Influence of sleep state on CO2 responsiveness. A study of the unloaded respiratory pump in humans.
We measured the ventilatory recruitment threshold for CO2 (RT) during wakefulness, nonrapid eye movement sleep (NREM), and rapid eye movement sleep (REM) in eight patients with respiratory failure. Because the lungs were mechanically ventilated during the RT measurements, we were able to define the effects of arousal state on the chemoresponsiveness of the unloaded respiratory system. Ventilator settings were held constant in each patient, assuring that mechanoreceptor input to the respiratory controller remained the same during all measurements. RT increased from 38 +/- 6 mm Hg during relaxed wakefulness to 42 +/- 8 mm Hg during NREM sleep (p less than or equal to 0.01), consistent with a blunting of chemoresponsiveness during sleep. In five subjects we were able to measure RT during REM sleep also. In four of them, REM RT exceeded the wakefulness measurement by at least 3 mm Hg. The remaining patient showed no demonstrable changes in RT during either sleep state. We conclude that the loss of a wakefulness stimulus contributes to sleep-induced hypercarbia in humans.
Ingrassia
T S
TS
Division of Thoracic Diseases, Mayo Clinic, Rochester, Minnesota 55905.
Nelson
S B
SB
Harris
C D
CD
Hubmayr
R D
RD
D000328:Adult; D000368:Aged; D002245:Carbon Dioxide / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012119:Respiration / Q000502:physiology*; D012121:Respiration, Artificial; D012129:Respiratory Function Tests / Q000295:instrumentation; D012131:Respiratory Insufficiency / Q000503:physiopathology / Q000628:therapy; D012894:Sleep Stages / Q000502:physiology*; D012895:Sleep, REM / Q000502:physiology; D014851:Wakefulness / Q000502:physiology
D002245:Carbon Dioxide