The purpose of this study is to assess how well cooling modalities work in reducing cardiovascular stress of the elderly to heat wave conditions
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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
NONE
Enrollment
100
Participants will receive water spraying on their body throughout the climate chamber exposure.
Participants will be exposed to a fan throughout the climate chamber exposure.
Participants will receive both water spraying and a fan throughout the climate chamber exposure.
Texas Health Presbyterian Hospital Dallas
Dallas, Texas, United States
RECRUITINGChange in core body temperature
Change in core body temperature will be measured either from a temperature sensor pill or from a rectal thermometer
Time frame: 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.
Time frame: 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
Heart rate
Heart rate will be measured from ECG electrodes attached to the participant
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: Within 60 minutes before each simulated heat wave exposure and within 30 minutes after each heat wave exposure.
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Participants will NOT receive either water spray or a fan 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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
Time frame: 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
Time frame: Within 60 minutes before each simulated heat wave exposure and during each simulated heat wave exposure (up to 3 hours)