HYPOXIC VENTILATORY RESPONSE DECREASES DURING SLEEP IN NORMAL MEN

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Abstract
Ventilatory drives are evidently important in the maintenance of ventilation during sleep. Although the hypercapnic ventilatory response has been shown to decrease during sleep, the hypoxic ventilatory response (HVR) has not been well studied in humans. The ventilatory response to isocapnic hypoxia was measured in 6 sleeping men. The HVR, measured as the slope of the relation between ventilation and decreasing Hb saturation, was significantly lower in all sleep stages than in wakefulness (1.07 .+-. 0.19 SEM [standard error of the mean] l/min per % saturation). The HVR decreased to 2/3 of this waking value in non-REM [rapid eye movement] sleep (0.63 .+-. 0.09 l/min per % saturation) with a further significant decrease in REM sleep when HVR was < 1/3 of the waking value (0.33 .+-. 0.04 l/min per % saturation). The decreased HVR may help to explain the REM-sleep-related hypoxemia found in normal persons and patients with various cardiorespiratory diseases.