Decompression Sickness Risk in Parachutist Dispatchers Exposed Repeatedly to High Altitude.

Area of Science:

• Aerospace Medicine
• Physiology
• Occupational Health

Background:

• Severe decompression sickness (DCS) incidents in military parachutist dispatchers at high altitudes necessitated a review of safety guidelines.
• Previous exposure limits may not adequately address the risks associated with dispatcher duties at extreme altitudes.

Purpose of the Study:

• To investigate the residual risks of DCS for dispatchers performing high-altitude parachute operations.
• To explore the feasibility of conducting multiple exposures within a single duty period without compromising safety.

Main Methods:

• Fifteen healthy men (ages 20-50) underwent two repeated hypobaric decompression profiles simulating dispatcher tasks.
• Profiles included ascents to 25,000 ft for 60-90 minutes and 22,000 ft for 90 minutes, with denitrogenation at 15,000 ft and 1-hour ground breaks between exposures.

Main Results:

• Five cases of limb pain DCS occurred at 25,000 ft, with initial onset at 29 minutes. Minor joint discomfort ('niggles') was also noted.
• No DCS or significant niggles were observed at 22,000 ft.
• Bubble loads were heavier and earlier at 25,000 ft, particularly in older subjects, while repeat exposures at 22,000 ft resulted in lighter, later bubble loads.

Conclusions:

• Parachutist dispatchers are at significant risk of DCS at 25,000 ft due to high exertion levels.
• Repeated ascents to 22,000 ft appear feasible within a duty period if ground break times are short.
• Older dispatchers with right-to-left shunts face increased risk of microbubble arterialization at high altitudes.