A fan-attached jacket worn in an environment exceeding body temperature suppresses an increase in core temperature

Practical Considerations for Using Personal Cooling Garments for Heat Stress Management in Physically Demanding Occupations: A Systematic Review and Meta-Analysis Using Realist Evaluation

INTRODUCTION

Due to rising temperature extremes, workplaces are seeking new solutions, such as using personal cooling garments (PCG) to mitigate and manage workplace heat exposure. This systematic review sought to assess the physiological and perceptual effects of PCGs on workers in standard work clothing performing moderate-to-heavy intensity tasks in hot environments.

METHODS

A peer-reviewed search strategy was conducted in MEDLINE, Embase, CINAHL, Scopus, Global Health, and Business Source Complete with no language or time limits. A meta-analysis using a realist evaluation framework was then performed to evaluate the effectiveness of the PCGs.

RESULTS

Thirty-three studies with 764 participants (98% male; average 21 ± 34 participants per study), conducted primarily in a laboratory setting (76%) were included. The studies were 193 ± 190 min in duration and consisted of a moderate-to-heavy work effort of 3.3 ± 1.0 METs in hot ambient conditions (temperature: 35.9 ± 3.3°C, 51.4 ± 12.1% relative humidity, wet bulb globe temperature [WBGT] 31.2 ± 2.6°C). The PCGs (n = 67) facilitated heat exchange through conduction (n = 39), evaporation (n = 4), convection (n = 2), radiation (n = 2), or hybrid combinations (n = 20). Conductive and hybrid PCGs offered the greatest thermoregulatory benefit, whereby core temperature (Tc) and heart rate (HR) reductions were consistently observed (Conductive: Tc: -0.3°C, HR: -12 bpm; Hybrid: Tc:-0.2°C, HR: -10 bpm), while PCGs directed at enhancing evaporative and radiative heat exchange had no or minimal effect on the physiological outcomes assessed (i.e., TC < 0.1°C, HR: < 0.7 bpm).

CONCLUSION

While the PCGs had a positive overall effect, conductive options offered the most consistent benefit to workers. WBGT, clothing insulation, and duration of wear significantly affected some physiological and perceptual outcomes.

Upper- vs. Whole-Body Cooling During Exercise with Thermal Protective Clothing in the Heat

INTRODUCTION: Firefighters operating in hot environments face challenges from protective garments that restrict heat dissipation, resulting in increased core temperature, thermal discomfort, and performance decline. Cooling vests represent a viable solution. The study aim was to compare effectiveness of the same amount of cooling power to the upper body (UB) or whole body (WB) in alleviating thermoregulatory and physiological stress, enhancing cognitive function, and reducing ratings of thermal discomfort and exertion, during 60 min of exercise in a hot environment (40°C, 40% relative humidity) while wearing firefighter turnout gear.METHODS: Eight healthy individuals (27.5 ± 3 y) participated in three conditions with either no cooling (Control) or active cooling with a liquid perfused shirt (UB cooling), or with a liquid perfused shirt and pants (WB cooling). In each trial, subjects performed three sets of 15 min of stepping (20 steps ⋅ min-1) and 5 min of rest.RESULTS: Both cooling strategies were beneficial compared to having no cooling at all. Subjects could only complete two exercise bouts during Control, but they completed all three bouts with active cooling. WB cooling provided an advantage over UB cooling for core and skin temperature, and thermal comfort and sensation. The advantage in minimizing the increase in core temperature was only evident during the third exercise bout.DISCUSSION: Active cooling is advantageous under these conditions. WB cooling provided some benefits vs UB cooling during heavy intensity exercise; however, it is uncertain whether these benefits would be observed during light-to-moderate exercise, which more likely reflects an actual firefighting scenario.Mansouri F, Talebian Nia M, Villar R, Cornish SM, Giesbrecht GG. Upper- vs. whole-body cooling during exercise with thermal protective clothing in the heat. Aerosp Med Hum Perform. 2024; 95(9):659-666.

The fan cooling vest use reduces thermal and perceptual strain during outdoor exercise in the heat on a sunny summer day

The fan cooling vest is coming into very common use by Japanese outdoor manual workers. We examined that to what extent using this vest reduces thermal strain and perception during outdoor exercise in the heat on a sunny summer day. Ten male baseball players in high school conducted two baseball training sessions for 2-h with (VEST) or without (CON) a commercially available fan cooling vest on a baseball uniform. These sessions commenced at 10 a.m. on separate days in early August. The fan airflow rate attached the vest was 62 L·s-1. Neither ambient temperature (Mean ± SD: VEST 31.9 ± 0.2°C; CON 31.8 ± 0.7°C), wet-bulb globe temperature (VEST 31.2 ± 0.4°C; CON 31.4 ± 0.5°C) nor solar radiation (VEST 1008 ± 136 W·m-2; CON 1042 ± 66 W·m-2) was different between trials. Mean skin temperature (VEST 34.5 ± 1.1°C; CON 35.1 ± 1.4°C), infrared tympanic temperature (VEST 38.9 ± 0.9°C; CON 39.2 ± 1.2°C), heart rate (VEST 127 ± 31 bpm; CON 139 ± 33 bpm), body heat storage (VEST 140 ± 34 W·m-2; CON 160 ± 22 W·m-2), thermal sensation (- 4-4: VEST 0 ± 2; CON 3 ± 1) and rating of perceived exertion (6-20: VEST 11 ± 2; CON 14 ± 2) were lower in VEST than CON (all P < 0.05). Total distance measured with a global positioning system (VEST 3704 ± 293 m; CON 3936 ± 501 m) and body fluid variables were not different between trials. This study indicates that the fan cooling vest use can reduce thermal strain and perception during outdoor exercise in the heat on a sunny summer day. Cooling with this vest would be effective to mitigate thermal risks and perceptual stress in athletes and sports participants under such settings.

Mitigating heat effects in the workplace with a ventilation jacket: Simulations of the whole-body and local human thermophysiological response with a sweating thermal manikin in a warm-dry environment

Climate change is increasingly affecting human well-being and will inevitably impact on occupational sectors in terms of costs, productivity, workers' health and injuries. Among the cooling garment developed to reduce heat strain, the ventilation jacket could be considered for possible use in workplaces, as it is wearable without limiting the user's mobility and autonomy. In this study, simulations with a sweating manikin are carried out to investigate the effects of a short-sleeved ventilation jacket on human thermophysiological responses in a warm-dry scenario. Simulations were performed in a climatic chamber (air temperature = 30.1 °C; air velocity = 0.29 m/s; relative humidity = 30.0 %), considering two constant levels of metabolic rate M (M1 = 2.4 MET; M2 = 3.2 MET), a sequence of these two (Work), and three levels of fan velocities (lf = 0; lf=2; lf=4). The results revealed a more evident impact on the mean skin temperature (Tsk) compared to the rectal temperature (Tre), with significant decreases (compared to fan-off) at all M levels, for Tsk from the beginning and for Tre from the 61st minute. Skin temperatures of the torso zones decreased significantly (compared to fan-off) at all M levels, and a greater drop was registered for the Back. The fans at the highest level (lf=4) were significantly effective in improving whole-body and local thermal sensations when compared to fan-off, at all M levels. At the intermediate level (lf=2), the statistical significance varied with thermal zone, M and time interval considered. The results of the simulations also showed that the Lower Torso needs to be monitored at M2 level, as the drop in skin temperature could lead to local overcooling and thermal discomfort. Simulations showed the potential effectiveness of the ventilation jacket, but human trials are needed to verify its cooling power in real working conditions.

Recovery with a fan-cooling jacket after exposure to high solar radiation during exercise in hot outdoor environments

The study aimed to investigate the effect of body cooling with a fan-cooling jacket on body temperature responses during recovery after exercise when exposed to high solar radiation in a hot outdoor environment. Nine males cycled using ergometer until their rectal temperature increased to 38.50 °C in hot outdoor environments, followed by body cooling recovery in warm indoor environments. Subjects repeatedly performed the cycling exercise protocol, which consisted of one set of 5 min at a load of 1.5 watt/kg body weight and 15 min at a load of 2.0 watt/kg body weight at 60 rpm. Body cooling recovery consisted of cold water ingestion (10°C: CON) or cold water ingestion + wearing a fan-cooling jacket (FAN) until the rectal temperature decreased to 37.75°C. The time for the rectal temperature to reach 38.5°C did not differ between the two trials. The rate of decrease in rectal temperature at recovery tended to be higher in FAN trial than in CON trial (P = 0.082). The rate of decrease in tympanic temperature was higher in FAN trials than in CON trials (P = 0.002). The rate of decrease in mean skin temperature at the first 20 min of recovery was higher in FAN than in CON trial (P = 0.013). Body cooling recovery with a fan-cooling jacket in addition to cold water ingestion may be effective in reducing elevated tympanic and skin temperatures after exercise in the heat under a clear sky, but may be difficult to decrease rectal temperature.

Partial cooling of the upper body with a water-cooled vest in an environment exceeding body temperature

OBJECTIVES

To evaluate the efficacy of water-cooled clothing that continuously cools restricted body areas to suppress body temperature increase as an anti-heatstroke measure for workers in hot environments that exceed body temperature.

METHODS

Ten healthy men were placed in Room A (air temperature: 25°C, relative humidity: 50%) for 15 min. They were then transferred to Room B (air temperature: 40°C, relative humidity: 50%), where they rested for 10 min, then put on cooling clothing, and again rested for 15 min (the control group rested for 25 min). They then performed intense ergometer exercise for 40 min at 40% maximal oxygen consumption after which they rested for 10 min. The three trial conditions were CON (long-sleeved summer work clothes), VEST (cooling vest), and P-VEST (partial cooling vest). In VEST and P-VEST, water-cooled clothing continuously recirculated with 10°C water was used to cool the upper body. In P-VEST, only the neck, axillae, and heart areas were in contact with the cooled clothing. The measured indices were the rectal, esophageal, and external auditory canal temperatures; heart rate; estimated sweat volume; and subjective evaluations.

RESULTS

Compared with the CON condition, the rectal, esophageal, and external auditory canal temperatures and the heart rate were significantly lower and the subjective indices were decreased in the VEST and P-VEST conditions.

CONCLUSIONS

Partial cooling showed a body cooling effect similar to that of whole upper body cooling. Partial body cooling promoted the heat dissipation, suggesting that partial cooling is efficient for maintaining body cooling in hot environments.

Application of tight-fitting half-facepiece breath-response powered air-purifying respirator for internal body cooling in occupational environment

In dust-generating scenarios in occupational environments, it is important to take measures to prevent not only pneumoconiosis, but also heatstroke. The aim of this study was to verify whether using a tight-fitting half-facepiece breath-response powered air-purifying respirator (PAPR) in combination with a self-produced cooling device could abate the deep body temperature while performing activities. We conducted a crossover study involving 10 subjects. The subjects were subjected to three conditions: wearing a PAPR equipped with a cooling device, PAPR, or a replaceable particulate respirator. During the experiment, the rectal temperature of the subjects was measured, along with the temperature near the PAPR inlet in container with the cooling device when the PAPR equipped with the cooling device was worn. The subjects rested in a cold chamber set at a dry-bulb temperature of 28°C and relative humidity of 45% for 20 min. Then, they moved to a hot chamber set to a dry-bulb temperature of 36°C (with the same relative humidity) in 5 min and exercised on a cycle ergometer for 30 min. After that, the subjects moved to the cold chamber for 5 min and rested for 20 min. Notably, the air inhaled by the subjects wearing PAPR equipped with the cooling device was approximately 10°C cooler than the ambient air. Furthermore, 35 min after the initiation of the experiment (after the middle of the exercise period), the rectal temperature of the participants wearing the PAPR equipped with the cooling device was lower than of those wearing PAPR or replaceable particulate respirators (p <0.05). Thus, we could deduce that the self-produced cooling device was useful in abating deep body temperature. PAPR is useful for its potential applications in hot occupational environments and can save lives in working environments where heat stress can result in major medical complications.