RANDOMIZED, PROSPECTIVE TRIAL OF BILEVEL VERSUS CONTINUOUS POSITIVE AIRWAY PRESSURE IN ACUTE PULMONARY-EDEMA

Objective: To evaluate whether bilevel positive airway pressure, by ac tively assisting inhalation, more rapidly improves ventilation, acidem ia, and dyspnea than continuous positive airway pressure (CPAP) in pat ients with acute pulmonary edema. Design: Randomized, controlled, doub le-blind trial. Setting: Emergency department in a university hospital . Patients: Twenty-seven patients, presenting with acute pulmonary ede ma, characterized by dyspnea, tachypnea, tachycardia, accessory muscle use, bilateral rales, and typical findings of congestion on a chest r adiograph. interventions: In addition to standard therapy, 13 patients were randomized to receive nasal CPAP (10 cm H2O), and 14 patients we re randomized to receive nasal bilevel positive airway pressure (inspi ratory and expiratory positive airway pressures of 15 and 5 cm H2O, re spectively) in the spontaneous/timed mode that combines patient flow-t riggering and backup time-triggering. Measurements and Main Results: A fter 30 mins, significant reductions in breathing frequency (32+/-4 to 26+/-5 breaths/min), heart rate (110+/-21 to 97+/-20 beats/min), bloo d pressure (mean 117+/-28 to 92+/-18 mm Hg), and Pace, (56+/-15 to 43/-9 torr [7.5+/-2 to 5.7+/-1.2 kPa]) were observed in the bilevel posi tive airway pressure group, as were significant improvements in arteri al pH and dyspnea scores (p<.05 for all of these parameters). Only bre athing frequency improved significantly in the CPAP group (32+/-4 to 2 8+/-5 breaths/min, p<.05). At 30 mins, the bilevel positive airway pre ssure group had greater reductions in Paco(2) (p=.057), systolic blood pressure (p=.005), and mean arterial pressure (p=.03) than the CPAP g roup. The myocardial infarction rate was higher in the bilevel positiv e airway pressure group (71%) compared with both the CPAP group (31%) and historically matched controls (38%) (p=.05). Duration of ventilato r use, intensive care unit and hospital stays, and intubation and mort ality rates were similar between the two groups. Conclusions: Bilevel positive airway pressure improves ventilation and vital signs more rap idly than CPAP in patients with acute pulmonary edema. The higher rate of myocardial infarctions associated with the use of bilevel positive airway pressure highlights the need for further studies to clarify it s effects on hemodynamics and infarction rates, and to determine optim al pressure settings.