HEMODYNAMIC-EFFECTS OF CONTINUOUS POSITIVE AIRWAY PRESSURE IN HUMANS WITH NORMAL AND IMPAIRED LEFT-VENTRICULAR FUNCTION

1. Continuous positive airway pressure increases intrathoracic pressur e, thereby decreasing left ventricular preload and afterload, We hypot hesized that there would be a dose-related alteration in cardiac and s troke volume indices in response to continuous positive airway pressur e in normal subjects and patients with congestive heart failure and th at the direction of response among those with heart failure would be r elated to left ventricular preload. 2. Cardiac and stroke volume indic es were measured at baseline and after 10 min of continuous positive a irway pressure at both 5 and 10 cmH(2)O (0.5 and 0.99 kPa respectively ) in 16 patients with heart failure and five control subjects with nor mal cardiac function, Among the eight patients with heart failure and elevated pulmonary capillary wedge pressure (greater than or equal to 12 mmHg) (greater than or equal to 1.6 kPa), cardiac index increased f rom 2.47+/-0.34 at baseline to 2.91+/-0.32 to 3.12+/- 0.40 l min(-1) m (-2) (P<0.025) while on 5 and 10 cm H2O of continuous positive airway pressure respectively, In the same patients stroke volume index increa sed from 27.8+/-3.9 to 33.9+/-4.2 to 36.8+/- 5.5 ml/m(2) (P<0.05). In contrast, in both the control subjects and patients with heart failure and normal pulmonary capillary wedge pressure (<12 mmHg) there was a dose-related decrease in cardiac and stroke volume indices while on co ntinuous positive airway pressure. 3. Continuous positive airway press ure causes dose-related increases in cardiac and stroke volume indices among patients with chronic heart failure and elevated left ventricul ar filling pressure, However, it induces dose-related reductions in ca rdiac and stroke volume indices among normal subjects as well as patie nts with heart failure and normal left ventricular filling pressures.