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"The critical airway"

University of Wisconsin Medical School, Madison, USA, E-mail: aamatioc{at}facstaff.wisc.edu

To the Editor:

In their editorial of March 2005, Murphy et al. propose a new paradigm for the difficult airway (DA) approach in the operating room (OR) centred on ventilation and oxygenation rather than intubation.¹ We extend this concept to the emergent airway management outside the OR and describe the "critical airway" (CA). The CA is defined as the airway management outside the OR in a patient requiring emergent oxygenation and ventilation secondary to pathology. It is the antithesis of the OR airway management as the situation is uncontrolled, tools are suboptimal and the patient, by definition, is critically ill.

Establishing an emergent airway in a remote location is "inherently difficult" as the routine airway assessment and management are changed producing failure rates much higher than would be acceptable in the "elective" setting. The OR paradigms of airway management need to be reassessed.

1. The anesthesiologist is not formally trained to manage the airway outside the OR. Predicting difficult laryngoscopic intubation in a critically ill unresponsive patient requiring emergency airway management is not practical as more than half of the clinical airway examination components suggested by the "Practice guidelines for management of the difficult airway" need a cooperative patient.²
   
2. The patient presents with acute comorbidities, a "full stomach", in immediate need for oxygenation and ventilation. A rapid sequence induction and intubation is not always indicated or applicable.³
   
3. The airway devices available are limited and the work environment suboptimal.
   
4. The time available to prepare and to successfully achieve ventilation and oxygenation is measured in seconds.
   

The goal of the CA management is efficient ventilation and oxygenation with no stomach inflation, regurgitation, and aspiration and without inducing comorbidities in an already critically ill patient (hypotension, hypertension, bradycardia, tachycardia, hypoxemia, hypercarbia, cardiac arrest, cervical injury).^4,5

The inability to efficiently bag mask ventilate and the persistence to intubate a "full" stomach patient are at the core of most complications in the remote setting.³ The CA is a dynamic concept that demands the anesthesiologist to be skilled in "all four dimensions" of the airway management techniques: bag mask ventilation (BMV), supraglottic airway (SGA; laryngeal mask airway, Combitube, laryngeal tube...), glottic airway (GA; laryngoscopy, endotracheal intubation, Eschmann), or infraglottic airway (IGA; cricothyroid membrane or surgical techniques); any of the techniques can be used as the first option (Figure).

View larger version (23K): [in this window] [in a new window]   FIGURE The management of the critical airway. BMV = bag mask valve; SGA = supraglottic airway; GA = glottic airway; IGA = infraglottic airway

It is ironic that when we should function at our best as "airway consultants," we relay on suboptimal or no airway assessment. Can we define predictors for airway management "difficulty" in "all four dimensions" outside the OR? Can we define optimal use of specific devices: BVM, SGA, GA, and IGA? How does the clinical status of the patient impact on our choice of airway devices?

As airway specialists, anesthesiologists should address through research and training the specific issues of the CA thus improving the outcome of the critically ill. We agree with Murphy et al. that we have "to change how we think about airway management" and to shift from intubation to oxygenation and ventilation. This principle applies both inside and outside the OR.

References

1 Murphy M, Hung O, Launcelott G, Law A, Morris I. Predicting the difficult laryngoscopic intubation: are we on the right track? (Editorial). Can J Anesth 2005; 53: 231–5.

2 American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2003; 98: 1269–77.[Medline]

3 Nolan JD. Prehospital and resuscitative airway care: should the gold standard be reassessed? Curr Opin Crit Care. 2001; 7: 413–21.[Medline]

4 Mort TC. The incidence and risk factors for cardiac arrest during emergency tracheal intubation: a justification for incorporating the ASA guidelines in the remote location. J Clin Anesth 2004; 16: 508–16.[Medline]

5 Schwartz DE, Matthay MA, Cohen NH. Death and other complications of emergency airway management in critically ill adults. A prospective investigation of 297 tracheal intubations. Anesthesiology 1995; 82: 367–76.[Medline]

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