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Trial registered on ANZCTR


Registration number
ACTRN12622000367741
Ethics application status
Approved
Date submitted
17/02/2022
Date registered
2/03/2022
Date last updated
26/05/2024
Date data sharing statement initially provided
2/03/2022
Type of registration
Prospectively registered

Titles & IDs
Public title
Cool water foot immersion, skin wetting and fan use as low-cost, at home cooling strategies for older adults during heat waves
Scientific title
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
Secondary ID [1] 306342 0
Nil Known
Universal Trial Number (UTN)
U1111-1274-0058
Trial acronym
OACS2: Older adults and cooling strategies, 2
Linked study record
This study is a follow up study to our previously registered studies: Request ID, ACTRN12619000938101 and ACTRN12618001913268

Health condition
Health condition(s) or problem(s) studied:
Heat related cardiovascular strain 325137 0
Heat related thermal strain 325138 0
Heat related changes in thermal perceptions (i.e., comfort and sensation) 325139 0
Condition category
Condition code
Injuries and Accidents 322542 322542 0 0
Other injuries and accidents
Cardiovascular 322543 322543 0 0
Normal development and function of the cardiovascular system
Public Health 322544 322544 0 0
Other public health

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
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.
Intervention code [1] 322773 0
Prevention
Comparator / control treatment
The comparator is a the no cooling condition in which participants will receive no cooling throughout the trial.
Control group
Active

Outcomes
Primary outcome [1] 330339 0
Core body temperature measure via a flexible rectal thermistor

The participant will be asked to insert a flexible sensor 10-12cm into their rectum. A marker is placed on the sensor using sterile surgical tape. The participant will insert the sensor until the tape reaches their anal surface. The insertion of the sensor may cause some mild discomfort and minor irritation; however, this sensation soon passes. The participant will receive proper instruction regarding the placement of the sensor to ensure their safety and comfort. The participant will be responsible for the insertion of this sensor. It will provide the researcher with an indication of the amount of heat stored in their body and will be tracked throughout the entirety of each experimental session
Timepoint [1] 330339 0
Difference between pre- to post- 3 h heat exposure
Primary outcome [2] 330340 0
Heart Rate

Heart rate will also be measured continuously during the screening and experimental visits via 12 lead ECG for safety. A polar monitor will also be used for increased sample rate for data collection purposes.
Timepoint [2] 330340 0
Difference between pre- to post- 3 h heat exposure.
Secondary outcome [1] 405863 0
Skin temperature

Skin temperature will be measured continuously during the study visits by taping 4 small sensors to the skin surface on the right side at the upper arm, chest, thigh and upper calf.
Timepoint [1] 405863 0
Difference between pre- to post- 3 h heat exposure.
Secondary outcome [2] 405864 0
Blood pressure

Blood pressure will be measured during the screening visit, as well as every 10 minutes during the study visits by automated auscultation of the brachial artery.
Timepoint [2] 405864 0
Difference between pre- to post- 3h heat exposure.
Secondary outcome [3] 405865 0
Cardiac output (MHI only)

Will be measured prior to and at the end of the heat exposure with an inert gas rebreathing technique where inert gas is inhaled and continuously monitored from a re-breathing bag.
Timepoint [3] 405865 0
Difference between pre- to post- 3 h heat exposure.
Secondary outcome [4] 405866 0
Skin blood flow

Skin blood flow will be measured continuously during the study visits on the forearm by laser-Doppler flowmetry.
Timepoint [4] 405866 0
Difference between pre- to post- 3 h heat exposure
Secondary outcome [5] 405867 0
Local sweat rate

Local sweat rate will be measured continuously during the study visits using a plastic capsule attached to the skin surface and ventilated with dry air on the upper left back.
Timepoint [5] 405867 0
Difference between pre- to post- 3h heat exposure.
Secondary outcome [6] 405868 0
Whole body sweat rate

Participants will provide a nude weight (in private) before and immediately after the heatwave exposure on a calibrated digital scale. Whole-body sweat rate will be calculated as the difference in the pre and post weight, divided by the time between recorded weigh-ins.
Timepoint [6] 405868 0
Difference between pre- to post- 3h heat exposure.
Secondary outcome [7] 405869 0
Perceptual changes in thermal discomfort

Thermal discomfort will be measured at baseline and every 20 minutes during the 3 h heat exposure protocol using a visual analog scale.
Timepoint [7] 405869 0
Difference between pre- to post- 3h heat exposure.
Secondary outcome [8] 405870 0
Cognitive function (USYD only)

Cognitive function will be measured at baseline and following the trial using the Stroop Colour Word Test.
Timepoint [8] 405870 0
Difference between pre- to post- 3h heat exposure.
Secondary outcome [9] 406675 0
Perceptual changes in thermal sensation
Timepoint [9] 406675 0
Thermal sensation will be measured at baseline and every 20 minutes during the 3 h heat exposure protocol using a visual analog scale.

Eligibility
Key inclusion criteria
Healthy Cohort (The University of Sydney, Sydney AU):
- 60+ 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.
Minimum age
60 Years
Maximum age
No limit
Sex
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Healthy Cohort (The University of Sydney, Sydney AU):
- Body mass index greater than or equal to 40 kg/m2.
- Hormonal replacement therapy.
- 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 a beta-blocker.
- Evidence of current fluid and electrolyte disorders
- Current diagnosis of anemia
- Abnormal thyroid function
- Arrhythmias at rest or during cardiac stress test
- Significant cognitive impairment, psychiatric disorder, substance abuse, 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.

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.

Study design
Purpose of the study
Prevention
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Participants will be randomised via a central computer database in a balanced order of males and females. Randomisation will occur separately for each cohort (i.e., Healthy and CAD).
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Open (masking not used)
Who is / are masked / blinded?



Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis
The sample size calculation is based on the primary outcome of a change in rectal temperature from baseline to the end of the 3-hour simulated hot and humid heatwave (38°C, 60% humidity) between no cooling intervention and cold water foot immersion alone. The expected mean difference and standard deviation for the change in rectal temperature was calculated from the data collected as part of phase 1 of this project. Based on these data, rectal temperature was (mean ± SD) 0.1 ± 0.2°C lower in the fan condition compared to no intervention during exposure to hot and humid heatwave conditions. Assuming a similar difference in rectal temperature (0.1 ± 0.2°C) between cold water foot immersion alone and no intervention and using a paired t-test, 34 participants are needed to detect this difference with a ß of 0.8 and a two-tailed a of 0.05.

A secondary objective of this study is to compare the change in heart rate between cold water foot immersion alone and no intervention during a simulated hot and dry heatwave (45°C and 10% humidity). Data collected as part of phase 1 of this project demonstrate that the change in heart rate is 5 ± 5 bpm lower in the skin wetting condition compared to no cooling intervention. Assuming a similar difference in heart rate (5 ± 5 bpm) between cold water foot immersion alone and no intervention and using a paired t-test, 10 participants are needed to detect this difference with a ß of 0.8 and a two-tailed a of 0.05.

Since participants will be invited to partake in all study visits for both heatwave types (i.e., hot humid and hot dry), a total of 34 participants will be required to be adequately powered for our research questions of interest. To account for a potential 20% loss to follow up, we expect to recruit up to 41 participants. Of note, this represents the total sample size to be recruited between the University of Sydney and our secondary site at the Montreal Heart Institute with an approximately 50/50 split (N=20 at each site).

Primary analysis:
During the hot and humid heat wave condition, the change in core temperature from baseline to end of the 3 hour heatwave exposure will be compared between no cooling intervention and cold water foot immersion using a paired t-test.

Secondary analysis:
During the hot and humid heat wave condition, the change in core temperature and the change in heart rate from baseline to end of the 3 hour heatwave exposure will be compared between the cold-water foot immersion alone and the cold-water foot immersion + fan (hot humid) conditions using paired t-tests.

During the hot dry heatwave condition, one-way repeated measures ANOVA models will be used to compare the end of trial change in core temperature or heart rate from baseline between the control, cold water foot immersion along and the cod water foot immersion + skin wetting conditions. Contrasts under these models will allow for the following two comparisons:
1. Control vs cold water foot immersion alone;
2. Cold water food immersion alone vs cold water foot immersion + skin wetting.

Tertiary analysis:
A one-way repeated measures ANOVA will be used to compare the end of trial change in all other variables from baseline between the control, cold water foot immersion only, and fan use + cold water foot immersion conditions during the 38°C, 60% humidity heatwave. The same model will be employed for the 45°C, 10% humidity heatwave for the control, cold water foot immersion and cold water foot immersion + skin wetting conditions.



Recruitment
Recruitment status
Recruiting
Date of first participant enrolment
Anticipated
1/04/2022
Actual
12/05/2022
Date of last participant enrolment
Anticipated
1/12/2024
Actual
Date of last data collection
Anticipated
31/12/2024
Actual
Sample size
Target
41
Accrual to date
9
Final
Recruitment in Australia
Recruitment state(s)
NSW
Recruitment postcode(s) [1] 36575 0
2001 - Sydney
Recruitment postcode(s) [2] 36574 0
2006 - The University Of Sydney
Recruitment outside Australia
Country [1] 24538 0
Canada
State/province [1] 24538 0
Montreal

Funding & Sponsors
Funding source category [1] 310697 0
Government body
Name [1] 310697 0
National Health and Medical Research Council
Country [1] 310697 0
Australia
Primary sponsor type
University
Name
The University of Sydney
Address
The University of Sydney
Camperdown
NSW
2006
Country
Australia
Secondary sponsor category [1] 311917 0
Hospital
Name [1] 311917 0
Montreal Heart Institute
Address [1] 311917 0
5000 Rue Belanger
Montreal, QC H1T 1C8, CA
Country [1] 311917 0
Canada

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 310280 0
The University of Sydney Human Research Ethics Committee
Ethics committee address [1] 310280 0
Research Integrity and Ethics Administration
Research Portfolio
Level 3, F23 Administration Building
The University of Sydney
Camperdown, NSW
2006
Ethics committee country [1] 310280 0
Australia
Date submitted for ethics approval [1] 310280 0
24/09/2021
Approval date [1] 310280 0
04/02/2022
Ethics approval number [1] 310280 0
2021/962
Ethics committee name [2] 310282 0
Human Ethics at the University of Montreal
Ethics committee address [2] 310282 0
5000, Bélanger street
Montréal H1T 1C8
Québec
Ethics committee country [2] 310282 0
Canada
Date submitted for ethics approval [2] 310282 0
21/10/2021
Approval date [2] 310282 0
09/12/2021
Ethics approval number [2] 310282 0
2022-3060

Summary
Brief 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.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 117106 0
Prof Ollie Jay
Address 117106 0
Thermal Ergonomics Laboratory, Room 901
Susan Wakil Health Building
The University of Sydney
Camperdown, NSW 2006
Country 117106 0
Australia
Phone 117106 0
+61 2 93519328
Fax 117106 0
Email 117106 0
ollie.jay@sydney.edu.au
Contact person for public queries
Name 117107 0
Prof Ollie Jay
Address 117107 0
Thermal Ergonomics Laboratory, Room 901
Susan Wakil Health Building
The University of Sydney
Camperdown, NSW 2006
Country 117107 0
Australia
Phone 117107 0
+61 2 93519328
Fax 117107 0
Email 117107 0
ollie.jay@sydney.edu.au
Contact person for scientific queries
Name 117108 0
Prof Ollie Jay
Address 117108 0
Thermal Ergonomics Laboratory, Room 901
Susan Wakil Health Building
The University of Sydney
Camperdown, NSW 2006
Country 117108 0
Australia
Phone 117108 0
+61 2 93519328
Fax 117108 0
Email 117108 0
ollie.jay@sydney.edu.au

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
Yes
What data in particular will be shared?
De-identified individual participant data will be available in published study results.
When will data be available (start and end dates)?
Immediately following publication - no end date.
Available to whom?
Within published journals and case by case at the discretion of the primary sponsor.
Available for what types of analyses?
Meta-analysis
How or where can data be obtained?
Access subject to approvals by the Principal Investigator with a requirement to sign data access agreements. Access can be obtained by emailing: ollie.jay@sydney.edu.au


What supporting documents are/will be available?

No Supporting Document Provided



Results publications and other study-related documents

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No documents have been uploaded by study researchers.

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