Consider Airway Pressure Release Ventilation for Delivering an Open-Lung Strategy
Anthony D. Slonim MD, DrPH
Airway pressure release ventilation (APRV) is a newer mode of mechanical ventilation that alternates between two levels of continuous positive airway pressure (CPAP). The set rate for this mode of ventilation is normally 20 or fewer breaths per minute to prevent inverse ratio ventilation. The levels of CPAP are referred to as the high-pressure and low-pressure limits and also need to be set to allow adequate oxygenation. In addition, the provider needs to set two times, which allow the ventilator to cycle between the high- and low-pressure levels for 0.5 to 1.5 seconds. When the machine cycles to the lower CPAP level, exhalation occurs.
Since APRV is a newer mode of ventilation, it has not been fully evaluated in clinical trials, but early data are encouraging regarding its effectiveness. The value of APRV is derived from its ability to provide adequate oxygenation at lower pressure levels. Intrapulmonary shunt with spontaneous breathing appears to be reduced with APRV. The high-pressure limit provides for an open-lung strategy, and the low-pressure limit prevents shear stress and cyclic alveolar collapse with atelectasis, both of which contribute to ventilator-induced lung injury. As the patient’s condition improves, the lung can be “deflated” by reducing the pressure limits and times to allow for normal pressure-limited mechanical ventilation. When the patient is able, the ventilator rate can be reduced to allow the patient to take on more of the work of breathing in preparation for extubation.