Airway pressure release ventilation

Abstract

Airway pressure release ventilation (APRV) was first described in 1987 by Stock and Downs [1]. It became available on commercial ventilators in the 1990s, and depending upon the brand, it may have any of the following names: APRV (Drager), BiLevel (Covidien), Bi-Vent (Maquet), Biphasic (CareFusion), and DuoPAP (Hamilton). APRV is based on the “open lung concept” and is a form of pressure-controlled intermittent mandatory ventilation using extreme inverse inspiratory-expiratory (I: E) ratios [1]. It can be most easily understood as a type of continuous positive airway pressure (CPAP) mode modified to apply two alternating levels of pressure. The majority of the respiratory cycle (Thigh) is spent at a high pressure (Phigh) to maximize alveolar recruitment, while a short period (Tlow) is spent at a low pressure (Plow) to allow CO2 clearance. Mandatory breaths are time-triggered, pressure-targeted, and time-cycled. The patient may breathe at any time during the respiratory cycle, though due to the extreme I: E time ratio, most spontaneous breathing takes place during Thigh (Fig. 19.1).