Decompression sickness during simulated extravehicular activity: ambulation vs. non-ambulation

Area of Science:

• Space medicine
• Physiology
• Decompression sickness research

Background:

• Extravehicular activity (EVA) in spaceflight primarily uses upper body movements due to lower body anchoring.
• The adynamic model simulates this by restricting lower body activity in earthbound studies.
• Decompression sickness (DCS) risk assessment is crucial for astronaut safety.

Purpose of the Study:

• To compare DCS symptom incidence between ambulatory and non-ambulatory high-altitude exposures.
• To determine if non-ambulatory (adynamic model) exposures provide analogous DCS risk estimates to ambulatory exposures.
• To validate the use of ambulatory data for simulated EVA DCS risk assessment.

Main Methods:

• Retrospective analysis of DCS symptoms from 2010 ambulatory and 330 non-ambulatory high-altitude exposures.
• Comparison of overall DCS incidence, joint-pain DCS, and location-specific DCS between the two exposure types.

Main Results:

• No significant difference in overall DCS or joint-pain DCS incidence between ambulatory (49%, 40%) and non-ambulatory (53%, 36%) exposures.
• Lower-body joint pain DCS was significantly higher in ambulatory exposures (28%) vs. non-ambulatory (18%).
• Non-ambulatory exposures had higher rates of non-joint-pain DCS (17%) and upper-body-only joint pain (18%) compared to ambulatory (9%, 11%).

Conclusions:

• Lower-body, weight-bearing activity redirects joint-pain DCS from the upper to the lower body without changing total DCS incidence.
• Ambulatory exposure data is a valid analogue for non-ambulatory activity in simulated EVA DCS risk studies.
• Findings support the use of ambulatory data for risk assessment in simulated extravehicular activities.