Estimating core temperature with external devices after exertional heat stress in thermal protective clothing.

BACKGROUND: Temperature measurement is important for emergency medical services (EMS) providers when identifying and treating heat illness or infection. Direct measures of body core temperature (T(c)) are often expensive (ingestible capsules) or impractical (rectal probes) in the field. Multiple devices for estimating T(c) have been adopted by EMS providers, with little understanding of the agreement between these devices and T(c). OBJECTIVE: To examine the agreement between the results of five external thermometers and T(c) after subjects experienced physical exertion while wearing protective clothing. METHODS: Fifty firefighters completed treadmill walking in thermal protective clothing in a hot environment. Measurements of core, temporal, tympanic, forehead, and skin temperatures were obtained during a 20-minute recovery period simulating emergency incident rehabilitation. RESULTS: The mean bias of external thermometers ranged from -1.31°C to -3.28°C when compared with T(c) and exceeded the predetermined clinical cutoff of ±0.5°C from T(c). The 95% limits of agreement ranged from 2.75°C to 5.00°C. CONCLUSIONS: External measuring devices failed to accurately predict T(c) in hyperthermic individuals following exertion. Confidence intervals around the bias were too large to allow for reasonable estimation of T(c). EMS providers should exercise caution when using any of these temperature estimation techniques.

The effect of hyperhydration on physiological and perceived strain during treadmill exercise in personal protective equipment.

Work in personal protective equipment (PPE) impairs thermoregulation causing cardiovascular stress, increased core body temperature, and hypohydration. We examined the effect of pretreating first responders performing treadmill exercise in PPE with an infusion of normal saline on physiological and perceptual strain. Ten (eight males, two females) euhydrated subjects performed treadmill exercise on two occasions wearing a chemical resistant coverall, air purifying respirator, butyl gloves, and heavy boots. During the hyperhydration session, normal saline was rapidly infused through an arm vein prior to donning PPE. Exercise duration and maximum core temperature did not differ between euhydrated and hyperhydrated conditions. Perceptual strain index (PeSI) was higher than physiological strain index (PhSI) in the euhydrated condition (P = 0.002) but neither index differed between the control and experimental conditions. Intravenous hyperhydration did not reduce physiological stress, increase exercise, or influence perceptual strain time when compared to the euhydrated condition in moderately fit individuals.