Abstract
Study Objectives: Arousals from sleep during the hyperpneic phases of Cheyne-Stokes respiration with central sleep apnea (CSR-CSA) in patients with heart failure are thought to cause ventilatory overshoot and a consequent longer apnea, thereby sustaining and exacerbating ventilatory instability. However, data supporting this model are lacking. We investigated the relationship between arousals, hyperpnea and post-hyperpnea apnea length during CSR-CSA. Methods: Breath-by-breath changes in ventilation associated with the occurrence of arousal were evaluated in 18 heart failure patients with CSR-CSA, apnea-hypopnea index ≥15/h and central apnea index ≥5/h. The change in apnea length associated with the presence of arousal during the previous hyperpnea was also evaluated. Potential confounding variables (chemical drive, sleep stage) were controlled for. Results: Arousals were associated with a large increase in ventilation at the beginning of the hyperpnea (+76 ± 35%, p < 0.0001), that rapidly declined during its crescendo phase. Around peak hyperpnea, the change in ventilation was -8 ± 26% (p = 0.14). The presence of arousal during the hyperpnea was associated with a median increase in the length of the subsequent apnea of +4.6% (Q1, Q2: -0.7%, 20.5%; range: -8.5%, 36.2%) (p = 0.021). The incidence of arousals occurring at the beginning of hyperpnea and mean ventilation in the region around its peak were independent predictors of the change in apnea length (p = 0.004 and p = 0.015, respectively; R(2) = 0.78). Conclusions: Arousals from sleep during CSR-CSA in heart failure patients are associated with a rapidly decreasing ventilatory overshoot at the beginning of the hyperpnea, followed by a tendency toward a slight ventilatory undershoot around its peak. On average, arousals are also associated with a modest increase in post-hyperpnea apnea length; however, large increases in apnea length (>20%) occur in about a quarter of the patients.