Hypoxia-altitude simulation test to predict altitude related adverse health effects in COPD patients

Amongst numerous travelers to high altitude are many with the highly prevalent chronic obstructive pulmonary disease (COPD), who are at particular risk for altitude-related adverse health effects (ARAHE). We investigated hypoxia altitude simulation testing (HAST) to predict ARAHE in COPD patients traveling to altitude.This prospective diagnostic accuracy study included 75 COPD patients (40 women, age 58±9 years, FEV1 40–80% pred.), SpO2≥92% and PaCO2<6kPa. Patients underwent baseline evaluation and HAST, breathing normobaric hypoxic air (FiO2of 15%) for 15 min, at low altitude (LA, 760m). Cutoff values for a positive HAST were set according to BTS-guidelines (PaO2<6.6kPa and/or SpO2<85%). The following day, patients traveled to high altitude (HA, 3100m) for 2 overnight stays where ARAHE development including acute mountain sickness (AMS), Lake Louise Score (LLS)≥4 and/or AMSc ≥0.7, severe hypoxemia (SpO2<80% for>30min or 75% for >15min) or intercurrent illness was observed. ARAHE occurred in 50 (66%) patients and 23/75 (30%) were positive in HAST by SpO2, 11/64 (17%) by PaO2. For SpO2/PaO2we report a sensitivity of 46/25%, specificity of 84/95%, positive predictive value of 85/92% and negative predictive value of 44/37%.In COPD patients ascending to HA, ARAHE are common. Despite an acceptable positive predictive value of HAST to predict ARAHE, its clinical use is limited by its insufficient sensitivity and overall accuracy. Counseling COPD patients before altitude travel remains challenging and best focuses on early recognition and therapy of ARAHE with oxygen and descent.