BACKGROUND Recent studies suggest that acute pulmonary congestion induces hyperventilation and that hyperventilation-related hypocapnia leads to ventilatory control instability and central sleep apnea. Whether chronic pulmonary congestion due to congestive heart failure (CHF) is associated with central apnea is unknown. We hypothesized that CHF patients with central apnea would have greater pulmonary capillary wedge pressure (PCWP) than patients without central apnea and that PCWP would correlate with central apnea severity. RESULTS Seventy-five stable CHF patients underwent right heart catheterization and, on the basis of overnight sleep studies, were divided into central apnea (n=33), obstructive apnea (n=20), or nonapnea groups (apnea-hypopnea index [AHI] <5 events per hour). Mean PCWP was significantly greater in the central than in the obstructive and nonapnea groups (mean+/-SEM [range]: 22. 8+/-1.2 [11 to 38] versus 12.3+/-1.2 [4 to 21] versus 11.5+/-1.5 [3 to 28] mm Hg, respectively; P<0.001). Within the central apnea group, PCWP correlated with the frequency and severity of central apnea (AHI: r=0.47, P=0.006) and degree of hypocapnia (PaCO2: r=-0.42, P=0. 017). Intensive medical therapy in 7 patients with initially high PCWP and central apneas reduced both PCWP (29.0+/-2.6 [20 to 38] to 22.0+/-1.8 [17 to 27] mm Hg; P<0.001) and central apnea frequency (AHI) (38.5+/-7.7 [7 to 62] to 18.5+/-5.3 [1 to 31] events per hour; P=0.005). CONCLUSIONS PCWP is elevated in CHF patients with central apneas compared with those with obstructive apnea or without apnea. Moreover, a highly significant relationship exists between PCWP, hypocapnia, and central apnea frequency and severity.