Evaluation of 2 Heat-Mitigation Methods in Army Trainees

A Systematic Review of Post-Work Core Temperature Cooling Rates Conferred by Passive Rest

Physical work increases energy expenditure, requiring a considerable elevation of metabolic rate, which causes body heat production that can cause heat stress, heat strain, and hyperthermia in the absence of adequate cooling. Given that passive rest is often used for cooling, a systematic search of literature databases was conducted to identify studies that reported post-work core temperature cooling rates conferred by passive rest, across a range of environmental conditions. Data regarding cooling rates and environmental conditions were extracted, and the validity of key measures was assessed for each study. Forty-four eligible studies were included, providing 50 datasets. Eight datasets indicated a stable or rising core temperature in participants (range 0.000 to +0.028 °C min^-1), and forty-two datasets reported reducing core temperature (-0.002 to -0.070 °C min^-1) during passive rest, across a range of Wet-Bulb Globe Temperatures (WBGT). For 13 datasets where occupational or similarly insulative clothing was worn, passive rest resulted in a mean core temperature decrease of -0.004 °C min^-1 (-0.032 to +0.013 °C min^-1). These findings indicate passive rest does not reverse the elevated core temperatures of heat-exposed workers in a timely manner. Climate projections of higher WBGT are anticipated to further marginalise the passive rest cooling rates of heat-exposed workers, particularly when undertaken in occupational attire.

An Overview of Exertional Heat Illness in Thoroughbred Racehorses: Pathophysiology, Diagnosis, and Treatment Rationale

Exertional heat illness (EHI) is a complex medical disease. The thoroughbred (TB) racehorse is at considerable risk because of the intensity of its exercise activity and its high rate of metabolic heat production. The pathophysiology of EHI can combine aspects of both the heat toxicity pathway and the heat sepsis or endotoxemic pathway. Treatment regimes depend upon the detection of earliest clinical signs, rapid assessment, aggressive cooling and judicious use of ancillary medications. Ice-cold water provides the most rapid cooling, consistent with the need to lower core body temperature before tissue damage occurs. Research into EHI/HS by inducing the condition experimentally is ethically unjustifiable. Consequently, leading researchers in the human field have conceded that "most of our knowledge has been gained from anecdotal incidents, gathered from military personnel and athletes who have collapsed during or following physical activity, and that retrospective and case studies have provided important evidence regarding recognition and treatment of EHI". The authors' review into EHI shares that perspective, and the recommendations made herein are based on observations of heat-affected racehorses at the racetrack and their response, or lack of response, to treatment. From 2014 to 2018, 73 race meetings were attended, and of the 4809 individual starters, signs of EHI were recorded in 457. That observational study formed the basis for a series of articles which have been published under the title, 'EHI in Thoroughbred racehorses in eastern Australia', and forms the background for this review.

Efficacy of two intermittent cooling strategies during prolonged work-rest intervals in the heat with personal protective gear compared with a control condition

INTRODUCTION

Personal protective equipment (PPE) inhibits heat dissipation and elevates heat strain. Impaired cooling with PPE warrants investigation into practical strategies to improve work capacity and mitigate exertional heat illness.

PURPOSE

Examine physiological and subjective effects of forearm immersion (FC), fan mist (MC), and passive cooling (PC) following three intermittent treadmill bouts while wearing PPE.

METHODS

Twelve males (27 ± 6 years; 57.6 ± 6.2 ml/kg/min; 78.3 ± 8.1 kg; 183.1 ± 7.2 cm) performed three 50-min (10 min of 40%, 70%, 40%, 60%, 50% vVO₂max) treadmill bouts in the heat (36 °C, 30% relative humidity). Thirty minutes of cooling followed each bout, using one of the three strategies per trial. Rectal temperature (T_core), skin temperature (T_sk), heart rate (HR), heart rate recovery (HRR), rating of perceived exertion (RPE), thirst, thermal sensation (TS), and fatigue were obtained. Repeated-measures analysis of variance (condition x time) detected differences between interventions.

RESULTS

Final T_core was similar between trials (P > .05). Cooling rates were larger in FC and MC vs PC following bout one (P < .05). HRR was greatest in FC following bouts two (P = .013) and three (P < .001). T_sk, fluid consumption, and sweat rate were similar between all trials (P > .05). TS and fatigue during bout three were lower in MC, despite similar T_core and HR.

CONCLUSION

Utilizing FC and MC during intermittent work in the heat with PPE yields some thermoregulatory and cardiovascular benefit, but military health and safety personnel should explore new and novel strategies to mitigate risk and maximize performance under hot conditions while wearing PPE.

2020 International Consensus on First Aid Science With Treatment Recommendations

This is the summary publication of the International Liaison Committee on Resuscitation's 2020 International Consensus on First Aid Science With Treatment Recommendations. It addresses the most recent published evidence reviewed by the First Aid Task Force science experts. This summary addresses the topics of first aid methods of glucose administration for hypoglycemia; techniques for cooling of exertional hyperthermia and heatstroke; recognition of acute stroke; the use of supplementary oxygen in acute stroke; early or first aid use of aspirin for chest pain; control of life- threatening bleeding through the use of tourniquets, haemostatic dressings, direct pressure, or pressure devices; the use of a compression wrap for closed extremity joint injuries; and temporary storage of an avulsed tooth. Additional summaries of scoping reviews are presented for the use of a recovery position, recognition of a concussion, and 6 other first aid topics. The First Aid Task Force has assessed, discussed, and debated the certainty of evidence on the basis of Grading of Recommendations, Assessment, Development, and Evaluation criteria and present their consensus treatment recommendations with evidence-to-decision highlights and identified priority knowledge gaps for future research. The 2020 International Consensus on Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care (ECC) Science With Treatment Recommendations (CoSTR) is the fourth in a series of annual summary publications from the International Liaison Committee on Resuscitation (ILCOR). This 2020 CoSTR for first aid includes new topics addressed by systematic reviews performed within the past 12 months. It also includes updates of the first aid treatment recommendations published from 2010 through 2019 that are based on additional evidence evaluations and updates. As a result, this 2020 CoSTR for first aid represents the most comprehensive update since 2010.

2020 International Consensus on First Aid Science With Treatment Recommendations

This is the summary publication of the International Liaison Committee on Resuscitation's 2020 International Consensus on First Aid Science With Treatment Recommendations. It addresses the most recent published evidence reviewed by the First Aid Task Force science experts. This summary addresses the topics of first aid methods of glucose administration for hypoglycemia; techniques for cooling of exertional hyperthermia and heatstroke; recognition of acute stroke; the use of supplementary oxygen in acute stroke; early or first aid use of aspirin for chest pain; control of life-threatening bleeding through the use of tourniquets, hemostatic dressings, direct pressure, or pressure devices; the use of a compression wrap for closed extremity joint injuries; and temporary storage of an avulsed tooth. Additional summaries of scoping reviews are presented for the use of a recovery position, recognition of a concussion, and 6 other first aid topics. The First Aid Task Force has assessed, discussed, and debated the certainty of evidence on the basis of Grading of Recommendations, Assessment, Development, and Evaluation criteria and present their consensus treatment recommendations with evidence-to-decision highlights and identified priority knowledge gaps for future research.

First aid cooling techniques for heat stroke and exertional hyperthermia: A systematic review and meta-analysis

BACKGROUND

Heat stroke is an emergent condition characterized by hyperthermia (>40 °C/>104 °F) and nervous system dysregulation. There are two primary etiologies: exertional which occurs during physical activity and non-exertional which occurs during extreme heat events without physical exertion. Left untreated, both may lead to significant morbidity, are considered a special circumstance for cardiac arrest, and cause of mortality.

METHODS

We searched Medline, Embase, CINAHL and SPORTDiscus. We used Grading of Recommendations Assessment, Development and Evaluation (GRADE) methods and risk of bias assessments to determine the certainty and quality of evidence. We included randomized controlled trials, non-randomized trials, cohort studies and case series of five or more patients that evaluated adults and children with non-exertional or exertional heat stroke or exertional hyperthermia, and any cooling technique applicable to first aid and prehospital settings. Outcomes included: cooling rate, mortality, neurological dysfunction, adverse effects and hospital length of stay.

RESULTS

We included 63 studies, of which 37 were controlled studies, two were cohort studies and 24 were case series of heat stroke patients. Water immersion of adults with exertional hyperthermia [cold water (14-17 °C/57.2-62.6 °F), colder water (8-12 °C/48.2-53.6 °F) and ice water (1-5 °C/33.8-41 °F)] resulted in faster cooling rates when compared to passive cooling. No single water temperature range was found to be associated with a quicker core temperature reduction than another (cold, colder or ice).

CONCLUSION

Water immersion techniques (using 1-17 °C water) more effectively lowered core body temperatures when compared with passive cooling, in hyperthermic adults. The available evidence suggests water immersion can rapidly reduce core body temperature in settings where it is feasible.

Wearable devices for remote vital signs monitoring in the outpatient setting: an overview of the field

Early detection of physiological deterioration has been shown to improve patient outcomes. Due to recent improvements in technology, comprehensive outpatient vital signs monitoring is now possible. This is the first review to collate information on all wearable devices on the market for outpatient physiological monitoring.

A scoping review was undertaken. The monitors reviewed were limited to those that can function in the outpatient setting with minimal restrictions on the patient’s normal lifestyle, while measuring any or all of the vital signs: heart rate, ECG, oxygen saturation, respiration rate, blood pressure and temperature.

A total of 270 papers were included in the review. Thirty wearable monitors were examined: 6 patches, 3 clothing-based monitors, 4 chest straps, 2 upper arm bands and 15 wristbands. The monitoring of vital signs in the outpatient setting is a developing field with differing levels of evidence for each monitor. The most common clinical application was heart rate monitoring. Blood pressure and oxygen saturation measurements were the least common applications. There is a need for clinical validation studies in the outpatient setting to prove the potential of many of the monitors identified.

Research in this area is in its infancy. Future research should look at aggregating the results of validity and reliability and patient outcome studies for each monitor and between different devices. This would provide a more holistic overview of the potential for the clinical use of each device.

Heatstroke management during the COVID-19 epidemic: recommendations from the experts in Japan

Fever and hyperthermia are the main symptoms of coronavirus disease (COVID-19) and heatstroke, and it is difficult to distinguish them. There is a need to discuss safe prevention and medical treatment for heatstroke. In view of the above issues, the Japanese Association for Acute Medicine "Committee on heatstroke and hypothermia" established a "Working group on heatstroke medical care given the COVID-19 epidemic" jointly with the Japanese Society for Emergency Medicine that focuses on emergency medical personnel, including paramedics and nurses, the Japanese Association for Infectious Diseases, an academic society of infectious disease, and the Japanese Respiratory Society, an academic organization on respiratory diseases. The precautions for prevention of heatstroke this summer during the coronavirus epidemic was summarized in "Proposals on heatstroke prevention based on the COVID-19 epidemic" as follows and was issued on 1 June, 2020. Based on the above, we have determined that guidance in clinical practice is necessary not only from the viewpoint of heatstroke prevention, but also medical treatment. As such, we have created this guidance in the form of supplementary recommendations.

Functional Performance of Firefighters After Exposure to Environmental Conditions and Exercise

CONTEXT

Slips, trips, and falls are leading causes of musculoskeletal injuries in firefighters. Researchers have hypothesized that heat stress is the major contributing factor to these fireground injuries.

OBJECTIVE

To examine the effect of environmental conditions, including hot and ambient temperatures, and exercise on functional and physiological outcome measures, including balance, rectal temperature, and perceived exertion.

DESIGN

Randomized controlled clinical trial.

SETTING

Laboratory environmental chamber.

PATIENTS OR OTHER PARTICIPANTS

A total of 13 healthy, active career firefighters (age = 26 ± 6 years [range = 19-35 years], height = 178.61 ± 4.93 cm, mass = 86.56 ± 16.13 kg).

INTERVENTION(S)

Independent variables consisted of 3 conditions (exercise in heat [37.41°C], standing in heat [37.56°C], and exercise in ambient temperature [14.24°C]) and 3 data-collection times (preintervention, postintervention, and postrecovery). Each condition was separated from the others by at least 1 week and lasted a maximum of 40 minutes or until the participant reached volitional fatigue or a rectal temperature of 40.0°C.

MAIN OUTCOME MEASURE(S)

Firefighting-specific functional balance performance index, rectal temperature, and rating of perceived exertion.

RESULTS

Exercise in the heat decreased functional balance, increased rectal temperature, and altered the perception of exertion compared with the other intervention conditions.

CONCLUSIONS

A bout of exercise in a hot, humid environment increased rectal temperature in a similar way to that reported in the physically active population and negatively affected measures of functional balance. Rather than independently affecting balance, the factors of exercise and heat stress appeared to combine, leading to an increased likelihood of slips, trips, and falls.