A Systematic Review and Meta-Analysis of Decompression Sickness in Altitude Physiological Training

Area of Science:

• Aerospace Medicine
• Physiology
• Occupational Health

Background:

• Decompression sickness (DCS) is a risk in altitude physiological training (APT).
• Understanding DCS prevalence across different APT programs is crucial for safety.
• Previous studies have reported varying DCS rates in APT.

Purpose of the Study:

• To review DCS cases from NASA's Johnson Space Center (JSC) APT program.
• To contextualize JSC findings within the broader prevalence of DCS in other APT centers.
• To perform a meta-analysis of DCS prevalence across multiple APT profiles.

Main Methods:

• Reviewed JSC records (1999-2016) and 14 publications on DCS in APT (1968-2004).
• Conducted a meta-analysis of 15 APT profiles, encompassing 488 DCS cases and 385,116 exposures.
• Utilized meta-regression to assess the relationship between exposure parameters and DCS probability, accounting for study heterogeneity.

Main Results:

• JSC in-house review identified 7 DCS cases (6 Type I, 1 Type II).
• NASA student pooled DCS prevalence was 0.44 cases/1000 exposures, lower than the 1.44 cases/1000 from published APT profiles.
• Overall pooled DCS prevalence was 1.16 cases/1000 exposures, with significant heterogeneity. Denitrogenation time, exposure pressure, and duration were associated with DCS risk.

Conclusions:

• Overall DCS prevalence in APT is low, but significant variability exists between training profiles.
• NASA APT profiles demonstrated a lower pooled DCS prevalence compared to the overall average.
• Further research into student and test-specific factors may elucidate the heterogeneity in DCS prevalence.