Hemoglobin Oxygen Saturation with Mild Hypoxia and Microgravity
Abstract
Introduction
Exposure to microgravity (μG) and the initial recovery phase following μG, particularly in conjunction with mild hypoxia, may elevate the alveolar-arterial oxygen (O2) partial pressure gradient.
Methods
In this study, four male astronauts from STS-69 (1995) and four from STS-72 (1996) underwent a sequential hypoxic challenge on Earth. They breathed mixtures of nitrogen and varying oxygen levels (18.0%, 14.9%, 13.5%, 12.9%, and 12.2%) for 4 minutes. The 18.0% O2 mixture at sea level yielded an inspired O2 partial pressure (PIo2) of 127 mmHg. This same PIo2 was replicated by inhaling 26.5% O2 at 527 mmHg during several days of μG aboard the Space Shuttle. Hemoglobin (Hb) oxygen saturation was monitored using a Novametrix CO2SMO Model 7100 via finger pulse oximetry (Spo2, %). A total of 12 in-flight measurements were recorded, with additional assessments on the day of return (R+0) and two days post-return (R+2). Linear mixed effects models were used to evaluate changes in Spo2 during and after μG exposure.
Results
Astronaut Spo2 levels at baseline, R+0, and R+2 did not significantly differ from in-flight levels, maintaining around 97% with a PIo2 of 127 mmHg. Additionally, no notable differences were observed in Spo2 levels between baseline and R+0 or R+2 during the hypoxic challenge.
Conclusions
The various physiological adaptations associated with μG, as well as the recovery process, did not impact astronaut Spo2 levels during hypoxic exposure.Conkin J, Wessel JH III, Norcross JR, Bekdash OS, Abercromby AFJ, Koslovsky MD, Gernhardt ML. Hemoglobin oxygen AT-527 saturation with mild hypoxia and microgravity. Aerosp Med Hum Perform. 2017; 88(6):527-534.