Airway Pressure Release Ventilation (APRV)

• 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:
  • P_high (high pressure): set at desired plateau pressure
  • T_high (time spent at the high pressure): 4-6 seconds
  • P_low (low pressure): 0 cm H₂O
  • T_low (time spent at the low pressure): 0.6-0.8 seconds
  • F_iO₂: 100%
• The pressure gradient between P_high and P_low, T_low, 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.