In patients with HF, untreated OSA is associated with an increased risk of death independently of confounding factors.

These novel findings suggest that overnight rostral fluid displacement from the legs, related to prolonged sitting, may play a previously unrecognized role in the pathogenesis of obstructive sleep apnea in nonobese men that is independent of body weight.

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Background-Obstructive sleep apnea (OSA) and central sleep apnea are common in patients with heart failure. We hypothesized that in such patients, severity of OSA is related to overnight rostral leg fluid displacement and increase in neck circumference, severity of central sleep apnea is related to overnight rostral fluid displacement and to sleep PCO 2 , and continuous positive airway pressure alleviates OSA in association with prevention of fluid accumulation in the neck. Methods and Results-In 57 patients with heart failure (ejection fraction Յ45%), we measured change in leg fluid volume and neck circumference before and after polysomnography, and we measured transcutaneous PCO 2 during polysomnography. Patients were divided into an obstructive-dominant group (Ն50% of apneas and hypopneas obstructive) and a central-dominant group (Ͼ50% of events central

Fluid displacement from the legs by LBPP increases neck circumference and Rph in healthy subjects. These findings suggest the hypothesis that fluid displacement to the upper body during recumbency may predispose to pharyngeal obstruction during sleep, especially in fluid overload states, such as heart and renal failure.

Background: Fluid accumulation in the neck during recumbency might narrow the upper airway (UA) and thereby contribute to its collapse in patients with obstructive sleep apnoea (OSA). It is hypothesised that acute fluid shifts from the legs to the upper body in healthy subjects would increase neck circumference and reduce the cross-sectional area of the UA (UA-XSA). Methods: In 27 healthy non-obese subjects of mean (SE) age 39 (3) years and body mass index 23.2 (0.6) kg/m 2 studied while supine, leg fluid volume was measured using bioelectrical impedance, neck circumference using a mercury strain gauge and mean UA-XSA between the velum and the glottis using acoustic pharyngometry at end expiration. Measurements were made at baseline after which subjects were randomly assigned to a 5 min time control period or to a 5 min application of lower body positive pressure (LBPP) at 40 mm Hg by anti-shock trousers, separated by a 15 min washout period. Subjects then crossed over to the opposite arm of the study. Conclusion: In healthy subjects, displacement of fluid from the legs by LBPP causes distension of the neck and narrowing of the UA lumen. Fluid displacement from the lower to the upper body while recumbent may contribute to pharyngeal narrowing and obstruction to airflow in patients with OSA. This may have particular pathological significance in oedematous states such as heart and renal failure.

Although peripheral and central nervous system involvement have been well recognized in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), autonomic nervous system (ANS) involvement has rarely been studied, and has shown conflicting results. We performed cardiovascular ANS assessment in 34 RA and 37 SLE patients, using standard cardiovascular reflex tests. The results in each patient were compared with age- and sex-matched healthy controls. Forty-seven percent of the RA patients and 19% of the SLE patients had symptoms suggesting ANS dysfunction. The heart rate variation in response to deep breathing was significantly decreased in both the RA and SLE patients (p = 0.001). This diminished heart rate response showed no correlation with the disease duration, the number of swollen joints, the Ritchie articular index, ESR, or rheumatoid factor in the RA group, or the disease duration, the SLEDAI score or ESR in the SLE group. The clinical significance of the diminished cardiovascular ANS response needs to be investigated.

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