CHEMO-RESPONSE AND BARORESPONSE DIFFER IN AFRICAN-AMERICANS AND CAUCASIANS IN SLEEP

To determine sleep effects an baro- and ventilatory responses to trans ient chemo- and barostimulation in African-Americans and Caucasians, 2 6 nonobese normotensive young subjects (13 African-Americans and 13 Ca ucasians) were studied awake and in non-rapid-eye movement (NREM) and rapid-eye-movement sleep during induced transient hypoxemia (N-2), hyp ertension (phenylephrine, PE), and concomitant hypoxemia and hypertens ion (N-2 + PE). Arterial blood pressure was recorded by plethysmograph ic volume clamp, minute ventilation by pneumotachograph, and arterial O-2 saturation by pulse oximeter. For all subjects, chronotropic baror esponse (Delta pulse interval/Delta systolic blood pressure, where Del ta is change) increased with NREM sleep (P = 0.007). Baroresponse slop e was greater in Caucasians than in African-Americans (ANOVA, P = 0.02 ). Hypoxemic ventilatory response (Delta minute ventilation/Delta arte rial O-2 saturation) was greater in African-Americans than in Caucasia ns in NREM sleep (P = 0.01), as was hypoxemic attenuation of barorespo nse (N-2 + PE, P = 0.03). These data suggest sleep-related differences in arterial chemo- and baroreceptor responses in normal young African -Americans and Caucasians, which may have implications concerning deve lopment of systemic hypertension.