Study objective: To determine whether the duration of the apnea-hyperpnea cycle is longer in patients with congestive heart failure (CHF) and obstructive sleep apnea (OSA) than in patients with OSA alone, and whether this is related to prolonged circulation time.
Design: Retrospective study.
Setting: Sleep laboratory of a university teaching hospital.
Patients and intervention: Male patients with OSA and CHF (n = 22) or without CHF (n = 18) underwent overnight polysomnography.
Measurements and results: Hyperpnea duration, time to peak tidal volume (Vt), and lung-to-ear circulation time (LECT) were measured in all patients. Compared to the non-CHF patients, those with CHF had significantly longer hyperpneas (25.7 +/- 7.8 s vs 17.6 +/- 5.6 s, p < 0.001) and LECT (14.9 +/- 3.4 s vs 9.0 +/- 1.8 s, p < 0.001) [mean +/- SD]. There was also a significant relationship between LECT and hyperpnea duration (r = 0.67, p < 0.001).
Conclusion: In patients with CHF, prolonged lung-to-chemoreceptor circulation time influences the cycling characteristics of OSA such that it prolongs hyperpnea and sculpts a pattern resembling Cheyne-Stokes respiration. These findings further suggest that the increased tendency to periodic breathing in CHF may predispose to, or alter the physiologic manifestations of OSA.