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. 2022 Dec 29;20(1):612.
doi: 10.3390/ijerph20010612.

Thermophysiological and Perceptual Responses of Amateur Healthcare Workers: Impacts of Ambient Condition, Inner-Garment Insulation and Personal Cooling Strategy

Yingying Zhao  1 , Meng Su  1 , Xin Meng  1 , Jiying Liu  1 , Faming Wang  2
Affiliations

Thermophysiological and Perceptual Responses of Amateur Healthcare Workers: Impacts of Ambient Condition, Inner-Garment Insulation and Personal Cooling Strategy

Yingying Zhao et al. Int J Environ Res Public Health. .

Abstract

While personal protective equipment (PPE) protects healthcare workers from viruses, it also increases the risk of heat stress. In this study, the effects of environmental heat stress, the insulation of the PPE inner-garment layer, and the personal cooling strategy on the physiological and perceptual responses of PPE-clad young college students were evaluated. Three levels of wet bulb globe temperatures (WBGT = 15 °C, 28 °C, and 32 °C) and two types of inner garments (0.37 clo and 0.75 clo) were chosen for this study. In an uncompensable heat stress environment (WBGT = 32 °C), the effects of two commercially available personal cooling systems, including a ventilation cooling system (VCS) and an ice pack cooling system (ICS) on the heat strain mitigation of PPE-clad participants were also assessed. At WBGT = 15 °C with 0.75 clo inner garments, mean skin temperatures were stabilized at 31.2 °C, Hskin was 60-65%, and HR was about 75.5 bpm, indicating that the working scenario was on the cooler side. At WBGT = 28 °C, Tskin plateaued at approximately 34.7 °C, and the participants reported "hot" thermal sensations. The insulation reduction in inner garments from 0.75 clo to 0.37 clo did not significantly improve the physiological thermal comfort of the participants. At WBGT = 32 °C, Tskin was maintained at 35.2-35.7 °C, Hskin was nearly 90% RH, Tcore exceeded 37.1 °C, and the mean HR was 91.9 bpm. These conditions indicated that such a working scenario was uncompensable, and personal cooling to mitigate heat stress was required. Relative to that in NCS (no cooling), the mean skin temperatures in ICS and VCS were reduced by 0.61 °C and 0.22 °C, respectively, and the heart rates were decreased by 10.7 and 8.5 bpm, respectively. Perceptual responses in ICS and VCS improved significantly throughout the entire field trials, with VCS outperforming ICS in the individual cooling effect.

Keywords: COVID-19; healthcare workers; personal cooling; personal protective equipment; thermal comfort.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Pictures of the experiment site. (a) Location of the testing site. (b) Layout of the experimental site.
Figure 2
Figure 2
Outdoor weather data acquired during the experimental period from 1 March to 31 August 2022.
Figure 3
Figure 3
Schematic showing details of experimental procedures.
Figure 4
Figure 4
Skin temperature responses under four testing scenarios (i.e., 15 °C–0.75 clo, 28 °C–0.75 clo, 28 °C–0.37 clo, 32 °C–0.37 clo; testing scenarios in the figures are presented as A–B, where A represents the WBGT value and B represents the insulation of the inner garments used in the testing). (a) Mean skin temperatures. (b) Local mean skin temperatures at 0–15 min. (c) Local mean skin temperatures at 90–105 min.
Figure 5
Figure 5
Skin relative humidity under the four testing scenarios (i.e., 15 °C–0.75 clo, 28 °C–0.75 clo, 28 °C–0.37 clo, 32 °C–0.37 clo; testing scenarios in the figures are presented as A–B, where A represents the WBGT value and B represents the insulation of the inner garments used in the testing). (a) Mean skin relative humidity. (b) Local mean skin relative humidity at 0–15 min; (c) Local mean skin relative humidity at 90–105 min.
Figure 6
Figure 6
Temporal variation of Tcore and HR under four different working conditions (i.e., 15 °C–0.75 clo, 28 °C–0.75 clo, 28 °C–0.37 clo, 32 °C–0.37 clo; testing scenarios in the figures are presented as A–B, where A represents the WBGT value and B represents the insulation of the inner garments used in the testing). (a) Mean core temperature. (b) Heart rate.
Figure 7
Figure 7
Temporal variations of thermal sensation votes, thermal comfort votes, humidity sensation votes, and ratings of perceived exertion under four different working conditions (i.e., 15 °C–0.75 clo, 28 °C–0.75 clo, 28 °C–0.37 clo, and 32 °C–0.37 clo; testing scenarios in the figures are presented as A–B, where A represents the WBGT value, and B represents the insulation of the inner garments used in the testing). (a) Thermal sensation votes. (b) Thermal comfort votes. (c) Humid sensation votes. (d) Borg’s rating of perceived exertion. (e) Thermal expectation votes.
Figure 8
Figure 8
Correlation between physiological parameters and WBGT (or perceptual responses). (a) Correlation heatmap of physiological parameters and WBGT. (b) Pearson correlation analysis between subjective evaluation and physiological parameters.
Figure 9
Figure 9
Temporal variations in physiological parameters in NCS, ICS, and VCS. (a) Mean skin temperature. (b) Mean skin relative humidity. (c) Mean chest skin temperature. (d) Mean chest skin relative humidity. (e) Mean core temperature. (f) Mean heart rate. **, p < 0.001 (NCS vs. ICS); ##, p < 0.001 (NCS vs. VCS); &&, p < 0.001 (ICS vs. VCS).
Figure 10
Figure 10
Comprehensive subjective evaluation voting in NCS, ICS, and VCS. (a) Thermal sensation votes. (b) Thermal comfort votes. (c) Humid sensation votes. (d) Borg’s rating of perceived exertion. *, p < 0.05, **, p < 0.001 (NCS vs. ICS); ##, p < 0.001 (NCS vs. VCS); &&, p < 0.001 (ICS vs. VCS).
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