Cool water foot immersion, skin wetting and fan use as low-cost, at home cooling strategies for older adults during heat waves
The efficacy of foot immersion alone or combined with fan use and skin wetting as a low-cost cooling strategy for older adults during hot humid and hot dry heatwaves
The University of Sydney
41 participants
May 12, 2022
Interventional
Conditions
Summary
Our laboratory has been conducting research in collaboration with the Montreal Heart Institute, Montreal, CA. examining the effect of fan use with and without skin wetting on thermal and cardiovascular strain in older adults with and without CAD during a 3-hour simulated heatwave. These data demonstrate that fan use during a hot and humid heatwave (38°C, 60% humidity) mitigates the rise in core temperature and heart rate compared to no fan use. During a hot and dry heatwave (45°C, 10% humidity), wetting the skin with 18°C water mitigates the rise in core temperature and heart rate compared to no cooling intervention. This study is is the second phase of identifying low-cost cooling strategies for older adults who are healthy and have heart disease to use in home during heat waves. In this study we aim to investigate whether there is an additional benefit of cold-water foot immersion when combined with fan use during a simulated hot and humid (38°C, 60% humidity) heat wave. A secondary aim of this study is to investigate whether there is an additional benefit of cold-water foot immersion when combined with skin wetting during a simulated hot and dry (45°C, 10% humidity) heatwave.
Eligibility
Inclusion Criteria8
- Healthy Cohort (The University of Sydney, Sydney AU):
- + years
- Non-smoker or ex-smoker (quit greater than 2 y prior)
- Otherwise healthy
- No difficult understanding or speaking English
- CAD Cohort (Montreal Heart Institute, Montreal CA):
- Age between 50 and 80 years.
- History of angiographic coronary artery disease (greater than or equal to 70% arterial diameter narrowing of at least one major epicardial coronary artery) and/or prior coronary revascularization and/or documented prior acute coronary syndrome and/or stable angina and/or perfusion defect during exercise or pharmacological stress testing.
Exclusion Criteria23
- Healthy Cohort (The University of Sydney, Sydney AU):
- Body mass index greater than or equal to 40 kg/m2.
- Uncontrolled hypertension (greater than 180/110 mmHg).
- Uncontrolled diabetes or severe complications of diabetes.
- Evidence of severe renal disease, liver disease, cerebrovascular disease, pulmonary disease, endocrine abnormalities, cognitive impairment, psychiatric disorder, substance abuse, degenerative neurological condition or any other medical condition deemed to pose risk during the study visits.
- Medication known to cause hyper- or hypo-hidrosis (except those taken for hypertension).
- Currently taking any of the following medications: strong anticholinergics, anti-Parkinson's agents, epinephrine, beta-blockers.
- Evidence of current fluid and electrolyte disorders
- Abnormal thyroid function
- Arrhythmias at rest or during cardiac stress test
- Significant cognitive impairment, psychiatric disorder, degenerative neurological condition
- Any other medical condition deemed to pose risk during the proposed testing or experiments, or preclude them from completing the screening stress test or following pre-trial instructions.
- CAD Cohort (Montreal Heart Institute, Montreal, CA):
- CAD-related hospitalisation or changes in cardiac medications or change in pattern of angina less than 3 months prior to enrolment.
- Body mass index greater than or equal to 40 kg/m2.
- Hormonal replacement therapy (less than 1 year) for female participants.
- Uncontrolled hypertension (greater than 180/110 mmHg).
- Uncontrolled diabetes or severe complications of diabetes.
- Recent (less than 3 months) coronary bypass surgery.
- Ejection fraction less than 40% and/or clinical evidence/history of heart failure.
- Significant valve heart disease.
- Resting ECG abnormalities interfering with observation of ST segment changes during testing.
- Evidence of severe renal disease, liver disease, cerebrovascular disease, pulmonary disease, endocrine abnormalities, cognitive impairment, psychiatric disorder, substance abuse, degenerative neurological condition or any other medical condition deemed to pose risk during the study visits.
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Interventions
Each participant will take part in 6 experimental trials consisting of 3 hour of simulated heatwave exposure randomised within each heat wave condition: Hot and dry heat wave: 1. No cooling (comparator) 2. Foot immersion 3. Foot immersion + skin wetting Hot and humid heat wave: 1. No cooling (comparator) 2. Foot immersion 3. Foot immersion + electric fan In each exposure, they will be asked to sit in a regulated environmental chamber at a temperature of either 45ºC, 10% RH (hot and dry heat wave) or 38ºC, 60% RH (hot and humid heat wave). Participants will be provided water to replenish fluid (i.e., sweat) losses equivalent to 1ml/kg of body weight every 20 min throughout the trial. Each trial will be separated by at least 72 h. Foot immersion: in all foot immersion trials, participants will place their feet in cool 18ºC water inside a 40L bucket up to their calf for 20 min, followed by 10 min out of the water, and repeated throughout the trial. In our previous study, we identified that skin wetting is the best cooling intervention in hot and dry heat waves, while electric fan is the best cooling intervention for hot and humid heatwaves. Therefore, the following combination interventions will also be studied: Foot immersion + skin wetting: in the foot immersion + skin wetting trials, foot immersion will be combined with wetting the skin using a spray bottle every 5 min intervals. Each 5 min throughout the protocol the researcher will spray the skin on the face, neck, upper and lower arms and upper and lower legs (except when inside the bucket) with tap water (~18ºC). A total of 18 sprays (1.2g water per spray) will be applied (1 x forehead; 1 x posterior neck; 1 x upper and 1 x lower of both arms; 3 x upper and 3 x lower of both legs) when feet are out of the water; and a total of 12 sprays will be applied (excluding lower sites of both legs) when feet are immersed in the water. Foot immersion + electric fan: in the foot immersion + electric fan trials, foot immersion will be combined with an 18" electric fan placed in 1.0m in front of the participant and directly blowing on them at a speed of 4.0m/s.
Locations(1)
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ACTRN12622000367741