Low-cost, at home cooling strategies for older adults during hot-and-humid heatwaves.

INTERVENTION: Each participant will take part in four three hour exposures which be randomised; 1. No fan with no skin wetting (comparator) 2. Fan use with no skin wetting 3. No fan use with skin wetting 4. Fan use with skin wetting They will be asked to sit in a thermally regulated environmental chamber at a temperature of 38°C and 60% relative humidity. In all fan exposures, participants will be seated 1.25m from an 18" diameter fan with an airflow of 4.0m/s. This is the velocity of a typical fan at highest speed. For the skin wetting exposure, moisture (tap water ‐18 degrees) will be applied using a damp cloth every 10 minutes to the forehead, face, arms and neck by a researcher. Additionally, in all exposures they will be given cold ( 18ºC) water equivalent to 3ml per kg at the end of each hour to drink. There will be a minimum of 72hours washout between each exposure. CONDITION: heat related illness;heat related cardiovascular strain;thermal discomfort ;dehydration; ; heat related illness ; heat related cardiovascular strain ; thermal discomfort ; dehydration Injuries and Accidents ‐ Other injuries and accidents Public Health ‐ Other public health PRIMARY OUTCOME: Core temperature via rectal thermometer:; ; Rectal temperature sensor: The participant will be asked to insert a flexible sensor 10‐12cm into their rectum. A marker is placed on the sensor using sterile surgical tape. The participant will insert the sensor until the tape reaches their anal surface. The insertion of the sensor may cause some mild discomfort and minor irritation; however, this sensation soon passes. The participant will receive proper instruction regarding the placement of the sensor to ensure their safety and comfort. The participant will be responsible for the insertion of this sensor. It will provide the researcher with an indication of the amount of heat stored in their body and will be tracked throughout the entirety of each experimental session[Immediately following the end of exposure ] Rate pressure product measured via blood pressure and heart rate at the end of the trial; ; An automated blood pressure monitor will be strapped to the participants arm and blood pressure will be used by researchers to calculate RPP(heart rate x systolic blood pressure). [At the end of exposure ] Whole body sweat loss:; ; The participant will be weighed on a platform scale immediately before and at the completion of the heatwave exposure in order to compare whole‐body sweat losses.[Immediately following the end of exposure ] SECONDARY OUTCOME: Blood pressure: ; ; An automated blood pressure monitor will be strapped to the participants arm and blood pressure will be taken.[Immediately following the end of exposure ] Cognitive performance: ; ; The participant will be asked to complete a short‐form of the Stroop Colour and Word Test (SCWT) immediately before and at the completion of the heatwave exposure. This test involves them looking at various words and identifying which colour the words are shown in.[Immediately following the end of exposure ] Evidence of orthostatic hypotension: ; ; At the completion of the heatwave exposure the participants blood pressure will be taken. They will then be asked to stand up and their blood pressure will be taken after 1 minute of standing and then again after 3 minutes of standing. This test is carried out to see if there is evidence of postural hypotension (a drop in blood pressure within 3 minutes of standing from a seated position).[Immediately following the end of exposure ] Heart rate: ; ; Heart rate will be measured using the ECG monitoring system[Immediately following the end of exposure ] Limb blood flow: ; ; Limb blood flow will be determined using venous occlusion plethysmography. This technique involves a rapidly inflating cuff around the participants arm to a pressure of 60 mmHg (compared to 180 mmHg during a blood pressure reading). A strain gauge that resembles an elastic band will be placed on their forearm and this will record minor changes in limb volume. [Immediately following the end of exposure ] Local sweat rate: ; ; A small plastic capsule connected to plastic tubing will be placed on the participants upper back and forearm. Dry air is passed through this capsule and a humidity sensor will pick up humidity from the skin and provides a measurement of local sweat rate throughout each experimental session.[Immediately following the end of exposure ] Rating of nausea and light headedness (composite outcome) at the end of exposure: ; ; The participant will be asked to rate how much (if any) nausea or light headedness they are experiencing and tick if they are experiencing any other symptoms (including paleness, muscle cramps, tiredness, weakness and headache).[Immediately following the end of exposure ] Skin blood flow: ; ; A flexible laser probe will measure skin blood flow non‐invasively at the upper back during the entirety of each experimental session. This measurement device does not result in any discomfort or residual medical effects.[Immediately following the end of exposure ] Skin temperature: ; ; Eight skin sensors will be taped to the participants skin surface with hypoallergenic tape. Some hair may need to be shaved (by the use of disposable razors) in order to secure the probes adequately. These probes give an indication of skin temperature and heat loss from the skin and will be recorded throughout the entirety of each experimental session.[Immediately following the end of exposure ] Thermal comfort: ; ; The participant will be asked to rate how uncomfortable the heat makes them on a visual analogue scale.[Immediately following the end of exposure ] Thermal sensation: ; ; The participant will be asked to rate how warm they feel on a visual analogue scale during each experimental session. [Immediately following the end of exposure ] INCLUSION CRITERIA: Non smokers (or 1 year since quitting) Over 60 years of age