Electric fans mitigate cardiovascular and thermal strain during extreme heat events (1104.5)

Abstract

Extreme heat events (EHEs) increase mortality rates due to heat related illness and are known to exacerbate underlying health conditions. Current international health guidelines warn against the fan use when ambient temperature exceeds 35°C; however no evidence exists supporting or refuting their use during EHEs. Our aim was to evaluate the critical environmental limits for cardiovascular and thermal strain with (F) and without (NF) a fan (v=4.0 m•s‐1) at an ambient temperature (Ta) of 36°C and 42°C in 4 separate trials. Six males (23.8 ± 3.5 y) sat in a climatic chamber regulated at either 36°C or 42°C while ambient water vapor pressure (Pa) was raised by 0.3 kPa every 7.5 min from 1.6 to 5.6 kPa. Heart rate (HR), esophageal temperature (Tes), and whole body sweat loss (WBSL) were measured. The critical Pa (Pa_crit) at which an upward inflection of HR was observed was significantly higher with F at both 36°C (F: 5.1±0.2 kPa; NF: 3.9±0.4 kPa, P<0.001) and 42°C (F: 4.4±0.4 kPa; NF: 3.2±0.4 kPa; P=0.01). Likewise, the Pa_crit for an upward inflection of Tes was significantly higher with F at 42°C (F: 4.8±0.1 kPa; NF: 4.1±0.4 kPa; P=0.01). However, WBSL was significantly greater with F at 42°C (F: 877±23 g; NF: 540±125 g, P=0.005) and 36°C (F: 391±23 g; NF: 353±32 g, P=0.02). Thus, contrary to current guidelines, fans mitigate cardiovascular and thermal strain at Ta values as high as 42°C, but necessitate a greater fluid intake.Grant Funding Source: Supported by NSERC