Reduced cerebrovascular and cardioventilatory responses to intermittent hypoxia in elderly

Abstract

BackgroundThe impact of aging on cerebrovascular function and tissue oxygenation during graded hypoxemia is incompletely known. This study compared the age effect on these variables during cyclic hypoxemia-reoxygenation. MethodsHypoxia-induced changes in arterial (SaO2) and cerebral tissue (ScO2) O2 saturation, middle cerebral arterial flow velocity (VMCA), estimated cerebral vascular conductance (CVC), heart rate (HR) and ventilation were compared between 12 elderly (71 ± 2 yr, 7 women) and 13 young (24 ± 3 yr, 5 women) adults during the first and fifth 5-min exposures to 10% O2. ResultsAlthough pre-hypoxia SaO2 did not differ between the groups, ScO2 was lower (P < 0.05) in the elderly (68.4 ± 1.2%) than young (73.8 ± 0.9%) adults, commensurate with a lower resting VMCA (P < 0.05). SaO2 fell less sharply (P < 0.05) in the elderly subjects during the first and fifth hypoxia exposures. Moreover, the responses of ScO2, VMCA, CVC, HR and breathing frequency to hypoxia were attenuated in the elderly subjects. Systolic and diastolic arterial pressures fell by 2–6 mmHg during hypoxia in both young and elderly. Thus, hypoxemia developed more gradually in elderly than young adults during normobaric hypoxia, concordant with a reduced metabolic demand in the elderly. ConclusionsThe elderly adults safely tolerated cyclic, moderate hypoxemia which lowered SaO2 by 20–25%, despite dampening of cerebrovascular and cardiac responses to hypoxemia.