Leg Fluid Shift in Patients With Chronic Heart Failure and Obstructive or Central Sleep Apnea

Chronic heart failure (CHF) is a common disease in general western population with high levels of morbidity and mortality. Prospective risk factors need to be identified and investigated. The prevalence for sleep disordered breathing (SDB) in patients with CHF is higher compared to general population. Especially the occurence of CSA with its special breathing pattern of Cheyne-Stokes-Respiration (CSR) is frequent in CHF patients.The pathophysiology and relation inbetween sleep apnea (SA) and CHF isn´t completely identified yet. Multiple theories with different strategies try to explain the pathophysics and development of SA. Following one of these theories, patients with CHF often develop edema in lower body compartments. The idea is a possible influence of retrograde nocturnal LFS from lower body to upper body compartments which could induce pulmonal congestion. Therefore, an increased pulmonary capillary wedge pressure (PCWP) could irritate special pulmonal receptors resulting in CSR with periods of hyperventilation, related hypocapnia and central apnea events. OSA could be induced by fluid accumulation in the upper airway by retrograde fluid shift. Patients with known CHF receive fluid measurements by b multi frequency bioimpedance analysis (mfBIA) the evening before and the morning after sleep is recorded using polygraphy (PG) or polysomnography (PSG) in hospital. Sleep results are analyzed by physicians using current guidelines of the American Academy of Sleep Medicine (AASM). Capillary blood gas (CBG) samples are taken before and after sleep to examine the relation of fluid shift and blood gas changes. A subgroup of the study group undergo additional investigation. Hemodynamic effects (e.g. reduced cardiac output (CO)) as a cause of a potential fluid shift is measured during wakefulness by using a tilting table. Hemodynamically relevant parameters are recorded non-invasively.