Altitude Decompression Sickness Risk and Physical Activity During Exposure.

Area of Science:

• Aerospace Medicine
• Physiology
• High-Altitude Research

Background:

• Previous studies identified a linear link between peak oxygen consumption (Vo2) and decompression sickness (DCS) incidence at high altitudes.
• The current study investigated if this relationship persists at a lower altitude exposure.

Purpose of the Study:

• To determine if the established linear relationship between oxygen consumption and DCS incidence holds true at a lower altitude.
• To assess DCS risk in subjects exposed to 22,500 ft while seated and nonambulatory.

Main Methods:

• Twenty male subjects were exposed to 22,500 ft (6.1 psi) for 4 hours breathing 100% oxygen.
• Subjects remained seated and nonambulatory throughout the exposure, with intermittent echo-imaging.
• Peak 1-minute oxygen consumption (Vo2) and activity levels were recorded and compared to prior research with higher activity levels.

Main Results:

• No cases of decompression sickness (DCS) or venous gas emboli were observed in any subjects.
• A strong linear relationship (r > 0.99) was confirmed between DCS incidence and the level of physical activity, consistent with previous findings.

Conclusions:

• Findings suggest that physiological safety margins may be extended or pre-breathing time reduced for high-altitude operations with minimal physical activity.
• The results may help explain differential DCS risk between observers and trainees in altitude chambers.
• Quantified activity levels could enhance current altitude DCS risk prediction models.