Ambient Heating for Heat Stress

Overseen By Taysom Wallace, MS

Age: 18+

Sex: Any

Trial Phase: Academic

Sponsor: University of Texas Southwestern Medical Center

Must not be taking: Beta blockers, Calcium channel blockers

Disqualifiers: Heart disease, Cancer, Diabetes, others

No Placebo Group All trial participants will receive the active study treatment (no placebo)

Compensation: Varies

Number of Visits: 1

20 Participants Needed

Trial Summary

What is the purpose of this trial?

The purpose of this study is to compare surface and intradermal skin temperature responses to heat stress with and without evaporative and convective cooling.

Will I have to stop taking my current medications?

Yes, if you are taking medications that affect how your body handles heat, like certain heart medications, you would need to stop taking them to participate in this trial.

What data supports the effectiveness of the treatment Ambient Heating for Heat Stress?

Research on passive heat therapy, which involves mild temperature elevations, shows it can help protect cells from damage and reduce stress, suggesting potential benefits for managing heat stress. ^{1 2 3 4 5}

Is ambient heating generally safe for humans?

Exposure to heat can cause the body to work harder, leading to increased heart activity and loss of salt and water, which can be risky, especially for older people or those with heart issues. However, exposure to heat levels considered safe by international standards is generally not harmful, but prolonged exposure to higher levels may not be safe for everyone. ^{4 6 7 8 9}

How does the treatment Ambient Heating differ from other treatments for heat stress?

Ambient Heating is unique because it involves adjusting the environment's temperature to help the body manage heat stress, rather than using medications or other direct interventions. This approach focuses on modifying the surrounding conditions to facilitate natural thermoregulation (body temperature control) and reduce heat strain. ^{1 4 10 11 12}

Research Team

Craig Crandall, Ph.D.

Principal Investigator

UT Southwestern Medical Center

Eligibility Criteria

This trial is for healthy individuals without significant medical issues, as determined by a detailed medical history and physical exam. Participants must have a normal resting electrocardiogram. It's not suitable for those with underlying health problems that could affect their response to heat stress.

Inclusion Criteria

Free of any significant underlying medical problems based upon a detailed medical history and physical exam

Normal resting electrocardiogram

Exclusion Criteria

I am a current smoker or have smoked regularly in the last 3 years.

Individuals who are pregnant, planning to become pregnant, or breastfeeding

I have a chronic condition like heart disease, diabetes, or high blood pressure that needs regular treatment.

Timeline

Screening

Participants are screened for eligibility to participate in the trial

1-2 weeks

Heat Stress Exposure

Participants are exposed to ambient heat stress with and without evaporative and convective cooling methods. Skin surface and intradermal temperatures are monitored.

2 hours

1 visit (in-person)

Follow-up

Participants are monitored for any delayed thermoregulatory responses or adverse effects after the heat stress exposure.

1 week

Treatment Details

Interventions

• Ambient Heating

Trial Overview The study aims to observe how skin surface and deeper skin temperatures react to being heated up in different conditions—with and without the help of sweat (evaporative cooling) and air movement (convective cooling).

Participant Groups

Group I: Healthy Adults Arm Experimental Treatment 1 Intervention

Healthy Subject will rest in an environmental chamber that is no hotter than 47°C (117 °F). While in the chamber, the study team will periodically use a water spray to wet subject's skin and turn on an electric fan. During this time, the temperature of skin on arm using a temperature probe placed on the surface of skin and another temperature probe placed within skin (intradermal) will be monitored.

Who Is Running the Clinical Trial?

University of Texas Southwestern Medical Center

Lead Sponsor

Trials

1,102

Recruited

1,077,000+

Findings from Research

The Effective Heat Strain Index (EHSI) is a practical tool that allows for on-site evaluation of heat stress conditions by using a hand calculator that incorporates temperature measurements and estimates of metabolism and air movement.

The EHSI provides clear classifications of heat strain levels (no strain, low strain, high strain) and suggests time limits for safe exposure, helping to ensure safety in hot environments.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Effective heat strain index using pocket computer. Kamon, E., Ryan, C.[2008]

Thermal stress in work environments can adversely impact human performance and behavior, highlighting the importance of understanding these effects for workplace safety.

The review indicates that variations in research methodology and definitions of thermal stress complicate the evaluation of its effects, suggesting a need for standardized approaches in future studies.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Thermal stress and human performance. Enander, AE., Hygge, S.[2019]

Passive heat therapy, such as using hot tubs or saunas, can enhance the body's resistance to oxidative and inflammatory stress, which is beneficial for cardiovascular health, as shown in a study using human endothelial cells.

Both mild heat exposure (at 39°C) and serum from individuals who underwent 8 weeks of heat therapy were effective in preventing cellular damage from hypoxia-reoxygenation, suggesting that heat therapy may offer protective mechanisms against ischemic events.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Passive heat therapy protects against endothelial cell hypoxia-reoxygenation via effects of elevations in temperature and circulating factors. Brunt, VE., Wiedenfeld-Needham, K., Comrada, LN., et al.[2019]

Thermal stress from extreme cold and heat can significantly impact health and productivity, with risks increasing in harsh environmental conditions and high workloads.

The body undergoes physiological changes to adapt to thermal stress, and understanding these adaptations is crucial for preventing heat and cold-related illnesses and implementing effective therapies.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Environmental thermal stress. Keim, SM., Guisto, JA., Sullivan, JB.[2008]

The study found that increased indoor heat exposure is associated with higher mortality and morbidity rates among the elderly in Houston, Texas, with a notable odds ratio of 1.16 for circulatory deaths per 5°C increase in indoor temperature.

Stronger associations were observed between indoor heat and emergency hospital admissions among African Americans compared to Whites, highlighting the need to consider demographic vulnerabilities when assessing health risks related to indoor heat exposure.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

A Case-Crossover Analysis of Indoor Heat Exposure on Mortality and Hospitalizations among the Elderly in Houston, Texas. O'Lenick, CR., Baniassadi, A., Michael, R., et al.[2021]

The body's natural response to heat stress, such as increased blood flow to the skin and sweating, can lead to significant health risks, especially in vulnerable populations like the elderly, as these responses can overload the heart and increase the risk of serious conditions like thrombosis.

Current safety guidelines for radiofrequency (RF) radiation exposure are considered trivial compared to the body's heat stress responses, but prolonged exposure to RF levels above recommended limits may pose health risks, highlighting the need for careful monitoring of heat stress in various environments.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Cardiovascular responses to heat stress and their adverse consequences in healthy and vulnerable human populations. Donaldson, GC., Keatinge, WR., Saunders, RD.[2022]

A meta-analysis of studies indicates that higher heat exposure is linked to an increase in occupational injuries, particularly affecting younger workers and males, with a reported 0.5% increase in injury odds for every 1°C rise in temperature.

While the exact mechanisms behind heat exposure leading to injuries are still being explored, effective prevention strategies have yet to be established, highlighting the need for tailored approaches that consider local conditions and involve community participation.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Heat Exposure and Occupational Injuries: Review of the Literature and Implications. Spector, JT., Masuda, YJ., Wolff, NH., et al.[2023]

In a study of 179 workers in the Monsoonal North region of Australia, 79% reported chronic heat stress symptoms and 47% reported severe symptoms, indicating a high prevalence of heat-related health issues in labor-intensive jobs.

Exposure to air-conditioning significantly reduced the likelihood of both chronic and severe heat stress symptoms, suggesting that implementing cooling strategies could effectively mitigate the negative impacts of heat exposure on workers.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

The impact of perceived heat stress symptoms on work-related tasks and social factors: A cross-sectional survey of Australia's Monsoonal North. Carter, S., Field, E., Oppermann, E., et al.[2021]

In a study of 46 industrial workers exposed to varying heat stress levels, heart rates and rectal temperatures were monitored, revealing that safety levels (HR ≤ 110 bpm, Tre ≤ 38.0 °C) were maintained in only 2.4% of cases at higher work rates during winter, indicating significant risks under these conditions.

Workers acclimatized to hot environments experienced fewer instances of excessive heart rates and temperatures, suggesting that acclimatization plays a crucial role in enhancing safety and performance in heat-stressed conditions.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Laboratory evaluation of permissible exposure limits for men in hot environments. Kuhlemeier, KV., Wood, TB.[2008]

Indoor temperature showed little variation across different seasons and locations, while indoor relative humidity varied significantly, indicating that indoor conditions do not always reflect outdoor measurements.

The study suggests that outdoor measurements of specific humidity are more reliable indicators of indoor moisture content than outdoor temperature and relative humidity, which is important for understanding health effects related to weather.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Daily indoor-to-outdoor temperature and humidity relationships: a sample across seasons and diverse climatic regions. Nguyen, JL., Dockery, DW.[2018]

The report develops a comprehensive theory on how the human body exchanges heat with the environment, focusing on factors like metabolic heat production during physical activity and the mechanisms of heat elimination through conduction, convection, evaporation, and radiation.

It also discusses various indices for measuring thermal comfort and stress, including the Fanger equations, which help assess wellbeing and discomfort related to temperature changes.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

[Heat exchange between human body and environment (theoretical bases of physiological measurement and evaluation)]. Pezzagno, G.[2008]

Understanding the physiological and psychological impacts of working in extreme conditions is crucial for preventing excessive strain, as factors like physical fitness, age, and sex influence an individual's maximal aerobic capacity.

The study highlights the importance of heat balance during work, emphasizing that metabolic heat production and heat exchange methods (radiation, convection, and evaporation) significantly affect physiological responses and mental performance under heat stress.

NCBI (Pubmed)

pubmed.ncbi.nlm.nih.gov

Ergonomics of heat and cold. Kamon, E.[2017]

References

1. United States pubmed.ncbi.nlm.nih.gov

Effective heat strain index using pocket computer. [2008]

2. Finland pubmed.ncbi.nlm.nih.gov

Thermal stress and human performance. [2019]

3. England pubmed.ncbi.nlm.nih.gov

Passive heat therapy protects against endothelial cell hypoxia-reoxygenation via effects of elevations in temperature and circulating factors. [2019]

4. Poland pubmed.ncbi.nlm.nih.gov

Environmental thermal stress. [2008]

5. United States pubmed.ncbi.nlm.nih.gov

A Case-Crossover Analysis of Indoor Heat Exposure on Mortality and Hospitalizations among the Elderly in Houston, Texas. [2021]

6. England pubmed.ncbi.nlm.nih.gov

Cardiovascular responses to heat stress and their adverse consequences in healthy and vulnerable human populations. [2022]

7. Switzerland pubmed.ncbi.nlm.nih.gov

Heat Exposure and Occupational Injuries: Review of the Literature and Implications. [2023]

8. England pubmed.ncbi.nlm.nih.gov

The impact of perceived heat stress symptoms on work-related tasks and social factors: A cross-sectional survey of Australia's Monsoonal North. [2021]

9. United States pubmed.ncbi.nlm.nih.gov

Laboratory evaluation of permissible exposure limits for men in hot environments. [2008]

10. United States pubmed.ncbi.nlm.nih.gov

Daily indoor-to-outdoor temperature and humidity relationships: a sample across seasons and diverse climatic regions. [2018]

11. Italy pubmed.ncbi.nlm.nih.gov

[Heat exchange between human body and environment (theoretical bases of physiological measurement and evaluation)]. [2008]

12. United States pubmed.ncbi.nlm.nih.gov

Ergonomics of heat and cold. [2017]