Objectives: To assess the effect of altitude and acclimatisation on cardio-respiratory function and well-being in healthy children.
Methods: A daily symptom diary, serial measurements of spirometry, end-tidal carbon dioxide (etCO2) and daytime and overnight pulse oximetry (SpO2), were undertaken at sea-level and altitudes up to 3500m in healthy children during a trekking holiday. SpO2 at altitude was compared with that in-flight and during an acute hypoxic challenge (breathing 15% O2) at sea-level.
Results: Measurements were obtained in nine children; 6-13 (median 8) years. SpO2 decreased significantly during the hypoxic challenge (difference -5%, 95% CI -6;-3% p<0.01) but remained above 90% in all children. There was a significant fall both in daytime and overnight SpO2 (95%CI -11.9;-7.5% and -12;-8 respectively) and etCO2 (-8.5; -4.5 mmHg) as the children ascended to 3500m,. There was a significant increase in SpO2 (95%CI 1.1; 4.9%), and further drop in etCO2 (-5.9;-0.8 mmHg) after a week at altitude, etCO2 being negatively correlated with SpO2. There was no correlation between SpO2 during hypoxic challenge, in-flight or at altitude. Lung function remained within 7% of baseline in all but two children, in whom reductions of up to 23% in FVC and 16% FEV1 were observed at altitude. The children generally remained well, but the Lake Louise Scoring system was unreliable in this age group.
Conclusions: A wide range of physiological responses to altitude are evident in healthy children. This study should inform future larger studies in children to improve understanding of responses to hypoxia in health and disease.