Cerebrovascular and ventilatory responses to acute normobaric hypoxia in girls and women. Issue 15 (3rd August 2017)

• Record Type: Journal Article
• Authors: Morris, Laura E.; Flück, Daniela; Ainslie, Philip N.; McManus, Ali M.
• Is Part Of: Physiological reports. Volume 5:Issue 15(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-08-03
• Subjects: Cerebral perfusion -- children -- hypoxia -- respiratory drive -- ventilation; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.13372
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: Physiological responses to hypoxia in children are incompletely understood. We aimed to characterize cerebrovascular and ventilatory responses to normobaric hypoxia in girls and women. Ten healthy girls (9.9 ± 1.7 years; mean ± SD; Tanner stage 1 and 2) and their mothers (43.9 ± 3.5 years) participated. Internal carotid (ICA) and vertebral artery (VA) velocity, diameter and flow (Duplex ultrasound) was recorded pre‐ and post‐1 h of hypoxic exposure (FIO2 = 0.126;~4000 m) in a normobaric chamber. Ventilation ( V ˙ E ) and respiratory drive ( V T / T I ) expressed as delta change from baseline (∆%), and end‐tidal carbon‐dioxide (PET CO2 ) were collected at baseline (BL) and 5, 30 and 60 min of hypoxia (5/30/60 HYP). Heart rate (HR) and oxygen saturation (SpO2 ) were also collected at these time‐points. 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 V ˙ E peaked at 30HYP in both girls (27%, P < 0.05) and women (19%, P < 0.05), as did ∆% V T / T I (girls, 41%; women, 27%, P 's < 0.05). Tidal volume ( V T ) increased in both girls and women at 5HYP, remaining elevated above baseline in girls at 30 and 60 HYP, but declined back toward baseline in women. Girls elicit similar increases in gCBF and ventilatory parameters in response to acute hypoxia as women, though the pattern and contributions mediating these responses appear developmentally divergent. Abstract : We observe for the first time in children, that cerebral perfusion of the extracranial arteries increases in response to an acute 1 h about of hypoxia. This response is mediated by greater increases in anterior flow in girls, opposed to posterior flow in women. Furthermore, the increase in ventilation and respiratory drive were comparable between girls and women, though the pattern of breathing differed.