Clinical trial NCT05601713: Mitigating Heat-induced Physiological Strain and Discomfort in Older Adults Via Lower Limb Immersion and Neck Cooling
Official title: Evaluating the Efficacy of Lower Leg Immersion With and Without Neck Cooling for Limiting Heat Strain in Elderly Adults During Extreme Heat Events
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Hyperthermia
Weather; Heat
Heat Stress
Heat Syncope
Aging
Keywords: Heat wave
Cooling intervention
Heat strain
Cardiovascular strain
Heat and health protection
Extreme heat events
Lead sponsor: University of Ottawa
Sponsor class: OTHER
First posted: 2022-11-01
Enrollment: 18
Sex: ALL
Minimum age (years): 65
Maximum age (years): 85
Standard ages: OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Intervention model description: Participant will complete 3 simulated extreme heat event exposures in random order: i) no cooling intervention (control); ii) lower limb water immersion; and iii) lower limb water immersion with application of cool wet towel to the neck.
Primary purpose: BASIC_SCIENCE

Brief summary: The incidence and severity of hot weather and extreme heat events (heat waves) is increasing. As such, there is an urgent need to develop heat-alleviation strategies that can provide targeted protection for older adults who are at an elevated risk for heat-induced illnesses or death due to impaired body temperature and cardiovascular regulation. While air-conditioning provides the most effective protection from extreme heat, it is inaccessible for many individuals and cannot be used during power outages (e.g., heat-related rolling blackouts). Immersion of the lower limbs in cold water and/or the application of cold towels to the neck have been recommended as simple and sustainable alternatives to air-conditioning. However, empirical data to support the efficacy of these interventions for mitigating physiological strain and discomfort in older adults is lacking. To address this knowledge gap, this randomized crossover trial will evaluate the effect of lower limb immersion with and without application of cold towels to the neck on body core temperature, cardiovascular strain and autonomic function, dehydration, and thermal comfort in adults aged 65-85 years exposed to simulated heat wave conditions (38°C, 35% relative humidity) for 6 hours.


Eligibility criteria: Inclusion Criteria:

* Male or female adults.
* Aged 65-85 years.
* Non-smoking.
* English or French speaking.
* Ability to provide informed consent.

Exclusion Criteria:

* Physical restriction (e.g., due to disease: intermittent claudication, renal impairment, active proliferative retinopathy, unstable cardiac or pulmonary disease, disabling stroke, severe arthritis, etc.).
* Use of or changes in medication judged by the patient or investigators to make participation in this study inadvisable (e.g., medications increasing risk of heat-related illness; beta blockers, anticholinergics, etc.)
* Cardiac abnormalities identified via 12-lead ECG during an incremental exercise test to volitional fatigue (performed for all participants).
* Peak aerobic capacity (VO2peak), as measured during an incremental exercise test to volitional fatigue, exceeding the 50th percentile of age- and sex-specific normative values published by the American College of Sports Medicine (ACSM).

Primary outcomes:
measure: Core temperature
timeFrame: End of heat exposure (hour 6)
Secondary outcomes:
measure: Heart rate
timeFrame: End of heat exposure (hour 6)
measure: Systolic blood pressure
timeFrame: End of heat exposure (hour 6)
measure: Diastolic blood pressure
timeFrame: End of heat exposure (hour 6)
measure: Rate pressure product
timeFrame: End of heat exposure (hour 6)
measure: Heart rate variability: SDNN
timeFrame: End of heat exposure (hour 6)
measure: Heart rate variability: RMSSD
timeFrame: End of heat exposure (hour 6)
measure: Cardiac response to standing from supine (30:15 ratio)
timeFrame: End of heat exposure (hour 6)
measure: Systolic response to standing from supine
timeFrame: End of heat exposure (hour 6)
measure: Integrated baroreflex sensitivity (sit-to-stand maneuvers)
timeFrame: End of heat exposure (hour 6)
measure: Fluid consumption
timeFrame: End of heat exposure (hour 6)
measure: Fluid loss
timeFrame: End of heat exposure (hour 6)
measure: Change in plasma volume
timeFrame: End of heat exposure (hour 6)
measure: Thermal comfort
timeFrame: End of heat exposure (hour 6)
measure: Orthostatic intolerance symptoms assessment
timeFrame: End of heat exposure (hour 6)
Other outcomes:
Locations:
city: Ottawa
country: Canada
facility: University of Ottawa
state: Ontario
Study officials:
affiliation: University of Ottawa
name: Glen P Kenny, PhD
role: PRINCIPAL_INVESTIGATOR
affiliation: University of Ottawa
name: Robert D Meade, PhD
role: PRINCIPAL_INVESTIGATOR
affiliation: University of Calgary
name: Ronald J Sigal, MD, MPH
role: PRINCIPAL_INVESTIGATOR
References: