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Heat stress effects for USAF anti-G suits with and without a counter-pressure vest.
Aviat Space Environ Med. 2002 May; 73(5):456-9.AS

Abstract

BACKGROUND

Aircrew have reported increased heat stress when wearing the USAF Combined Advanced Technology Enhanced Design G-Ensemble or COMBAT EDGE (CE). The perceived thermal burden has been attributed to the fact that CE includes an inflatable counter-pressure vest to ease the work of positive pressure breathing during G (PBG). This study compared the heat load of CE with that of the standard USAF anti-G system (STD) without the vest, and measured heat stress effects on G-tolerance in both suits.

METHODS

This study had 12 subjects (6 of them aircrew) who participated. Simulated preflight thermal stress (20 min walking at 35 degrees C with 85% relative humidity and radiant heat) was followed by return to a cooler environment (21 degrees C). G-tolerance and subjective stress levels were determined on the human centrifuge before and after the heat stress. Body weight, rectal and skin temperatures, and blood parameters were also assessed.

RESULTS

Baseline relaxed tolerance for +Gz gradual onset runs (GORs) were (mean +/- SD) 7.6 +/- 1.3 G for CE and 7.1 +/- 0.8 G for STD (p < 0.05). Maximal rectal temperature following heat stress peaked at 38.1 +/- 0.4 degrees C for both CE and STD, and mean nude weight loss was 1.10 +/- 0.24 kg for both. Relaxed GOR tolerances after heat stress were 7.1 +/- 1.3 for CE and 6.3 +/- 0.9 for STD (p < 0.01). The heat stress significantly reduced G tolerance for both CE and STD (p < 0.01).

CONCLUSIONS

Simulated preflight activity in hot conditions revealed no significant difference between CE and STD with regard to maximal core and skin temperature elevations or dehydration levels. CE supported a significantly higher baseline relaxed G-tolerance than STD, an advantage that persisted after heat stress and dehydration.

Authors+Show Affiliations

Air Force Research Laboratory, Biodynamics and Protection Division, Brooks Air Force Base, Texas 78235-5104, USA. ulf.balldin@brooks.af.milNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

12014604

Citation

Balldin, Ulf I., et al. "Heat Stress Effects for USAF anti-G Suits With and Without a Counter-pressure Vest." Aviation, Space, and Environmental Medicine, vol. 73, no. 5, 2002, pp. 456-9.
Balldin UI, O'Connor RR, Werchan PM, et al. Heat stress effects for USAF anti-G suits with and without a counter-pressure vest. Aviat Space Environ Med. 2002;73(5):456-9.
Balldin, U. I., O'Connor, R. R., Werchan, P. M., Isdahl, W. M., Demitry, P. F., Stork, R. L., & Morgan, T. R. (2002). Heat stress effects for USAF anti-G suits with and without a counter-pressure vest. Aviation, Space, and Environmental Medicine, 73(5), 456-9.
Balldin UI, et al. Heat Stress Effects for USAF anti-G Suits With and Without a Counter-pressure Vest. Aviat Space Environ Med. 2002;73(5):456-9. PubMed PMID: 12014604.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Heat stress effects for USAF anti-G suits with and without a counter-pressure vest. AU - Balldin,Ulf I, AU - O'Connor,Robert R, AU - Werchan,Paul M, AU - Isdahl,Wayne M, AU - Demitry,Peter F, AU - Stork,Roger L, AU - Morgan,Thomas R, PY - 2002/5/17/pubmed PY - 2002/11/26/medline PY - 2002/5/17/entrez SP - 456 EP - 9 JF - Aviation, space, and environmental medicine JO - Aviat Space Environ Med VL - 73 IS - 5 N2 - BACKGROUND: Aircrew have reported increased heat stress when wearing the USAF Combined Advanced Technology Enhanced Design G-Ensemble or COMBAT EDGE (CE). The perceived thermal burden has been attributed to the fact that CE includes an inflatable counter-pressure vest to ease the work of positive pressure breathing during G (PBG). This study compared the heat load of CE with that of the standard USAF anti-G system (STD) without the vest, and measured heat stress effects on G-tolerance in both suits. METHODS: This study had 12 subjects (6 of them aircrew) who participated. Simulated preflight thermal stress (20 min walking at 35 degrees C with 85% relative humidity and radiant heat) was followed by return to a cooler environment (21 degrees C). G-tolerance and subjective stress levels were determined on the human centrifuge before and after the heat stress. Body weight, rectal and skin temperatures, and blood parameters were also assessed. RESULTS: Baseline relaxed tolerance for +Gz gradual onset runs (GORs) were (mean +/- SD) 7.6 +/- 1.3 G for CE and 7.1 +/- 0.8 G for STD (p < 0.05). Maximal rectal temperature following heat stress peaked at 38.1 +/- 0.4 degrees C for both CE and STD, and mean nude weight loss was 1.10 +/- 0.24 kg for both. Relaxed GOR tolerances after heat stress were 7.1 +/- 1.3 for CE and 6.3 +/- 0.9 for STD (p < 0.01). The heat stress significantly reduced G tolerance for both CE and STD (p < 0.01). CONCLUSIONS: Simulated preflight activity in hot conditions revealed no significant difference between CE and STD with regard to maximal core and skin temperature elevations or dehydration levels. CE supported a significantly higher baseline relaxed G-tolerance than STD, an advantage that persisted after heat stress and dehydration. SN - 0095-6562 UR - https://www.unboundmedicine.com/medline/citation/12014604/Heat_stress_effects_for_USAF_anti_G_suits_with_and_without_a_counter_pressure_vest_ L2 - https://medlineplus.gov/heatillness.html DB - PRIME DP - Unbound Medicine ER -