Ventilatory and cerebrovascular responses to exercise in lowlander children acclimatizing to high‐altitude

Maturational differences in chemoreception and cerebral blood flow are evident at sea‐level, yet the age‐related comparisons in cardiopulmonary and cerebrovascular responses to high‐altitude exercise are unknown. Lowland living children (n = 8: 7–14 years) and adults (n = 10: 23–44 years) performed incremental cycle exercise to exhaustion at sea‐level and following 6 days at 3800 m. Ventilation (VE), end‐tidal carbon dioxide ( P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_2}}}$ ) and pulse oximetry estimation of oxygen saturation ( S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_2}}}$ ), as well as cerebrovascular measures of middle (MCA) and posterior (PCA) cerebral artery velocities (v) were measured at rest and throughout exercise. At high‐altitude, both children and adults showed comparable increases in VE and reductions in P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_2}}}$ and S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_2}}}$ at rest (altitude: P < 0.001, group: P ≥ 0.22). During exercise, VE increased at high‐altitude compared to sea‐level (P < 0.001), with no significant group differences (P = 0.134). Adults exhibited greater elevations in P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_2}}}$ at sea‐level compared to children (P = 0.023), but no significant group differences were present at high‐altitude (P = 0.144). S p O 2 ${S_{{\mathrm{p}}{{\mathrm{O}}_2}}}$ reductions during high‐altitude exercise were greater in adults than in children (80.4 ± 4.4% versus 85.8 ± 3.5%, P = 0.002), with both groups showing significant declines from sea‐level (P < 0.001). No group differences in exercise induced changes in MCAv (P = 0.159) or PCAv (P = 0.674) were present at sea‐level, but at high‐altitude, children displayed greater MCAv (82.8 ± 9.7 versus 71.6 ± 7.8 cm s−1, P = 0.014) and PCAv responses versus adults (61.8 ± 8.1 versus 46.7 ± 10.0 cm s−1, P = 0.001). Exposure to high‐altitude resulted in a greater cerebral blood velocity response during exercise in children, despite a greater preservation of oxygenation and a comparable degree of hypocapnia, suggesting differential thresholds of O2 and CO2 prioritization. image Key points: Children and adults exhibit distinct ventilatory and cerebrovascular responses to exercise, which may influence their acclimatization to high‐altitude environments. Children (ages 7–14 years) and adults (ages 23–44 years) were brought from sea‐level to high‐altitude (3800 m), where changes in cardiopulmonary and cerebrovascular responses were assessed during incremental exercise. At high‐altitude, both groups showed comparable increases in ventilation and similar levels of hypocapnia. However, children showed a lower magnitude of peripheral oxygen desaturation during high‐altitude exercise. Despite better preservation of oxygenation, children showed a greater increase in cerebral blood velocity during exercise, suggesting an increased prioritization of oxygen delivery to the brain. These results improve our understanding of the age‐related differences in cerebrovascular sensitivity during exercise at sea‐level and high‐altitude, indicating a dominance of hypoxic vasodilatation and reduced sensitivity to endogenous carbon dioxide during exercise.