Cerebrovascular Response to CO₂ Following 10 Days of Intermittent Hypoxia in Humans

INTRODUCTION: It has been demonstrated that the cerebrovascular response to hypoxia is blunted following 10 d of intermittent hypoxia (IH) in healthy humans. The purpose of this study was to test the hypothesis that IH reduces the cerebrovascular response to CO₂.METHODS: Healthy male subjects (N = 8; 25 ± 2 yr) were exposed to 10 consecutive days of IH (12% O₂ for 5 min followed by 5 min of normoxia for 1 h/d). The cerebrovascular response to CO₂ was assessed prior to (PRE-IH) and following (POST-IH) the IH paradigm with transcranial Doppler ultrasound.RESULTS: There was no change in eupnic measures during or following the IH paradigm; however, the ventilatory response to IH increased by the last exposure (3.0 ± 2.8 L · min⁻¹). Cerebral blood flow velocity decreased and increased with hypocapnia and hypercapnia, respectively, but cerebrovascular sensitivity to CO₂ remained unchanged with IH (PRE-IH: 2.58 ± 0.50%/mmHg; POST-IH: 2.59 ± 0.74%/mmHg).DISCUSSION: Our data indicates that 10 d of IH in healthy humans does not alter the cerebrovascular response to CO₂. Redundancy of cerebrovascular regulation mechanisms to CO₂ may work to counteract IH-induced dysregulation and protect cerebral tissue.Querido JS, Welch JF, Ayas NT, Sheel AW. Cerebrovascular response to CO₂ following 10 days of intermittent hypoxia in humans. Aerosp Med Hum Perform. 2015; 86(9):782–786.