Facial continuous positive airway pressure therapy for cardiogenic pulmonary oedema: a study to assess its efficacy in an emergency department setting within the UK

Introduction

Recent studies outside the UK suggest that patients with acute cardiogenic pulmonary oedema (CPO) may benefit from the application of facial continuous positive airway pressure (CPAP) support in emergency departments. The aim of this pilot study was to assess the impact of facial CPAP on patients with CPO within a UK emergency department and to determine the sample size needed for a definitive randomised controlled study.

Methods

A prospective powered study comparing CPAP to supplemental oxygen at ambient pressure, using historical controls matched for CPO severity. Forty patients with internationally accepted criteria for CPO were included. Twenty patients received 20 min of facial CPAP using a dedicated Drager CPAP system with a 5 cmH₂O positive end-expiratory pressure valve and maximal inspired oxygen (Group CPAP). Twenty controls received identical therapy but received maximal inspired oxygen via a non-rebreathing mask (Group C). Outcome measures compared were arterial partial pressures of oxygen and carbon dioxide, objective clinical signs, intubation rate and death. Statistical analysis was by a t-test and 95% Confidence intervals (CI).

Results

Patients receiving CPAP had a better improvement in arterial blood gas indices compared to controls, with higher mean oxygenation (CPAP = 8.4 kPa & C = 3.5 kPa, P = 0.017, CI = 0.92-8.77), and better mean excretion of CO₂ (CPAP = -0.9 kPa & C = +0.9 kPa, P = 0.011, CI = -3.27 to -0.45). CPAP produced a higher mean reduction in respiratory rate, and lower mean reductions in blood pressure/pulse rate, although these were not statistically significant. The median length of in-patient stay (CPAP = 4, C = 5 days) and intubation rates (CPAP = 0, C = 3) differed between groups, but were not statistically significant. There was no difference in hospital mortality between groups (CPAP = 3, C = 3).

Conclusions

CPAP utilisation in the emergency department impacts favourably on the physiological manifestations of CPO. Consequently to achieve a statistical power of 90% in a future randomised study, a sample size of 913 patients is required to show a 5% difference in mortality.