When should oxygen be given to children at high altitude? A systematic review to define altitude-specific hypoxaemia.

BACKGROUND: Acute respiratory infections (ARI) cause 3 million deaths in children worldwide each year. Most of these deaths occur from pneumonia in developing countries, and hypoxaemia is the most common fatal complication. Simple and adaptable indications for oxygen therapy are important in the management of ARI. The current WHO definition of hypoxaemia as any arterial oxygen saturation (SpO(2)) <90% does not take into account the variation in normal oxygen saturation with altitude. This study aimed to define normal oxygen saturation and to estimate the threshold of hypoxaemia for children permanently living at different altitudes.
METHODS: We carried out a systematic review of the literature addressing normal values of oxygen saturation in children aged 1 week to 12 years. Hypoxaemia was defined as any SpO(2) at or below the 2.5th centile for a population of healthy children at a given altitude. Meta-regression analysis was performed to estimate the change in mean SpO(2) and the hypoxaemia threshold with increasing altitude.
RESULTS: 14 studies were reviewed and analysed to produce prediction equations for estimating the expected mean SpO(2) in normal children, and the threshold SpO(2) indicating hypoxaemia at various altitudes. An SpO(2) of 90% is the 2.5th centile for a population of healthy children living at an altitude of approximately 2500 m above sea level. This decreases to 85% at an altitude of approximately 3200 m.
CONCLUSIONS: For health facilities at very high altitudes, giving oxygen to all children with an SpO(2) <90% may be too liberal if oxygen supplies are limited. In such settings, Spo(2) <85% may be more appropriate to identify children most in need of oxygen supplementation.