Hagen am Teuteburger Wald, Germany
Hagen am Teuteburger Wald, Germany

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Schafer T.,Ruhr University Bochum | Schafer T.,Institute For Klinische Physiologie | Schlafke M.E.,Ruhr University Bochum | Schlafke M.E.,Institute For Klinische Physiologie
Somnologie | Year: 2011

Breathing is part of a transport system that serves gas exchange of the body. Rhythmic breathing movements are controlled by the neuronal respiratory network in the medulla oblongata, which is dependent on tonic afferents. These are partly closed feedback loops to guarantee the homeostasis of blood gases and acid-base balance, and partly non-feedback stimuli as the so-called "wakefulness drives." Orexinergic neurons in the hypothalamus seem to play an important role in the tonic drive of respiration during wakefulness. Sleep onset markedly reduces tonic afferents, decreases the sensitivity to hypoxia and hypercapnia, and elevates arousal thresholds. Sleep unmasks the apnea threshold. If the arterial carbon dioxide partial pressure drops below this threshold due to short hyperpneic episodes, the respiratory rhythm arrests. Restless sleep with frequent changes in sleep states destabilizes the breathing pattern. The muscle atonia especially during REM sleep also affects the upper airway muscles and the intercostal muscles. Consequently, there is an increase in airway resistance. The diaphragm has to compensate these challenges by increased work. Nevertheless, in healthy subjects the blood gases only slightly change from wakefulness to sleep. © 2011 Springer.


Schafer T.,Institute For Klinische Physiologie | Schafer T.,Ruhr University Bochum
Somnologie | Year: 2012

In healthy subjects, respiratory regulation adapts alveolar ventilation to metabolic carbon dioxide production. A dysproportional decrease in alveolar ventilation after sleep onset with a consecutive rise in arterial carbon dioxide partial pressure is called sleep-related hypoventilation, which usually coincides with longer lasting arterial oxygen desaturation. Limits of normal pCO2 values during sleep in the literature are inconsistent. The International Classification of Sleep Disorders (ICSD-2) distinguishes five types of sleep-related hypoventilation. As pathophysiological mechanisms, "central" mechanisms, caused by impairment of central nervous regulation of respiration are differentiated from "peripheral" mechanisms, caused by medical or neurological conditions. The diagnosis is based on the detection of hypercapnia. Taking into account the methodological limitations, this can be done using transcutaneous or end-tidal pCO2 measurements. © Springer-Verlag 2012.

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