Life jacket design affects dorsal head and chest exposure, core cooling, and cognition in 10 degrees C water.
OBJECTIVE
Personal floatation devices (PFDs) differ in whether they maintain the head out of the water or allow the dorsum of the head to be immersed. Partial head submersion may hasten systemic cooling, incapacitation, and death in cold water.


METHODS
Six healthy male volunteers (mean age = 26.8 yr; height = 184 cm; weight = 81 kg; body fat = 20%) were immersed in 10 degrees C water for 65 min, or until core temperature = 34 degrees C, under three conditions: PFD#1 maintained the head and upper chest out of the water; PFD#2 allowed the dorsal head and whole body to be immersed; and an insulated drysuit (control) allowed the dorsal head to be immersed. Mental performance tests included: logic reasoning test; Stroop word-color test; digit symbol coding; backward digit span; and paced auditory serial addition test (PASAT).


RESULTS
Core cooling was significantly faster for PFD#2 (2.8 +/- 1.6 degrees C x h(-1)) than for PFD#1 (1.5 +/- 0.7 degrees C x h(-1)) or for the drysuit (0.4 +/- 0.2 degrees C x h(-1)). Although no statistically significant effects on cognitive performance were noted for the individual PFDs and drysuit, when analyzed as a group, four of the tests of cognitive performance (Stroop word-color, digit symbol coding, backward digit span, and PASAT) showed significant correlations between decreasing core temperature to 34 degrees C and diminished cognitive performance.


CONCLUSIONS
Performance in more complicated mental tasks was adversely affected as core temperature decreased to 34 degrees C. The PFD that kept the head and upper chest out of the water preserved body heat and mental performance better than the PFD that produced horizontal flotation.
Lockhart
Tamara L
TL
Laboratory for Exercise and Environmental Medicine, Health, Leisure and Human Performance Research Institute, University of Manitoba, Winnipeg, Canada.
Jamieson
Christopher P
CP
Steinman
Alan M
AM
Giesbrecht
Gordon G
GG
D000059:Accidents; D000328:Adult; D001831:Body Temperature; D003072:Cognition Disorders / Q000209:etiology; D003080:Cold Temperature / Q000009:adverse effects*; D004867:Equipment Design; D006804:Ergonomics; D006257:Head; D006801:Humans; D007035:Hypothermia / Q000517:prevention & control*; D008297:Male; D011481:Protective Clothing; D013534:Survival; D013909:Thorax; D014867:Water
D014867:Water