Airway pressure release ventilation in acute lung injury/acute respiratory distress syndrome patients

Introduction

Advocates of airway pressure release ventilation (APRV) suggest that this mode is lung-protective for patients with ALI/ARDS, while providing additional benefits of spontaneous breathing, including improved haemodynamics, decreased need for sedation, and better patient comfort. However, there are few available data on the clinical experience with APRV.

Methods

We conducted a retrospective audit of consecutive patients receiving APRV from January 2004 to August 2006 in three academic ICUs in Toronto. APRV was initiated at the discretion of the attending physician; a protocol guiding the implementation of APRV was introduced in July 2006. We recorded data describing: baseline characteristics; how APRV was used; its potential ramifications including oxygenation and sedation/analgesia doses; and outcomes.

Results

Thirty patients, all with ALI/ARDS, received 39 trials of APRV during the study period – median age 52 years, 60% male, 50% pulmonary ALI risk factor, median APACHE II score 28. They had ALI for a median of 4.5 days with a median 135 hours of CMV before APRV. They received a median of 38 hours APRV. By 12 hours, oxygenation improved significantly (P/F ratio from 103 to 159, P < 0.01), with a concomitant decrease in FiO2 requirements (from 0.70 to 0.50, P < 0.0006). At 72 hours, the median P/F ratio had improved to 196 on a median FiO₂ of 0.40 (both P < 0.01). Administration and dosages of sedatives (midazolam equivalents, propofol) and analgesics (morphine equivalents) did not change significantly over the period from 24 hours before to 24 hours after APRV initiation. There were two episodes of barotrauma during APRV; neither required therapeutic drainage. The 30-day mortality was 13/30 (43%), most commonly due to multiorgan failure and withdrawal of life-support.

Conclusion

In our patients APRV use appeared safe, led to improved oxygenation, but did not change needs for sedation/analgesia. Future studies are needed to determine the optimal timing and methods for ARPV use; these should be followed by randomized trials to confirm safety and document the effects of APRV on patient-centered outcomes.