Heat Waves and the Elderly - Cooling Modalities

Study Overview
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Brief Summary
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The purpose of this study is to assess how well cooling modalities work in reducing cardiovascular stress of the elderly to heat wave conditions

Detailed Description
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Heat waves are lethal and cause a disproportionate number of deaths in the elderly relative to any other age group. Such deaths are primarily cardiovascular, not hyperthermia itself, in origin. The central hypothesis of this work is that cardiovascular stress during heat wave conditions in the elderly can be reduced by applying low-energy cooling modalities. Comprehensive cardiovascular and thermal responses in the elderly will be evaluated during exposure to two prolonged heat wave conditions: hot and humid (replicating the 1995 Chicago heat wave), very hot and dry (replicating the 2018 Los Angeles heat wave). With each of these heat wave conditions individuals will be exposed to the following cooling modalities: no cooling (control), water spray, fan use, and fan use plus water spray.

Official Title
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Heat Waves in the Elderly: Reducing Thermal and Cardiovascular Consequences

Conditions
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Aging, Hyperthermia

Intervention / Treatment
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* Other: Water Spray
* Other: Fan
* Other: Water Spray and Fan
* Other: Control


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: 65 years of age or older Free of any significant underlying medical problems based upon a detailed medical history and physical exam Exclusion Criteria: Known heart disease Other chronic medical conditions requiring regular medical therapy including cancer, diabetes, uncontrolled hypertension, and uncontrolled hypercholesterolemia etc; Abnormality detected on routine screening suggestive of provokable ischemia or previously undetected cardiac disease or resting left bundle branch block on screening electrocardiogram. Current smokers, as well as individuals who regularly smoked within the past 3 years Subject with a body mass index ≥31 kg/m2 Pregnant individuals

Ages Eligible for Study
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Minimum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: The investigators will conduct a randomized crossover design study. Older individuals will be exposed to one of two heat wave conditions (Very hot and dry or hot and humid). For each heat wave condition the individual will receive one of the following cooling strategies, with each cooling strategy applied on a different day: A) a control trial, B) skin wetting only trial, C) fan only trial, and D) a combination of skin wetting with a fan trial. Thus, to complete the trial for a selected heat wave condition (e.g., either very hot and dry or hot and humid) four experimental visits will be required - one visit for each cooling strategy.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Very hot and dry<br>Subjects will be exposed to 3 hours in a climate chamber set to approximately 47 deg C and 15% relative humidity, which reflects a very hot and dry heat wave condition similar to the 2018 Los Angeles heat wave. Four visits will be required to complete this arm, with each visit a different cooling modality applied. | Other: Water Spray<br>* Participants will receive water spraying on their body throughout the climate chamber exposure.<br>Other: Fan<br>* Participants will be exposed to a fan throughout the climate chamber exposure.<br>Other: Water Spray and Fan<br>* Participants will receive both water spraying and a fan throughout the climate chamber exposure.<br>Other: Control<br>* Participants will NOT receive either water spray or a fan exposure.<br>|
| Experimental: Hot and humid<br>Subjects will be exposed to 3 hours in a climate chamber set to approximately 41 deg C and 40% relative humidity, which reflects hot and humid heat wave similar to the 1995 Chicago heat wave. Four visits will be required to complete this arm, with each visit a different cooling modality applied. | Other: Water Spray<br>* Participants will receive water spraying on their body throughout the climate chamber exposure.<br>Other: Fan<br>* Participants will be exposed to a fan throughout the climate chamber exposure.<br>Other: Water Spray and Fan<br>* Participants will receive both water spraying and a fan throughout the climate chamber exposure.<br>Other: Control<br>* Participants will NOT receive either water spray or a fan exposure.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in core body temperature | Change in core body temperature will be measured either from a temperature sensor pill or from a rectal thermometer | Body core temperature will be obtained within 60 min before the heat wave exposure after the 3 hour heat wave exposure. | 
| Change in left ventricular function | Measures of left ventricular function, such as ventricular wall motion and ventricular filling, will be obtained from echocardiography images. | Within 60 minutes before each simulated heat wave exposure, around minute 90 of the heat wave exposure, and at the end of the 3 hour heat wave exposure | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Heart rate | Heart rate will be measured from ECG electrodes attached to the participant | Prior to and throughout each simulated heat wave exposure; approximately 420 minutes | 
| Cardiac output | Cardiac output (how much blood is ejected from the heart) will be measured using 3D echocardiography. | Within 60 minutes before each simulated heat wave exposure and during each simulated heat wave exposure (up to 3 hours) | 
| Arterial blood pressure | Arterial blood pressure will be measured using a standard arm blood pressure cuff. | Prior to and throughout each simulated heat wave exposure; an average of 480 minutes | 
| Whole body sweat rate | Whole body sweat rate will be measured by through nude weight of the participant. | Within 60 minutes before each simulated heat wave exposure and within 30 minutes after each heat wave exposure. | 
| Markers of renal function and injury - Cystatin C | Markers of renal function and injury (e.g., cystatin C) will be evaluated from blood sampling collection. | Within 60 minutes before each simulated heat wave exposure, during each simulated heat wave exposure (up to 3 hours), and within 2 hours after the simulated heat wave exposure | 
| Markers of renal function and injury - Creatinine Clearance | Markers of renal function and injury (e.g., creatinine clearance) will be evaluated from blood sampling and urine collection. | Within 60 minutes before each simulated heat wave exposure, during each simulated heat wave exposure (up to 3 hours), and within 2 hours after the simulated heat wave exposure | 
| Markers of renal function and injury - Insulin-like growth factor-binding protein 7 | Markers of renal function and injury (e.g., Insulin-like growth factor-binding protein 7) will be evaluated from urine sampling. | Within 60 minutes before each simulated heat wave exposure, during each simulated heat wave exposure (up to 3 hours), and within 2 hours after the simulated heat wave exposure | 
| Markers of renal function and injury - Tissue inhibitor of metalloproteinases 2 | Markers of renal function and injury (e.g., Tissue inhibitor of metalloproteinases 2) will be evaluated from urine sampling. | Within 60 minutes before each simulated heat wave exposure, during each simulated heat wave exposure (up to 3 hours), and within 2 hours after the simulated heat wave exposure | 
| Cerebral perfusion | Cerebral perfusion will be measured by Doppler ultrasound of the internal carotid and vertebral arteries. | Within 60 minutes before each simulated heat wave exposure and during each simulated heat wave exposure (up to 3 hours) | 
| High sensitive cardiac troponin | A plasma-based marker of cardiac stress (high sensitive cardiac troponin) be evaluated from blood sampling. | Within 60 minutes before each simulated heat wave exposure, during each simulated heat wave exposure (up to 3 hours), and within 2 hours after the simulated heat wave exposure | 
| Skin temperature | Skin temperature will be measured from small temperature sensitive electrodes attached to the participant's skin | Within 60 minutes before each simulated heat wave exposure and during each simulated heat wave exposure (up to 3 hours) | 
| Forced vital capacity (FVC) | Forced vital capacity will be obtained from spirometry | Within 60 minutes before each simulated heat wave exposure and during each simulated heat wave exposure (up to 3 hours) | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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aging, heat wave, cardiovascular, low-energy cooling