Aging, Hyperthermia
Conditions
Keywords
aging, heat wave, cardiovascular, low-energy cooling
Brief summary
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
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.
Interventions
OTHERWater Spray
Participants will receive water spraying on their body throughout the climate chamber exposure.
OTHERFan
Participants will be exposed to a fan throughout the climate chamber exposure.
OTHERWater Spray and Fan
Participants will receive both water spraying and a fan throughout the climate chamber exposure.
OTHERControl
Participants will NOT receive either water spray or a fan exposure.
Sponsors
University of Texas Southwestern Medical Center
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
PREVENTION
Masking
NONE
Intervention 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.
Eligibility
Sex/Gender
ALL
Age
65 Years to No maximum
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Change in core body temperature | Body core temperature will be obtained within 60 min before the heat wave exposure after the 3 hour heat wave exposure. | Change in core body temperature will be measured either from a temperature sensor pill or from a rectal thermometer |
| Change in left ventricular function | 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 | Measures of left ventricular function, such as ventricular wall motion and ventricular filling, will be obtained from echocardiography images. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Arterial blood pressure | Prior to and throughout each simulated heat wave exposure; an average of 480 minutes | Arterial blood pressure will be measured using a standard arm blood pressure cuff. |
| Whole body sweat rate | Within 60 minutes before each simulated heat wave exposure and within 30 minutes after each heat wave exposure. | Whole body sweat rate will be measured by through nude weight of the participant. |
| Markers of renal function and injury - Cystatin C | 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 (e.g., cystatin C) will be evaluated from blood sampling collection. |
| Markers of renal function and injury - Creatinine Clearance | 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 (e.g., creatinine clearance) will be evaluated from blood sampling and urine collection. |
| Markers of renal function and injury - Insulin-like growth factor-binding protein 7 | 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 (e.g., Insulin-like growth factor-binding protein 7) will be evaluated from urine sampling. |
| Heart rate | Prior to and throughout each simulated heat wave exposure; approximately 420 minutes | Heart rate will be measured from ECG electrodes attached to the participant |
| Cerebral perfusion | Within 60 minutes before each simulated heat wave exposure and during each simulated heat wave exposure (up to 3 hours) | Cerebral perfusion will be measured by Doppler ultrasound of the internal carotid and vertebral arteries. |
| High sensitive cardiac troponin | 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 | A plasma-based marker of cardiac stress (high sensitive cardiac troponin) be evaluated from blood sampling. |
| Skin temperature | Within 60 minutes before each simulated heat wave exposure and during each simulated heat wave exposure (up to 3 hours) | Skin temperature will be measured from small temperature sensitive electrodes attached to the participant's skin |
| Forced vital capacity (FVC) | Within 60 minutes before each simulated heat wave exposure and during each simulated heat wave exposure (up to 3 hours) | Forced vital capacity will be obtained from spirometry |
| Markers of renal function and injury - Tissue inhibitor of metalloproteinases 2 | 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 (e.g., Tissue inhibitor of metalloproteinases 2) will be evaluated from urine sampling. |
| Cardiac output | Within 60 minutes before each simulated heat wave exposure and during each simulated heat wave exposure (up to 3 hours) | Cardiac output (how much blood is ejected from the heart) will be measured using 3D echocardiography. |
Countries
United States
Contacts
Primary ContactRachel Cottle, PhD
Backup ContactErin Harper, BS
Outcome results
None listed