CARDIAC-OUTPUT RESPONSE TO CONTINUOUS POSITIVE AIRWAY PRESSURE IN CONGESTIVE-HEART-FAILURE

The effects of nasal continuous positive airway pressure (CPAP) were examined during cardiac catheterization in 22 patients with congestive heart failure (CHF). CPAP was applied at a level of 5 cm H2O pressure. Hemodynamic measurements were made at baseline and while on CPAP. We hypothesized that patients with high left ventricular (LV) diastolic pressures would experience an increase in cardiac index (Cl). To test this hypothesis, patients were divided into two groups based on their baseline pulmonary capillary wedge pressure (PCWP): one group of 11 whose PCWP was greater-than-or-equal-to 12 mm Hg (high-PCWP group) and a second group of 11 whose PCWP was < 12 mm Hg (low-PCWP group). Among the hihg-PCWP group (mean PCWP +/- SEM = 19.0 +/- 2.7 mm Hg), Cl rose significantly while on CPAP (from 2.48 +/- 0.26 to 2.82 +/- 0.26 L/min/m2, p < 0.01). Stroke volume index (SVI) also rose significantly (from 52.6 +/- 7.0 to 64.1 +/- 8.0 ml/m2, p < 0.001). In contrast, among the low-PCWP group (PCWP = 8.3 +/- 0.6 mm Hg), Cl decreased significantly while on CPAP (from 3.14 +/- 0.44 to 2.89 +/- 0.62 ml/m2, p < 0.025). SVl fell but not significantly while on CPAP (from 75.5 +/- 8.4 to 74.2 +/- 8.5 ml/m2). Multiple stepwise linear regression analysis revealed that the only significant correlate of the magnitude of change in Cl in response to CPAP was baseline PCWP (r = 0.50, p < 0.02). We conclude that among patients with CHF, application of CPAP at 5 cm H2O increases Cl and SVl in a subgroup who have poorer baseline hemodynamics and higher LV diastolic pressures.