Biphasic positive airway pressure (BIPAP) is a mode of mechanical ventilation that allow unrestricted spontaneous breathing independent of ventilator cycling, using an active expiratory valve. BIPAP mode is pressure-limited and time-cycled, Ventilation occurs via the time-cycled switching between two set pressure levels. In the absence of spontaneous breathing, this mode resemble conventional pressure controlled ventilation.~A proposed advantage of BIPAP compared to conventional pressure-controlled ventilation is the improved distribution of gas to dependent lung regions as the result of spontaneous breathing enabled during the inspiratory and expiratory time cycles, so prevents atelectasis and promotes alveolar recruitment resulting in an improved ventilation-perfusion matching.~ARDS is an acute diffuse, inflammatory lung injury, leading to increased pulmonary vascular permeability, increased lung weight, and loss of aerated lung tissue with hypoxemia and bilateral radiographic opacities, associated with increased venous admixture, increased physiological dead space and decreased lung compliance.~In patients with ARDS, BIPAP with spontaneous breathing contributes to improved pulmonary gas exchange, systemic blood flow and oxygen supply to the tissue. This is reflected by clinical improvement in the patient's condition, which is associated with significantly fewer days on ventilatory support, earlier extubation and a shorter stay in the intensive care unit.
Evaluation of biphasic positive airway pressure as a new mode of ventilation in management of acute respiratory failure constituted in ARDS as a category of hypoxaemic respiratory failure in comparison to conventional ventilation.