LAUSR

Under healthy condition, when awake, the breathing process is built up of regular, constant and repeated sequences of inhalation and exhalation. The volume and frequency of breathing is under control of a negative feedback system that keeps the partial pressure of arterial oxygen and carbon dioxide at constant level. In awake man, breathing is dependent on 3 different control systems. The behavioral control is intentional and arises from the cortex of the forebrain and corticospinal tract. The metabolic (autonom) control of breathing originates from the medulla oblongata as well as from the ventrolateral spinal tract. The metabolic control maintains the acid-base balance and O2-homeostasis. The third control level is the wakefulness stimulus, which affects breathing during wakefulness through the reticular activating system, independent of human intention. During sleep, these control systems undergo substantial alterations. The mechanism of alveolar ventilation/hypoventilation is complex, in which the changes of the central control of breathing play a prominent role. In this process, the outfall of the intentional influence of breathing through diminished vigilance level, furthermore, the inhibition of the reticular activating system during transitional sleep lead to disappearance of the cortical control mechanisms and to reduced mechanical and metabolic control of breathing. All these changes are the physiological background for the characteristic breathing pattern and also for the development of pathological breathing forms during sleep that can be visualised during polysomnography.