[Cardiorespiratory coupling in obstructive sleep apnea (OSA)]

Even if different mechanisms of various interactions during sleep are known, it is still unsolved by which mechanisms physiological reactions during sleep may start a pathophysiological course. Hypoxia, Hypercapnia and repetitive sympathetic elevations are well known elements in the control of the arterial resistance. Furthermore investigations in patients with sleep apnea showed changes of the pulsatile secretion pattern within the renin-angiotensin-system and the antinatriuretic peptides. These changes were reversible under nasal CPAP-therapy, nycturia as a frequent symptom disappeared. Nevertheless neither hypoxia nor intrathoracic pressure changes nor the arousals can assert the longterm influence on the blood pressure alone, a multifactorial confluence must be assumed. Further it is unclear how a tonic increase of the arterial blood pressure may occur in dependence of the REM- and NREM-sleep cycle changes as well as during daytime. First investigations in sleeping man seem to indicate, that a disturbance of the physiological coupling of breathing and circulation may present a pathogenetic element. Finally it remains open, whether the changes of the cardiorespiratory coupling during sleep of control persons and of patients with OSA are comparable, and whether they may be procured for an explanation of the pathogenesis of arterial and pulmonary hypertension. Further investigations in the control mechanisms of breathing and circulation related to the circuits of chemo- and baroreception, thresholds during wakefulness and sleep may be of decisive help to process the question, to what extent clinical states find a correlate in a disturbed cardiorespiratory coupling and, much more significantly, whether a disturbance in the physiological cardiorespiratory coupling appears already in early states of a disease. Sleep with ist complex physiology as well as with its characteristic pathophysiological phenomenon of sleep related breathing disorders has opened a new interdisciplinary field where tools like the polysomnography and electronic data analysis are used by physiologists, pathophysiologists as well as by physicians.