As emergency physicians manage mechanically ventilated patients for longer periods of time, it is important to be familiar with newer, alternative modes of ventilation
APRV is an open-lung ventilation strategy designed to provide oxygenation benefits while augmenting ventilation for patients with low compliance lung disease
APRV has been described as CPAP with brief, regular, intermittent releases in airway pressure - essentially cycling between two CPAP levels
The degree of ventilatory support is determined by the duration at each of the 2 CPAP levels and the distending pressure
The 5 major parameters of APRV, along with suggested initial settings include:
Phigh (high pressure): set at desired plateau pressure
Thigh (time spent at the high pressure): 4-6 seconds
Plow (low pressure): 0 cm H2O
Tlow (time spent at the low pressure): 0.6-0.8 seconds
FiO2: 100%
The pressure gradient between Phigh and Plow, Tlow, and the patient's spontaneous minute ventilation are the primary determinants of alveolar ventilation
When using APRV, be sure to optimize intravascular volume to offset the decrease in venous return that results from prolonged positive intrathoracic pressure
References
Stawicki SP, Goyal M, Sarani B. High-frequency oscillatory ventilation and airway pressure release ventilation: A practical guide. Journal of Intensive Care Medicine 2009;24(4):215-29.
