Continuous Positive Airway Pressure

Excerpt

Continuous positive airway pressure (CPAP) is a type of positive airway pressure, where the air flow is introduced into the airways to maintain a continuous pressure to constantly stent the airways open, in people who are breathing spontaneously. Positive end-expiratory pressure (PEEP) is the pressure in the alveoli above atmospheric pressure at the end of expiration. CPAP is a way of delivering PEEP but also maintains the set pressure throughout the respiratory cycle, during both inspiration and expiration. It is measured in centimeters of water pressure (cm H2O). CPAP differs from bilevel positive airway pressure (BiPAP) where the pressure delivered differs based on whether the patient is inhaling or exhaling. These pressures are known as inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP). In CPAP no additional pressure above the set level is provided, and patients are required to initiate all of their breaths.

The application of CPAP maintains PEEP, can decrease atelectasis, increases the surface area of the alveolus, improves V/Q matching, and hence, improves oxygenation. It can also indirectly aid in ventilation, although CPAP alone is often inadequate for supporting ventilation, which requires additional pressure support during inspiration (IPAP on BiPAP) for non-invasive ventilation.