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Chronic Heat Therapy for Improving Vascular Health (CHT)

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ClinicalTrials.gov Identifier: NCT02518399
Recruitment Status : Completed
First Posted : August 7, 2015
Last Update Posted : October 26, 2017
Sponsor:
Information provided by (Responsible Party):
Christopher T Minson, PhD, University of Oregon

Brief Summary:
The purpose of the study is to investigate whether long-term heat therapy (i.e. 8 weeks of hot tub 4-5x per week) improves biomarkers of cardiovascular health in young, healthy, able-bodied individuals. Although exercise is a potent means of improving cardiovascular health, many patients are unable to exercise effectively, and thus there is high demand for novel therapies to better manage cardiovascular risk in these patients. If successful, this study will set the groundwork for heat therapy to be used as an alternative treatment in patients who have limited exercise capabilities for the prevention of cardiovascular disease.

Condition or disease Intervention/treatment Phase
Cardiovascular Diseases Other: Heat therapy Other: Thermoneutral water immersion Not Applicable

Detailed Description:
Exercise training is a potent means of improving cardiovascular (CV) risk; however, exercise is challenging for many patient populations. Passive heat therapy may provide a simple and effective alternative to exercise for improving CV health, and no one has yet studied the physiological benefits of chronic heat exposure in humans. Heat exposure induces the expression of heat shock proteins, which can have a multitude of beneficial effects on the CV system, many of which are common to exercise training. In particular, these benefits include upregulation of many cellular pathways associated with improved vascular function, a predominant contributor to CV health. The goal of the study is to determine the effects of chronic passive heat therapy on vascular function in young, healthy, able-bodied individuals. The investigators will perform a randomized-controlled trial in which subjects participate in 8 weeks of either heat therapy or thermoneutral water immersion (sham). Heat therapy will entail 8 weeks of hot water immersion sufficient to raise core temperature >38.5°C for 1h, 4-5 times per week. Thermoneutral water immersion will entail 8 weeks of immersion in 36°C water for the same duration as heat therapy. In both subject groups, the investigators will measure various well-established biomarkers of vascular function before and after 8 weeks of heat therapy, including measures of arterial stiffness (arterial compliance, beta-stiffness, and pulse wave velocity), endothelium-dependent dilation (flow-mediated dilation), and intima media thickness. The investigators will investigate the effects of heat therapy on the microvasculature and on the mechanisms behind improvements in vascular function in the cutaneous microcirculation, an ideal site for pharmacodissecting the molecular pathways involved, using microdialysis paired with laser-Doppler flowmetry. If successful, these studies will serve as a basis for developing heat therapy as a novel means of improving CV risk, which has the potential to reshape the treatment of patient populations with limited exercise capabilities.

Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 20 participants
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)
Primary Purpose: Prevention
Official Title: Chronic Heat Therapy for Improving Biomarkers of Vascular Health in Young, Healthy, Humans
Actual Study Start Date : April 2013
Actual Primary Completion Date : September 2015
Actual Study Completion Date : April 30, 2016

Arm Intervention/treatment
Experimental: Heat therapy
Subjects will report to the laboratory 4-5x per week for 8 weeks (36 sessions total) for heat therapy sessions. In each session, subjects will be immersed in a 40°C hot tub for up to 90min in order to increase body core temperature to 38.5°C and, once there, maintain it between 38.5-39.0°C for 60min.
Other: Heat therapy
Subjects will report to the laboratory 4-5x per week for 8 weeks (36 sessions total) for heat therapy sessions. In each session, subjects will be immersed in a 40°C hot tub for up to 90min in order to increase body core temperature to 38.5°C and, once there, maintain it between 38.5-39.0°C for 60min.

Sham Comparator: Thermoneutral water immersion
Subjects will report to the laboratory 4-5x per week for 8 weeks (36 sessions total) for thermoneutral water immersion sessions. In each session, subjects will be immersed in a 36°C tub for 90min in order to maintain body core temperature at a constant level.
Other: Thermoneutral water immersion
Subjects will report to the laboratory 4-5x per week for 8 weeks (36 sessions total) for thermoneutral water immersion sessions. In each session, subjects will be immersed in a 36°C tub for 90min in order to maintain body core temperature at a constant level.




Primary Outcome Measures :
  1. Change in flow-mediated dilation [ Time Frame: 8 weeks ]
    The change in percent dilation of the brachial artery following release of a 5-min arterial occlusion, measured using ultrasonography. This test is highly prognostic of cardiovascular risk and mortality.

  2. Femoral dynamic arterial compliance [ Time Frame: 8 weeks ]
    The change in compliance of the superficial femoral artery relative to blood pressure, measured using ultrasonography-tonometry. This is a measure of arterial stiffness.

  3. Intima media thickness [ Time Frame: 8 weeks ]
    Change in wall thickness of the common carotid artery, measured using ultrasonography. This is predictive of future development of cardiovascular disease, in particular, atherosclerosis.

  4. Mean arterial blood pressure [ Time Frame: 8 weeks ]
    Change in blood pressure measured using brachial oscillation following >20 min supine rest.


Secondary Outcome Measures :
  1. Cutaneous nitric oxide-dependent dilation [ Time Frame: 8 weeks ]
    Change in the difference between cutaneous microdialysis sites receiving a nitric oxide inhibitor (L-NNA, IND # 124,303) and Lactated Ringer's (control). Measured using laser-Doppler flowmetry during a local heating protocol.


Other Outcome Measures:
  1. Carotid dynamic arterial compliance [ Time Frame: 8 weeks ]
    Change in compliance of the common carotid artery relative to blood pressure, measured using ultrasonography-tonometry. This is a measure of arterial stiffness.



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Ages Eligible for Study:   18 Years to 40 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Young, healthy, able-bodied

Exclusion Criteria:

  • Diagnosis of any chronic diseases related to the cardiovascular system (e.g. hypertension, cardiovascular disease, diabetes, etc.),
  • Currently taking prescription medications (except contraceptives)
  • Body mass index over 27 kg/m2
  • Current smoking
  • Currently pregnant or breast-feeding

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT02518399


Locations
United States, Oregon
University of Oregon
Eugene, Oregon, United States, 97403
Sponsors and Collaborators
University of Oregon

Publications of Results:
Responsible Party: Christopher T Minson, PhD, Professor, University of Oregon
ClinicalTrials.gov Identifier: NCT02518399     History of Changes
Other Study ID Numbers: 09272013.025
14PRE20380300 ( Other Grant/Funding Number: American Heart Association )
First Posted: August 7, 2015    Key Record Dates
Last Update Posted: October 26, 2017
Last Verified: October 2017

Keywords provided by Christopher T Minson, PhD, University of Oregon:
Blood vessels
Heat
Cardiovascular diseases

Additional relevant MeSH terms:
Cardiovascular Diseases
Benzocaine
Anesthetics, Local
Anesthetics
Central Nervous System Depressants
Physiological Effects of Drugs
Sensory System Agents
Peripheral Nervous System Agents