TcPO2 changes are more pronounced than SpO2 changes during simulated altitude changes in a hypobaric oxygen chamber: a nonrandomized controlled trial

Hypoxia is a significant risk factor of hypertension. However, no studies have used transcutaneous tissue partial pressure of oxygen (TcPO2) and partial pressure of carbon dioxide (TcPCO2) monitors to measure the respective partial pressures in healthy individuals. Oxygen saturation (SpO2) is often used for traditional monitoring of vital signs. This study investigated the changes in TcPO2 and SpO2 values during rapid changes in altitude. The trial was registered at ClinicalTrials.gov (registration no. NCT06076057). Healthy adult volunteers were instructed to sit vertically in a hypobaric oxygen chamber, which ascended from 0 m to 2500 m at a uniform speed within 10 min. The Danish Radiometer TCM4 was used to measure TcPO2 and TcPCO2 with the ventral side of the upper arm as the measurement site. The Shenzhen Kerokan P0D-1 W pulse oximeter was used to measure heart rate and SpO2, with values recorded once every 500 m. Altogether, 49 healthy volunteers were recruited between March 2023 and August 2023. With increasing altitude, TcPO2 and SpO2 decreased significantly (P < 0.01). During the ascent from 0 m, TcPO2 began to change statistically at 500 m (P < 0.05), whereas SpO2 began to change statistically at 1000 m (P < 0.05). At the same altitude, the difference in TcPO2 was greater than the difference in SpO2. At 1000 m, there were statistically significant changes in TcPO2 and SpO2 (P < 0.001). At altitudes >500 m, statistical significance was identified between TcPO2 in both sexes (P < 0.05). Statistical significance in TcPCO2 and heart rate was observed at the different elevations (P < 0.05). In acutely changing low-pressure hypoxic environments, TcPO2 changed more dramatically than SpO2.