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Mitigating Heat-induced Physiological Strain and Discomfort in Older Adults Via Lower Limb Immersion and Neck Cooling

Primary Purpose

Hyperthermia, Weather; Heat, Heat Stress

Status
Completed
Phase
Not Applicable
Locations
Canada
Study Type
Interventional
Intervention
No cooling (control)
Lower limb immersion
Lower limb immersion + neck cooling
Sponsored by
University of Ottawa
About
Eligibility
Locations
Arms
Outcomes
Full info

About this trial

This is an interventional basic science trial for Hyperthermia focused on measuring Heat wave, Cooling intervention, Heat strain, Cardiovascular strain, Heat and health protection, Extreme heat events

Eligibility Criteria

65 Years - 85 Years (Older Adult)All SexesAccepts Healthy Volunteers

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).

Sites / Locations

  • University of Ottawa

Arms of the Study

Arm 1

Arm 2

Arm 3

Arm Type

Active Comparator

Experimental

Experimental

Arm Label

No cooling intervention (control)

Lower limb immersion

Lower limb immersion + neck cooling

Arm Description

Adults aged 65-85 years with or without type 2 diabetes and/or hypertension.

Adults aged 65-85 years with or without type 2 diabetes and/or hypertension.

Adults aged 65-85 years with or without type 2 diabetes and/or hypertension.

Outcomes

Primary Outcome Measures

Core temperature
Rectal temperature measured as an index of core temperature (15 minute average)

Secondary Outcome Measures

Heart rate
Heart rate derived from 3-lead electrocardiogram (15 minute average)
Systolic blood pressure
Systolic blood pressure measured in triplicate via automated oscillometry (~60 seconds between measures)
Diastolic blood pressure
Diastolic blood pressure measured in triplicate via automated oscillometry (~60 seconds between measures)
Rate pressure product
Rate pressure product, an index of myocardial work and strain, calculated as systolic blood pressure x heart rate.
Heart rate variability: SDNN
Standard deviation of normal-to-normal RR intervals (SDNN) measured during 5 minutes of paced breathing (15 breaths/min) with participants in the seated position. SDNN will be evaluated twice, during two paced breathing periods (separated by 4 min of seated rest).
Heart rate variability: RMSSD
Root mean squared standard deviation of normal-to-normal RR intervals (RMSSD) measured during 5 minutes of paced breathing (15 breaths/min) with participants in the seated position. RMSSD will be evaluated twice, during two paced breathing periods (separated by 4 min of seated rest).
Cardiac response to standing from supine (30:15 ratio)
Cardiac response to standing evaluated as the ratio between the highest RR interval (lowest heart rate) measured at the 30th heart beat after standing from supine (+/- 5 beats) and the lowest RR interval (highest heart rate) measured at the 15th heart beat after standing (+/- 5 beats). Cardiac response to standing will be evaluated twice, during two lying-to-standing tests (separated by 10 min of supine rest).
Systolic response to standing from supine
Systolic blood pressure response to standing evaluated as the difference in blood pressure measured between the standing and supine. Standing systolic blood pressure will be taken as the lowest value of those measured after 60 and 120 seconds of standing. Systolic response to standing will be evaluated twice, during two lying-to-standing tests (separated by 10 min of supine rest).
Integrated baroreflex sensitivity (sit-to-stand maneuvers)
Determined from beat-to-beat arterial pressures and heart rate (volume-clamp technique) during 5 min of sit-to-stand maneuvers performed at 0.05 Hz (3 cycles per min; 15 total cycles).
Fluid consumption
Cumulative fluid consumption calculated by weighing participant water intake at the start and end of each hour of exposure.
Fluid loss
Fluid loss calculated as the change in body mass during each exposure presented as a percentage of baseline body mass (corrected for food consumption)
Change in plasma volume
Change in plasma volume from baseline values calculated from duplicate measurements of hemoglobin and hematocrit at the start and end of each exposure using the technique by Dill and Costill.
Thermal comfort
Thermal comfort assessed via a visual analog scale ("How comfortable does your body temperature feel?") ranging from extremely uncomfortable to extremely comfortable (midpoint: neutral).
Orthostatic intolerance symptoms assessment
Cumulative sum of scores on 6 questions asking participant to rank symptoms associated with orthostatic intolerance during the last 1-2 hours (including the lying-to-standing and sit-to-stand tests). All symptoms scored on a scale from 0 (none) to 10 (worst possible) and include feelings of: (1) "dizziness, lightheadedness, feeling faint, or feeling like you might black out"; (2) "Problems with vision (blurring, seeing spots, tunnel vision, etc.)"; (3) "Weakness"; (4) "Fatigue"; (5) "Trouble concentrating"; and (6) "Head and neck discomfort".

Full Information

First Posted
October 19, 2022
Last Updated
May 9, 2023
Sponsor
University of Ottawa
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1. Study Identification

Unique Protocol Identification Number
NCT05601713
Brief Title
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

2. Study Status

Record Verification Date
May 2023
Overall Recruitment Status
Completed
Study Start Date
September 28, 2022 (Actual)
Primary Completion Date
May 4, 2023 (Actual)
Study Completion Date
May 4, 2023 (Actual)

3. Sponsor/Collaborators

Responsible Party, by Official Title
Principal Investigator
Name of the Sponsor
University of Ottawa

4. Oversight

Studies a U.S. FDA-regulated Drug Product
No
Studies a U.S. FDA-regulated Device Product
No
Data Monitoring Committee
No

5. Study Description

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.

6. Conditions and Keywords

Primary Disease or Condition Being Studied in the Trial, or the Focus of the Study
Hyperthermia, Weather; Heat, Heat Stress, Heat Syncope, Aging
Keywords
Heat wave, Cooling intervention, Heat strain, Cardiovascular strain, Heat and health protection, Extreme heat events

7. Study Design

Primary Purpose
Basic Science
Study Phase
Not Applicable
Interventional Study Model
Crossover Assignment
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.
Masking
ParticipantOutcomes Assessor
Masking Description
Participants will be informed of the study interventions before providing informed consent but will be masked to the specific trial until exposure (i.e., participants will not know the cooling intervention before the trial or during baseline measurements). Data will be blinded prior to analysis.
Allocation
Randomized
Enrollment
18 (Actual)

8. Arms, Groups, and Interventions

Arm Title
No cooling intervention (control)
Arm Type
Active Comparator
Arm Description
Adults aged 65-85 years with or without type 2 diabetes and/or hypertension.
Arm Title
Lower limb immersion
Arm Type
Experimental
Arm Description
Adults aged 65-85 years with or without type 2 diabetes and/or hypertension.
Arm Title
Lower limb immersion + neck cooling
Arm Type
Experimental
Arm Description
Adults aged 65-85 years with or without type 2 diabetes and/or hypertension.
Intervention Type
Other
Intervention Name(s)
No cooling (control)
Intervention Description
Participants are exposed to 38°C, 35% relative humidity for 6 hours without cooling interventions (control condition). Drinking water is available ad libitum.
Intervention Type
Other
Intervention Name(s)
Lower limb immersion
Intervention Description
Participants are exposed to 38°C, 35% relative humidity for 6 hours. For the last 40 min of each hour, participants lower limbs are immersed in cool water (~20°C) up to the level of mid calf. Drinking water is available ad libitum.
Intervention Type
Other
Intervention Name(s)
Lower limb immersion + neck cooling
Intervention Description
Participants are exposed to 38°C, 35% relative humidity for 6 hours. For the last 40 min of each hour, participants lower limbs are immersed in cool water (~20°C) up to the level of mid calf. During limb immersion, a towel soaked in cool water (~20°C) is placed around the participants neck. The towel is re-wet half way through the 40-min limb immersion. Drinking water is available ad libitum.
Primary Outcome Measure Information:
Title
Core temperature
Description
Rectal temperature measured as an index of core temperature (15 minute average)
Time Frame
End of heat exposure (hour 6)
Secondary Outcome Measure Information:
Title
Heart rate
Description
Heart rate derived from 3-lead electrocardiogram (15 minute average)
Time Frame
End of heat exposure (hour 6)
Title
Systolic blood pressure
Description
Systolic blood pressure measured in triplicate via automated oscillometry (~60 seconds between measures)
Time Frame
End of heat exposure (hour 6)
Title
Diastolic blood pressure
Description
Diastolic blood pressure measured in triplicate via automated oscillometry (~60 seconds between measures)
Time Frame
End of heat exposure (hour 6)
Title
Rate pressure product
Description
Rate pressure product, an index of myocardial work and strain, calculated as systolic blood pressure x heart rate.
Time Frame
End of heat exposure (hour 6)
Title
Heart rate variability: SDNN
Description
Standard deviation of normal-to-normal RR intervals (SDNN) measured during 5 minutes of paced breathing (15 breaths/min) with participants in the seated position. SDNN will be evaluated twice, during two paced breathing periods (separated by 4 min of seated rest).
Time Frame
End of heat exposure (hour 6)
Title
Heart rate variability: RMSSD
Description
Root mean squared standard deviation of normal-to-normal RR intervals (RMSSD) measured during 5 minutes of paced breathing (15 breaths/min) with participants in the seated position. RMSSD will be evaluated twice, during two paced breathing periods (separated by 4 min of seated rest).
Time Frame
End of heat exposure (hour 6)
Title
Cardiac response to standing from supine (30:15 ratio)
Description
Cardiac response to standing evaluated as the ratio between the highest RR interval (lowest heart rate) measured at the 30th heart beat after standing from supine (+/- 5 beats) and the lowest RR interval (highest heart rate) measured at the 15th heart beat after standing (+/- 5 beats). Cardiac response to standing will be evaluated twice, during two lying-to-standing tests (separated by 10 min of supine rest).
Time Frame
End of heat exposure (hour 6)
Title
Systolic response to standing from supine
Description
Systolic blood pressure response to standing evaluated as the difference in blood pressure measured between the standing and supine. Standing systolic blood pressure will be taken as the lowest value of those measured after 60 and 120 seconds of standing. Systolic response to standing will be evaluated twice, during two lying-to-standing tests (separated by 10 min of supine rest).
Time Frame
End of heat exposure (hour 6)
Title
Integrated baroreflex sensitivity (sit-to-stand maneuvers)
Description
Determined from beat-to-beat arterial pressures and heart rate (volume-clamp technique) during 5 min of sit-to-stand maneuvers performed at 0.05 Hz (3 cycles per min; 15 total cycles).
Time Frame
End of heat exposure (hour 6)
Title
Fluid consumption
Description
Cumulative fluid consumption calculated by weighing participant water intake at the start and end of each hour of exposure.
Time Frame
End of heat exposure (hour 6)
Title
Fluid loss
Description
Fluid loss calculated as the change in body mass during each exposure presented as a percentage of baseline body mass (corrected for food consumption)
Time Frame
End of heat exposure (hour 6)
Title
Change in plasma volume
Description
Change in plasma volume from baseline values calculated from duplicate measurements of hemoglobin and hematocrit at the start and end of each exposure using the technique by Dill and Costill.
Time Frame
End of heat exposure (hour 6)
Title
Thermal comfort
Description
Thermal comfort assessed via a visual analog scale ("How comfortable does your body temperature feel?") ranging from extremely uncomfortable to extremely comfortable (midpoint: neutral).
Time Frame
End of heat exposure (hour 6)
Title
Orthostatic intolerance symptoms assessment
Description
Cumulative sum of scores on 6 questions asking participant to rank symptoms associated with orthostatic intolerance during the last 1-2 hours (including the lying-to-standing and sit-to-stand tests). All symptoms scored on a scale from 0 (none) to 10 (worst possible) and include feelings of: (1) "dizziness, lightheadedness, feeling faint, or feeling like you might black out"; (2) "Problems with vision (blurring, seeing spots, tunnel vision, etc.)"; (3) "Weakness"; (4) "Fatigue"; (5) "Trouble concentrating"; and (6) "Head and neck discomfort".
Time Frame
End of heat exposure (hour 6)

10. Eligibility

Sex
All
Minimum Age & Unit of Time
65 Years
Maximum Age & Unit of Time
85 Years
Accepts Healthy Volunteers
Accepts Healthy Volunteers
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).
Overall Study Officials:
First Name & Middle Initial & Last Name & Degree
Glen P Kenny, PhD
Organizational Affiliation
University of Ottawa
Official's Role
Principal Investigator
First Name & Middle Initial & Last Name & Degree
Robert D Meade, PhD
Organizational Affiliation
University of Ottawa
Official's Role
Principal Investigator
First Name & Middle Initial & Last Name & Degree
Ronald J Sigal, MD, MPH
Organizational Affiliation
University of Calgary
Official's Role
Principal Investigator
Facility Information:
Facility Name
University of Ottawa
City
Ottawa
State/Province
Ontario
ZIP/Postal Code
K1N6N5
Country
Canada

12. IPD Sharing Statement

Plan to Share IPD
Yes
IPD Sharing Plan Description
Deidentified participant data will be made available with approved analysis plan and signed access agreement
IPD Sharing Time Frame
Following publication of the main study report(s)
IPD Sharing Access Criteria
Approved analysis plan and signed access agreement

Learn more about this trial

Mitigating Heat-induced Physiological Strain and Discomfort in Older Adults Via Lower Limb Immersion and Neck Cooling

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