Objective: Continuous positive airway pressure (CPAP) by face mask is an effective method of treating severe cardiogenic pulmonary edema (CPE). However, to our knowledge, no study has provided a precise evaluation of the effects of CPAP on cardiac function in patients presenting with CPE and preserved left ventricular (LV) function.
Design: Prospective observational clinical study.
Setting: A 14-bed, medical ICU at a university hospital.
Patients: Nine consecutive patients presenting with hypoxemic acute CPE.
Interventions: All patients were selected for 30 min of CPAP with 10 cm H2O by mask with fraction of inspired oxygen adjusted for a cutaneous saturation > 90%. Doppler echocardiography was performed before CPAP application and during the last 10 min of breathing with CPAP. Two-tailed, paired t-tests were used to compare data recorded at baseline (oxygen alone) and after CPAP.
Measurements and results: Four patients presented CPE with preserved left ventricular (LV) function (a preserved LV ejection fraction [LVEF] > 45%, and/or aortic velocity time integral > 17 cm in the absence of aortic stenosis or hypertrophic cardiomyopathy). Oxygenation and ventilatory parameters were improved by CPAP in all patients. Hemodynamic monitoring and Doppler echocardiographic analysis demonstrated that in patients with preserved LV systolic function, mean arterial pressure and LV end-diastolic volume were decreased significantly by CPAP (p < 0.04). In patients with LV systolic dysfunction, CPAP improved LVEF (p < 0.05) and decreased LV end-diastolic volume (p = 0.001) significantly.
Conclusion: CPAP improves oxygenation and ventilatory parameters in all kinds of CPE. In patients with preserved LV contractility, the hemodynamic benefit of CPAP results from a decrease in LV end-diastolic volume (preload).