Effect of sleep on hypoxic stimulation of breathing at sea level and altitude

¹ Department of Physiology, University of California, Berkeley and San Francisco; and White Mountain Research Station, Big Pine, California

The effect of sleep on the level of hypoxia in four adult male, sea-level residents was studied at sea level, during 23 days at 14,250 ft. and after return to sea level. The subjects, awake and asleep, breathed graded O₂-N₂ mixtures, each followed by a high O₂ gas. Sleep did not significantly affect the hypoxic drive of breathing as evaluated from the steady-state levels of ventilation or from the immediate respiratory depression produced by interrupting hypoxia. At the ambient altitude O₂ tension, arterial O₂ saturation indicated by ear oximeter fell 4–8% with sleep. This fall in arterial oxygenation is believed to be sufficient to help explain the increased severity of mountain sickness which is commonly associated with sleep at altitude.