Gait instability and estimated core temperature predict exertional heat stroke

2022 ◽  
pp. bjsports-2021-104081
Author(s):  
Mark Buller ◽  
Rebecca Fellin ◽  
Max Bursey ◽  
Meghan Galer ◽  
Emma Atkinson ◽  
...  
Keyword(s):  
Heart Rate ◽  
Core Temperature ◽  
Military Personnel ◽  
Core Body Temperature ◽  
Heat Stroke ◽  
False Negative ◽  
Exertional Heat Stroke ◽  
Us Military ◽  
Hot Environments ◽  
Cns Dysfunction

ObjectiveExertional heat stroke (EHS), characterised by a high core body temperature (Tcr) and central nervous system (CNS) dysfunction, is a concern for athletes, workers and military personnel who must train and perform in hot environments. The objective of this study was to determine whether algorithms that estimate Tcr from heart rate and gait instability from a trunk-worn sensor system can forward predict EHS onset.MethodsHeart rate and three-axis accelerometry data were collected from chest-worn sensors from 1806 US military personnel participating in timed 4/5-mile runs, and loaded marches of 7 and 12 miles; in total, 3422 high EHS-risk training datasets were available for analysis. Six soldiers were diagnosed with heat stroke and all had rectal temperatures of >41°C when first measured and were exhibiting CNS dysfunction. Estimated core temperature (ECTemp) was computed from sequential measures of heart rate. Gait instability was computed from three-axis accelerometry using features of pattern dispersion and autocorrelation.ResultsThe six soldiers who experienced heat stroke were among the hottest compared with the other soldiers in the respective training events with ECTemps ranging from 39.2°C to 40.8°C. Combining ECTemp and gait instability measures successfully identified all six EHS casualties at least 3.5 min in advance of collapse while falsely identifying 6.1% (209 total false positives) examples where exertional heat illness symptoms were neither observed nor reported. No false-negative cases were noted.ConclusionThe combination of two algorithms that estimate Tcr and ataxic gate appears promising for real-time alerting of impending EHS.

scholarly journals Characterisation of Physiological Performance Measures in Arid and Humid Military Operational Environments

2021 ◽  
Author(s):  
Edward Tom Ashworth ◽  
Lauren Catherine Keaney ◽  
James David Cotter ◽  
Andrew Edward Kilding
Keyword(s):  
Heart Rate ◽  
Cognitive Performance ◽  
Core Temperature ◽  
Military Personnel ◽  
Thermal Sensation ◽  
Arid Environment ◽  
Time To Exhaustion ◽  
Humid Environment ◽  
Performance Predictors ◽  
Hot Environments

Abstract BackgroundMilitary personnel often deploy into hot environments that impose substantial strain on physical and cognitive performance. Hot environments can present as arid or humid and occur in different terrains, requiring different operational approaches. The aim of this study was to characterise the physiological, cognitive and perceptual strain experienced by military personnel during typical operations in arid and humid environments. MethodsNine pack-fit military personnel participated in two heat-stress tests to exhaustion, one in an arid environment (44°C, 21% humidity) and the other in a humid environment (33°C, 78% humidity). Participants walked at 5 km.h-1 while physiological, cognitive and perceptual measures were recorded. Tests were terminated volitionally, or by excessive core temperature or heart rate. Results The operational environments induced similar physiological stress, resulting in no difference in time to exhaustion (p = .155). The humid environment saw a greater elevation in core temperature (+0.3°C, p < .001) and heart rate (+5 b.min-1, p < .001). Skin temperature was greater in the arid environment (+0.4, p < .001) as was sweat evaporation (+0.3 L.h1, p = .045). Baseline performance predictors only provided moderate predictions of performance, whereas changes in perceptual measures provided the best performance predictors during the exercise, specifically perceptions relating to thermal sensation (β = -.65 - -.80) and sleepiness (β = -.79 - -.87). While no differences in cognitive performance were observed, greater cognitive stress was reported by participants over time, regardless of environment (all p < .011). ConclusionsThe humid operational environment elicited a greater thermal strain that may threaten safety, and impair performance, to a greater degree than the arid environment. Perceptual measures of thermal sensation and sleepiness were the best predictors of test termination and could likely be used to monitor thermal tolerance in field settings.

scholarly journals The Fire from Within: Multiorgan Failure with Bimodal Rhabdomyolysis from Exertional Heat Stroke

2020 ◽  
Vol 2020 ◽  
pp. 1-7 ◽  
Author(s):  
Onion Gerald V. Ubaldo ◽  
Khia Quiwa ◽  
Rohana Elise Rollan ◽  
Edhel Tripon ◽  
Elizabeth Sebastian
Keyword(s):  
Liver Transplantation ◽  
Liver Failure ◽  
Liver Transplant ◽  
Core Body Temperature ◽  
Multiorgan Failure ◽  
Heat Stroke ◽  
Exertional Heat Stroke ◽  
Liver Support ◽  
Central Nervous System Dysfunction ◽  
Extracorporeal Liver Support

Heat stroke (HS) is a condition characterized by a rise in core body temperature and central nervous system dysfunction. It is divided into two types: classical and exertional. Exertional heat stroke (EHS) is accompanied by organ failure. Liver injury, presenting only with a rise in liver enzymes, is common but in rare conditions, acute liver failure (ALF) may ensue, leading to a potentially lethal condition. Most cases of EHS-induced ALF are managed conservatively. However, liver transplantation is considered for cases refractory to supportive treatment. Identifying patients eligible for liver transplantation in the context of an EHS-induced ALF becomes a medical dilemma since the conventional prognostic criterion may be difficult to apply, and there is paucity of literature about these specific sets of individuals. Recently, extracorporeal liver support has been gaining popularity for patients with liver failure as a bridge to liver transplant. In this case report, we present a young Filipino athlete with symptoms and clinical course consistent with EHS that developed multiorgan failure, initially considered a candidate for liver transplant and total plasma exchange, but clinically improved with supportive management alone. This patient was also found to have bimodal rhabdomyolysis during the course of his hospital stay as manifested by the bimodal rise in his creatine kinase enzymes.

scholarly journals Controversies in exertional heat stroke diagnosis, prevention, and treatment

2019 ◽  
Vol 127 (5) ◽  
pp. 1338-1348 ◽  
Author(s):  
Orlando Laitano ◽  
Lisa R. Leon ◽  
William O. Roberts ◽  
Michael N. Sawka
Keyword(s):  
Physical Activity ◽  
Core Temperature ◽  
Recovery Period ◽  
Heat Stroke ◽  
Tolerance Test ◽  
Body Core Temperature ◽  
Exertional Heat Stroke ◽  
Immediate Recovery ◽  
Body Core ◽  
Inflammatory Drugs

During the past several decades, the incidence of exertional heat stroke (EHS) has increased dramatically. Despite an improved understanding of this syndrome, numerous controversies still exist within the scientific and health professions regarding diagnosis, pathophysiology, risk factors, treatment, and return to physical activity. This review examines the following eight controversies: 1) reliance on core temperature for diagnosing and assessing severity of EHS; 2) hypothalamic damage induces heat stroke and this mediates “thermoregulatory failure” during the immediate recovery period; 3) EHS is a predictable condition primarily resulting from overwhelming heat stress; 4) heat-induced endotoxemia mediates systemic inflammatory response syndrome in all EHS cases; 5) nonsteroidal anti-inflammatory drugs for EHS prevention; 6) EHS shares similar mechanisms with malignant hyperthermia; 7) cooling to a specific body core temperature during treatment for EHS; and 8) return to physical activity based on physiological responses to a single-exercise heat tolerance test. In this review, we present and discuss the origins and the evidence for each controversy and propose next steps to resolve the misconception.

scholarly journals Cooling Effectiveness of a Modified Cold-Water Immersion Method After Exercise-Induced Hyperthermia

2016 ◽  
Vol 51 (11) ◽  
pp. 946-951 ◽  
Author(s):  
Katherine E. Luhring ◽  
Cory L. Butts ◽  
Cody R. Smith ◽  
Jeffrey A. Bonacci ◽  
Ramon C. Ylanan ◽  
...  
Keyword(s):  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Effect Size ◽  
Cold Water ◽  
Water Immersion ◽  
Heat Stroke ◽  
Cold Water Immersion ◽  
Whole Body ◽  
Exertional Heat Stroke

Context: Recommended treatment for exertional heat stroke includes whole-body cold-water immersion (CWI). However, remote locations or monetary or spatial restrictions can challenge the feasibility of CWI. Thus, the development of a modified, portable CWI method would allow for optimal treatment of exertional heat stroke in the presence of these challenges. Objective: To determine the cooling rate of modified CWI (tarp-assisted cooling with oscillation [TACO]) after exertional hyperthermia. Design: Randomized, crossover controlled trial. Setting: Environmental chamber (temperature = 33.4°C ± 0.8°C, relative humidity = 55.7% ± 1.9%). Patients or Other Participants: Sixteen volunteers (9 men, 7 women; age = 26 ± 4.7 years, height = 1.76 ± 0.09 m, mass = 72.5 ± 9.0 kg, body fat = 20.7% ± 7.1%) with no history of compromised thermoregulation. Intervention(s): Participants completed volitional exercise (cycling or treadmill) until they demonstrated a rectal temperature (Tre) ≥39.0°C. After exercise, participants transitioned to a semirecumbent position on a tarp until either Tre reached 38.1°C or 15 minutes had elapsed during the control (no immersion [CON]) or TACO (immersion in 151 L of 2.1°C ± 0.8°C water) treatment. Main Outcome Measure(s): The Tre, heart rate, and blood pressure (reported as mean arterial pressure) were assessed precooling and postcooling. Statistical analyses included repeated-measures analysis of variance with appropriate post hoc t tests and Bonferroni correction. Results: Before cooling, the Tre was not different between conditions (CON: 39.27°C ± 0.26°C, TACO: 39.30°C ± 0.39°C; P = .62; effect size = −0.09; 95% confidence interval [CI] = −0.2, 0.1). At postcooling, the Tre was decreased in the TACO (38.10°C ± 0.16°C) compared with the CON condition (38.74°C ± 0.38°C; P &lt; .001; effect size = 2.27; 95% CI = 0.4, 0.9). The rate of cooling was greater during the TACO (0.14 ± 0.06°C/min) than the CON treatment (0.04°C/min ± 0.02°C/min; t15 = −8.84; P &lt; .001; effect size = 2.21; 95% CI = −0.13, −0.08). These differences occurred despite an insignificant increase in fluid consumption during exercise preceding CON (0.26 ± 0.29 L) versus TACO (0.19 ± 0.26 L; t12 = 1.73; P = .11; effect size = 0.48; 95% CI = −0.02, 0.14) treatment. Decreases in heart rate did not differ between the TACO and CON conditions (t15 = −1.81; P = .09; effect size = 0.45; 95% CI = −22, 2). Mean arterial pressure was greater at postcooling with TACO (84.2 ± 6.6 mm Hg) than with CON (67.0 ± 9.0 mm Hg; P &lt; .001; effect size = 2.25; 95% CI = 13, 21). Conclusions: The TACO treatment provided faster cooling than did the CON treatment. When location, monetary, or spatial restrictions are present, TACO represents an effective alternative to traditional CWI in the emergency treatment of patients with exertional hyperthermia.

scholarly journals Sex-dependent responses to exertional heat stroke in mice

2018 ◽  
Vol 125 (3) ◽  
pp. 841-849 ◽  
Author(s):  
Christian K. Garcia ◽  
Alex J. Mattingly ◽  
Gerard P. Robinson ◽  
Orlando Laitano ◽  
Michelle A. King ◽  
...  
Keyword(s):  
Core Temperature ◽  
Body Surface ◽  
Military Service ◽  
Heat Stroke ◽  
Internal Heat ◽  
Aerobic Performance ◽  
Power Performance ◽  
Exertional Heat Stroke ◽  
Female Mice ◽  
Heat Loads

With increasing participation of females in endurance athletics and active military service, it is important to determine if there are inherent sex-dependent susceptibilities to exertional heat injury or heat stroke. In this study we compared responses of male and female adult mice to exertional heat stroke (EHS). All mice were instrumented for telemetry core temperature measurements and were exercise-trained for 3 wk before EHS. During EHS, environmental temperature was 37.5°C (35% RH) while the mice ran on a forced running wheel, using incremental increases in speed. The symptom-limited endpoint was loss of consciousness, occurring at ~42.2°C core temperature. Females ran greater distances (623 vs. 346 m, P < 0.0001), reached faster running speeds (7.2 vs. 5.1 m/min, P < 0.0001), exercised for longer times (177 vs. 124 min, P < 0.0001), and were exposed to greater internal heat loads (240 vs.160°C·min; P < 0.0001). Minimum Tc during hypothermic recovery was ~32.0°C in both sexes. Females lost 9.2% body weight vs. 7.5% in males ( P < 0.001). Females demonstrated higher circulating corticosterone (286 vs 183 ng/ml, P = 0.001, at 3 h), but most plasma cytokines were not different. A component of performance in females could be attributed to greater body surface area/mass and greater external power performance. However, there were significant and independent effects of sex alone and a crossed effect of “sex × power” on performance. These results demonstrate that female mice have greater resistance to EHS during exercise in hyperthermia and that these effects cannot be attributed solely to body size. NEW & NOTEWORTHY Female mice are surprisingly more resistant to exertional heat stroke than male mice. They run faster and longer and can withstand greater internal heat loads. These changes cannot be fully accounted for by increased body surface/mass ratio in females or on differences in aerobic performance. Although the stress-immune response in males and females was similar, females exhibited markedly higher plasma corticosteroid levels, which were sustained over 14 days of recovery.

scholarly journals Test and Evaluation of Heart Rate Derived Core Temperature Algorithms for Use in NCAA Division I Football Athletes

2020 ◽  
Vol 5 (3) ◽  
pp. 46
Author(s):  
Joshua Hagen ◽  
Aaron Himmler ◽  
Joseph Clark ◽  
Jad Ramadan ◽  
Jason Stone ◽  
...  
Keyword(s):  
Heart Rate ◽  
Body Composition ◽  
Core Temperature ◽  
Injury Risk ◽  
Core Body Temperature ◽  
American Football ◽  
Upper Body ◽  
Stress Monitoring ◽  
Test And Evaluation ◽  
Division I Football

The purpose of this study was to assess the validity of utilizing heart rate to derive an estimate of core body temperature in American Football athletes. This was evaluated by combining commercially available Zephyr Bioharness devices, which includes an embedded estimated core temperature (ECT) algorithm, and an ingestible radio frequency core temperature pill during the highest heat injury risk timepoint of the season, summer training camp. Results showed a concordance of 0.643 and 78% of all data points fell within +/−1.0 °F. When the athletes were split into Upper (>/=6.0%) and Lower (<6.0%) body composition groups, there was a statistical improvement in accuracy with the Upper Body Fat% reaching 0.834 concordance and 93% of all values falling within +/−1.0 °F of the Gold Standard. Results suggest that heart rate derived core temperature assessments are a viable tool for heat stress monitoring in American football, but more work is required to improve on accuracy based on body composition.

scholarly journals Exertional Heat Stroke in Athletes

2013 ◽  
Vol 1 (1) ◽  
pp. 135-139
Author(s):  
Metodija Kjertakov ◽  
Yoram Epstein
Keyword(s):  
Core Temperature ◽  
Water Immersion ◽  
Heat Stroke ◽  
Medical Emergency ◽  
Body Core Temperature ◽  
Exertional Heat Stroke ◽  
Hot Environment ◽  
Body Core ◽  
Nerve System ◽  
Ice Water

Exercising in hot and especially humid environment can cause rise in body core temperature to such a critical level that it does not only reduce performance, but also may ultimately lead to exertional heat stroke (EHS). This illness is true medical emergency that can result in significant morbidity and mortality, if not early recognized and promptly treated. Diagnostic criteria for EHS are body core temperature above 40ºC and central nerve system dysfunction. Any athlete experiencing such symptoms should be immediately exposed to aggressive cooling treatment aimed to lower the elevated core temperature to near normal as quickly as possible. Ice water immersion is highly recommended as a cooling method because it provides the fastest cooling rates and is associated with lowest mortality rates. Athletes cooled rapidly soon after the onset of EHS usually recover without complications and are able to return to normal training in hot environment within a few weeks. EHS is also a preventable condition, and its occurrence can be minimized by implementing a few simple measures.

scholarly journals A Case of Exertional Heat Stroke Complicated by Hypoxic Hepatitis

2020 ◽  
Vol 2020 ◽  
pp. 1-4
Author(s):  
Bertram K. Woitok ◽  
Shawki Bahmad ◽  
Gregor Lindner
Keyword(s):  
Supportive Care ◽  
Liver Failure ◽  
Acute Liver Failure ◽  
Multiorgan Failure ◽  
Heat Stroke ◽  
Exertional Heat Stroke ◽  
Hypoxic Hepatitis ◽  
Threatening Condition ◽  
Life Threatening ◽  
Delayed Referral

Background.Exertional heat stroke is a life-threatening condition often complicated by multiorgan failure. We hereby present a case of a 25-year-old male presenting with syncope after a 10  km run in 28°C outside temperature who developed acute liver failure. Case Presentation. Initial temperature was found to be 41.1°C, and cooling measures were rapidly applied. He suffered from acute renal failure and rhabdomyolysis and proceeded to acute liver failure (ASAT 6100 U/l and ALAT 6561 U/l) due to hypoxic hepatitis on day 3. He did not meet criteria for emergency liver transplantation and recovered on supportive care. Conclusions. Acute liver failure due to heat stroke is a life-threatening condition with often delayed onset, which nevertheless resolves on supportive care in the majority of cases; thus, a delayed referral to transplant seems to be reasonable.

scholarly journals Helminth infections in the US military: from strongyloidiasis to schistosomiasis

2021 ◽  
Author(s):  
Alyssa R Lindrose ◽  
Indrani Mitra ◽  
Jamie Fraser ◽  
Edward Mitre ◽  
Patrick W Hickey
Keyword(s):  
Military Personnel ◽  
International Classification Of Diseases ◽  
Data Repository ◽  
Military Health ◽  
Intestinal Nematode ◽  
Us Military ◽  
Helminth Infections ◽  
The Us ◽  
East And Southeast Asia ◽  
The Military

Abstract Background Helminth infections caused by parasitic worms, including nematodes (roundworms), cestodes (tapeworms) and trematodes (flukes), can cause chronic symptoms and serious clinical outcomes if left untreated. The US military frequently conducts activities in helminth-endemic regions, particularly Africa, the Middle East and Southeast Asia. However, the military does not currently screen for these infections, and to date, no comprehensive surveillance studies have been completed to assess the frequency of helminth diagnoses in the military personnel and their families. Methods To determine the burden of helminth infections in the US Military Health System (MHS), we conducted a retrospective analysis of International Classification of Diseases (ICD)-9/10 diagnosis codes from all medical encounters in the MHS Data Repository (MDR) from fiscal years (FY) 2012 to 2018. Chart reviews were conducted to assign ICD diagnoses as incorrect, suspected, probable or confirmed based on the laboratory results and symptoms. Results Abstraction of MHS data revealed over 50 000 helminth diagnoses between FY 2012 and FY 2018. Of these, 38 445 of diagnoses were amongst unique subjects. After chart review, we found there were 34 425 validated helminth infections diagnosed amongst the unique subjects of US military personnel, retirees and dependents. Nearly 4000 of these cases represented infections other than enterobiasis. There were 351 validated strongyloidiasis diagnoses, 317 schistosomiasis diagnoses and 191 diagnoses of cysticercosis during the study period. Incidence of intestinal nematode infection diagnoses showed an upward trend, whilst the incidence of cestode infection diagnoses decreased. Conclusions The results of this study demonstrate that helminth infections capable of causing severe morbidity are often diagnosed in the US military. As helminth infections are often asymptomatic or go undiagnosed, the true burden of helminth infections in US military personnel and dependents may be higher than observed here. Prospective studies of US military personnel deployed to helminth-endemic areas may be indicated to determine if post-deployment screening and/or empirical treatment are warranted.

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