Voluntary Isocapnic Hyperpnea in Hypoxia to Mitigate Acute Mountain Sickness

Blood gas analysis was conducted using a Radiometer™ ABL90 FLEX (Radiometer Medical ApS, Brønshøj, Denmark). The following parameters were assessed: hydrogen ion concentration (pH), bicarbonate ion concentration (HCO₃-), partial pressure of oxygen (pO₂), and partial pressure of carbon dioxide (pCO₂). All measurements were taken in duplicate using 45 µL capillary blood samples collected from the fingertip. Analyses were performed immediately following collection by a trained technician following the manufacturer's instructions. Peripheral blood pressure was measured digitally using the OMRON M2 monitor (OMRON Healthcare, Kyoto, Japan). SpO₂ was estimated at the fingertip using a pulse oximeter (NONIN Onyx Vantage 9590, Nonin Medical, Inc., Plymouth, MN, USA). The 2018 Lake Louise AMS Score questionnaire was presented to the participants before the experiment for familiarization and then used to evaluate symptoms of AMS based on a combination of subjective self-reports and clinical findings. All the measurements were performed by qualified and experienced specialists. The participants were blinded to the obtained results, except for the 2018 Lake Louise AMS Score, which was self-reported.