Anterior cerebral blood velocity and end-tidal CO2 responses to exercise differ in children and adults

作者：Ellis Lindsay A; Ainslie Philip N; Armstrong Victoria A; Morris Laura E; Simair Ryan G; Sletten Nathan R; Tallon Christine M; McManus Ali M^*

来源：American Journal of Physiology - Heart and Circulatory Physiology, 2017, 312(6): H1195-H1202.

DOI：10.1152/ajpheart.00034.2017

• cerebral blood flow
• ventilation
• exercise
• children
• growth and development

Little is known about the response of the cerebrovasculature to acute exercise in children and how these responses might differ with adults. Therefore, we compared changes in middle cerebral artery blood velocity (MCAVmean), end-tidal PCO2 (PETCO2), blood pressure, and minute ventilation (VE) in response to incremental exercise between children and adults. Thirteen children [age: 9 +/- 1 (SD) yr] and thirteen sex-matched adults (age: 25 +/- 4 yr) completed a maximal exercise test, during which MCAV(mean), PETCO2, and VE were measured continuously. These variables were measured at rest, at exercise intensities specific to individual ventilatory thresholds, and at maximum. Although MCAV(mean) was higher at rest in children compared with adults, there were smaller increases in children (1-12%) compared with adults (12-25%) at all exercise intensities. There were alterations in PETCO2 with exercise intensity in an age-dependent manner [F(2.5,54.5) = 7.983, P < 0.001; eta(2) = 0.266], remaining stable in children with increasing exercise intensity (37-39 mmHg; P > 0.05) until hyperventilation-induced reductions following the respiratory compensation point. In adults, PETCO2 increased with exercise intensity (36-45 mmHg, P < 0.05) until the ventilatory threshold. From the ventilatory threshold to maximum, adults showed a greater hyperventilation-induced hypocapnia than children. These findings show that the relative increase in MCAV(mean) during exercise was attenuated in children compared with adults. There was also a weaker relationship between MCAV(mean) and PETCO2 during exercise in children, suggesting that cerebral perfusion may be regulated by different mechanisms during exercise in the child.
NEW & NOTEWORTHY These findings provide the first direct evidence that exercise increases cerebral blood flow in children to a lesser extent than in adults. Changes in end-tidal CO2 parallel changes in cerebral perfusion in adults but not in children, suggesting agedependent regulatory mechanisms of cerebral blood flow during exercise.

• 出版日期2017-6