Cerebrovascular and ventilatory responses to acute normobaric hypoxia in girls and women

• Main Author: Morris, Laura
• Language: English
• Published: University of British Columbia 2017
• Online Access: http://hdl.handle.net/2429/62806

Physiological responses to hypoxia in children are incompletely understood. We aimed to characterize cerebrovascular and ventilatory responses to normobaric hypoxia in girls and women. Methods: Ten healthy girls (9.9 +/- 1.7y; mean +/- SD; Tanner stage 1 and 2) and their mothers (43.9 +/- 3.5y) participated. Internal carotid (ICA) and vertebral artery (VA) velocity, diameter and flow (Duplex ultrasound) was recorded pre- and post-1h of hypoxic exposure (FIO₂=0.126;~4000m) in a normobaric chamber. Ventilation (VE) and respiratory drive (VT/TI) expressed as delta change from baseline (∆%), and end-tidal carbon-dioxide (PETCO₂) were collected at baseline (BL) and 5, 30 and 60 minutes of hypoxia (5/30/60 HYP). Heart rate (HR) and oxygen saturation (SpO₂) were also collected at these time-points. Results: SpO₂ declined similarly in girls (BL-97%; 60HYP-80%, P<0.05) and women (BL-97%; 60HYP-83%, P<0.05). Global cerebral blood flow (gCBF) increased in both girls (BL-687; 60HYP-912 ml.min-¹, P<0.05) and women (BL-472; 60HYP-651 ml.min-¹, P<0.01), though the ratio of ICA:VA (%) contribution to gCBF differed significantly (girls, 75:25%; women, 61:39%). The relative increase in VE peaked at 30HYP in both girls (27%, P<0.05) and women (19%, P<0.05), as did ∆%VT/TI (girls, 41%; women, 27%, P’s<0.05). Tidal volume (VT) increased in both girls and women at 5HYP, remaining elevated above baseline in girls at 30 and 60HYP, but declined back toward baseline in women. Conclusion: Girls elicit similar increases in gCBF and ventilatory parameters in response to acute hypoxia as women, though the pattern of these responses appear developmentally divergent. === Graduate Studies, College of (Okanagan) === Graduate