None listed
Conditions
Brief summary
In Australia and globally, mean yearly temperatures and heatwaves are on the rise, causing elevated morbidity and mortality rates. It is typically the elderly, poor, and socially isolated who suffer most. Often, these groups lack access to air conditioning, whereas less privileged groups have started using air conditioning more regularly, causing the electricity demand during hot weather periods to increase faster than what existing infrastructure can supply. This mismatch causes regular power failures during heatwaves, which deprive life-saving electricity to those who truly need it. Clearly, alternatives to air conditioning are required. While many cooling alternatives exist, most have never been objectively tested under heatwave conditions. This lack of evidence is detrimental and leads to the spread of misinformation. For example, many major health organizations, including the World Health Organization (WHO), currently advise against the use of electric fans in hot conditions. On the contrary, a recent (2012) Cochrane review concluded that no evidence whatsoever currently exists in the literature supporting or refuting the use of electric fans during heat waves. Following-on, we recently (2015) published a study in the Journal of the American Medical Association demonstrating fan use was better than no fan use for young healthy adults in humid environments at 36°C and 42°C; both conditions at which fan use is commonly discouraged. From a theoretical standpoint, electric fans should be effective in hot and humid conditions because they help increase sweating efficiency, i.e. the amount of sweat that we produce which actually contributes to heat loss. Unlike hot humid conditions, in very-hot and dry conditions, sweating efficiency may be at 100% and therefore fan use may not be beneficial as the increased air speed (when air temperature is above skin temperature) would increase heat gain from the environment through convection without any supplying any additional evaporative heat loss. Therefore, the purpose of this study will be to objectively test the effectiveness of electric fan use for cooling healthy adults during heatwaves in two heatwave conditions (very-hot-and-dry and hot-and-humid). We hypothesize that in very-hot-and-dry conditions, electric fan use will make people hotter, more uncomfortable, increase their cardiovascular strain and increase their rate of dehydration, whereas in the hot-and-humid conditions, fan use will cool people, make them more comfortable and lower their cardiovascular strain at the cost of a slightly elevated sweat rate.
Interventions
Two target heatwave conditions will be tested: ~46degC with 10% relative humidity and ~40degC with 50% relative humidity. All participants will be exposed to both conditions two times: once with an electric fan for cooling and once without (control trial). All participants will complete four experimental trials in total.
For each of the four experimental trials, participants will arrive at the laboratory, be instrumented in temperate (~22degC) conditions outside of the climatic chamber, have th
Two target heatwave conditions will be tested: ~46degC with 10% relative humidity and ~40degC with 50% relative humidity. All participants will be exposed to both conditions two times: once with an electric fan for cooling and once without (control trial). All participants will complete four experimental trials in total. For each of the four experimental trials, participants will arrive at the laboratory, be instrumented in temperate (~22degC) conditions outside of the climatic chamber, have their pre-exposure body weight measured, then will enter the climatic chamber set to one of the two environmental conditions, where they will sit passively for 2 hours before re-measuring their body mass, then exiting the climatic chamber to be de-instrumented. In all four trials, participants will be given 250 ml of cool (~22degC) tap water, at 30, 60 and 90 min of exposure (750 ml total water consumption throughout the entire two-hour exposure). In the conditions using an electric fan, a common 44.5 cm diameter standing floor fan will be placed 1.25 meters in front of the participants and placed on the “high” setting, eliciting an air speed of approximately 2.0 meters per second. The fan will be turned on immediately following the participants assuming their seated position within the climatic chamber and will remain on throughout the 2-hour exposure. For safety purposes, as well as to ensure the participant remains seated throughout the 2 hour exposure and the exact experimental protocol is followed, one member of the research team will remain inside the climatic chamber with the participant at all times, while a second research team member will remain outside of the climate chamber, in order to provide assistance, in case it is needed. At least 24 hours will separate all experimental trials and all four experimental trials will be completed within a one-month period, in order to minimize seasonal variations in physiological responses. Only data from participants who have completed all four experimental trials will be included. In the event of a participant starting data collection but being unable or unwilling to complete data collection, their de-identified data will be kept with the rest of the study data, but not included in the analysis, and another participant will be recruited to replace them in order to ensure an adequate sample size. In order to minimize participant dropout, all participants will have the experimental procedures and measurement equipment explained to them thoroughly prior to testing in order to minimize participants being caught off-guard/ unprepared for the discomforts and inconveniences associated with this type of research.
Sponsors
Associate Professor Ollie Jay
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Prevention
Masking
Open (masking not used)
Eligibility
Sex/Gender
Male
Age
18 Years to 40 Years
Healthy volunteers
Yes
Inclusion criteria
Healthy young adult males who are healthy (no self-reported history of respiratory, metabolic, cardiovascular, blood pressure disease, or of diabetes and not currently on any medication related to these conditions). Non-smokers.
Exclusion criteria
Females (due to differences in thermoregulatory responses owing to hormonal variations across the menstrual cycle), those older than 40 or younger than 18, anyone with metabolic, cardiovascular or autonomic disorders. Anyone currently taking prescription medication.
Outcome results
None listed