Dissection of the Posterior Pharynx Resulting in Acute Airway Obstruction

A 46-yr-old male patient with a history of a gunshot wound to the spine with subsequent paraplegia 18 yr before the current admission was admitted from a chronic nursing care facility for surgical management of sacral/perineal decubiti. Oral tracheal intubation, anesthesia, and surgery were uneventful. At the conclusion of the case, the anesthetic agents were discontinued, neuromuscular blockade was reversed, and the trachea was extubated. After extubation, the patient responded to loud verbal stimulus with a deep breath and transient eye-opening. However, the patient became somnolent with very shallow respirations in the absence of repeated stimulus. A nasal airway (Concord/Portex. SIMS, Keene, NH) was placed, resulting in transient improvement in alertness and respiratory rate (approximately 12 breaths/min), and the patient was transported to the postanesthesia care unit (PACU). Within 5 min of PACU arrival, the patient's oxyhemoglobin saturation (Sp^O2) had decreased to 88% with a simultaneous decrease in mental status to obtundation. Evaluation by the PACU staff demonstrated that chin-lift was required to maintain airway patency, and Sp^O2increased to 100% with FI^O2at 1.0.

Fifteen minutes after PACU admission, Sp^O2again decreased to 80%, and despite chin-lift and verbal stimulation, the respiratory rate remained low with minimal air movement by auscultation. Bag-valve-mask-assisted ventilation with 100% Oxygen²was initiated to improve oxygenation and ventilation. The decreased mental status and hypoventilation did not improve with 0.4 mg of intravenous naloxone and continued bag-valve-mask ventilation. Peripheral nerve stimulation demonstrated intact train-of-four without fade and sustained tetany. However, because the blood gas revealed a pH of 6.97, Pa^CO2of 111 mmHg, and a Pa^O2of 157 mmHg, the decision was made to reintubate the trachea.

During direct laryngoscopy, a bullous lesion was noted in the posterior pharynx that obstructed the majority of the pharyngeal space. Palpation of this lesion demonstrated it to be an air-filled sac within the submucosal tissue. A quick survey of the neck and upper chest failed to demonstrate any subcutaneous emphysema. Because clinical suspicion included a pharyngeal dissection, suction was connected to the nasal airway with subsequent reduction and disappearance of the bullous lesion. Once the airway obstruction was reduced, the nasal airway was removed and the trachea was reintubated orally, with rapid improvement in clinical condition.

Examination by an otolaryngologist demonstrated that the nasal airway had dissected into the retropharyngeal position, with a small (1.5 cm diameter) residual submucosal bulla. The trachea was left intubated overnight and was extubated the next morning without incident. No antibiotics were given. Subsequent evaluation by the otolaryngology service demonstrated no scarring or other chronic airway difficulty.

Nasal airways (so-called "trumpets") are airway adjuncts commonly used in PACUs and in intensive care units. Trumpets cause less stimulation than do oral airways and are commonly used immediately after extubation to help maintain airway patency in patients emerging from anesthesia. In addition to airway protection, trumpets allow easy access to the pharynx for suctioning and airway clearance, plus facilitation of bag-valve-mask-assisted ventilation. The established risks of nasal trumpets include traumatic injury to nasal turbinates, bleeding, and obstruction of sinus passages. We were unable to find any reports of dissection of the posterior pharyngeal wall using a nasal airway.

Dissection of the posterior wall of the oropharynx as well as other nasopharyngeal trauma seen with endotracheal tubes is related to the anatomic arrangement of tissues in the head and neck (Figure 1and Figure 2). The posterior wall of the pharynx is composed of a mucosal layer, a submucosal muscular layer, and a less well delineated connective tissue layer, which includes both the pharyngobasilar fascia and buccopharyngeal fascia. The pharyngobasilar fascia is well developed in the upper portion of the pharynx, diminishing lower in the airway. The nasal portion of the pharyngeal wall is lined by pseudostratified columnar epithelium and has relatively less musculature than the hypopharynx, which is lined with stratified squamous epithelium. [6]The pseudostratified epithelium presumably is more susceptible to perforation by an artificial airway entering at an acute angle. The airway then may track underneath the mucosa, well contained by the stratified squamous tissue of the hypopharynx. The space generated can serve as a compartment containing blood (hematoma), pus (abscess), or in this case, air. Once within the submucosa, air may track further into the neck and chest, resulting in subcutaneous emphysema. It is unclear why in this patient air did not dissect into his mediastinum or subcutaneous tissue, despite the size of the loculated air pocket in the posterior pharynx.

The nasal airway employed was made of polyvinyl chloride, which is somewhat stiffer than the red rubber used by other manufacturers. Whether the physical properties of the tube contributed to this complication cannot be established. Retropharyngeal perforation by standard polyvinyl chloride endotracheal tubes has been estimated to occur 2% of the time during emergent tracheal intubation in an emergency department. [1]Presumably this number is far less in the controlled setting of the operating room, but no data are available. Perforation by nasal airway, with or without inflation of the retropharyngeal space, is likewise a rare occurrence but must be considered in the appropriate setting as a cause of acute airway obstruction.