BACKGROUND: This is a cross-sectional observational study to investigate the safety and feasibility of integrating changing body positions and physical activity in a hypoxic challenge test (HCT). The secondary objective was to compare oxygen saturation (S_po₂) in two different locations (forehead and finger).METHODS: Included were 12 pediatric to young adult patients with congenital heart (N = 7) or lung disease (N = 5). An HCT was performed using breathing room air (21% oxygen) while sitting and breathing a normobaric hypoxic gas mixture (15% oxygen) through a facemask while seated, lying supine, standing, walking 3 km/h, and walking 5 km/h in a nonrandomized order.RESULTS: All patients, except one, successfully passed the HCT. Three patients reported symptoms, possibly related to hypoxia. Median S_po₂ during the HCT decreased in all body positions compared with room air. In 9/12 (finger oximeter) vs. 6/12 (forehead oximeter) patients S_po₂ decreased below 90% in one or more body positions at rest. In 11/12 (finger oximeter) vs. 3/12 (forehead oximeter) patients S_po₂ decreased below 90% during mild exercise. There was no significant difference in S_po₂ between the different body positions. However, patients desaturated significantly more during mild exercise (walking 3km/h and 5 km/h). S_po₂% measured at the forehead gave significantly higher values compared to the index finger.DISCUSSION: HCT is safe and feasible in children and adolescents with congenital heart or lung disease, and gives additional information about oxygenation during physical activity in addition to resting conditions. Simulated hypoxia of 8202 ft (2500 m) induced a small but significant decrease in S_po₂%.Spoorenberg ME, Hulzebos EHJ, Takken T. Feasibility of hypoxic challenge testing in children and adolescents with congenital heart and lung disease. Aerosp Med Hum Perform. 2016; 87(12):1004–1009.