Personal protective equipment (PPE) recommended for use in West Africa during the Ebola outbreak increased risk for heat illness, and countermeasures addressing this issue would be valuable.

The purpose of this study was to examine the physiological impact and heat perception of four different personal cooling devices (PCDs) under impermeable PPE during low-intensity exercise in a hot and humid environment using thermal manikin modeling and human testing.

Six healthy male subjects walked on a treadmill in a hot/humid environment (32°C/92% relative humidity [RH]) at three metabolic equivalents (METs) for 60 minutes wearing PPE recommended for use in West Africa and one of four different personal cooling devices (PCDs; PCD1, PCD2, PCD3, and PCD4) or no PCD for control (CON). The same ensembles were tested with thermal manikin modeling software in the same conditions to compare the results.

All PCDs seemed to reduce physiological heat stress characteristics when worn under PPE compared to CON. Both the manikin and human testing provided similar results in core temperature (Tc) and heat sensation (HS) in both magnitude and relationship. While the manikin and human data provided similar skin temperature (Tsk) characterization, Tsk estimation by the manikin seemed to be slightly over-estimated. Weight loss, as estimated by the manikin, was under-estimated compared to the human measurement.

Personal cooling device use in conjunction with impermeable PPE may be advantageous in mitigating physiological and perceptual burdens of heat stress. Evaluation of PCDs worn under PPE can be done effectively via human or manikin testing; however, Tsk may be over-estimated and weight loss may be under-estimated. Thermal manikin testing of PCDs may provide fast and accurate information to persons recommending or using PCDs with PPE.

QuinnT, KimJH, SeoY, CocaA. Comparison of Thermal Manikin Modeling and Human Subjects’ Response During Use of Cooling Devices Under Personal Protective Ensembles in the Heat. Prehosp Disaster Med. 2018;33(3):279–287.

Personal protective equipment (PPE) provides health care workers with a barrier to prevent human contact with viruses like Ebola and potential transmission of the disease. However, PPE can also introduce an additional physiological burden from potentially increased heat stress. This study evaluated the human physiological and subjective responses to continuous light exercise within environmental conditions similar to those in West Africa while wearing 3 different, commonly used PPE ensembles (E1, E2, and E3).

Six healthy individuals were tested in an environmental chamber (32°C, 92% relative humidity) while walking (3 METs, 2.5 mph, 0% incline) on a treadmill for 60 minutes. All subjects wore medical scrubs and PPE items. E1 also had a face shield and fluid-resistant surgical gown; E2 additionally included goggles, coverall, and separate hood; and E3 also contained a highly impermeable coverall, separate hood, and surgical mask cover over the N95 respirator.

Heart rate and core temperature at the end of the exercise were significantly higher for E2 and E3 than for E1. Subjective perceptions of heat and exertion were significantly higher for E2 and E3 than for E1.

Heat stress and PPE training, as well as the implementation of a work-to-rest ratio that avoids dehydration and possible heat stress issues, are recommended. (Disaster Med Public Health Preparedness. 2017;11:580–586)

Experience with the use of personal protective equipment (PPE) ensembles by health care workers responding to the Ebola outbreak in the hot, humid conditions of West Africa has prompted reports of significant issues with heat stress that has resulted in shortened work periods.

A sweating thermal manikin was used to ascertain the time to achievement of a critical core temperature of 39°C while wearing 4 different PPE ensembles similar to those recommended by the World Health Organization and Médecins Sans Frontières (Doctors Without Borders) at 2 different ambient conditions (32°C/92% relative humidity and 26°C/80% relative humidity) compared with a control ensemble.

PPE ensembles that utilized coveralls with moderate to high degrees of impermeability attained the critical core temperature in significantly shorter times than did other ensembles. Encapsulation of the head and neck region resulted in higher model-predicted subjective impressions of heat sensation.

To maximize work capacity and to protect health care workers in the challenging ambient conditions of West Africa, consideration should be given to adjustment of work and rest schedules, improvement of PPE (e.g., using less impermeable and more breathable fabrics that provide the same protection), and the possible use of cooling devices worn simultaneously with PPE. (Disaster Med Public Health Preparedness. 2015;9:536–542)

To determine core temperature (Tc) elevations in hazardous materials (HazMat) technicians wearing level-A fully encapsulated, chemically resistive suits (FECRSs) during training scenarios.

Cross-sectional, observational feasibility study with Institutional Review Board approval.

HazMat training scenarios held during the summer of 1994. Weather conditions included both rainy and sunny days, with a mean ambient temperature of 75.8°F(24.3°C) (range 69–83° F [20.6–28.3°C).

Nine male firefighters participating in training scenarios in the Midwestern United States.

Each volunteer swallowed a capsule containing a Tc sensor developed by the National Aeronautics and Space Administration. The capsule continuously monitored Tc and stored data in an ambulatory recorder worn under the level-A FECRS during training.

Mean age of the volunteers was 34 years, mean weight was 92.6 kg, and average baseline Tc was 36.7°C (97.1°F) (range 35.3–38.2°C [95.5–100°F]). Time in the FECRS averaged 25.4 minutes (range 14–35 minutes). All subjects demonstrated increased Tc while in the suit; the mean Tc increase was 0.8°C (1.4°F) (range 0.2–1.3°C [0.4–2.3°F]). The Tc continued to increase during wet decontamination procedures and after suit removal. Mean heat storage values (ΔTcx LBMx 3.47 kJ) were calculated, and found to be moderately elevated to 3.6 kJ/kg (range 2.1–4.6 kJ/kg).

These observations support the validity and significance of implementing prophylactic measures for firefighters using protective clothing. Simple protective measures include enforced time limitations, hydration, and efforts to minimize heat buildup by avoiding both direct sunlight and unnecessary time encapsulated in the suit.