Sleep is a physiological process involving different biological systems, from molecular to organ level; its integrity is essential for maintaining health and homeostasis in human beings. Although in the past sleep has been considered a state of quiet, experimental and clinical evidences suggest a noteworthy activation of different biological systems during sleep. A key role is played by the autonomic nervous system (ANS), whose modulation regulates cardiovascular functions during sleep onset and different sleep stages. Therefore, an interest on the evaluation of autonomic cardiovascular control in health and disease is growing by means of linear and non-linear heart rate variability (HRV) analyses. The application of classical tools for ANS analysis, such as HRV during physiological sleep, showed that the rapid eye movement (REM) stage is characterized by a likely sympathetic predominance associated with a vagal withdrawal, while the opposite trend is observed during non-REM sleep. More recently, the use of non-linear tools, such as entropy-derived indices, have provided new insight on the cardiac autonomic regulation, revealing for instance changes in the cardiovascular complexity during REM sleep, supporting the hypothesis of a reduced capability of the cardiovascular system to deal with stress challenges. Interestingly, different HRV tools have been applied to characterize autonomic cardiac control in different pathological conditions, from neurological sleep disorders to sleep disordered breathing (SDB). In summary, linear and non-linear analysis of HRV are reliable approaches to assess changes of autonomic cardiac modulation during sleep both in health and diseases. The use of these tools could provide important information of clinical and prognostic relevance.
Background COVID‐19 long‐term sequelae are ill‐defined since only few studies have explored the long‐term consequences of this disease so far. Objective to evaluate the 6‐month respiratory outcomes and exercise capacity of COVID‐19 acute respiratory failure (ARF) patients treated with continuous positive airway pressure (CPAP) during the first wave of the ongoing COVID‐19 pandemic. Design retrospective observational study. Patients COVID‐19 patients with ARF. Interventions CPAP during hospitalization and 6‐month follow‐up. Main Measures frailty assessment through frailty index (FI), pO2/FiO2 during hospitalization and at follow‐up, respiratory parameters, 6‐min walking test (6MWT) and the modified British Medical Research Council (mMRC) and Borg scale at follow‐up. Key Results more than half of the patients had no dyspnoea according to the mMRC scale. Lower in‐hospital pO2/FiO2 correlated with higher BORG scale levels after 6MWT (ρ 0.27; p 0.04) at follow up visit. FI was positively correlated with length of hospitalization (ρ 0.3; p 0.03) and negatively with the 6MWT walked distance (ρ ‐0.36; p 0.004). Conclusions robust and frail patients with COVID‐19 ARF treated with NIV outside the intensive care unit setting had good respiratory parameters and exercise capacity at 6‐month follow‐up, although more severe patients had slightly poorer respiratory performance compared to patients with higher PaO2/FiO2 and lower FI. This article is protected by copyright. All rights reserved.
Recent experimental data indicate a pathogenic role of complement activation in congestive heart failure (CHF). The aim of this study was to evaluate contact and complement systems activation in patients hospitalized for an acute episode of CHF. Forty-two of 80 consecutive patients admitted at our hospital with confirmed diagnosis of acute CHF were enrolled. They underwent blood sampling within 24 h from admission (T0) and at clinical stability (T1). Patients were stratified for ejection fraction (EF) based on echocardiographic test. We measured plasma levels of C3, C4, sC5b-9 and cleaved high molecular weight kininogen (contact activation marker). At T1, C3 levels increased significantly compared to T0 (97 ± 2 versus 104 ± 3% of total pooled plasma, P < 0·01). Classifying patients according to EF, only patients with preserved EF presented a significant increase of C3 from T0 to T1 (99 ± 3 versus 108 ± 4%, P = 0·03). When the sample was stratified according to clinical outcome, C3 (98 ± 3 versus 104 ± 4%, P = 0·03) and sC5b-9 levels (204 ± 10 versus 230 ± 11 ng/ml, P = 0·03) were increased in patients who had positive outcome after hospitalization. CHF patients with preserved EF and positive outcome after hospitalization showed higher levels of sC5b-9 in the T1 period compared with T0 (211 ± 14 versus 243 ± 14 ng/ml, P = 0·04). Our results suggest that the complement system reacts differently if CHF occurs with preserved or reduced EF. This finding is interesting if we consider the difference in epidemiology, pathogenesis and possible therapeutic approaches of these two clinical entities.
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