Pulse oximetry in neonates at high altitudes: a modified Colorado protocol

Pulse oximetry for detecting critical CHD produces more false positive tests at high altitudes than at sea level, because at altitude the average resting saturation is lower and the variability is higher. This increases diagnostic difficulties, especially in small isolated communities without paediatric echocardio-graphy, and requires expensive transport to a regional medical centre. One way of reducing diagnostic errors is to measure arterial oxygen saturation while the infant is breathing 100% oxygen. In the absence of right-to-left shunting through the heart, the ductus, or the lungs, arterial oxygen tension will exceed 150 mmHg and arterial oxygen saturation will be 100%. With right-to-left shunting, arterial oxygen tension will be <100 mmHg, and thus <96% (usually much lower).