Reliability and validity of the Hypoxico Everest Summit II altitude generator

Abstract

The Hypoxico Everest Summit II Altitude Generator produces normobaric hypoxic conditions, which are commonly used in altitude acclimation. Despite being used routinely within applied sport science, this system is yet to be independently validated. Thus, the aim of this study was to explore within- and between-day inter- and intra-machine reliability and validity. Two Hypoxico Everest Summit II Altitude Generators were investigated for six altitude settings in a randomised order (0.5, 3.0, 5.5, 8.0, 10.5, 12.0). Following institutional ethics approval, Hypoxico generated air was sequentially pumped into three Douglas bags, each with a 1-min collection period. Samples were collected on eight occasions, measuring inter- and intra-machine reliability, both within-day (9 AM–2 PM) and between-day (48-h) with samples analysed to determine FiO2 (%) and volume (L·min−1). Coefficient of variation (CV) was calculated for FiO2 and volume for each altitude setting. Mean CV for FiO2 did not exceed 0.42% within-day, 0.49% between-day and 0.81% inter-machine. Volume mean CV did not exceed 0.85% within-day, 0.91% between-day and 1.17% inter-machine. One-sampled t-tests were conducted comparing Hypoxico reference values with collected samples using equivalent FiO2 for each altitude setting with a Bonferroni corrected significance set at p < 0.004. Settings 3.0, 5.5, 8.0, 10.5 and 12.0 all produced significantly different (p < 0.001) FiO2 concentrations than the reference values stated (−0.51, −0.97, −0.72, +0.41 and +0.40%, respectively). Altitude setting and 1-min volume had an inverse relationship. All settings produced a significantly lower (p < 0.001) volume by 21.80 to 35.40 L·min−1 as compared to the company’s claim of 126.6 L·min−1. The Hypoxico Everest Summit II produced a reliable and consistent air feed; however, the manufacturer’s reference values demonstrated poor agreement with machine produced FiO2 and volume. Therefore, it is recommended that athletes, practitioners and researchers self-validate the altitude generator post-warm-up using an accurate oxygen sensor for accuracy and safety purposes.