To the Editor:—

We read with great interest the case report by Baraka entitled “Tension Pneumothorax Complicating Jet Ventilation via  a Cook Airway Exchange Catheter”1and the accompanying editorial view, “Airway Exchange Catheters: Simple Concept, Potentially Great Danger,” by Benumof. 2We agree with the authors as to the importance of airway exchange catheters (AECs) in airway management but wish to address the following issues.

  • 1. the etiology of barotrauma

Barotrauma associated with the use of AECs has been reported as a result of direct trauma to the tracheobronchial tree by the catheter 3,4and that caused by an increase in lung volume or pressure. 1We would like to suggest the blast effect of air impacting on intact human tissue as a third possible etiologic factor. Figure 1 

Fig. 1. Photograph of the blast effect of a jet stream impacting intact human tissue. Notice the tissue response to the enormous, uncontrolled force. Transmission of this considerable force, especially to the small-caliber airways, may have potentially devastating effects.

Fig. 1. Photograph of the blast effect of a jet stream impacting intact human tissue. Notice the tissue response to the enormous, uncontrolled force. Transmission of this considerable force, especially to the small-caliber airways, may have potentially devastating effects.

shows the effect of a force generated by applying 25 psi into the proximal part of a 3-mm ID AEC made by Cook Critical Care (Bloomington, IN). Although we found no documentation in the literature as to the effect of this high force on the trachea and bronchial tree, this cannot possibly be benign, especially when it is exerted on the bronchial tree or in a small-diameter airway with low run-off.

  • 2. the safety of jet ventilation through an AEC

The guidelines proposed by Benumof 2for the safe administration of jet ventilation through an AEC can be summarized by three major principles, including the limitation of a driving pressure to 25 psi, limiting inspiratory time to less than 1 s and ensuring an equivalent annular air exit of more than a 4-mm ID endotracheal tube. 5,6The only relevant study in the literature reports the incidence of barotrauma when using a jet ventilation technique through an AEC as 11%. 7We believe that this high complication rate is a function of several variables during jet ventilation. The three most important factors include static and dynamic compliances of the lung in varying states of health, unique physical properties of different AECs, and unpredictable effective flows in the jet system. Our current technology does not allow for predetermining jet ventilation variables (driving pressure, inspiratory time, and so forth). We simply are unable to deliver safe and effective ventilation through an AEC with use of a hand-controlled jet ventilation technique in light of these multiple factors. Also, there does not appear to be an appropriate monitoring device for qualifying or quantifying ventilation with any degree of certainty. The only method for evaluating the delivery of a tidal volume is a rudimentary visual observation of chest expansion. 1,7 

  • 3. the acceptable complication rate for any medical procedure

There is no human study in the literature that evaluates jet ventilation with use of a hand-controlled interrupter valve via  an AEC through an in situ  endotracheal tube. The study by Cooper 7reports 11% barotrauma when an AEC is used to provide jet ventilation in the absence of an endotracheal tube.

One must consider the clinical usefulness of any medical procedure associated with an 11% severe complication rate even for experienced users of the technique. We believe the anesthesiology community must be hard pressed to find alternative approaches or abandon altogether the use of jet ventilation through an AEC.

Finally, Benumof notes that “airway management options provided by an AEC are extremely important  and are well-recognized  by the American Society of Anesthesiologists”2(emphasis added). In the citation for Benumof’s assertion, 8the introductory statement is, “Practice guidelines are subject to revision from time to time, as warranted by the evolution of medical knowledge, technology and practice.” Perhaps the time has come to revise the American Society of Anesthesiologists practice guidelines for management of the difficult airway.

Because jet ventilation should not be necessary during the brief period of time essential for tube exchange 1,7and because both the risk and the severity of complications associated with jet ventilation through AEC is high, we believe the title of Benumof’s letter should be more emphatic and should read “Prohibitive Dangers Associated with Jet Ventilation through These Catheters,” instead of “Potentially Great Danger.”

1.
Baraka AS: Tension pneumothorax complicating jet ventilation via  a Cook airway exchange catheter. A nesthesiology 1999; 91:557–8
2.
Benumof JL: Airway exchange catheters: Simple concept, potentially great danger. A nesthesiology 1999; 91:342–4
3.
deLima LG, Bishop MJ: Lung laceration after tracheal extubation over a plastic tube changer. Anesth Analg 1991; 73:350–1
4.
Seitz PA, Gravenstein N: Endobronchial rupture from endotracheal reintubation with an endotracheal tube guide. J Clin Anesth 1989; 1:214–7
5.
Dworkin R, Benumof JL, Benumof R, Karagianes TG: The effective tracheal diameter that causes air trapping during jet ventilation. J Cardiothorac Anesth 1990; 4:731–6
6.
Takara M, Benumof JL, Ozaki GT: Confirmation of endotracheal intubation over a jet stylet: in vitro studies. Anesth Analg 1995; 80:800–5
7.
Cooper RM: The use of an endotracheal ventilation catheter in the management of difficult extubations. Can J Anaesth 1996; 43:90–3
8.
Caplan RA, Benumof JL, Berry FA, Blitt CD, Bode RH, Cheney FW, Connis RT, Guidry OF, Ovassapian A: Practice guidelines for the management of difficult airway. A report by the American Society of Anesthesiologists Task Force on the Management of the Difficult Airway. A nesthesiology 1993; 78:597–602