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Introduction: Prenatal studies and postnatal physical exam leave 13- 55% of neonates with CCHD undiagnosed leading to presentation in extremis or death. The AHA has endorsed newborn pulse oximetry screening to capture these infants prior to hospital discharge. Moderate altitude can impart higher screening failure rates. We therefore evaluated a modified CCHD screening protocol in an attempt to reduce false positive screenings at a moderate altitude of 6200 feet (1890 m). Methods: We prospectively enlisted well newborn infants greater than 35 weeks. Near 24 hours of life, trained nursing staff performed pulse oximetry on the right hand and either foot. Those with saturations ≤95% with < 3% difference between hand and foot measurements passed. Infants with saturations <86% failed. Infants with saturations between 86-94% or >3% difference in saturations were placed in an oxygen hood with FiO2 designed to replicate sea level atmospheric oxygen tension for 20 minutes to accelerate neonatal transition. These infants were tested again up to 2 additional screens in room air with standard sea level protocol. Providers were notified and echocardiograms ordered for all infants deemed to have failed. Results: A total of 2005 infants completed the protocol. The failure rate was 0.3% (7/2005), which was not different from the sea level rate of 0.2%. Sea level CCHD screening criteria would have given a failure rate of 0.75%. An additional 2.1% (42/2005) had incomplete screening and were not passing at the time the test was stopped. We found 5/7 (71.4%) infants failed secondary to low saturations, 1/7 (14.3%) failed secondary differential saturations, and 1 infant failed for multiple reasons. Three of the seven infants with failing screens were discharged prior to echocardiogram. None of the infants receiving echocardiograms had critical congenital heart disease. Conclusions: We found a failure rate of 0.3% using an alternate algorithm adjusted for altitude. This failure rate approximates the overall screening failures reported at sea level and is significantly lower than prior reports at altitude. Additional research is needed specifically addressing sensitivity and positive predictive value for screening at moderate altitudes.

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