Feasibility of Hypoxic Challenge Testing in Youth with Congenital Heart and Lung Disease

Abstract

At altitude the partial pressure of oxygen declines and causes hypobaric hypoxia. This may leads to hypoxemia in patients with congenital heart or lung disease, because of their limited compensatory cardiorespiratory capacity. For this reason a hypoxic challenge test (HCT), usually performed in resting conditions, is recommended. However, also the possible effects of changing body position and physical activity at altitude can be relevant, because it may lead to further desaturation. PURPOSE: The primary aim of this study was to investigate the effects of integrating changing body positions and physical activity in a HCT among youth with severe congenital heart or lung disease. METHODS: SpO2 and heart rate were monitored in 12 pediatric patients with congenital heart or lung disease undergoing a modified HCT, breathing room air (21% oxygen) while sitting and breathing 15% oxygen in nitrogen while seated, lying supine, standing, walking 3 km/hr and walking 5 km/hr in a non-randomized order. Data were analyzed using a Friedman test. RESULTS: All patients, except one, passed successfully through the entire HCT protocol. Three patients reported symptoms, possible related to altitude hypoxia. Median pulse oximeter saturation breathing 15% oxygen decreased from 99% to 95% in all body positions (seated, supine, standing) compared with room air (p<0.0001). There were no significant differences in pulse oximeter saturations between the different body positions. During mild exercise breathing 15% oxygen the pulse oximeter saturations decreased significantly from 99% to 94% compared to breathing 21% oxygen at rest (p<0.001). No significant differences between mild exercise breathing 15% oxygen and breathing 15% oxygen at rest was found. Several patients had SpO2 values below 90% at some point during the HCT. The pulse oximeter attached to the forehead registered significantly higher saturations (median and minimum values) than the pulse oximeter attached to the index finger (medians: 92% vs 94/95% respectively; p≤0.05). CONCLUSION: Simulated hypoxia of 2500 meter induced a small but significant decrease in SpO2% in pediatric patients with congenital heart or lung disease. These values were not further lowered during walking 3 and 5 km/hr. Supported by a grant of the Prof Dr Jongbloed Foundation.