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2.1.1 What Is the Challenge of Difficult and Failed Airway Management?
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Airway management is fundamental to the practice of anesthesia, emergency medicine, emergency medical services (EMS), critical care medicine, hospital medicine, and other areas of care. The focus of this chapter is the management of the difficult and failed airway in an emergency or urgent situation. Management of the predicted difficult intubation is dealt with in Chapter 3 and in Section II of this book.
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The airway practitioner in this situation is faced with two particular challenges: to be able to accurately predict a difficult airway, and to be able to recognize when airway management has failed.1 No matter the situation, reliably and reproducibly ensuring or establishing timely and effective oxygenation and ventilation is imperative.
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Appropriate planning, selection of the correct device and technique, and calm execution based on learned methods and experience enhances success even in these most difficult cases. In an airway crisis, there is no question that having a logical and simple approach based on a planned strategy is most likely to be successful.
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2.1.2 How Reliably Can We Predict a Difficult Airway?
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There are five ways by which effective gas exchange occurs:
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- Spontaneous patient driven
- Bag-mask-ventilation (BMV)
- Extraglottic device (EGD)
- Laryngoscopy and endotracheal intubation
- Surgical airways
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Four of these are artificial or nonnatural interventions, or methods of active airway management. In the event that a patient is unable to sustain adequate spontaneous gas exchange, or if in the course of therapy the patient's ability to maintain adequate gas exchange (eg, due to the use of medications) is compromised or eliminated, one of these four methods must be employed successfully to assure survival. They constitute the four dimensions of airway management. Hence, the assessment for difficulty is focussed on these four independent operations:
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- Difficult bag-mask-ventilation
- Difficult EGD
- Difficult laryngoscopy and orotracheal intubation
- Difficult surgical airway
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Health-care professionals are experts at evaluating whether or not a patient is adequately ventilating and oxygenating on their own and whether or not they will be able to sustain it in the near term (minutes to hours). It is therefore only reasonable to expect that if an airway practitioner is to intervene in such a manner that the spontaneous patient-driven method of gas exchange is to be hindered or eliminated, the practitioner must also be able to predict that an alternative artificial method of gas exchange will be successful.
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In elective situations, difficulty with mask-ventilation is uncommon. Langeron prospectively reviewed the management of 1502 patients undergoing elective surgery under general anesthesia.2 Difficult mask-ventilation was defined as (1) an inability to maintain SaO2 greater than 92% while using 100% O2 via the anesthesia circuit bag-mask unit; (2) significant gas leak around the face-mask; (3) a need to increase the fresh gas flow to rates ...