The Difficult Airway - 1Learning Objectives:
Students will be able to:
Overall, in general:
Optimally manage the difficult airway, thereby reducing the incidence of adverse outcomes.
1. Explain the operational significance of the difference between:
a) difficult direct laryngoscopy (DL), and
b) difficult ventilation due to airway disorder.
2. Explain the ASA Task Force definitions of terms related to the difficult airway.
3. Identify patients at risk for airway difficulty.
4. Explain the use of adjuvants and alternatives to DL to secure the airway.
5. Explain the use of adjuvants and alternatives to mask ventilation to provide gas exchange.
6. Develop and explain a comprehensive advance plan for dealing with airway difficulty; e.g., the ASA Difficult Airway Algorithm (2003), and the ASA Algorithm emphasizing the role of the LMA.
7. Choose at least two adjuvants and/or alternatives to mask ventilation and to direct laryngoscopy and decide to incorporate them into their regular practice.
Why?Review of the ASA Closed Claims Project data suggests that the most frequent cause of anesthetic-related morbidity and mortality is failure to adequately manage the airway. Thirty-three percent of all deaths completely attributable to anesthesia are due to airway mismanagement.
An Important DifferenceSome of our future patients (maybe 1 per 100) will be "impossible to intubate" using our usual technic of DL. Essentially all of these patients are now walking and talking and sleeping and breathing through excellent upper airways with no difficulty whatsoever. If we should ever decide to intubate one of these citizens, it ought to be an entirely elective procedure that, with proper preparation, will be safe and fun and easy. We never want to interfere with or injure one of these excellent airways. This interference or injury may cause dangerous difficulty of ventilation due to (iatrogenic) airway disorder, converting a nice elective procedure into a messy urgent or emergent situation. Some patients, on the other hand, will first present to us with difficult ventilation due to airway disorder. Yes, we must learn to relatively promptly help these patients with ventilation. However, let's not convert the patient with impossible DL but good airway into a patient with difficult ventilation due to airway disorder. Multiple, repeated DL can cause dangerous airway disorder due to trauma, bleeding and swelling, leading in turn to brain damage and death! Decide now to master alternatives to mask ventilation and direct laryngoscopy!
Notwithstanding the critical difference explained above, note that the ASA Task Force on Management of the Difficult Airway lumps the two in the first of the following definitions.
ASA Task Difficult Airway Task Force 2003 - Defintions:difficult airway = the clinical situation in which a conventionally trained anesthesiologist experiences difficulty with face mask ventilation, difficulty with tracheal intubation, or both.
difficult face mask ventilation = (a) It is not possible for the anesthesiologist to provide adequate face mask ventilation due to one or more of the following problems: inadequate mask seal, excessive gas leak, or excessive resistance to the ingress or egress of gas. (b) Signs of inadequate face mask ventilation include (but are not limited to) 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 (SpO2), absent or inadequate exhaled carbon dioxide, absent or inadequate spirometric measures of exhaled gas flow, and hemodynamic changes associated with hypoxemia or hypercarbia (e.g., hypertension, tachycardia, arrhythmia).
difficult laryngoscopy = not being able to see any part of the vocal cords with conventional laryngoscopy (i.e, Grade III or IV laryngoscopic view)
difficult intubation = tracheal intubation requires multiple attempts, in the presence or absence of tracheal pathology.
failed intubation = placement of the endotracheal tube fails after multiple intubation attempts.