The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

EVALUATION OF AIRWAY PRESSURE RELEASE VENTILATION COMPARED TO LOW TIDAL VOLUME VENTILATION IN ALI: PROSPECTIVE RANDOMIZED PILOT STUDY

Sunil Patel, M.D.; Kenneth Miller, RRT, MEd; Linda Cornman, RRT-NPS; Michael Pasquale, M.D.; Mark Cipolle, M.D. Lehigh Valley Hospital, Allentown, PA, 18105-1556

Introduction: Multiple mechanical ventilation strategies have been researched to determine the optimal method to maximize gas exchange with minimal lung damage in patients with acute lung injury. Low tidal volume ventilation(ARDSNet) has become the golden standard to achieve this end-point. However there exists some patients whose clinical end-points cannot be achieved via the ARDSnet strategy or may not be a candidate for this strategy. Airway Pressure Release Ventilation (APRV) is a ventilatory strategy that may benefit such patients that are refractory to ARDSnet or are not candidates. To determine that this was a feasible option, we compared the safety/efficacy of APRV with ARDSNet in adults with acute lung injury and/or acute respiratory distress syndrome(ALI/ARDS).

Hypothesis: APRV is as safe and effective as low tidal volume ventilation(ARDSNet) for adults with ALI/ARDS.

Methods: A prospective randomized pilot study was conducted from 7/1/03-8/31/04 in all patients admitted to a level I trauma center with ALI/ARDS as defined by ARDSNet criteria. Patients were randomized to either mode of ventilation within 24 hours of meeting criteria. Age, gender, diagnosis, primary versus secondary etiology arterial blood gases, pre-study days, days on protocol, PF ratio, mean airway pressures (MAP), and hemodynamic changes were recorded at protocol initiation and daily thereafter. Primary endpoints were ventilator-free days and mortality at 30 days. Student t-test and chi-square analysis was used to test for significance.

Results: Nineteen patients were randomized to APRV(n=12) and ARDSNet(n=7). There were no significant differences between groups for age, pre-study/study days, initial PF ratios, pH, PCO2, complications, or hemodynamic changes. There was significant initial improvement in PF ratios for both groups: APRV 142.09 to 271.47(p< 0.001); ARDSNet 164.06 to 241.71(p< 0.04). MAP decreased from 20.41 to 16.75(p=0.17) in APRV and from 16.14 to 10.71(p< 0.01) in ARDSNet group. There were no complications or significant hemodynamic changes in either group. There were 2 deaths at 30 days in each group. At 30 days, 3(25%) of 12 were ventilator-free in APRV group vs 1(14.3%) of 7 in the ARDSNet group. Similarly 7(58%) of 12 in APRV group and 4(57%) of 7 in ARDSNet group were ventilated at 30 days.

Conclusions: This pilot study demonstrates both modes of ventilation improve oxygenation when applied early in ALI/ARDS. Safety and outcomes appear comparable in APRV and low tidal volume ventilation. More patients from multiple centers need to be enrolled in this ongoing trial to further compare outcomes between these ventilatory strategies in the treatment of ALI.

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