Decompression to altitude: assumptions, experimental evidence, and future directions

Area of Science:

• Aerospace Medicine
• Physiology
• Biochemistry

Background:

• Hypobaric and hyperbaric exposures share physiological similarities, offering insights into decompression stress.
• Decompression sickness (DCS) is known in aviators and ground simulations but not in orbital spacewalks (extravehicular activities - EVAs).
• The influence of gravity on nitrogen washout and skeletal muscle activity in decompression outcomes remains unclear.

Purpose of the Study:

• To investigate the relationship between muscle activity, decompression, and microgravity.
• To review unresolved topics concerning decompression sickness (DCS) and skeletal muscle exercise.
• To provide an overview of factors influencing altitude decompression.

Main Methods:

• Comparative analysis of hypobaric and hyperbaric exposures.
• Review of experimental evidence on skeletal muscle activity and bubble formation.
• Synthesis of existing literature on decompression physiology and microgravity effects.

Main Results:

• Skeletal muscle exercise/activity plays a role in bubble formation and DCS occurrence, with dualistic effects.
• No cases of DCS have been reported during actual EVAs in microgravity.
• Uncertainty exists regarding gravity's influence on decompression outcomes via nitrogen washout or muscle activity.

Conclusions:

• Further research is needed to understand the interplay of muscle activity, gravity, and decompression.
• Addressing these uncertainties is crucial for future human space exploration, including lunar and Martian missions.
• Optimizing EVA protocols requires a deeper understanding of decompression physiology in microgravity.