a supraglottic airway and lighted stylet (Category B3-B evidence).⁵²⁵  Case reports also observed intubation success for unanticipated and emergency airway patients when combination techniques were used (Category B4-B evidence).^526–536  The literature is insufficient to evaluate which of the above devices are most effective when attempted first after failed intubation, nor is the literature sufficient to evaluate the most effective order of devices to be used for attempted intubation of an unanticipated or emergency difficult airway.

Invasive airway management interventions for unanticipated and emergency difficult airway management include retrograde wire–guided intubation, front-of-neck percutaneous or surgical cricothyrotomy/tracheostomy, awake cricothyrotomy/tracheostomy, jet ventilation, and ECMO. A case series of two patients reported successful intubation using retrograde wire–guided intubation after failed intubation through a supraglottic airway (Category B4-B evidence).⁵³⁷  Observational findings from a randomized controlled trial comparing percutaneous dilatational tracheotomy with percutaneous cricothyrotomy reported successful procedure rates of 97.6 and 95.3% (Category B3-B evidence),⁵³⁸  and case reports also observed success with percutaneous procedures (Category B4-B evidence).^539–544 

A retrospective observational study reported restoration of oxygen saturation levels to above 90% when rescue transtracheal jet ventilation was used (Category B3-B evidence),⁵⁴⁵  and case reports observed improvements in oxygen saturation levels with supraglottic jet oxygenation in “cannot intubate, cannot ventilate” situations (Category B4-B evidence).^546,547  Case reports observed oxygen saturations of 72 to 100% with the use of ECMO for difficult airways before intubation attempts for emergency procedures (Category B4-B evidence).^548–550 

The consultants and members of participating organizations strongly agree with recommendations to determine the benefit of waking and/or restoring spontaneous breathing upon encountering an unanticipated difficult airway; determine the benefit of a noninvasive versus invasive approach to airway management; and identify a preferred sequence of noninvasive devices to use for airway management if a noninvasive approach is selected.

The consultants strongly agree and members of participating organizations agree or strongly agree that if difficulty is encountered with individual techniques, combination techniques may be performed. The consultants and members of participating organizations strongly agree with recommendations to be aware of the passage of time, the number of attempts, and oxygen saturation; provide and test mask ventilation between attempts; limit the number of attempts at tracheal intubation or supraglottic airway placement to avoid potential injury and complications; identify a preferred intervention if an invasive approach to the airway is necessary (i.e., cannot intubate, cannot ventilate); ensure that an invasive airway is performed by an individual trained in invasive airway techniques, whenever possible; ensure that an invasive airway is performed as rapidly as possible; and identify an alternative invasive intervention if the selected invasive approach fails or is not feasible.

• •

  Call for help.

• •

  Optimize oxygenation.^‖‖‖‖

• •

  When appropriate, refer to an algorithm^#### and/or cognitive aid.

• •

  Upon encountering an unanticipated difficult airway:

  • ◦

    Determine the benefit of waking and/or restoring spontaneous breathing.

  • ◦

    Determine the benefit of a noninvasive versus invasive approach to airway management.

  • ◦

    If a noninvasive approach is selected, identify a preferred sequence of noninvasive devices to use for airway management.^*****

    • ▪

      If difficulty is encountered with individual techniques, combination techniques may be performed.

    • ▪

      Be aware of the passage of time, the number of attempts, and oxygen saturation.

    • ▪

      Provide and test mask ventilation after each attempt, when feasible.

    • ▪

      Limit the number of attempts at tracheal intubation or supraglottic airway placement to avoid potential injury and complications.

  • •

    If an invasive approach to the airway is necessary (i.e., cannot intubate, cannot ventilate), identify a preferred intervention.^{†††††}

  • ◦

    Ensure that an invasive airway is performed by an individual trained in invasive airway techniques, whenever possible.

  • ◦

    Ensure that an invasive airway is performed as rapidly as possible.

  • ◦

    If the selected invasive approach fails or is not feasible, identify an alternative invasive intervention.

    • ▪

      Initiate ECMO when/if appropriate and available.

Studies with observational findings indicate that capnography or end-tidal carbon dioxide monitoring confirms tracheal intubation in 88.5 to 100% of difficult airway patients (Category B3-B evidence).^551,552  Case reports also observed intubation confirmation with capnography Category B4-B evidence).^354,553  The literature is insufficient to evaluate whether visualization (any technique), flexible bronchoscopy, ultrasonography, or radiography can be effective in confirming appropriate tracheal intubation.

The consultants and members of participating organizations strongly agree with the recommendation to confirm tracheal intubation using capnography or end-tidal carbon dioxide monitoring. The consultants strongly agree and members of participating organizations agree or strongly agree with the recommendation that when uncertain about the location of the tracheal tube, determine whether to either remove it and attempt ventilation or use additional techniques to confirm positioning of the tube.

• •

  Confirm tracheal intubation using capnography or end-tidal carbon dioxide monitoring.

• •

  When uncertain about the location of the tracheal tube, determine whether to either remove it and attempt ventilation or use additional techniques to confirm positioning of the tracheal tube.^‡‡‡‡

An extubation strategy includes interventions that may be used to facilitate airway management associated with extubation of a difficult airway. Extubation intervention topics addressed by these guidelines include: (1) assessment of patient readiness for extubation, (2) the presence of a skilled individual to assist with extubation, (3) selection of an appropriate time and location for extubation, (4) planning for possible reintubation, (5) elective tracheostomy, (6) awake extubation or supraglottic airway removal, (7) supplemental oxygen throughout the extubation process, and (8) extubation with an airway exchange catheter or supraglottic airway. The task force regards the concept of an extubation strategy as a logical extension of the intubation strategy.

A retrospective observational study comparing successfully extubated patients with patients who failed extubation observed differences in duration of intubation; conditions associated with failed extubation included airway granulations and subglottic stenosis (Category B1-H evidence).⁵⁵⁴  An observational study reported that staged extubation and reintubation with a Cook airway exchange catheter was successful in 92% of known or presumed difficult extubation patients (Category B3-B evidence).⁵⁵⁵  Another observational study reported single occurrences of a wire in the esophagus, a nontolerable cough, and gagging or salivation with a Cook airway exchange catheter (Category B3-H evidence).⁵⁵⁶  A case report observed successful extubation with an airway exchange catheter (Category B3-B evidence).⁵⁵⁷  Another case report observed an esophageal misplacement of an airway exchange catheter during extubation of a difficult airway patient (Category B3-H evidence).⁵⁵⁸  The literature is insufficient to evaluate the benefits of the presence of a skilled individual to assist with extubation, selection of an appropriate time and location for extubation, awake extubation or supraglottic airway removal, supplemental oxygen, planning for possible reintubation, and elective tracheostomy for difficult airway patients.

The consultants and members of participating organizations strongly agree with recommendations to have a preformulated strategy for extubation and subsequent airway management, ensure that a skilled individual is present to assist with extubation, and select an appropriate time and location for extubation when possible. The consultants strongly agree and members of participating organizations agree or strongly agree with recommendations to assess the relative clinical merits and feasibility of the short-term use of an airway exchange catheter and/or supraglottic airway that can serve as a guide for expedited reintubation and evaluate the risks and benefits of elective surgical tracheostomy before attempting extubation. The consultants and members of participating organizations strongly agree with recommendations to evaluate the risks and benefits of awake extubation versus extubation before the return to consciousness and assess the clinical factors that may produce an adverse impact on ventilation after the patient has been extubated.

• •

  Have a preformulated strategy for extubation and subsequent airway management.

  • ◦

    This strategy will depend, in part, on the surgery/procedure, other perioperative circumstances, the condition of the patient, and the skills and preferences of the clinician.

• •

  Assess patient readiness for extubation.

• •

  Ensure that a skilled individual is present to assist with extubation when feasible.

• •

  Select an appropriate time and location for extubation when possible.

• •

  Assess the relative clinical merits and feasibility of the short-term use of an airway exchange catheter and/or supraglottic airway that can serve as a guide for expedited reintubation.^§§§§§

  • ◦

    Minimize the use of an airway exchange catheter with pediatric patients.

• •

  Before attempting extubation, evaluate the risks and benefits of elective surgical tracheostomy.

• •

  Evaluate the risks and benefits of awake extubation versus extubation before the return to consciousness.

• •

  When feasible, use supplemental oxygen throughout the extubation process.

• •

  Assess the clinical factors that may produce an adverse impact on ventilation after the patient has been extubated.

Follow-up care includes the topics of: (1) postextubation care (i.e., steroids, racemic epinephrine), (2) postextubation counseling (i.e., informing and advising the patient or responsible individual of the occurrence and potential complications associated with a difficult airway), (3) documentation of difficult airway and management in the medical record and to the patient, and (4) registration with a difficult airway notification service.

The literature is insufficient to evaluate the benefits of postextubation steroids or epinephrine, counseling, documentation in the medical record, or registration with a difficult airway notification service. A case report of a difficult airway patient who was awakened after failed intubation indicated that records of previous difficult intubations were unavailable (Category B4-H evidence).⁵⁵⁹ 

The consultants and members of participating organizations strongly agree with the recommendation to inform the patient (or responsible person) of the airway difficulty that was encountered to provide the patient (or responsible person) with information to guide and facilitate the delivery of future care and to document the presence and nature of the airway difficulty in the medical record to guide and facilitate the delivery of future care.

• •

  Use postextubation steroids and/or racemic epinephrine when appropriate.

• •

  Inform the patient or a responsible person of the airway difficulty that was encountered to provide the patient (or responsible person) with a role in guiding and facilitating the delivery of future care.

  • ◦

    The information conveyed may include (but is not limited to) the presence of a difficult airway, the apparent reasons for difficulty, how the intubation was accomplished, and the implications for future care.

• •

  Document the presence and nature of the airway difficulty in the medical record to guide and facilitate the delivery of future care.^{‖‖‖‖‖}

• •

  Instruct the patient to register with an emergency notification service when appropriate and feasible.

Support was provided solely by the American Society of Anesthesiologists (Schaumburg, Illinois).

Dr. Apfelbaum was supported by a salary paid in part through National Institutes of Health (Bethesda, Maryland) grant No. ROHG009938-01A1. Dr. Hagberg received research grant support from Ambu (Copenhagen, Denmark), Karl Storz Endoscopy (Tuttlingen, Germany), and Vyaire Medical Inc. (Mettawa, Illinois); received honoraria/royalties from UpToDate and Elsevier (Amsterdam, The Netherlands); and is a Helen Shafer Fly Distinguished Professor. Dr. Connis is a paid consultant for the American Society of Anesthesiologists (Schaumburg, Illinois). Dr. Abdelmalak is a past president of the Society for Ambulatory Anesthesia (Milwaukee, Wisconsin), the Society for Head and Neck Anesthesia, and the Ohio Society of Anesthesiologists (Columbus, Ohio); is a board of directors member of the ASA; received consultant fees from the Acacia Pharma (Indianapolis, Indiana) advisory board and from Medtronic (Minneapolis, Minnesota); and received royalties from Cambridge University Press (London, United Kingdom). Dr. Dutton holds equity in U.S. Anesthesia Partners (Dallas, Texas) and serves on the ex-officio board of directors of the Trauma Anesthesiology Society (Houston, Texas). Dr. Fiadjoe received a grant from the Anesthesia Patient Safety Foundation (Rochester, Minnesota); serves on the board of directors of the Society for Pediatric Anesthesia (Richmond, Virginia) and as the director of the American Board of Anesthesiology (Raleigh, North Carolina); provides expert witness testimony for the University of Michigan (Ann Arbor, Michigan); and received honoraria from Penn State Health (Hershey, Pennsylvania), Atrium Health (Charlotte, North Carolina), the Missouri Society of Anesthesiologists (Jefferson City, Missouri), the American Board of Anesthesiologists, and Stanford University (Palo Alto, California). Dr. Greif received a 2018 Karl Storz Research Grant (Tuttlingen, Germany); is a past president of the European Airway Management Society (Bern, Switzerland); and serves as the board director of education and training for the European Resuscitation Council (Niel, Belgium). Dr. Mercier received material support from Teleflex (Athlone, Ireland) and Karl Stortz Endoscopy (Tuttlingen, Germany); serves on the ASA House of Delegates and Committee on Standards and Practice Parameters; and is the chairman of the Committee on Long Range Planning and a former president of the Texas Society of Anesthesiologists. Dr. Myatra is president of the All India Difficult Airway Association (Karnataka, India). Dr. O’Sullivan is a council member and trustee of the Royal College of Anaesthetists (London, United Kingdom). Dr. Rosenblatt received honoraria from Medtronics (Dublin, Ireland) and is owner of Airway On Demand Limited Liability Corporation (Hamden, Connecticut), and is a consultant for Ambu (Copenhagen, Denmark). Dr. Sorbello is a paid consultant for Teleflex Medical (Athlone, Ireland), Deas Italia (Castelbolognese, Italy), and Merck Sharp and Dohme (Rome, Italy). Dr. Tung is employed as a section editor for Anesthesia & Analgesia (International Anesthesia Research Society, San Francisco, California). The other authors declare no competing interests.

• •

  Before the initiation of anesthetic care or airway management, ensure that an airway risk assessment is performed by the person(s) responsible for airway management whenever feasible to identify patient, medical, surgical, environmental, and anesthetic factors (e.g., risk of aspiration) that may indicate the potential for a difficult airway.

  • ◦

    When available in the patient’s medical records, evaluate demographic information, clinical conditions, diagnostic test findings, patient/family interviews, and questionnaire responses.

  • ◦

    Assess multiple demographic and clinical characteristics to determine a patient’s potential for a difficult airway or aspiration.

• •

  Before the initiation of anesthetic care or airway management, conduct an airway physical examination to further identify physical characteristics that may indicate the potential for a difficult airway.

  • ◦

    The physical examination may include assessment of facial features^##### and assessment of anatomical measurements and landmarks.^******

  • ◦

    Additional evaluation to characterize the likelihood or nature of the anticipated airway difficulty may include bedside endoscopy, virtual laryngoscopy/bronchoscopy, or three-dimensional printing.^{††††††}

• •

  Assess multiple airway features to determine a patient’s potential for a difficult airway or aspiration.

• •

  Ensure that airway management equipment is available in the room.^{‡‡‡‡‡‡}

• •

  Ensure that a portable storage unit that contains specialized equipment for difficult airway management is immediately available.^§§§§§§

• •

  If a difficult airway is known or suspected:

  • ◦

    Ensure that a skilled individual is present or immediately available to assist with airway management when feasible.

  • ◦

    Inform the patient or responsible person of the special risks and procedures pertaining to management of the difficult airway.

  • ◦

    Properly position the patient, administer supplemental oxygen before initiating management of the difficult airway,^{‖‖‖‖‖‖} and continue to deliver supplemental oxygen whenever feasible throughout the process of difficult airway management, including extubation.^######

• •

  Ensure that, at a minimum, monitoring according to the ASA Standards for Basic Anesthesia Monitoring is performed immediately before, during, and after airway management of all patients.^*******

• •

  Have a preformulated strategy for management of the anticipated difficult airway.

  • ◦

    This strategy will depend, in part, on the anticipated surgery, the condition of the patient, patient cooperation/consent, the age of the patient, and the skills and preferences of the anesthesiologist.

  • ◦

    Identify a strategy for: (1) awake intubation, (2) the patient who can be adequately ventilated but is difficult to intubate, (3) the patient who cannot be ventilated or intubated, and (4) difficulty with emergency invasive airway rescue.

  • ◦

    When appropriate, perform awake intubation if the patient is suspected to be a difficult intubation and one or more of the following apply: (1) difficult ventilation (face mask/supraglottic airway), (2) increased risk of aspiration, (3) the patient is likely incapable of tolerating a brief apneic episode, or (4) there is expected difficulty with emergency invasive airway rescue.^{†††††††}

  • ◦

    The uncooperative or pediatric patient may restrict the options for difficult airway management, particularly options that involve awake intubation. Airway management in the uncooperative or pediatric patient may require an approach (e.g., intubation attempts after induction of general anesthesia) that might not be regarded as a primary approach in a cooperative patient.

  • ◦

    Proceed with airway management after induction of general anesthesia when the benefits are judged to outweigh the risks.

  • ◦

    For either awake or anesthetized intubation, airway maneuver(s) may be attempted to facilitate intubation.

  • ◦

    Before attempting intubation of the anticipated difficult airway, determine the benefit of a noninvasive versus invasive approach to airway management.

    • ▪

      If a noninvasive approach is selected, identify a preferred sequence of noninvasive devices to use for airway management.^{‡‡‡‡‡‡‡}

• •

  If difficulty is encountered with individual techniques, combination techniques may be performed.^{§§§§§§§}

• •

  Be aware of the passage of time, the number of attempts, and oxygen saturation.

• •

  Provide and test mask ventilation after each attempt, when feasible.

• •

  Limit the number of attempts at tracheal intubation or supraglottic airway placement to avoid potential injury and complications.

  • ▪

    If an elective invasive approach to the airway is selected, identify a preferred intervention.^{‖‖‖‖‖‖‖}

• •

  Ensure that an invasive airway is performed by an individual trained in invasive airway techniques, whenever possible.

• •

  If the selected approach fails or is not feasible, identify an alternative invasive intervention.

  • ◦

    Initiate ECMO when/if appropriate and available.

• •

  Call for help.

• •

  Optimize oxygenation.^#######

• •

  When appropriate, refer to an algorithm^******** and/or cognitive aid.

• •

  Upon encountering an unanticipated difficult airway:

  • ◦

    Determine the benefit of waking and/or restoring spontaneous breathing.

  • ◦

    Determine the benefit of a noninvasive versus invasive approach to airway management.

  • ◦

    If a noninvasive approach is selected, identify a preferred sequence of noninvasive devices to use for airway management.^{††††††††}

    • ▪

      If difficulty is encountered with individual techniques, combination techniques may be performed.

    • ▪

      Be aware of the passage of time, the number of attempts, and oxygen saturation.

    • ▪

      Provide and test mask ventilation after each attempt, when feasible.

    • ▪

      Limit the number of attempts at tracheal intubation or supraglottic airway placement to avoid potential injury and complications.

• •

  If an invasive approach to the airway is necessary (i.e., cannot intubate, cannot ventilate), identify a preferred intervention.^{‡‡‡‡‡‡‡‡}

  • ◦

    Ensure that an invasive airway is performed by an individual trained in invasive airway techniques, whenever possible.

  • ◦

    Ensure that an invasive airway is performed as rapidly as possible.

  • ◦

    If the selected invasive approach fails or is not feasible, identify an alternative invasive intervention.

    • ▪

      Initiate ECMO when/if appropriate and available.

• •

  Confirm tracheal intubation using capnography or end-tidal carbon dioxide monitoring.

• •

  When uncertain about the location of the tracheal tube, determine whether to either remove it and attempt ventilation or use additional techniques to confirm positioning of the tracheal tube.^{§§§§§§§§}

• •

  Have a preformulated strategy for extubation and subsequent airway management.

  • ◦

    This strategy will depend, in part, on the surgery/procedure, other perioperative circumstances, the condition of the patient, and the skills and preferences of the clinician.

• •

  Assess patient readiness for extubation.

• •

  Ensure that a skilled individual is present to assist with extubation when feasible.

• •

  Select an appropriate time and location for extubation when possible.

• •

  Assess the relative clinical merits and feasibility of the short-term use of an airway exchange catheter and/or supraglottic airway that can serve as a guide for expedited reintubation.^{‖‖‖‖‖‖‖‖}

  • ◦

    Minimize the use of an airway exchange catheter with pediatric patients.

• •

  Before attempting extubation, evaluate the risks and benefits of elective surgical tracheostomy.

• •

  Evaluate the risks and benefits of awake extubation versus extubation before the return to consciousness.

• •

  When feasible, use supplemental oxygen throughout the extubation process.

• •

  Assess the clinical factors that may produce an adverse impact on ventilation after the patient has been extubated.

• •

  Use postextubation steroids and/or racemic epinephrine when appropriate.

• •

  Inform the patient or a responsible person of the airway difficulty that was encountered to provide the patient (or responsible person) with a role in guiding and facilitating the delivery of future care.

  • ◦

    The information conveyed may include (but is not limited to) the presence of a difficult airway, the apparent reasons for difficulty, how the intubation was accomplished, and the implications for future care.

• •

  Document the presence and nature of the airway difficulty in the medical record to guide and facilitate the delivery of future care.^########

• •

  Instruct the patient to register with an emergency notification service when appropriate and feasible.

For these updated guidelines, a systematic search and review of peer-reviewed published literature was conducted, with scientific findings summarized and reported below and in the document. Assessment of conceptual issues, practicality, and feasibility of the guideline recommendations were also evaluated, with opinion data collected from surveys and other sources. The systematic literature review is based on evidence linkages or statements regarding potential relationships between interventions and outcomes associated with difficult airway management. The evidence model below guided the search, providing inclusion and exclusion information regarding patients, procedures, practice settings, providers, clinical interventions, and outcomes. The opinion data were obtained from surveys based on proposed recommendations derived from the literature findings (see “Consensus-based evidence” below).

After review of all evidentiary information, the task force placed each recommendation into one of three categories: (1) provide the intervention or treatment, (2) provide the patient with the intervention or treatment based on circumstances of the case and the practitioner’s clinical judgment, or (3) do not provide the intervention or treatment. The policy of the ASA Committee on Standards and Practice Parameters is to update practice guidelines every 5 yr. The ASA Committee on Standards and Practice Parameters reviews all practice guidelines at the ASA annual meeting and determines update and revision timelines.

• •

  Inclusion criteria:

  • ◦

    Patients with or at risk of difficult mask ventilation

  • ◦

    Patients with or at risk of difficult laryngoscopy (direct or indirect)^*********

  • ◦

    Patients with or at risk of difficult ventilation using a supraglottic airway

  • ◦

    Patients with or at risk of difficult/failed tracheal intubation

  • ◦

    Patients with or at risk of difficult/failed extubation

  • ◦

    Anticipated difficult airway patients

  • ◦

    Unanticipated difficult airway patients

  • ◦

    Adult patients

  • ◦

    Pediatric patients including infants and neonates

  • ◦

    Obstetric patients

  • ◦

    ICU/critically ill patients

• •

  Exclusion criteria

  • ◦

    Patients where difficult airways are not encountered

  • ◦

    Physiologically difficult airways that are not anatomically difficult^{†††††††††}

• •

  Inclusion criteria:

  • ◦

    Procedures requiring general anesthesia

  • ◦

    Procedures requiring sedation or regional anesthesia

  • ◦

    Elective/emergency airway management without a procedure

  • ◦

    Diagnostic procedures

  • ◦

    Elective procedures

  • ◦

    Emergency procedures

  • ◦

    Invasive airway access

• •

  Exclusion criteria:

  • ◦

    Airway management during cardiopulmonary resuscitation

• •

  Inclusion criteria:

  • ◦

    In-hospital

    • ▪

      Perioperative care settings

    • ▪

      Nonoperating room anesthetic setting

    • ▪

      Emergency department setting

    • ▪

      ICU/critical care setting

  • ◦

    Ambulatory surgery centers

  • ◦

    Office-based procedure/anesthesia locations

  • ◦

    Out-of-hospital or prehospital (i.e., field) settings, included only if emergency invasive airway is performed

• •

  Exclusion criteria:

  • ◦

    Out-of-hospital or prehospital (i.e., field) settings, excluded except for emergency invasive airway

• •

  Inclusion criteria:

  • ◦

    Anesthesia care providers

• •

  Exclusion criteria:

  • ◦

    Individuals who do not deliver anesthetic care and airway management

• •

  Evaluation of the airway

  • ◦

    Risk prediction (for difficult airway or aspiration) obtained from history/medical records

    • ▪

      Demographic conditions (e.g., age, sex)

    • ▪

      Clinical conditions (e.g., body mass index, previous difficult airway, diabetes, obesity)

    • ▪

      Diagnostic test findings (e.g., radiography, computed tomography, magnetic resonance imaging, bedside endoscopy, bedside ultrasound)

    • ▪

      Patient interview/questionnaires (e.g., MACOCHA, STOP-Bang)

  • ◦

    Airway assessment/exam (bedside and advanced) when a difficult airway is known or suspected

    • ▪

      Assessment of facial features (e.g., mouth opening, nose slope, neck slope, ratio of brow to nose to chin, full beard)

    • ▪

      Upper lip bite test

    • ▪

      Anatomical measurements and landmarks (e.g., Mallampati/modified Mallampati, neck circumference, neck mobility (neck radiation changes), prognathism, ruler or finger measurements of thyromental, sternomental, or temporomandibular distance)

• •

  Individual measures contained in airway scoring systems (e.g., Wilson risk sum scores, simplified airway risk index scores, El-Ganzouri scores)

• •

  Imaging

  • ◦

    Ultrasound

  • ◦

    Virtual laryngoscopy/bronchoscopy (magnetic resonance imaging/computed tomography reconstruction)

  • ◦

    3D printing

  • ◦

    Bedside endoscopy

  • ◦

    Direct laryngoscopy (e.g., Cormac–Lehane grades)

  • ◦

    Bronchoscopy

  • ◦

    Nasopharyngoscopy

• •

  Preparation for difficult airway management

  • ◦

    Availability of equipment for airway management (i.e., items for anesthetizing locations, portable storage unit, cart, or trolley for difficult airway management)

  • ◦

    Availability of an assigned individual to provide assistance when a difficult airway is encountered (from previous evidence model)

  • ◦

    Informing the patient with a known or suspected difficult airway

  • ◦

    Preoxygenation^{‡‡‡‡‡‡‡‡‡}

    • ▪

      Preoxygenation versus room air

    • ▪

      3 to 5 min of O₂ (3 to 5 min at tidal volume, Fio₂ = 1) versus 1 min (1 min at tidal volume, Fio₂ = 1)

    • ▪

      3 to 5 min of O₂ (3 to 5 min at tidal volume, Fio₂ = 1) versus 4 to 12 deep breaths at forced vital capacity in 1 min or the shortest time lag (Fio₂ = 1)

    • ▪

      3 min of preoxygenation to reach an end-tidal oxygen concentration of 0.90 of higher (EtO₂ ≥ 0.9)

    • ▪

      Preoxygenation using noninvasive ventilation (pressure support with positive end expiratory pressure)

  • ◦

    Patient positioning (e.g., sniffing, sitting, head/neck extension, head-elevated laryngoscopy, ramped)

  • ◦

    Sedative versus hypnotic administration

  • ◦

    Local anesthesia versus no local anesthesia

  • ◦

    Supplemental oxygen during airway management^{§§§§§§§§§}

  • ◦

    Patient monitoring (according to ASA standards)

• •

  Anticipated difficult airway management.

  • ◦

    Awake tracheal intubation (any device)

    • ▪

      Awake/sedated intubation versus intubation after induction

    • ▪

      Awake/sedated versus anesthetized intubation in patients with full stomach

  • ◦

    Anesthetized tracheal intubation

    • ▪

      Rapid sequence induction/intubation

• •

  With versus without cricoid pressure (Sellick maneuver)

• •

  Pressure-limited mask ventilation versus ablation of spontaneous ventilation

  • ▪

    Maintenance of spontaneous ventilation versus ablation of spontaneous ventilation

  • ▪

    Administration of neuromuscular blockade to improve mask ventilation

  • ▪

    Rocuronium with sugammadex versus suxamethonium or succinylcholine

• ◦

  Both awake and anesthetized intubation

  • ▪

    Airway maneuvers (e.g., jaw thrust chin lift, external laryngeal manipulation, backwards/upwards/rightwards pressure)

• ◦

  Airway management devices

  • ▪

    Rigid laryngoscopic blades of alternative design and size: with adequate face mask ventilation after induction (alternatives to standard blades such as Macintosh, Miller)

  • ▪

    Adjuncts – introducers, bougies, stylets, alternative tracheal tubes

  • ▪

    Video/video-assisted laryngoscopy

• •

  Video/video-assisted laryngoscopy versus direct laryngoscopy

• •

  Video/video-assisted laryngoscopy versus fiberoptic laryngoscopy

• •

  Channel-guided versus non–channel-guided videolaryngoscopes^{‖‖‖‖‖‖‖‖‖}

• •

  Hyperangulated versus nonangulated devices

  • ▪

    Flexible intubation scopes

• •

  Flexible intubation scopes versus blind tracheal or nasotracheal intubation

• •

  Flexible intubation scopes versus rigid laryngoscopic intubation

  • ▪

    Supraglottic airway

• •

  Supraglottic airway versus face mask for ventilation

• •

  Intubation with versus without a supraglottic airway

• •

  Intubating techniques with a supraglottic airway

  • ▪

    Laryngoscopic intubation with a supraglottic airway versus blind intubation with a supraglottic airway

  • ▪

    Flexible scope intubation with a supraglottic airway versus standard laryngoscopic intubation with a supraglottic airway

  • ▪

    Optically/image-guided intubation with a supraglottic airway versus standard laryngoscopic intubation with a supraglottic airway

• •

  Second versus first generation supraglottic airway

  • ▪

    Lighted stylet, light wand, optical stylet

• •

  Lighted stylet, light wand, or optical stylet versus blind intubation

• •

  Lighted stylet, light wand, or optical stylet versus laryngoscopic intubation

  • ▪

    Rigid bronchoscope

• •

  Intubation with versus without a supraglottic airway

• •

  Intubating techniques with a supraglottic airway

• •

  Laryngoscopic intubation with a supraglottic airway versus blind intubation with a supraglottic airway

• •

  Flexible scope intubation with a supraglottic airway versus standard laryngoscopic intubation with a supraglottic airway

• •

  Optically/image-guided intubation with a supraglottic airway versus standard laryngoscopic intubation with a supraglottic airway

  • ◦

    Additional airway management interventions (with anticipated failure of airway management devices)

    • ▪

      Retrograde wire–guided intubation

    • ▪

      Invasive airway

• •

  Cricothyrotomy (percutaneous)

• •

  Cricothyrotomy (surgical)

• •

  Tracheostomy/tracheotomy

• •

  Scalpel bougie technique or scalpel bougie tube technique versus needle cannula technique

• •

  Awake/sedated cricothyrotomy/tracheostomy for invasive airway

  • ◦

    Combination techniques^#########

• •

  Unanticipated and emergency (i.e., cannot oxygenate or ventilate) difficult airway management.

  • ◦

    Call for help

  • ◦

    Maximize oxygenation

    • ▪

      Nasal oxygen during efforts securing a tube

    • ▪

      Expiratory ventilation assistance

    • ▪

      High-flow nasal cannula oxygen/transnasal humidified rapid insufflation ventilatory exchange

  • ◦

    Use of a cognitive aid

  • ◦

    Airway management devices

    • ▪

      Rigid bronchoscope

    • ▪

      Rigid laryngoscopic blades of alternative design and size: with adequate face mask ventilation after induction (alternatives to standard blades such as Macintosh, Miller)

    • ▪

      Lighted stylet, light wand, optical stylet

• •

  Lighted stylet, light wand, or optical stylet versus blind intubation

• •

  Lighted stylet, light wand, or optical stylet versus laryngoscopic intubation

  • ▪

    Flexible intubation scopes)

• •

  Flexible scope intubation versus blind tracheal or nasotracheal intubation

• •

  Flexible scope intubation versus rigid laryngoscopic intubation

  • ▪

    Video/video-assisted laryngoscopy

• •

  Video/video-assisted laryngoscopy versus direct laryngoscopy

• •

  Video/video-assisted laryngoscopy versus flexible scope intubation

• •

  Hyperangulated versus nonangulated devices

• •

  Channel-guided versus non–channel-guided videolaryngoscopes

• •

  Alternative optical laryngoscopes

  • ▪

    Adjuncts – introducers, bougies, stylets, alternative tracheal tubes

  • ▪

    Supraglottic airway

• •

  Supraglottic airway versus face mask for ventilation

• •

  Intubation with versus without a supraglottic airway

• •

  Intubating techniques with a supraglottic airway

  • ▪

    Laryngoscopic intubation with a supraglottic airway versus blind intubation with a supraglottic airway

  • ▪

    Flexible scope intubation with a supraglottic airway versus standard laryngoscopic intubation with a supraglottic airway

  • ▪

    Optically/image-guided intubation with a supraglottic airway versus standard laryngoscopic intubation with a supraglottic airway

• •

  Second- versus first-generation supraglottic airway

  • ◦

    Additional airway management interventions (with anticipated failure of airway management devices)

    • ▪

      Retrograde wire–guided intubation

    • ▪

      Emergency invasive airway

• •

  Cricothyrotomy (percutaneous)

• •

  Cricothyrotomy (surgical)

• •

  Tracheostomy/tracheotomy

• •

  Scalpel bougie technique or scalpel bougie tube technique versus needle cannula technique

• •

  Awake/sedated cricothyrotomy/tracheostomy for emergency invasive airway

  • ▪

    ECMO

  • ▪

    Jet ventilation

  • ▪

    Combination techniques

• •

  Confirmation of successful intubation

  • ◦

    Pulse oximetry (for oxygen saturation levels/desaturation/ hypoxemia/hypoxia)

  • ◦

    Capnography for carbon dioxide levels/hypercarbia/hypercapnia

    • ▪

      Capnography versus capnometry

    • ▪

      Capnography versus colorimetry

  • ◦

    Visualization (any technique)

  • ◦

    Flexible bronchoscopy

  • ◦

    Ultrasound

  • ◦

    Radiography

• •

  Extubation

  • ◦

    Assess readiness for extubation

  • ◦

    Presence of a skilled individual to assist

  • ◦

    Selection of ideal time and location

  • ◦

    Plan for possible reintubation

  • ◦

    Elective tracheostomy

  • ◦

    Awake extubation or supraglottic airway removal

    • ▪

      Awake tracheal tube extubation versus asleep (anesthetized) extubation

    • ▪

      Awake supraglottic airway removal versus anesthetized supraglottic airway removal

    • ▪

      Apnea versus spontaneous ventilation during extubation

  • ◦

    Supplemental oxygen throughout extubation (e.g., by mask, blow-by, nasal cannula, continuous positive airway pressure, bilevel positive airway pressure, or high-flow nasal cannula)

  • ◦

    Supplemental oxygen after extubation

  • ◦

    Staged extubation

• •

  Airway exchange catheter

• •

  Supraglottic airway exchange catheter (Bailey maneuver)

• •

  Follow-up care

  • ◦

    Postextubation steroids

  • ◦

    Postextubation epinephrine

  • ◦

    Postextubation counseling (i.e., informing and advising the patient or responsible patient of the occurrence and potential complications associated with a difficult airway)

  • ◦

    Documentation of difficult airway and management in the medical record and to the patient

  • ◦

    Registration with an emergency notification service

• •

  Human factors

• •

  Interventions not addressing any aspect of airway and anesthetic management

• •

  Lung separation

  • ◦

    Double lumen tube

  • ◦

    Bronchial blocker

• •

  Physiologically difficult airway

• •

  Details of awake intubation techniques

• •

  Submental intubation

• •

  Cardiopulmonary bypass

• •

  Effects of anesthetics/sedatives on ease of intubation/supraglottic airway insertion (e.g., propofol)

• •

  Details of ECMO

• •

  Inclusion criteria:

  • ◦

    Identification of patient characteristics at risk of difficult intubation

  • ◦

    Identification of patient characteristics leading to awake intubation

  • ◦

    Intubation/ventilation success/failure:

    • ▪

      Face/bag mask ventilation (success/failure, easy/difficult)

    • ▪

      supraglottic airway placement (success/failure, number of attempts)

    • ▪

      Laryngoscopy (success/failure, number of attempts)

    • ▪

      Tracheal intubation (success/failure, number of attempts)

    • ▪

      Invasive airway

• •

  Percutaneous cricothyrotomy (success/failure)

• •

  Surgical cricothyrotomy (success/failure)

• •

  Tracheostomy (success/failure)

• •

  Scalpel bougie technique or scalpel bougie tube technique versus needle catheter technique (success/failure)

  • ▪

    Restoration of failed oxygenation (success/failure)

  • ▪

    Esophageal intubation

  • ▪

    Barotrauma (pneumothorax, pneumomediastinum)

  • ▪

    Subcutaneous emphysema

  • ▪

    Gastric rupture

  • ▪

    Tracheal rupture

  • ▪

    Delayed tracheal stenosis

• ◦

  Physiologic outcomes (measurement of physiologic functioning)

  • ▪

    Oxygenation/desaturation

  • ▪

    Carbon dioxide levels

  • ▪

    Hemodynamic levels (e.g., mean arterial pressure, central venous pressure)

• ◦

  Clinical outcomes

  • ▪

    Hypoxemia/hypoxia

  • ▪

    Hypercapnia/hypercarbia

  • ▪

    Hemodynamic instability

  • ▪

    Aspiration

  • ▪

    Airway injury/trauma

  • ▪

    Soft tissue injuries/blind spot injuries

  • ▪

    Sore throat

  • ▪

    Palatal injury

  • ▪

    Oral/dental damage

  • ▪

    Cardiac events (e.g., cardiac arrest)

  • ▪

    Neurologic injury

  • ▪

    Unplanned tracheotomy/surgical airway

  • ▪

    Neurologic deficit of less than 72 h

• ◦

  Permanent (long-term) outcomes

  • ▪

    Death

  • ▪

    Respiratory system damage

• •

  Airway trauma

• •

  Pneumothorax

• •

  Aspiration

  • ▪

    Nerve/brain damage

• •

  Nerve damage

• •

  Neurologic/memory deficit

• •

  Permanent brain damage

• •

  Brain injury (anoxic encephalopathy)

  • ▪

    Cardiovascular damage

• •

  Cardiopulmonary arrest

  • ▪

    Fetal/newborn damage

  • ▪

    Functional deficit

• •

  Awareness/fright

• •

  Loss of employment

  • ◦

    Nonclinical outcomes

    • ▪

      Unplanned ICU admission

    • ▪

      Unplanned hospital admission

    • ▪

      Surgery postponed/cancelled

    • ▪

      Length of hospital stay

    • ▪

      Patient satisfaction

• •

  Exclusion criteria:

  • ◦

    No exclusion criteria

• •

  Literature inclusion criteria:

  • ◦

    Randomized controlled trials

  • ◦

    Prospective nonrandomized comparative studies (e.g., quasiexperimental, cohort)

  • ◦

    Retrospective comparative studies (e.g., case control)

  • ◦

    Observational studies (e.g., correlational or descriptive statistics)

  • ◦

    Case reports, case series

• •

  Literature exclusion criteria (except to obtain new citations):

  • ◦

    Editorials

  • ◦

    Literature reviews

  • ◦

    Meta-analyses conducted by others

  • ◦

    Unpublished studies

  • ◦

    Studies in non–peer-reviewed journals

  • ◦

    Newspaper articles

• •

  Survey evidence:

  • ◦

    Expert consultant survey

  • ◦

    ASA membership survey

  • ◦

    Membership surveys of other participating organizations

  • ◦

    Reliability survey

  • ◦

    Feasibility survey

For the systematic review, potentially relevant clinical studies were identified via electronic and manual searches. Bibliographic database searches included PubMed and EMBASE. The searches covered a 9.25-yr period from January 1, 2012, through March 31, 2021. Citation searching (backward and forward) of relevant meta-analyses and other systematic reviews was also performed. No search for gray literature was conducted. Publications identified by task force members were also considered. Accepted studies from the previous guidelines were re-reviewed, covering the period of January 1, 2002, through June 31, 2012. Only studies containing original findings from peer-reviewed journals were acceptable. Editorials, letters, and other articles without data were excluded. A literature search strategy and PRISMA* flow diagram are available as Supplemental Digital Content 2, https://links.lww.com/ALN/C695. In total, 12,544 unique new citations were identified, with 1,026 full articles assessed for eligibility. After review, 619 were excluded, with 407 new studies meeting inclusion criteria. These studies were combined with 190 pre-2012 articles from the previous guidelines, resulting in a total of 597 articles accepted as evidence for these guidelines. In this document, 559 are referenced, with a complete bibliography of articles used to develop these guidelines, organized by section, available as Supplemental Digital Content 3, https://links.lww.com/ALN/C696.

Each pertinent outcome reported in a study was classified by evidence category and level and designated as beneficial, harmful, or equivocal. Findings were then summarized for each evidence linkage and reported in the text of the updated guidelines.

Evidence categories refer specifically to the strength and quality of the research design of the studies. Category A evidence represents results obtained from randomized controlled trials, and category B evidence represents observational results obtained from nonrandomized study designs or randomized trials without pertinent comparison groups. When available, category A evidence is given precedence over category B evidence for any particular outcome. These evidence categories are further divided into evidence levels. Evidence levels refer specifically to the strength and quality of the summarized study findings (i.e., statistical findings, type of data, and the number of studies reporting/replicating the findings). In this document, the highest level of evidence is included in the summary report for each intervention–outcome pair, including a designation of benefit, harm, or equivocality.

Randomized controlled trials report comparative findings between clinical interventions for specified outcomes. Statistically significant (P < 0.01) outcomes are designated as either beneficial (B) or harmful (H) for the patient; statistically nonsignificant findings are designated as equivocal (E).

The literature contains a sufficient number of randomized controlled trials to conduct meta-analysis,^********** and meta-analytic findings from these aggregated studies are reported as evidence.

The literature contains multiple randomized controlled trials, but the number of randomized controlled trials is not sufficient to conduct a viable meta-analysis for the purpose of these guidelines. Findings from these randomized controlled trials are reported separately as evidence.

The literature contains a single randomized controlled trial, and findings from this study are reported as evidence.

Observational studies or randomized controlled trials without pertinent comparison groups may permit inference of beneficial or harmful relationships among clinical interventions and clinical outcomes. Inferred findings are given a directional designation of beneficial (B), harmful (H), or equivocal (E). For studies that report statistical findings, the threshold for significance is P < 0.01.

The literature contains nonrandomized comparisons (e.g., quasiexperimental, cohort [prospective or retrospective], or case-control research designs) with comparative statistics between clinical interventions for a specified clinical outcome.

The literature contains noncomparative observational studies with associative statistics (e.g., correlation, sensitivity, and specificity).

The literature contains noncomparative observational studies with descriptive statistics (e.g., frequencies, percentages).

The literature contains case reports.

The lack of sufficient scientific evidence in the literature may occur when the evidence is either unavailable (i.e., no pertinent studies found) or inadequate. Inadequate literature cannot be used to assess relationships among clinical interventions and outcomes, either, because a clear interpretation of findings is not obtained due to methodologic concerns (e.g., confounding of study design or implementation) or the study does not meet the criteria for content as defined in the “focus” of the guidelines.

Literature addressing risk prediction reported sensitivity, specificity, positive and negative predictive, and other common values for age, sex, body mass index, weight, height, and history of snoring. Values for airway assessment were reported for facial and jaw features, anatomical landmarks, and measurements.

Literature relating to videolaryngoscopes contained enough studies with well defined experimental designs and statistical information to conduct formal meta-analyses (table 4). Outcomes assessed were (1) laryngoscopic view, (2) intubation success, (3) first attempt intubation success, (4) assist maneuvers used for intubation, and (5) time to intubation. For meta-analyses of studies reporting frequency of events, event rates and odds ratios were pooled. Time to intubation was pooled using mean differences (continuous outcomes) for clinical relevance. Fixed-effects models were fitted using Mantel–Haenszel or inverse variance weighting as appropriate. Random-effects models were fitted with inverse variance weighting using the DerSimonian and Laird estimate of between-study variance. Sensitivity to effect measure was also examined. Heterogeneity was quantified with I² and a significance level of P < 0.01 was applied for analyses. Statistics for individual studies and forest plots are available as Supplemental Digital Content 4, https://links.lww.com/ALN/C697.

Interobserver agreement among task force members and two methodologists was assessed for this update, with agreement levels using a κ statistic for two-rater agreement pairs as follows: (1) research design, κ = 0.55 to 0.61; (2) type of analysis, κ = 0.55 to 0.83; (3) evidence linkage assignment, κ = 0.67 to 0.79; and (4) literature inclusion for database, κ = 0.08 to 0.79. Three-rater κ values between two methodologists and task force reviewers were (1) research design, κ = 0.61; (2) type of analysis, κ = 0.65; (3) linkage assignment, κ = 0.67; and (4) literature database inclusion, κ = 0.15. These values represented low to moderate levels of agreement.

Validation of the concepts addressed by these guidelines and subsequent recommendations proposed was obtained by consensus from multiple sources, including (1) survey opinion from expert consultants who were selected based on their knowledge or expertise in difficult airway management; (2) survey opinions from randomly selected samples of active members of the ASA and participating organizations; and (3) internet commentary. All opinion-based evidence relevant to each topic was considered in the development of these guidelines. However, only findings obtained from formal surveys are reported in the document. Opinion surveys were developed by the task force to address each clinical intervention identified in the document. Identical surveys were distributed to expert consultants, a random sample of ASA members, and members of the participating organizations.

Survey responses were recorded using a five-point scale and summarized based on median values^{††††††††††}:

• Strongly agree: Median score of 5 (at least 50% of the responses are 5)

• Agree: Median score of 4 (at least 50% of the responses are 4 or 4 and 5)

• Equivocal: Median score of 3 (at least 50% of the responses are 3, or no other response category or combination of similar categories contains at least 50% of the responses)

• Disagree: Median score of 2 (at least 50% of responses are 2 or 1 and 2)

• Strongly disagree: Median score of 1 (at least 50% of responses are 1)

For consultant respondents, the rate of return for the survey addressing guideline recommendations was 82% (n = 174 of 212), and the results are presented in table 5. For membership respondents, the survey totals were as follows: American Society of Anesthesiologists (ASA) = 220; All India Difficult Airway Association (AIDAA) = 74; European Airway Management Society (EAMS) = 79; Italian Society of Anesthesiology, Analgesia, Resuscitation and Intensive Care (SIAARTI) = 177; Learning, Teaching and Investigation Difficult Airway Group (FIDIVA) = 24; Society for Ambulatory Anesthesia (SAMBA) = 47; Society for Airway Management (SAM) = 70; Society for Head and Neck Anesthesia (SHANA) = 27; Society for Pediatric Anesthesia (SPA) = 268; Society of Critical Care Anesthesiologists (SOCCA) = 85; and Trauma Anesthesiology Society (TAS) = 21. Survey results for each organization are presented as Supplemental Digital Content 5, https://links.lww.com/ALN/C698.

An additional survey was sent to the consultants accompanied by a draft of the guidelines asking them to indicate which, if any, of the recommendations would change their clinical practices if the guidelines were instituted. The rate of return was 31% (n = 68 of 218). The percentage of responding consultants expecting no change associated with each linkage were as follows: (1) evaluation of the airway = 82%, (2) availability of airway management equipment = 79%, (3) the presence of a skilled individual to assist = 82%, (4) supplemental oxygen delivery = 76%, strategy for management of an anticipated difficult airway = 88%, awake intubation strategy = 81%, selection of an elective invasive airway = 84%, preferred sequence of devices for attempting intubation = 93%, strategy for management of an unanticipated difficult airway = 88%, strategy for management of an emergency difficult airway = 87%, use of an algorithm, cognitive aid, or infographic = 65%, use of capnography for confirmation of intubation = 90%, strategy for invasive management of a difficult airway = 82%, supplemental oxygen delivery for extubation = 87%, and documentation of the encountered difficult airway = 81%. Of all the respondents, 91% indicated that the guidelines would have no effect on the amount of time spent on a typical case, 7% indicated that there would be an increase of the amount of time spent on a typical case, and 1% indicated a decrease in time with the implementation of these guidelines; 72% indicated that new equipment, supplies, or training would not be needed to implement the guidelines; and 86% indicated that implementation of the guidelines would not require changes in practice that would affect costs.