Biphasic PAP/airway pressure release ventilation in ALI

Biphasic positive airway pressure (BIPAP)/airway pressure release ventilation (APRV) is a mechanical ventilation mode based on a high flow or demand-valve continuous positive airway pressure (CPAP) system, in which the level of CPAP is switched between a higher and a lower pressure in a time-dependent manner, generating time-cycled, pressure-limited ventilation. Supported and unsupported spontaneous breathing is possible at both levels of airway pressure, but the optimal level of spontaneous breathing has yet to be determined. BIPAP/APRV has proved efficient in increasing oxygenation compared with controlled mechanical ventilation in acute respiratory distress syndrome (ARDS). In addition, BIPAP/APRV with spontaneous breathing waives the need for muscle paralysis, and allows reduced sedation, as well as cardiovascular support with drugs. BIPAP/APRV with spontaneous breathing seems to be a useful ventilatory strategy for patients with less severe hypoxaemic respiratory failure, but caution is required in those patients with more severe lung injury, as reflected by an arterial oxygen tension(Pa,O2)/inspiratory oxygen fraction (FI,O2) of <120 mmHg