Introduction

A trained anaesthetist rarely has significant difficulty in maintaining a patent airway and ventilating the patient's lungs. When difficulty occurs the degree of difficulty encountered covers a spectrum, at the far end of which is the situation where the patient is consuming oxygen faster than the anaesthetist can deliver it; for the purpose of this chapter this is the definition of the lost airway. Other terms are ‘can't ventilate, can't intubate' (CVCI) or ‘can't intubate, can't oxygenate’ (CICO). This extreme situation is rare in elective general surgery with an incidence of 1 : 10,000 to 1 : 50,000. Diagnosis and management must be complete within minutes of the onset of the problem to have a chance of a successful outcome.

Pathophysiology

An adult patient requires 200–250 ml min–1 of oxygen to sustain life. After induction of anaesthesia if this amount of oxygen cannot be delivered to the patient's lungs they will use up their reserves over 1–2 min (longer if well preoxygenated, sooner in the obese or those with increased requirements) and then they will start to desaturate. Without intervention to increase oxygen delivery to the lungs the patient will die. How long an individual patient will survive will depend on many factors. Anecdotal accounts of death due to airway obstruction (judicial execution by hanging) suggest that about 10 min of complete airway obstruction will result in cardiac arrest.

Most general anaesthetic agents decrease upper airway tone tending to lead to compromise of the natural upper airway and minor degrees of difficulty with facemask ventilation around the time of induction of anaesthesia.