TY - JOUR
T1 - Decompression Sickness Risk in Parachutist Dispatchers Exposed Repeatedly to High Altitude
AU - Connolly, Desmond M.
AU - D’Oyly, Timothy J.
AU - Harridge, Stephen D.R.
AU - Smith, Thomas G.
AU - Lee, Vivienne M.
N1 - Funding Information:
This work was funded by the UK Ministry of Defence under the Aircrew Systems Research Project. The authors would like to thank the many volunteers, subjects, investigators, colleagues, collaborators and advisers, too numerous to mention individually, who have helped make these demanding experiments not just possible, but even enjoyable and rewarding, at a particularly challenging time due to the pandemic. Besides the risk of DCS, in many cases their support has incurred considerable personal inconvenience, but has been freely and enthusiastically offered and has proven invaluable.
Publisher Copyright:
© the Aerospace Medical Association, Alexandria, VA.
PY - 2023/9/1
Y1 - 2023/9/1
N2 - INTRODUCTION: Occurrences of severe decompression sickness (DCS) in military parachutist dispatchers at 25,000 ft (7620 m) prompted revision of exposure guidelines for high altitude parachuting. This study investigated residual risks to dispatchers and explored the potential for safely conducting repeat exposures in a single duty period. METHODS: In this study, 15 healthy men, ages 20–50 yr, undertook 2 profiles of repeated hypobaric chamber decompression conducting activities representative of dispatcher duties. Phase 1 comprised two ascents to 25,000 ft (7620 m) for 60 and then 90 min. Phase 2 included three ascents first to 25,000 ft for 60 min, followed by two ascents to 22,000 ft (6706 m) for 90 min. Denitrogenation was undertaken at 15,000 ft (4572 m) with successive ascents separated by 1-h air breaks at ground level. RESULTS: At 25,000 ft (7620 m), five cases of limb (knee) pain DCS developed, the earliest at 29 min. Additionally, multiple minor knee “niggles” occurred with activity but disappeared when seated at rest. No DCS and few niggles occurred at 22,000 ft (6706 m). Early, heavy, and sustained bubble loads were common at 25,000 ft, particularly in older subjects, but lighter and later loads followed repeat exposure, especially at 22,000 ft. DISCUSSION: Parachutist dispatchers are at high risk of DCS at 25,000 ft (7620 m) commensurate with their heavy level of exertion. However, the potential exists for repeated safe ascents to 22,000 ft (6706 m), in the same duty period, if turn-around times breathing air at ground level are brief. Older dispatchers (>40 yr) with functional right-to-left (intracardiac or pulmonary) vascular shunts will be at risk of arterialization of microbubbles.
AB - INTRODUCTION: Occurrences of severe decompression sickness (DCS) in military parachutist dispatchers at 25,000 ft (7620 m) prompted revision of exposure guidelines for high altitude parachuting. This study investigated residual risks to dispatchers and explored the potential for safely conducting repeat exposures in a single duty period. METHODS: In this study, 15 healthy men, ages 20–50 yr, undertook 2 profiles of repeated hypobaric chamber decompression conducting activities representative of dispatcher duties. Phase 1 comprised two ascents to 25,000 ft (7620 m) for 60 and then 90 min. Phase 2 included three ascents first to 25,000 ft for 60 min, followed by two ascents to 22,000 ft (6706 m) for 90 min. Denitrogenation was undertaken at 15,000 ft (4572 m) with successive ascents separated by 1-h air breaks at ground level. RESULTS: At 25,000 ft (7620 m), five cases of limb (knee) pain DCS developed, the earliest at 29 min. Additionally, multiple minor knee “niggles” occurred with activity but disappeared when seated at rest. No DCS and few niggles occurred at 22,000 ft (6706 m). Early, heavy, and sustained bubble loads were common at 25,000 ft, particularly in older subjects, but lighter and later loads followed repeat exposure, especially at 22,000 ft. DISCUSSION: Parachutist dispatchers are at high risk of DCS at 25,000 ft (7620 m) commensurate with their heavy level of exertion. However, the potential exists for repeated safe ascents to 22,000 ft (6706 m), in the same duty period, if turn-around times breathing air at ground level are brief. Older dispatchers (>40 yr) with functional right-to-left (intracardiac or pulmonary) vascular shunts will be at risk of arterialization of microbubbles.
KW - decompression sickness (DCS)
KW - high-altitude parachuting
KW - parachutist dispatcher
KW - venous gas emboli (VGE)
UR - http://www.scopus.com/inward/record.url?scp=85168255052&partnerID=8YFLogxK
U2 - 10.3357/AMHP.6231.2023
DO - 10.3357/AMHP.6231.2023
M3 - Article
C2 - 37587625
AN - SCOPUS:85168255052
SN - 2375-6314
VL - 94
SP - 666
EP - 677
JO - Aerospace medicine and human performance
JF - Aerospace medicine and human performance
IS - 9
ER -