Continuous positive airway pressure plus low flow oxygen versus usual care of severe acute cardiogenic pulmonary edema in the pre-hospital setting: A randomised controlled trial

Abstract

Background: Acute cardiogenic pulmonary edema (ACPE) is characterized by acute breathlessness and hypoxia and is associated with poor prognosis. Standard pre-hospital management of ACPE includes high-flow oxygen, nitroglycerin and, in severe cases, assisted ventilation. Patients with ACPE can be supported with newer modalities of non-invasive ventilation, specifically continuous positive airway pressure (CPAP). The aim of this study was to determine whether patients with ACPE treated with CPAP plus low-flow oxygen pre-hospitally have a lower mortality rate than those treated conventionally.  Methods: This study was a pre-hospital randomised, non-blinded controlled trial conducted July 2009–July 2010. Included were all participants transported by ambulance and admitted to the Royal Hobart Hospital, Tasmania, Australia. The study population was consecutive persons ≥18 years of age with sudden onset of severe respiratory distress, diagnosed as ACPE. Patients were included if they required ventilatory assistance. Patients required a GCS >12 and blood pressure >90 mmHg systolic to safely receive CPAP. The primary outcome was pre- or in-hospital mortality.  Results: In total, 50 patients were enrolled with mean age of 79.8 (±11.9) years. There were two deaths (8.3%) in the CPAP arm and nine (34.6%) in the control arm (RR, −0.24; 95% CI, 0.06–1.00; p=0.051) with a number needed to treat of 4. CPAP plus low-flow oxygen was significantly less likely to result in respiratory acidosis (mean difference in pH, −0.11; 95% CI, −0.04–−0.17; p=0.002), with elevated pCO2 (mean difference, −10.0 mmHg; 95% CI, −19.2–−0.78; p=0.026). The length of hospital stay was significantly shorter in the surviving patients who received CPAP (ratio of means, 0.45; 95% CI, 0.29–0.70; p≤0.001).  Discussion: This study, which provides interim results due to early termination of the trial, shows CPAP in the pre-hospital setting for ACPE is practicable and is associated with improved patient outcomes.