Use of continuous positive airway pressure (CPAP) in the critically ill--physiological principles

CPAP therapy helps improve oxygenation in patients who are awake and able to maintain a good respiratory drive. In many cases this means that intubation and ventilation can be avoided. The main goals of CPAP are to minimise alveolar collapse, improve compliance, decrease work of breathing and improve ventilation/perfusion matching. These effects work together to improve arterial oxygenation. A clear, concise and straightforward discussion of CPAP is difficult to find in the existing literature. As CPAP has developed into a common therapy for patients with respiratory failure, it is essential that nurses using this therapy are familiar with the equipment and the physiological effects it produces. Assessment and management of the patient receiving CPAP therapy are also important. This paper will address the physiological principles of CPAP therapy so that nurses working with critically ill patients receiving CPAP therapy understand the system and are accurate and astute in their respiratory assessment, in order to provide optimum care.