Introduction

The provision of a patent airway from the external atmosphere to the lower trachea is commonly required to facilitate mechanical ventilation in the critically ill. A cuffed tracheal tube provides the highest degree of airway maintenance and protection and this is the most frequently used device.

Core competencies for airway management in cardiothoracic critical care include relevant physiology and pharmacology, care of the intubated patient, strategies for intubation and extubation, intubation of a patient at risk of aspiration, the management of failed intubation and failed ventilation and specialized techniques for lung isolation.

Physiology

In normal adults breathing air, alveolar minute ventilation is approximately 3.5 L/min. The Pao2 for a given inspired oxygen concentration can be calculated from the alveolar gas equation.

A decrease in alveolar minute ventilation will cause a reduction in Pao2 and elevation in Paco2. Hypoxaemia secondary only to a reduction in minute ventilation can be treated easily by increasing the inspired oxygen.

The relationship between Pao2 and Paco2 is more complex and is influenced by venous admixture and cardiac output. With a venous admixture or shunt fraction greater than 20% to 25%, it may prove impossible to raise the Pao2 to normal, even with 100% inspired oxygen.