2007, Piran, Slovenia

Personal protective equipment
REDUCING UNCOMPENSABLE HEAT STRESS IN A BOMB
DISPOSAL (EOD) SUIT: A LABORATORY BASED ASSESSMENT
C. Douglas Thake and Mike J. Price
Coventry University, Coventry, UK
Contact person: d.thake@coventry.ac.uk
INTRODUCTION
Protection against potential blast is essential to the bomb disposal operative. However, the
combination of wearing an Explosive Ordanance Disposal (EOD) suit and consequent
increased metabolic heat production have a negative effect on heat balance of the body and
result in heat storage. During this condition of uncompensable heat stress (UHS), the
progression of heat illness, which is associated with significant physical and psychological
impairment (Cheung et al., 2000) can be rapid, therefore placing the individual at increased
risk. Furthermore, the rate of heating will be augmented during operations in hot compared to
temperate environments. Hence approaches to attenuate heat strain have the potential to
reduce physiological strain and increase safe operating time. Recent developments in this area
include the integration of cooling devices and altered equipment configuration.
The direct assessment of physiological measurements in the field is often impractical
(Hanson, 1999). However, data acquired from laboratory-based simulations are potentially
useful. The current prospective investigation incorporated the development of a laboratorybased
protocol to reflect the activities undertaken by EOD personnel; an assessment of the
physiological strain associated with EOD activities alongside assessing the effectiveness of a
dry ice based cooling device, and a lighter weight trouser designed to optimise thermal
comfort in hot conditions.
METHODS
A protocol was designed that incorporated physical activities commonly performed by EOD
personnel (Figure 1). With local ethical committee approval four subjects (age 30.5 ±10.1 y;
body mass 78.3 ±5.7 kg), including one expert participant used to wearing the EOD suit,
undertook five trials in a randomised cross-over design. These consisted of wearing the full
suit (FS) or a light-weight trouser designed to optimise comfort in hot conditions (SL), both
with (C) and without (NC) a dry ice based cooling system, and not wearing the EOD suit
(NS). Trials were separated by at least 5 days. Baseline measures were made immediately
before and after donning the EOD suit at an ambient temperature ≈25°C. At each trial,
subjects were asked to complete four activity cycles (66:00 min:sec in total; Figure 1) in an
ambient temperature of 40.5 ±1.1°C. The EOD suit was then removed, and recovery measures
made after 15 min. Heart rate (HR; Polar Vantage), rectal temperature (Tcore), skin
temperatures (Tskin; arm, chest, thigh and calf; Ramanathan, 1964) were monitored
throughout. Mean sweat rate was calculated using pre- and post-test nude body mass.
Differential ratings of perceived exertion (Borg, 1970) and thermal strain (Young et al., 1987)
were sought at specified intervals. Psychological tasks consisted of the Stroop test (30
responses in 60 sec) followed by a manual dexterity test (1 min of adjoining nuts and bolts).
In addition subjects were asked to score symptoms of headache, sickness, light-headedness,
mental confusion, tiredness and difficulty breathing on a scale of 0 (none at all) to 3 (severe).
General linear model analysis of variance and, where appropriate, post hoc paired t-tests were
conducted on ranked data. The nonparametric ‘L’ statistic was calculated and significance
determined using a Chi 2 table (Thomas et al., 1999; Research Quarterly for Exercise and
Sport, 70, 11-23).
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