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

Background Hypoxia is a significant risk factor of hypertension. However, no studies have used transcutaneous tissue partial pressure of oxygen (TcPO 2 ) and partial pressure of carbon dioxide (TcPCO 2 ) monitors to measure the respective partial pressures in healthy individuals. Oxygen saturation (SpO 2 ) is often used for traditional monitoring of vital signs. This study investigated the changes in TcPO 2 and SpO 2 values during rapid changes in altitude. The trial was registered at ClinicalTrials.gov (registration no. NCT06076057). Methods 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 TcPO 2 and TcPCO 2 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 SpO 2 , with values recorded once every 500 m. Results Altogether, 49 healthy volunteers were recruited between March 2023 and August 2023. With increasing altitude, TcPO 2 and SpO 2 decreased significantly ( P < 0.01). During the ascent from 0 m, TcPO 2 began to change statistically at 500 m ( P < 0.05), whereas SpO 2 began to change statistically at 1000 m ( P < 0.05). At the same altitude, the difference in TcPO 2 was greater than the difference in SpO 2 . At 1000 m, there were statistically significant changes in TcPO 2 and SpO 2 ( P < 0.001). At altitudes >500 m, statistical significance was identified between TcPO 2 in both sexes ( P < 0.05). Statistical significance in TcPCO 2 and heart rate was observed at the different elevations ( P < 0.05). Conclusion In acutely changing low-pressure hypoxic environments, TcPO 2 changed more dramatically than SpO 2 .