Control of breathing during sleep

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.