Respiratory pathophysiology: sleep-related breathing disorders

A widespread network of respiratory-related neurons within the brainstem controls the regular respiratory cycle, which is dependent upon unspecific and specific drives like hypoxia or hypercapnia. This respiratory network and its respiratory drives are subjects to typical changes during the transition from wakefulness to sleep and within the various sleep states, which favor a destabilization of breathing during sleep. There is also a respiratory-related innervation of the dilating and stiffening pharyngeal muscles as well as a local reflex control of the basic tone of upper airway muscles, both of which are influenced by the different states of wakefulness and sleep. These sleep-related changes cause an increase in upper airway resistance during sleep. In healthy subjects, however, these features during sleep are almost completely compensated and the gas exchange is hardly hindered. However, in the case of illness, severe disordered breathing, disturbed gas exchange and interrupted sleep may occur. The central hypoventilation syndrome, central apnea-hypopnea syndromes, as well as the obstructive sleep apnea syndrome belong to these diseases. Because of the intense research, we have a detailed picture of the pathophysiological mechanisms of the origin and the maintenance of sleep-related breathing disorders.