Blood biochemical and cellular changes during decompression and simulated extravehicular activity

Area of Science:

• Space Medicine
• Human Physiology
• Biochemistry

Background:

• Extravehicular activity (EVA) requires prebreathing protocols to prevent decompression sickness.
• Understanding blood parameter changes during simulated EVA is crucial for astronaut safety.
• Venous gas emboli (VGE) formation susceptibility varies among individuals.

Purpose of the Study:

• To assess blood biochemical and cellular responses to a simulated 6-hour EVA decompression schedule.
• To compare blood parameters between subjects susceptible and resistant to VGE formation.
• To determine the clinical significance of observed blood parameter changes.

Main Methods:

• Human subjects underwent a 6-hour oxygen prebreathing protocol followed by simulated EVA with exercise at 29.6 kPa.
• Blood samples were collected pre- and post-exposure.
• Analysis included white blood cell count, prothrombin time, total bilirubin, triglycerides, VLDL cholesterol, and blood urea nitrogen.

Main Results:

• No significant differences in blood parameters were found between VGE-susceptible and VGE-resistant subjects.
• Statistically significant changes (P < 0.05) included increased white blood cells, prothrombin time, and total bilirubin.
• Decreases were observed in triglycerides, very-low-density lipoprotein cholesterol, and blood urea nitrogen.
• All observed changes were small in magnitude and remained within normal clinical ranges.

Conclusions:

• The simulated EVA decompression protocol did not induce clinically significant blood alterations.
• The findings suggest that this decompression schedule is unlikely to pose a blood-related risk to astronauts during EVA.
• Individual susceptibility to VGE formation did not correlate with significant blood parameter deviations.