BACKGROUND: False negative pulse oximeter results occur in new born infants with critical congenital heart disease who have an oximeter saturation ≥95%. Some of these infants have abnormal physical findings but others do not.
OBJECTIVES: To determine the causes of false negative results.
METHODS: Mathematical analysis of determinants of arterial oxygen saturation and discussion of oximeter bias.
RESULTS: False negative oximeter results are not rare; the sensitivity of pulse oximetry screening for critical congenital heart disease is about 80%. The high saturation may be due to a very small right-to-left shunt at the time of study, a relatively high cardiac output and mixed venous saturation, or to positive bias in oximeter readings. It may also be due to some critical congenital heart lesions that do not show desaturation at the time of testing.
CONCLUSIONS: A diagnosis of a normal heart based on a negative oximeter test is presumptive, and requires careful follow-up for 1–2 weeks after birth.