Potential Causes of Recurrent Apneas During Sleep

Abstract

The body contains chemoreceptors which respond to changes in PCO₂ and PO₂ and which operate within the respiratory system to keep arterial levels of PCO₂ and PO₂ within fairly narrow limits¹. Chemoreceptors send signals to neurons in the brain which, in turn, actuate respiratory muscles which ventilate the lungs and change the content of O₂ and CO₂ in the blood. Blood is pumped by the heart to the tissues where it is used to metabolize nutrients and provide energy. The blood is then returned to the lungs where the process repeats itself. Increases in ventilation raise levels of arterial O₂ content and lower CO₂ while the opposite occurs when ventilation is decreased. This system is subject to a variety of disturbances, because of changes in the O₂ and CO₂ content of the inspired air or because of altered levels of metabolism. Other disturbances occur because the respiratory muscles are used not only to breathe but to maintain posture, for temperature regulation, and in digestion. In addition, because respiration can be altered voluntarily, disturbance in blood gas tensions can occur because of this behavioral control when there are changes in light intensity or noise levels in the environment, and when the respiratory muscles are used in speaking or to express emotion.