Cardiopulmonary and cerebrovascular acclimatization in children and adults at 3800 meters

Maturational differences exist in cardiopulmonary and cerebrovascular function at sea-level, but the impact of maturation on acclimatization responses to high-altitude is unknown. 10 children (9.8±2.5 y) and 10 adults (34.7±7.1 y) were assessed at sea-level (BL), 3000 m, and twice over 4 days at 3800 m (B1, B4). Measurements included minute ventilation (V̇E), end-tidal partial pressures of oxygen (PETO2) and carbon dioxide, echocardiographic assessment of pulmonary artery systolic pressure (PASP) and stroke volume (SV), and ultrasound assessment of blood flow through the internal carotid and vertebral arteries was performed to calculate global cerebral blood flow (gCBF).

At 3000 m, V̇E increased from BL by 19.6±19.1% (P = 0.031) in children, but not in adults (P = 0.835); SV was reduced in children (-11±13%, P = 0.020) but not adults (P = 0.827), which was compensated for by a larger increase in heart rate in children (+26 beats·min−1 vs. +13 beats·min−1, P = 0.019). Between B1 and B4, adults increased V̇E by 38.5±34.7% (P = 0.006), while V̇E did not increase further in children. The rise in PASP was not different between groups; however, ∆PASP from BL was related to ∆PETO2 in adults (R2 = 0.288, P = 0.022), but not children. At BL, gCBF was 43% higher in children than adults (P = 0.017), and this difference was maintained at high altitude, with a similar pattern and magnitude of change in gCBF between groups (P = 0.845). Despite V̇E increasing in children but not adults at a lower altitude, the pulmonary vascular and cerebrovascular responses to prolonged hypoxia are similar between children and adults.