Sleep–wake fluctuations and respiratory events during Cheyne–Stokes respiration in patients with heart failure
Fluctuations in sleep–wake state are thought to contribute to the respiratory instability of Cheyne–Stokes respiration in patients with heart failure by promoting the rhythmic occurrence of central apnea and ventilatory overshoot. There are no data, however, on the relationship between vigilance state and respiratory events. In this study we used a novel method to detect the occurrence of state transitions (time resolution: 0.25 s, minimum duration of state changes: 2 s) and to assess their time relationship with apnoeic events. We also evaluated whether end‐apnoeic arousals are associated with a ventilatory overshoot. A polysomnographic, daytime laboratory recording (25 min) was performed during Cheyne–Stokes respiration in 16 patients with heart failure. Automatic state classification included wakefulness and non‐rapid eye movement sleep stages 1–2. As a rule, wakefulness occurred during hyperpnoeic phases, and non‐rapid eye movement sleep occurred during apnoeic events. Ninety‐two percent of the observed central apneas (N = 272) were associated with a concurrent wakefulness → non‐rapid eye movement sleep → wakefulness transition. The delay between wakefulness → non‐rapid eye movement sleep transitions and apnea onset was −0.3 [−3.1, 3.0] s [median (lower quartile, upper quartile); P = 0.99 testing the null hypothesis: median delay = 0], and the delay between non‐rapid eye movement sleep → wakefulness transitions and apnea termination was 0.2 [−0.5, 1.2] s (P = 0.7). A positive/negative delay indicates that the state transition occurred before/after the onset or termination of apnea. Non‐rapid eye movement sleep → wakefulness transitions synchronous with apnea termination were associated with a threefold increase in tidal volume and a twofold increase in ventilation (all P < 0.001), indicating ventilatory overshoot. These findings highlight that wakefulness → non‐rapid eye movement sleep → wakefulness transitions parallel apnoeic events during Cheyne–Stokes respiration in patients with heart failure. The relationships between state changes and respiratory events are consistent with the notion that state fluctuations promote ventilatory instability.
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