Efficiency of three cooling methods for hyperthermic military personnel linked to water availability

Post-exercise management of exertional hyperthermia in dogs participating in dog sport (canicross) events in the UK

Exercise is a common trigger of heat-related illness (HRI) events in dogs, accounting for 74% of canine HRI cases treated under primary veterinary care in the United Kingdom. However, few empirical studies have evaluated the effectiveness of differing cooling methods for dogs with exertional hyperthermia or HRI. This study aimed to prospectively evaluate effects of ambient conditions and post-exercise management practices (cooling methods and vehicular confinement) on the post-exercise temperature change of dogs participating in UK canicross events. Canine temperature was recorded at three intervals post-exercise: as close as possible to 0- (immediately post-exercise), 5-, and 15-min post-exercise. Ambient conditions and post-exercise management were recorded for 115 cooling profiles from 52 dogs. In 28/115 (24.4%) profiles, the dog's temperature increased during the first 5-min post-exercise. Overall, 68/115 (59.1%) profiles included passive cooling (stood or walked outside), 35 (30.4%) active cooling (cold-water immersion or application of a cooling coat), and 12 (10.4%) involved no cooling and were immediately housed in vehicles. No dogs developed hypothermia during the study and no adverse effects were observed from any cooling method. In hyperthermic dogs, overall post-exercise body temperature change was significantly negatively associated (i.e. the dogs cooled more) with 0-min post-exercise body temperature (β = -0.93, p < 0.001), and not being housed in a vehicle (β = -0.43, p = 0.013). This study provides evidence cold-water immersion (in water at 0.1-15.0 °C) can be used to effectively and safely cool dogs with exertional hyperthermia. Progressive temperature increases in many dogs - even after exercise has terminated - supports the message to "cool first, transport second" when managing dogs with HRI. When transporting dogs post-exercise or with HRI even after active cooling, care should be taken to cool the vehicle before entry and promote air movement around the dog during transport to facilitate ongoing cooling and prevent worsening of hyperthermia during travel.

Body Bag Cooling with Two Different Water Temperatures for the Treatment of Hyperthermia

INTRODUCTION: Exertional heatstroke (EHS) is a life-threatening condition that requires quick recognition and cooling for survival. Experts recommend using cooling modalities that reduce rectal temperature (TREC) faster than 0.16°C/min though rates above 0.08°C/min are considered "acceptable." Hyperthermic individuals treated in body bags filled with ice water (∼3°C) have excellent cooling rates (0.28 ± 0.09°C/min). However, clinicians may not have access to large amounts of ice or ice water when treating EHS victims. The purpose of this study was to determine if using a body bag filled with water near the upper limits of expert recommendations for EHS treatment would produce acceptable (>0.08°C/min) or "ideal (>0.16°C/min)" TREC cooling rates or different nadir values.METHODS: A total of 12 individuals (9 men, 3 women; age: 21 ± 2 yr; mass: 74.6 ± 10.2 kg; height: 179.5 ± 9.6 cm) exercised in the heat until TREC was 39.5°C. They lay supine while 211.4 ± 19.5 L of 10°C (Ten) or 15°C (Fifteen) water was poured into a body bag. Subjects cooled until TREC was 38°C. They exited the body bag and rested in the heat for 10 min.RESULTS: Subjects exercised in similar conditions and for similar durations (Ten = 46.3 ± 8.6 min, Fifteen = 46.2 ± 7.8 min). TREC cooling rates were faster in Ten than Fifteen (Ten = 0.18 ± 0.07°C/min, Fifteen = 0.14 ± 0.09°C/min). TREC nadir was slightly higher in Fifteen (37.3 ± 0.2°C) than Ten (37.1 ± 0.3°C).DISCUSSION: Body bag cooling rates met expert definitions of acceptable (Fifteen) and ideal (Ten) for EHS treatment. This information is valuable for clinicians who do not have access to or the resources for ice water cooling to treat EHS.Miller KC, Amaria NY. Body bag cooling with two different water temperatures for the treatment of hyperthermia. Aerosp Med Hum Perform. 2024; 95(4):194-199.

Enhancing physiological recovery and subsequent exercise performance in the heat using a phase-change material cooling blanket

This study aimed to assess the effect of a phase-change material (PCM) cooling blanket for cooling between exercise bouts on recovery of physiological parameters and subsequent exercise performance in the heat. Eighteen male volunteers were recruited to participate in human trials involving two exhaustive treadmill running bouts (Bout1 for 3 km and Bout2 for 1.5 km) in a climate chamber (temperature = 33 °C; relative humidity = 40%). Participants were randomly subjected to one of two cooling conditions for a 10-min period between exercise bouts: CON: natural cooling; 10-min PCM: with a PCM cooling blanket for 10 min. Several physiological parameters including mean skin temperature (Tskin), oral temperature (Toral), core temperature (Tcore), heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), peripheral capillary oxygen saturation (SpO2), average running speed and rating of perceived exertion (RPE) scale score were analyzed. The results showed that compared to the CON group, participants in the 10-min PCM group had a significant lower Tskin, Tcore, HR and RR at post-cooling, as well as greater reductions in mean skin temperature (ΔTskin) and core temperature (ΔTcore) from post-Bout1 to post-cooling. Additionally, the 10-min PCM group exhibited significantly lower peak Tcore, peak HR and RPE scale score during Bout2, while the average running speed during Bout2 was significantly higher. The present study suggests that cooling with a PCM cooling blanket can enhance physiological recovery and subsequent exercise performance in the heat.

Tarp-Assisted Cooling for Exertional Heat Stroke Treatment in Wildland Firefighting

INTRODUCTION

Exertional heat stroke is a life-threatening emergency necessitating immediate treatment with rapid body cooling. A field-expedient alternative may be tarp-assisted cooling, requiring only water and a tarp. The objective of this study was to compare core temperature (Tc) cooling rates of tarp-assisted cooling using the limited resources available to a wildland firefighter and the current standard care provided in wilderness settings.

METHODS

This cross-over, randomized control trial of 17 healthy individuals consisted of exercise in a 42±1°C, 32±4% relative humidity environment while wearing wildland firefighter attire, followed by cooling. Body cooling consisted of either pouring 11 L of 25±1°C water over the torso while lying supine on a tarp configured to hold water close to the individual (Tarp) or dousing the water on the participant followed by lying supine with a light breeze, current standard care in the wilderness (Current Care). Cooling occurred until Tc reached 38°C.

RESULTS

Participants walked until a similar Tc was achieved in Tarp (39.59±0.04°C) and Current Care (39.55±0.22°C; P=0.36). Core temperature cooling rate was not different between Tarp (0.076±0.042°C·min-1) and Current Care (0.088±0.046°C·min-1; P=0.41).

CONCLUSIONS

In hyperthermic individuals, Tarp did not provide a faster cooling rate compared to the current exertional heat stroke care provided in the wilderness, and both provided a slower cooling rate than that provided by the traditional method of cold water immersion (>0.20°C·min-1) to treat exertional heat stroke patients.

Cooling Methods Used to Manage Heat-Related Illness in Dogs Presented to Primary Care Veterinary Practices during 2016-2018 in the UK

The management of heat-related illness (HRI) in dogs has received limited attention in the veterinary literature, especially regarding effective cooling methods. Guidelines published in 2016 for prehospital management of dogs with HRI advised "cool first, transport second", and recommended using cold-water immersion and evaporative cooling (water application with air movement) as the optimal approaches to reduce the patient's temperature. The current retrospective cross-sectional observation study analysed electronic patient records from the VetCompass programme to describe the cooling methods used in dogs with HRI presented to primary care veterinary practices during 2016-2018. Of 623 HRI events identified, 341 (54.74%, 95% CI 50.81-58.60%) included information on cooling in their clinical record. Of these, 74/341 (21.70%, 95% CI 17.65-26.38%) were cooled prior to transport for veterinary care. Overall, 23.97% (95% CI 19.24-29.44%) were cooled using one of the two recommended cooling methods, whilst the most common cooling method recorded was the application of wet towels (51.31%, 95% CI 45.34-57.24%). Canine cooling guidance and messaging in both the public and veterinary sectors requires urgent review to ensure that the most effective cooling methods are promoted because delays to canine temperature reduction worsen patient outcomes.

Phase-change material cooling blanket: A feasible cooling choice during transport after exercise-induced hyperthermia

BACKGROUND

Exercise-induced hyperthermia preceding the onset of exertional heatstroke requires a rapid reduction in the body core temperature (T_core) to ensure safety. In recent years, phase-change material (PCM) cooling devices have been increasingly used for rapid cooling after hyperthermia due to their superior capacity for heat absorption.

OBJECTIVES

This study aimed to evaluate the cooling performance and effectiveness of a PCM cooling blanket on heart rate (HR) and heart rate variability (HRV) recovery after exercise-induced hyperthermia.

DESIGN

Randomized cross-over.

METHODS

The study participants were 12 male volunteers who were engaged in professional training and completed an endurance exercise for approximately 30 min in a hot and humid environment (temperature ≈ 30 °C; relative humidity ≈ 66%). The participants underwent a 30-min cooling trial after exercise, receiving either treatment with a PCM cooling blanket (PCM group) or natural cooling (CON group). The T_core, HR, and HRV time-domain indices were used for analysis.

RESULTS

The T_core values were significantly lower in the PCM group during cooling. Reductions in the T_core from precooling to 20 min of cooling were significantly greater in the PCM group than in the CON group. The HR in the PCM group was lower than that recorded in the CON group at 10 and 20 min of cooling. The reduction in HR during cooling from precooling was also significantly greater in the PCM group. HRV time-domain indices during cooling in the PCM group were significantly lower compared with the CON group while elevations in some HRV time-domain indices from precooling to postcooling were significantly greater in the PCM group than in the CON group.

CONCLUSIONS

The PCM cooling blanket had good cooling performance and the ability to hasten recovery of both HR and HRV. It may serve as a feasible cooling choice during transport after exercise-induced hyperthermia.