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The influence of age and sex on cerebrovascular reactivity and ventilatory response to hypercapnia in children and adults
Author(s) -
Tallon Christine M.,
Barker Alan R.,
NowakFlück Daniela,
Ainslie Philip N.,
McManus Ali M.
Publication year - 2020
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/ep088293
Subject(s) - hypercapnia , middle cerebral artery , medicine , reactivity (psychology) , cerebral blood flow , cardiology , young adult , anesthesia , respiratory system , ischemia , alternative medicine , pathology
New FindingsWhat is the central question of this study? In this study, we investigated intracranial cerebrovascular and ventilatory reactivity to 6% CO 2 in children and adults and explored dynamic ventilatory and cerebrovascular onset responses.What is the main finding and its importance? We showed that cerebrovascular reactivity was 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 between children and adults and to explore the dynamic response of the middle cerebral artery mean velocity (MCA V ). Children ( n = 20; 9.9 ± 0.7 years of age) and adults ( n = 21; 24.4 ± 2.0 years of age) completed assessment of CVR over 240 s using a fixed fraction of inspired CO 2 (0.06). Baseline MCA V was higher in the adult females compared with the males ( P ≤ 0.05). The MCA V was greater in female children compared with male children ( P ≤ 0.05) and in female adults compared with male adults ( P ≤ 0.05) with hypercapnia. Relative CVR was similar in children and adults (3.71 ± 1.06 versus 4.12 ± 1.32% mmHg −1 ; P = 0.098), with absolute CVR being higher in adult females than males (3.27 ± 0.86 versus 2.53 ± 0.70 cm s −1 mmHg −1 ; P ≤ 0.001). Likewise, the hypercapnic ventilatory response did not differ between the children and adults (1.89 ± 1.00 versus 1.77 ± 1.34 l min −1 mmHg −1 ; P = 0.597), but was lower in adult females than males (1.815 ± 0.37 versus 2.33 ± 1.66 l min −1 mmHg −1 ; P ≤ 0.05). The heart rate response to hypercapnia was greater in children than in adults ( P = 0.001). A monoexponential 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 versus 74 ± 28 s; P = 0.001). Our study provides new insight into the impact of age and sex on CVR and the dynamic response of the MCA V to hypercapnia.