The purpose of this study is to determine if enhanced endothelial arterial distensibility observed with heat therapy translates into improved cardiorespiratory fitness. The following aims are proposed: Aim 1: to determine if chronic heat therapy results in improvements in cardiovascular function. Aim 2: To examine potential mechanism(s) of action of heat therapy in cardiovascular function.
The National Institute of Health recognizes heart failure as a major public health problem with a prevalence of over 5.8 million Americans and 23 million people worldwide. Commonly prescribed medications to treat the symptoms associated with this disease are expensive and many are not covered by major health insurance companies. There is a critical need to develop novel treatment and prevention strategies for heart failure. Emerging research highlights the benefits of heat therapy (HT) on metabolic and cardiovascular disease risk. The Geiger laboratory has demonstrated that in obese rats fed a high- fat diet for 12 weeks, weekly HT restored whole body glucose tolerance and skeletal muscle insulin sensitivity. The first comprehensive investigation of long-term HT in young, sedentary humans resulted in improved endothelial function and hemodynamics that were on par with what is typically observed with exercise training in previously sedentary subjects. The purpose of this pilot study is to determine if the enhanced endothelial arterial distensibility observed with HT translates into improved cardiorespiratory fitness. The following aims are proposed: Aim 1: To determine if chronic HT results in improvements in cardiovascular function. The study team hypothesizes that repeated HT will result in improvement in hemodynamic variables related to arterial distensibility (blood pressure, stroke volume, stroke volume variation, cardiac index and systemic vascular resistance) and that these changes translate to improved cardiovascular function as measured by VO2max. Aim 2: To examine potential mechanism(s) of action of HT in cardiovascular function. The study team hypothesizes that HT may exerts its beneficial effects via the effect of heat shock proteins (HSPs) on Nitric Oxide (NO) bioavailability. This will be tested by measuring HSPs, NO mediators and inflammatory markers at baseline and post-intervention. There is rapidly growing interest in the use of HT as a global therapeutic approach and alternative or complementary therapy to exercise training for patients with chronic disease. Study findings would be clinically significant as both men and women with higher cardiorespiratory fitness (as indicated by maximal oxygen consumption, VO2max) are at lower risk for cardiovascular disease. These studies will be the first to examine the ability of chronic heat therapy to increase cardiorespiratory fitness as measured by maximal oxygen consumption, VO2max. These findings could lead to HT as a simple and effective tool for improving cardiovascular health in a variety of populations, particularly those with exercise limitations and comorbid disease states like type 2 diabetes, dementia and cardiovascular disease.
Subjects will undergo 10 hot water immersions of 40.5 degrees Celsius for approximately 45 minutes per session over 14 days. Subjects will be immersed up to the shoulder until rectal temperature reacher 38.5 degrees Celsius (approximately 15-20 minutes). Subjects will then remain in the water bath submerged at waist level to maintain between 38.5 to 39.0 degrees Celsius for another 30 minutes. Following hot water immersion, subjects will be monitored for 10 minutes, or until temperature falls below 38.5 degrees Celsius.
University of Kansas Medical Center
Kansas City, Kansas, United States
Change in Blood Pressure
Systolic and diastolic blood pressure will be monitored using the noninvasive Clearsight (Edward Lifesciences, Irvine, CA) monitor, which incorporates a disposable, single use fingertip cuff.
Time frame: Blood pressure will be assessed at baseline and 24-48 hours after the last heat therapy session (end of study, ~2.5 weeks after first study visit). As a safety measure only, blood pressure will be monitored during every heat therapy treatment.
Change in Stroke Volume
Stroke volume will be monitored using the noninvasive Clearsight (Edward Lifesciences, Irvine, CA) monitor incorporates a disposable, single use fingertip cuff.
Time frame: Stroke volume will be assessed at baseline and 24-48 hours after the last heat therapy session (end of study, ~2.5 weeks after first study visit).
Change in Stroke Volume Variation
Stroke volume variation will be monitored using the noninvasive Clearsight (Edward Lifesciences, Irvine, CA) monitor incorporates a disposable, single use fingertip cuff.
Time frame: Stroke volume variation will be assessed at baseline and 24-48 hours after the last heat therapy session (end of study, ~2.5 weeks after first study visit).
Change in Cardiac Index
Cardiac index will be monitored using the noninvasive Clearsight (Edward Lifesciences, Irvine, CA) monitor incorporates a disposable, single use fingertip cuff.
Time frame: Cardiac index will be assessed at baseline and 24-48 hours after the last heat therapy session (end of study, ~2.5 weeks after first study visit).
Change in Systemic Vascular Resistance
Systemic vascular resistance will be monitored using the noninvasive Clearsight (Edward Lifesciences, Irvine, CA) monitor incorporates a disposable, single use fingertip cuff.
Time frame: Systemic vascular resistance will be assessed at baseline and 24-48 hours after the last heat therapy session (end of study, ~2.5 weeks after first study visit).
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Study Type
INTERVENTIONAL
Allocation
NA
Purpose
TREATMENT
Masking
NONE
Enrollment
15
Change in Maximum Oxygen Consumption (VO2max)
Maximum oxygen consumption (VO2max) will be measured using the Bruce Ramp protocol. The Bruce Ramp protocol is a standardized treadmill exercise commonly used in clinical laboratories.
Time frame: VO2max assessment will be performed at baseline and 24-48 hours after the last heat therapy session (end of study, ~2.5 weeks after first study visit).
Change in Concentration of Heat Shock Proteins
Serum levels of heat shock proteins (HSP72, HSP25) and the primary heat shock protein transcription factor (HSF1) will be assessed for change post heat therapy treatment.
Time frame: Blood analyses will be performed at baseline and 24-48 hours after the last heat therapy session (end of study, ~2.5 weeks after first study visit).
Change in Concentration of Nitric Oxide
Nitric oxide (NO) bioavailability will be assessed for change post heat therapy treatment by measuring nitric oxide and endothelial nitric oxide synthase (eNOS).
Time frame: Blood analyses will be performed at baseline and 24-48 hours after the last heat therapy session (end of study, ~2.5 weeks after first study visit).
Change in Concentration of Pro/Anti-inflammatory Markers
Pro/anti-inflammatory markers (IL1ra, IL-10, IL-8, IFN, and CRP) will be assessed for change post heat therapy treatment.
Time frame: Blood analyses will be performed at baseline and 24-48 hours after the last heat therapy session (end of study, ~2.5 weeks after first study visit).