ABSTRACT
In recent years it has become apparent that sleep is a different state not only mentally but physiologically. Quantitative and sometimes qualitative differences have been noted in many body systems during sleep than those present during wakefulness. Of all the physiological differences in sleep versus wakefulness discovered in the last decade, the changes in respiratory control are the most dramatic. At sleep onset there is a decrease in breathing rate, mostly because more time is spent breathing in. Concurrently there is an overall decrease in response to carbon dioxide to about 1/2 of that of waking values, but of greater importance is the response to levels of oxygen in the blood. It takes more effort to breathe during sleep because there is more resistance to air flow in the airways and changes in the efficiency of the muscles used for breathing.
