МОДЕЛЮВАННЯ ТЕПЛОВИХ РЕАКЦІЙ ЛЮДИНИ ПІД ЧАС ЗАНУРЕННЯ У ТЕПЛУ ВОДУ

Background. This paper describes the mathematical model for human thermoregulation in warm water and demonstrates results for impact of warm water immersion in man during resting conditions and exercises. The purpose of the work is to describe a mathematical model of human thermoregulation in warm water and demonstrate the effects of immersion in warm water on a person under conditions of rest and exercise. Materials and methods. Model is realized as friendly user computer simulator. The model makes prediction based on the human data, metabolic rate, environmental conditions and clothing biophysics. Results. Modeling resulted in the conclusion that human immersion in warm water is the rapid time process demanding severe control. Comparison of modeling results with measurements in volunteers approved these data. It was demonstrated that dynamics of human heating is highly sensitive to residence time in water. Model predicted main significant effect of human exercises on thermoregulatory responses and human temperatures in different warm water. Physical activity in warm water accelerates the time processes and gains human heating. Additional metabolic heat producing during performance in warm water elevates core temperature significantly. Conclusions. Modeling showed that steady state depends on human time in water. During short time of immersion even at high water temperature it could be no danger of human overheating, however as human stays in water the danger of overheating become critical.У статті наведено математичну модель терморегуляції людини у теплій воді і результати впливу теплої води на людину в умовах спокою та фізичного навантаження. Розглянуто діапазон занурення у воду від 35 °C до 38 °C. Модель реалізовано у вигляді зручного для користувача комп'ютерного симулятора. Модель дає прогнози на основі даних про людину, швидкості метаболізму, умов навколишнього середовища та біофізики одягу. За результатами моделювання зроблено висновок, що занурення людини в теплу воду—це стрімкий, швидкий за часом процес, що вимагає жорсткого контролю. Порівняння результатів моделювання з вимірами на добровольцях підтвердило ці дані. Показано, що динаміка нагріву людини істотно залежить від температури води та часу занурення. Під час короткочасного занурення навіть за високої температури води немає загрози перегрівання людини, однак тривалість занурення може призвести до перегрівання

Modeling Thermoregulatory Responses to Cold Environments

The ability to model and simulate the rise and fall of core body temperature is of significant interest to a broad spectrum of organizations. These organizations include the military, as well as both public and private health and medical groups. To effectively use cold models, it is useful to understand the first principles of heat transfer within a given environment as well as have an understanding of the underlying physiology, including the thermoregulatory responses to various conditions and activities. The combination of both rational or first principles and empirical approaches to modeling allow for the development of practical models that can predict and simulate core body temperature changes for a given individual and ultimately provide protection from injury or death. The ability to predict these maximal potentials within complex and extreme environments is difficult. The present work outlines biomedical modeling techniques to simulate and predict cold-related injuries, and discusses current and legacy models and methods

서열 환경에서 개인보호복 착용 작업자의 서열부담 추정을 위한 비침습적 항목 탐색과 지표의 타당성 평가

학위논문(박사) -- 서울대학교대학원 : 생활과학대학 의류학과, 2023. 2. 이주영.본 연구는 더운 환경에서 개인보호장비(Personal Protective Equipment: PPE)를 착용한 작업자를 대상으로 실시간 모니터링 시스템에서 활용할 수 있는 비침습적 생리학적 지표의 타당성을 탐색하고 평가하는 것을 목적으로 하였다. Moran et al. (1998)은 직장 온도(Tre)와 심박수(HR)를 기반으로 생리적부담지수[Physiological Strain Index: PSI = 5 · (Tret - Tre0) · (39.5 - Tre0)-1 + 5 · (HRt – HR0) · (180 – HR0)-1] 처음 개발하였으며, 작업자의 서열부담 추정과 주로 실험실 환경에서 개별적 서열부담을 평가하는데 널리 사용되었다. 그러나, 직장온도 측정은 실제 작업현장에서 측정하기 쉽지 않으며, 작업자가 직접 센서를 삽입해야 한다는 단점이 있다. 이에 비침습적 측정을 통한 심부온 추정 방법이 많은 연구에서 제안되고 있다. 그러나 여전히 작업현장에서 활용되기엔 몇몇 기술적 한계가 존재한다. 따라서 이러한 한계점을 고려하여 본 연구에서는 보다 실용적이고 비침습적 생리부담 지표를 제시하는 것을 목표로 하였다. 본 연구는 두 부분으로 구성되었다. Part 1에서는 고온 환경에서 PPE를 착용 시 발생하는 서열부담을 평가하기 위해 실험[A(2018), B(2019)]를 각각 수행하였다. 실험 A는 9명 피험자가 기온 28 °C, 33 °C, 38 °C 및 상대습도 70%인 3가지 환경조건에서 일상복과 전신보호복(Level D, Tyvek)인 2가지 의복조건에 참여하였다. 실험A는 총 80분간 (10분 휴식–60분 운동–10분 회복)으로 구성되었다. 실험 B는 7명의 피험자가 기온 33 °C 및 상대습도70% 환경에서 4가지 다른 보호 수준의 PPE조건에 참여하였다. 실험B는 10분간 안정 후 직장온도 39 °C에 도달할 때까지 운동을 지속하였다. 실험 A와 B의 결과를 바탕으로 기존 PSI식의 직장온도를 대체할 비침습적 항목을 선정하였으며, 총 3가지의 비침습적 PSI식으로 수정되었다. 비침습적 식의 타당성 검사를 위해 기존 PSI식과 새로 수정된 비침습적 추정식을 비교하여 상관관계 및 일관성 분석을 수행하였다. Part 1의 결과, 직장온도를 대체할 수 있는 비침습적 측정항목으로 이마, 발 또는 발가락으로 나타났다. 비침습적 식 중 Model 2 (NIPSI33)가 기존 PSI와 가장 높은 상관관계와 일관성을 보였다. 또한 Model1 (NIPSI)도 함께 분석하여 Model 2 (NIPSI33)를 사용하는 것보다 더 정확한 개별 모니터링이 가능한지 확인하였다. Model 1 (NIPSI) = 5 (Tskt – Tsk0) · (39.5 – Tsk0)-1 + 5 (HRt – HR0) · (180 – HR0)-1 *Tret는 Tforehead, Tfoot, 또는 Ttoe로 대체되며, Tre0 은 초기 피부온도인 Tsk0로 대체됨. Model 2 (NIPSI33) = 5 (Tskt – 33) · (39.5 –33)-1 + 5 (HRt – HR0) · (180 – HR0)-1 *Tret는 Tforehead, Tfoot, 또는 Ttoe로 대체되며, Tre0 은 33 °C로 초기온도를 고정함. Part 2는 실험 A 및 B와 겹치지 않는 새로운 13개 실험의 데이터 세트를 수집하여 분석에 사용하였고, Part 1에서 도출된 비침습적 추정식의 타당성을 검증하였다. 총 123명의 피험자에게서 얻어진 직장온도, 피부온도, 심박수를 사용하여 기존 PSI와 Model 1, Model 2를 비교하였다. Part 2의 결과, Model 1 (NIPSI)보다 Model 2 (NIPSI33)가 기존 PSI와 더 높은 상관을 보였다. 발 또는 발가락 온도를 사용한 대부분의 비침습적 추정식이 이마보다 더 큰 타당성을 보였다. 따라서 본 연구는 세 부위(이마, 발, 발가락) 중에서 발 또는 발가락 온도를 이용하는 것이 작업자의 서열부담을 추정하는데 가장 적합할 것으로 사료된다. 다만, Model 2 (NIPSI33_ 발가락/발등)에 적용할 수 있는 조건에는 한계가 존재하며, 1) 환경온도 30 °C 이상의 환경조건 시, 2) 개인보호구 착용 시, 그리고 3) 일정 시간에 걸쳐 작업 또는 운동이 수행된 경우, 본 연구에서 도출된 비침습적 추정식이 적용될 수 있음을 확인하였다. 본 연구논문은 고온 환경에서 전신보호복을 착용하는 작업자들의 서열부담을 추정하여 열 질환을 예방할 수 있는 실시간 서열부담 모니터링 시스템의 개발에 도움이 될 수 있을 것이다.Initially, physiological strain index (PSI) was developed based on rectal temperature (Tre) and heart rate (HR) to estimate heat strain and heat illness from workers: 5 (Tret − Tre0) ∙ (39.5 − Tre0)-1 + 5 (HRt – HR0) ∙ (180 – HR0)-1, and this method was widely used to evaluate individual thermal strain in experimental settings. However, the difficulties of measuring Tre in the field, and the need to directly insert the sensor into workers for measurement have hindered the further application of this method. Accordingly, the estimation of core temperature (Tc) through non-invasive measurement has been proposed in numerous studies. However, there are still some technical limitations on measurement in an actual field. Therefore, this study aimed to present a more practical, non-invasive physiological strain index. To this end, this study aimed to explore and evaluate the validity of non-invasive physiological parameters that can be used for the real-time monitoring of workers wearing personal protective equipment (PPE) in hot environments. This study was divided into two parts. In Part 1, experiments A and B were conducted to evaluate the heat strain of wearing PPE in hot environments. In Experiment A, two clothing conditions were used: 1) daily clothes and 2) full-body protective clothing under three temperature conditions (28, 33, and 38 °C) at 70% relative humidity (RH). Heat strain assessment was performed according to the 80 min experimental protocol (10 min rest – 60 min exercise – 10 min recovery). In Experiment B, PPE with four different protective levels was worn by seven subjects at 33 °C and 70% RH. The Experimental protocol consisted of 10 min rest and exercise on a treadmill until Tre reached 39oC, after which the recovery time was recorded if possible. The original PSI equation was modified into three non-invasive PSI equations using non-invasive parameters based on the results obtained in experiments A and B. To validate the results, correlation and consistency analysis was conducted by comparing the original PSI and the newly modified non-invasive PSIs. Consequently, the forehead, foot, and toe were selected as non-invasive measurement sites for Part 1. Among the non-invasive equations, Model 2 (Non-invasive PSI; NIPSI33) exhibited the highest correlation and consistency with the original PSI. In addition, Model 1 (NIPSI) was also analyzed to confirm if it could achieve a more accurate individual monitoring than Model 2. 1) Model 1 (NIPSI) = 5 (Tskt – Tsk0) · (39.5 – Tsk0)-1 + 5 (HRt – HR0) · (180 – HR0)-1 *Tret was replaced to Tforehead, Tfoot, or Ttoe; and Tre0 was replaced to Tsk0. 2) Model 2 (NIPSI33) = 5 (Tskt – 33) · (39.5 –33)-1 + 5 (HRt – HR0) · (180 – HR0)-1 *Tret was replaced to Tforehead, Tfoot, or Ttoe; and Tre0 was replaced to 33 °C. In Part 2, data sets from 13 experiments were collected and analyzed to verify the validity of the equations derived from Part 1. Rectal temperature, skin temperature, and heart rate of 123 subjects were used by comparing the original PSI, Model 1, and Model 2. Lastly, applicable conditions were suggested based on the clothing, environment, and activity level. For the Part 2 experiments, Model 2 exhibited higher correlation coefficients than Model 1. Additionally, most equations derived using the foot or toe temperature exhibited greater validity than those derived using the forehead. This indicates that among the three regions (the forehead, foot, and toe), the use of the foot or toe temperature is the most appropriate for the estimation of a workers heat strain. However, there are limitations on the conditions which can be applied to the NIPSI33. 1) the environment temperature must be above 30 °C, 2) the environment wearing personal protective equipment, and 3) a state in which work or exercise over a certain period has been performed, indicating the applicability of the above situation. This research paper can aid in the development of a heat strain monitoring system that can prevent heat-related illness by estimating the heat strain of workers wearing full-body protective clothing in a high-temperature environment.Chapter 1. Introduction 1 Chapter 2. Theoretical background 4 2.1 Personal protective equipment (PPE) and protection levels 4 2.2 Heat stress and heat strain 10 2.3 Significance of monitoring heat strain in the workplace 12 2.4 Determination parameters of thermal or heat strain 13 2.5 Skin temperature as a parameter of core temperature estimation 15 2.6 Physiological strain index with non-invasive measurements 18 Chapter 3. Methods 21 3.1 Research framework 21 3.2 [Part 1] Investigation of non-invasive parameters 23 3.2.1 Ethical approval and subjects 20 3.2.2 Experimental procedure and protocols 24 3.2.3 Measurements 29 3.2.4 Modified equations of physiological strain index 32 3.2.5 Data analysis 33 3.3 [Part 2] Validity of the non-invasive PSIs 35 3.3.1 Overall description of 13 experiments and key features 35 3.3.2 Characteristics of subjects in 13 experiments 41 3.3.3 Experimental conditions and protocols 42 3.3.4 Procedure of data collection and measurements 48 3.3.5 Data analysis 48 Chapter 4. Results and Discussion 49 4.1 [Part 1] Investigation of non-invasive parameters 49 4.1.1 Rectal, ear-canal temperature and heart rate for evaluation of heat strain 49 4.1.2 Correlations of temperatures in rectal temperature with regional skin temperatures 52 4.1.3 Consistency of temperatures in rectal temperature with regional skin temperatures 56 4.1.4 Modified equations of the original physiological strain index 61 4.1.5 Summary 65 4.2 [Part 2] Validity of the non-invasive PSIs 66 4.2.1 Validity of the non-invasive PSIs in different environments 66 4.2.2 Validity between the non-invasive PSIs in different types of clothing 75 4.2.3 Validity between various activities, environments, and clothing conditions 81 4.2.4 Summary 86 Chapter 5. Summary and Conclusions 89 Bibliography 91 국문 초록 103박

Heat Strain Decision Aid (HSDA) accurately predicts individual-based core body temperature rise while wearing chemical protective clothing

Purpose: We examined the accuracy of the Heat Strain Decision Aid (HSDA) as a predictor of core body temperature in healthy individuals wearing chemical protective clothing during laboratory and field exercises in hot and humid conditions. Methods: The laboratory experiment examined three chemical protective clothing ensembles in eight male volunteers (age 24 ± 6 years; height 178 ± 5 cm; body mass 76.6 ± 8.4 kg) during intermittent treadmill marching in an environmental chamber (air temperature 29.3 ± 0.1 °C; relative humidity 56 ± 1%; wind speed 0.4 ± 0.1 m s −1 ). The field experiment examined four different chemical protective clothing ensembles in twenty activity military volunteers (26 ± 5 years; 175 ± 8 cm; 80.2 ± 12.1 kg) during a prolonged road march (26.0 ± 0.5 °C; 55 ± 3%; 4.3 ± 0.7 m s −1 ). Predictive accuracy and precision were evaluated by the bias, mean absolute error (MAE), and root mean square error (RMSE). Additionally, accuracy was evaluated using a prediction bias of ±0.27 °C as an acceptable limit and by comparing predictions to observations within the standard deviation (SD) of the observed data. Results: Core body temperature predictions were accurate for each chemical protective clothing ensemble in laboratory (Bias −0.10 ± 0.36 °C; MAE 0.28 ± 0.24 °C; RMSE 0.37 ± 0.24 °C) and field experiments (Bias 0.23 ± 0.32 °C; MAE 0.30 ± 0.25 °C; RMSE 0.40 ± 0.25 °C). From all modeled data, 72% of all predictions were within one standard deviation of the observed data including 92% of predictions for the laboratory experiment (SD ± 0.64 °C) and 67% for the field experiment (SD ± 0.38 °C). Individual-based predictions showed modest errors outside the SD range with 98% of predictions falling <1 °C; while, 81% of all errors were within 0.5 °C of observed data. Conclusion: The HSDA acceptably predicts core body temperature when wearing chemical protective clothing during laboratory and field exercises in hot and humid conditions. </p

The Gastrointestinal Exertional Heat Stroke Paradigm: Efficacy Of Acute Oral Glutamine Supplementation

Exertional heat stroke (EHS) is the most severe form of heat related illness. In military settings, it is considered a largely preventable cause of morbidity, however, prevalence has remained high into the 21st Century. To support disease management, various policy documents provide occupational guidance on effective risk mitigation strategies, however, these can be criticised for focussing solely on the thermoregulatory pathology of the disease. The gastrointestinal (GI) EHS paradigm is a novel pathophysiological model that links EHS to luminal microbial translocation (MT) downstream of structural GI barrier integrity disturbance. Whilst this model is still in its infancy, recent investigations have established practical nutritional interventions that can support GI barrier integrity in populations at risk of EHS. The aims of this thesis were therefore to: (1) characterise the response of GI barrier integrity biomarkers to exertional�heat stress; and (2) examine the efficacy of acute oral L-glutamine (GLN) as a nutritional countermeasure to protect GI barrier integrity. From the experimental evidence reported in this thesis, several major conclusions were derived. First, GI barrier integrity can be reliably examined in blood samples taken at rest and following exertional-heat stress using the dual-sugar absorption test, intestinal�fatty acid binding protein and claudin-3 (chapter 4). Second, GI MT can be reliably examined in blood samples taken at rest and following exertional-heat stress using lipopolysaccharide binding protein and total 16S bacterial DNA, but not Bacteroides/total 16S DNA (chapter 4). Third, individuals with high-aerobic fitness experience blunted small intestinal epithelial injury and MT compared with untrained individuals during a fixed load exertional-heat stress test (chapter 5). Fourth, acute GLN supplementation (0.30, 0.60, 0.90 g·kg·FFM-1) causes mild dose-dependent GI symptoms at rest that generally lasted < 4 hours (chapter 6). Fifth, 0.30 g·kg·FFM-1 acute GLN supplementation does not protect GI permeability, small intestinal epithelial injury or MT when consumed 1-hour before either a low-intensity (chapter 7) or high-intensity (chapter 8) exertional-heat stress test. Taken together, GI barrier integrity loss reliably occurred in response to exertional-heat stress, a response that was blunted in individuals with high-aerobic fitness, but not following acute oral GLN supplementation

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 385)

This bibliography lists 536 reports, articles and other documents introduced into the NASA Scientific and Technical Information System Database. Subject coverage includes: aerospace medicine and physiology, life support systems and man/system technology, protective clothing, exobiology and extraterrestrial life, planetary biology, and flight crew behavior and performance