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Cheyne-Stokes respiration (CSR), a rhythmic rise and fall in ventilation often experienced by patients with heart failure during sleep, is typically accompanied by an oscillation in heart rate (HR) at the same frequency. The mechanisms responsible for this oscillation are still debated. In this study, we used the experimental model of the transient hypoxia test (i.e., a laboratory test that mimics the transient nature of the cyclic desaturations that occur during hyperpnoeic phases of CSR) to assess accurately the temporal relationship between the HR response to transient hypoxia and the tidal volume response in six heart failure patients. The same relationship was assessed during CSR using polysomnographic signals. We hypothesized that this relationship would provide important insights into the key mechanisms contributing to the HR response. During transient hypoxia, HR started to increase around the onset of tidal volume increase but continued to increase after the peak of the latter had been reached. The time delay between the two peaks (HR vs. tidal volume) was 7.9 ± 4.8 s. The same delay during hyperpnoeic phases of CSR was 1.0 ± 0.9 s. In addition, the increases in lung volume were much greater than those found in the laboratory tests. Based on the known dynamics of vagal and sympathetic control of HR, we speculate that the HR response to transient hypoxia might be attributable predominantly to the sympathetically mediated tachycardic effect of the increased central inspiratory drive, whereas the fast, vagally mediated pulmonary inflation reflex might be the predominant mechanism during CSR., (© 2025 The Author(s). Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)

Background: Chronic heart failure (CHF) is often associated with cognitive, psychological, and functional disorders. In addition, since patients suffering from this condition are often older adults, the presence of frailty could worsen the clinical situation., Methods: The present multicentric observational study aimed to investigate, through a multidimensional evaluation, the associations between clinical, functional, cognitive, psychological, and frailty variables of older (age ≥65) CHF inpatients undergoing cardiac rehabilitation and to identify the eventual independent predictors of the frailty status., Results: The study included 85 patients (mean age 73.88±5.84). The disease severity of the sample was moderate (left ventricular ejection fraction = 41.79±15.40). Among the patients, 32.94% had cognitive impairment, 12.94% and 14.11% reported moderate to severe anxious or depressive symptoms, respectively, and 34.12% were classified as frail (Clinical Frailty Scale [CFS] score ≥5). The CFS score showed a negative correlation with cognitive status (Addenbrooke's Cognitive Examination III [ACE III] [r=-0.48, P≤0.0001] and Frontal Assessment Battery [FAB] [r=-0.33, P=0.0001]) and functional status (Short Physical Performance Battery [SPPB] [r=-0.55, P≤0.0001] and Barthel Index [r=-0.52, P≤0.0001]), while showing a positive correlation with comorbidities (Cumulative Illness Rating Scale [CIRS] [r=0.40, P≤0.0001]). The stepwise regression analysis revealed that ACE III, SPPB, and CIRS were independent predictors of frailty status (CFS)., Conclusions: Frailty is an important variable that should be considered since it is linked with most of the variables that play a role in the management and outcomes of older CHF patients and, thus, its evaluation should be integrated into the usual assessment in cardiac rehabilitation.