Abstract

Objectives: To assess the effect of altitude and acclimatisation on cardiorespiratory 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 3500 m in healthy children during a trekking holiday. SpO₂ at altitude was compared with that in flight and during acute hypoxic challenge (breathing 15% oxygen) at sea level.

Results: Measurements were obtained in nine children aged 6–13 years (median 8). SpO₂ decreased significantly during the hypoxic challenge (difference −5%, 95% CI −6 to −3%, p<0.01) but remained above 90% in all children. There was a significant fall in daytime and overnight SpO₂ (95% CI −11.9 to −7.5% and −12 to −8, respectively) and etCO₂ (−8.5 to −4.5 mm Hg) as the children ascended to 3500 m. There was a significant increase in SpO₂ (95% CI 1.1 to 4.9%) and a further drop in etCO₂ (−5.9 to −0.8 mm Hg) 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.