  A laboratory-based hypoxic exercise test, performed on a cycle ergometer, can
be used to predict susceptibility to severe high-altitude illness (SHAI)
through the calculation of a clinicophysiological SHAI score. Our objective was
to design a field-condition test and compare its derived SHAI score and various
physiological parameters, such as peripheral oxygen saturation (SpO2), and
cardiac and ventilatory responses to hypoxia during exercise (HCRe and HVRe,
respectively), to the laboratory test. A group of 43 healthy subjects (15
females and 28 males), with no prior experience at high altitude, performed a
hypoxic cycle ergometer test (simulated altitude of 4,800 m) and step tests (20
cm high step) at 3,000, 4,000, and 4,800 m simulated altitudes. According to
tested altitudes, differences were observed in O2 desaturation, heart rate, and
minute ventilation (p < 0.001), whereas the computed HCRe and HVRe were not
different (p = 0.075 and p = 0.203, respectively). From the linear
relationships between the step test and SHAI scores, we defined a risk zone,
allowing us to evaluate the risk of developing SHAI and take adequate
preventive measures in field conditions, from the calculated step test score
for the given altitude. The predictive value of this new field test remains to
be validated in real high-altitude conditions.
