Background: Airway pressure release ventilation (APRV) is used both as a rescue therapy for patients with acute lung injury and as a primary mode of ventilation. Unlike assist-control volume (ACV) ventilation that uses spontaneous breathing trials, APRV weaning consists of gradual decreases in supporting pressure. We hypothesized that the APRV weaning process increases total ventilator days compared with those of spontaneous breathing trials-based weaning.
Methods: A retrospective review of a Level I trauma center's database identified trauma admissions from January 1, 2007, to December 31, 2010, which required mechanical ventilation for more than 24 hours and survived. Demographics, injuries, in-hospital complications, ventilation mode(s), and total ventilator days were abstracted.
Results: A total of 362 patients fulfilled study entry criteria; 53 patients with more than one ventilator mode change were excluded. Seventy-five patients were successfully liberated from mechanical ventilation on APRV and 234 on ACV. The APRV and ACV groups, respectively, were similar in age (46.1 vs. 44.6 years) and sex (72% vs. 73% male) but differed in Injury Severity Score (20.8 vs. 17.5; p = 0.03). Patients on APRV had higher rates of abdominal compartment syndrome (6.7% vs. 0.8%, p = 0.003) and were more likely to have a higher chest Abbreviated Injury Scale (AIS) score ≥3 (57.3% vs. 30.8%, p < 0.001). Ventilator days were significantly greater in the APRV group (19.6 vs. 10.7 days, p < 0.001). Multiple regression was performed to adjust for the clinical differences between the two groups, identifying APRV as an independent predictor for increased number of ventilator days (B = 6.2 ± 1.5, p < 0.001) in addition to male sex, abdomen AIS score of 3 or higher, spine AIS score of 3 or higher, acute renal failure, and sepsis.
Conclusion: APRV is frequently used for patients who are more severely injured or who develop in-hospital complications such as pneumonia. However, after controlling for potential confounding factors in a multiple regression model, the APRV mode itself seems to increase ventilator days.