Outcomes in ARDS Due to H1N1 Pneumonia in Patients Receiving Airway Pressure Release Ventilation

Abstract

PURPOSE: A variety of rescue therapies were proposed to treat acute respiratory distress syndrome (ARDS) during the H1N1 influenza pandemic when conventional ventilation strategies failed. Here we report outcomes in patients with ARDS from H1N1 pneumonia who received Airway Pressure Release Ventilation (APRV). METHODS: We retrospectively identified and reviewed charts of adults admitted to our intensive care units (2/1/2009-1/31/2010) with H1N1 pneumonia requiring mechanical ventilation. RESULTS: 22 patients with respiratory failure due to H1N1 influenza required mechanical ventilation. APRV was used in 9 patients (33±12 years of age, 5/9 on vasopressors, and 6/9 females) due to refractory hypoxemia. All of these patients had ARDS with a mean PaO2:FiO2 ratio of 64±25 mm Hg. Prior to initiation of APRV, patients were treated with an average PEEP of 17±4 cm H20. Maximum APRV settings were Phigh 34±5 cm, Plow 0±0 cm, Thigh 5.3±1.5 sec and Tlow 0.56±0.12 sec. APRV resulted in a significant improvement in gas exchange with increased PaO2:FiO2(77±39 vs. 128±58 mm Hg; p=0.028), decreased FiO2(0.92±0.19 vs. 0.82±0.21; p=0.042) with no change in PaCO2 (52±8 vs. 51±14 mm Hg). These settings were well tolerated and only one patient required increased vasopressor dose. Average duration of APRV was 6.1 ± 2.2 days. Mortality rates were similar for the patients receiving APRV (2/9; 22%) and other types of mechanical ventilation (4/13; 31%). CONCLUSIONS: APRV may be a useful rescue mode of ventilation in patients with ARDS due to H1N1 pneumonia. CLINICAL IMPLICATIONS: Attention has focused on extracorporeal membrane oxygenation (ECMO) as a rescue mode in the treatment of ARDS due to H1N1. APRV is potentially simpler to institute with little evidence of ventilatory and hemodynamic compromise. Even severe cases of ARDS may respond to APRV and importantly the overall mortality rate with APRV was not greater than that reported with ECMO (21%). These preliminary results support the further investigation of APRV for the treatment of ARDS. DISCLOSURE: The following authors have nothing to disclose: Vikas Grover, Jeffrey Gold, Daniel Hagg, David Jacoby, Hussain Lakdawalla, Jennifer Letourneau, Stephen Smith