Objectives

The objectives of this chapter are to:

• discuss the rationale for airway assessment

• outline a pre-anaesthetic patient assessment

• evaluate methods of airway assessment

• identify patients who may be difficult to ventilate and/or intubate

• identify patients that may require a different airway intervention.

Introduction

During elective anaesthesia a failed airway (‘can't intubate, can't ventilate’) occurs in 0.01–0.03% of cases. Difficult intubation, defined as the need for more than three attempts, occurs in 1.15–3.8% of elective surgical cases, and is usually related to a poor view at laryngoscopy. However, the characteristics of patients requiring intubation or assisted ventilation outside the operating theatre are different to those undergoing elective surgical procedures, and the incidence of difficult intubation is significantly higher in emergency departments. More importantly, a failed airway may occur at least ten times more frequently in the emergency setting: in the United States, 0.5% of intubations recorded in the National Emergency Airway Registry (NEAR) required a surgical airway. In a recent Scottish study, 57/671 (8.5%) of patients undergoing rapid sequence induction in the emergency department had Cormack and Lehane grade 3 or 4 views at laryngoscopy (see below), and two (0.3%) required a surgical airway.

Given these data, difficulties with the airway must be expected in all emergency patients, and appropriate preparation undertaken. Some features may indicate a particularly high likelihood of airway difficulties, and in these cases modification of practice may reduce complications and improve outcome.

Definition of a difficult airway

A difficult airway is categorized by the following.