The influence of age and sex on cerebrovascular reactivity and ventilatory response to hypercapnia in children and adults

Abstract

New Findings What is the central question of this study? This study investigated intracranial cerebrovascular and ventilatory reactivity to 6% CO₂ in children and adults and explored dynamic ventilatory and cerebrovascular onset responses. What is the main finding and its importance? We show cerebrovascular reactivity is similar in children and adults, but the intracranial blood velocity onset response was markedly attenuated in children. Sex differences were apparent, with greater increases in intracranial blood velocity in females, and lower ventilatory reactivity in adult females. Our study confirms the importance of investigating dynamic onset responses when assessing the influence of development on cerebrovascular regulation. Abstract The purpose of this study was to compare the integrated intracranial cerebrovascular reactivity (CVR) and hypercapnic ventilatory response (HCVR) between children and adults, as well as explore the dynamic response of the middle cerebral artery mean velocity (MCA_V). Children (n = 20; 9.9 ± 0.7 years) and adults (n = 21; 24.4 ± 2.0 years) completed assessment of CVR over 240s using a fixed concentration of inspired CO₂ (F_ICO₂, 0.06). Baseline MCA_V was higher in the adult females compared to the males (p ≤ .05). MCA_V was greater in female children compared to male children (p ≤ .05), and in female adults compared to male adults (p ≤ .05) with hypercapnia. Relative CVR was similar in children and adults (3.71 ± 1.06 vs. 4.12 ± 1.32 %/mmHg; p = .098), with absolute CVR higher in adult females than males (3.27 ± .86 vs. 2.53 ± .70 cm/s/mmHg; p ≤ . 001). Likewise, HCVR did not differ between the children and adults (1.89 ± 1.00 vs. 1.77 ± 1.34 L/min/mmHg; p = .597), but was lower in adult females than males (1.815 ± 37 vs. 2.33 ± 1.66 L/min/mmHg; p ≤ .05). The heart rate response to hypercapnia was greater in children than adults (p = 001). A mono‐exponential regression model was used to characterize the dynamic onset, consisting of a delay term, amplitude and time constant (τ). The results revealed that MCA_V τ was faster in adults than in children (34 ± 18 vs .74 ± 28 s; p = .001). Our study provides new insight into the impact of age and sex on CVR and the dynamic response of the MCA_V to hypercapnia. This article is protected by copyright. All rights reserved