Performance of emergency underwater breathing systems in cool (25 degrees C) and cold (12 degrees C) water.
BACKGROUND
The shortfall between breath-hold time on cold-water immersion and the time required to make an underwater escape from a helicopter provides the rationale for emergency underwater breathing systems (EUBS) for passengers flying over cold water. This study compared three types of EUBS: a compressed gas system (CG); a rebreather system (RB); and a hybrid system (H).


METHODS
Each EUBS was examined during water deployment (W(dep)) and over 90 s in cool (25 degrees C) and cold water (12 degrees C) immersion to the neck (Imm) and submersion (Subm). Subjects wore standardized clothing, including dry suit. Measures included: W(dep) time, stay time (Imm and Subm), dyspnea rating, O2 and CO2 remaining in rebreather bags [H and RB (partial pressure mmHg)], and gas volume used (CG).


RESULTS
Mean data show W(dep) was slowest in the H (17.7 s) compared to the RB (10.0 s) and CG (8.1 s). Stay time was greatest in the H (90.0 s) compared to the RB (68.3 s) and CG (87.0 s); stay time in CG was also greater than RB. Dyspnea ratings were greater in RB trials (6.5 cm) compared to the CG (2.4 cm) and H (1.9 cm). Across devices, stay time in cold water was shorter during submersion than immersion (85.9 s vs. 70.1 s). During submersion stay time was shorter in cold compared to cool water (12 degrees C: 62.8 s; 25 degrees C: 77.5 s).


CONCLUSIONS
The data suggest that the CG and H devices outperformed the RB device, but the H device required longer to deploy.
Department of Sport and Exercise Science, University of Portsmouth, Portsmouth, Hampshire, UK. martin.barwood@port.ac.uk
Martin J
MJ
Barwood
Jo
J
Corbett
Susan
S
Coleshaw
Geoff
G
Long
Michael J
MJ
Tipton
D000328:Adult; D003080:Cold Temperature; D004242:Diving; D004867:Equipment Design; D005260:Female; D006801:Humans; D007101:Immersion; D008297:Male; D011482:Protective Devices; D012121:Respiration, Artificial / Q000295:instrumentation*; D013534:Survival; D055815:Young Adult