The administration of 100% oxygen to a patient (typically a neonate) to determine the cause of respiratory distress, hypoxemia, cyanosis, and/or shock. The resolution of cyanosis with treatment usually indicates that the cause of the hypoxia is a lung disease, e.g., pneumonia. If the PaO2 at the conclusion of the test is > 150 torr, cardiac disease can usually be excluded. Failure of neonates to respond to 100% oxygen is usually an indication of severe congenital heart disease.
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