Sleep-promoting and hypothermic effects of daytime melatonin administration in humans. The automatic control of breathing is determined by rhythmic activity of brainstem respiratory neurons. In wakefulness automatic control is present, but modulated by CNS activity associated with maintaining alertness and controlling behavior. In NREM sleep automatic control strongly predominates. The result of the variation in control of breathing is state-related differences in ventilatory effort and patterns in normal individuals, and clinically relevant ventilatory impairment in certain diseases.
Sleep embarrasses the respiratory system in obese or cardiopulmonary patients.
The fall in ventilation with sleep in patients with obesity, neuromuscular disease, and kyphoscoliosis may result in profound hypercapnia and hypoxemia. Some patients may develop tolerance to high PC02 which permits them to stay asleep but worsens ventilatory failure. Other patients with severe cardiopulmonary disease preserve breathing effort but awaken frequently and have severe sleep disruption. During REM, inhibition of the rib cage and accessory muscles of respiration further disables the respiratory system. As a result, ventilatory failure is generally much more severe in REM than NREM sleep.