Prediction of the thermoregulatory response for clothed immersion in cold water

A 3-D virtual human model for simulating heat and cold stress

In this study, we extended our previously developed anatomically detailed three-dimensional (3-D) thermoregulatory virtual human model for predicting heat stress to allow for predictions of heat and cold stress in one unified model. Starting with the modified Pennes bioheat transfer equation to estimate the spatiotemporal temperature distribution within the body as the underlying modeling structure, we developed a new formulation to characterize the spatial variation of blood temperature between body elements and within the limbs. We also implemented the means to represent heat generated from shivering and skin blood flow that apply to air exposure and water immersion. Then, we performed simulations and validated the model predictions with experimental data from nine studies, representing a wide range of heat- and cold-stress conditions in air and water and physical activities. We observed excellent agreement between model predictions and measured data, with average root mean squared errors of 0.2°C for core temperature, 0.9°C for mean skin temperature, and 27 W for heat from shivering. We found that a spatially varying blood temperature profile within the limbs was crucial to accurately predict core body temperature changes during very cold exposures. Our 3-D thermoregulatory virtual human model consistently predicted the body's thermal state accurately for each of the simulated hot and cold environmental conditions and exertional heat stress. As such, it serves as a reliable tool to assess whole body, localized tissue, and, potentially, organ-specific injury risks, helping develop injury prevention and mitigation strategies in a systematic and expeditious manner.NEW & NOTEWORTHY This work provides a new, unified modeling framework to accurately predict the human body's thermal response to both heat and cold stress caused by environmental conditions and exertional physical activity in one mathematical model. We show that this 3-D anatomically detailed model accurately predicts the spatiotemporal temperature distribution in the body under extreme conditions for exposures to air and water and could be used to help design medical interventions and countermeasures to prevent injuries.

Mid-Air Tactile Stimulation for Pain Distraction

Using the human sense of touch, pain control has been studied for decades. With the rise of Virtual Reality (VR) and haptic technologies, creating VR and haptic sensations provide a unique opportunity for pain distraction. In this paper, we present an experimental study to test whether VR and mid-air ultrasound tactile stimulation reduce perceived pain simulated via the cold pressor test, i.e., submerging a human hand in cold water (2 C) for as long as the test subject can. Fifty right-handed subjects participated in the study and three tasks were considered: task 1 involved experiencing the cold pressor test with no distraction (considered as the control task), task 2 involved playing a simple VR game with no tactile feedback, and task 3 utilized the same VR game with tactile feedback; tasks 2 and 3 were assigned in random order after task 1. The tolerance time, perceived pain rating, and quality of experience were evaluated and compared for the three tasks. Results demonstrated that when a VR task involves physical (touch) interaction, tactile stimulation plays a significant role in increasing pain tolerance time. Furthermore, the study demonstrated that for high pain tolerance participants, tactile stimulation is more effective for pain distraction compared to low pain tolerance participants. Although there are no significant differences in perceived pain and quality of experience between VR and VR+Tactile tasks, there are significant differences in tolerance time (Wilcox signed rank test, p 0.05). It is presumed that VR and the tactile stimulation induces positive emotions when utilized (for both valence and arousal).

International Commission for Mountain Emergency Medicine Consensus Guidelines for On-Site Management and Transport of Patients in Canyoning Incidents

Canyoning is a recreational activity that has increased in popularity in the last decade in Europe and North America, resulting in up to 40% of the total search and rescue costs in some geographic locations. The International Commission for Mountain Emergency Medicine convened an expert panel to develop recommendations for on-site management and transport of patients in canyoning incidents. The goal of the current review is to provide guidance to healthcare providers and canyoning rescue professionals about best practices for rescue and medical treatment through the evaluation of the existing best evidence, focusing on the unique combination of remoteness, water exposure, limited on-site patient management options, and technically challenging terrain. Recommendations are graded on the basis of quality of supporting evidence according to the classification scheme of the American College of Chest Physicians.

Thermoregulatory model for prediction of long-term cold exposure

A multi-segmental mathematical model has been developed for predicting shivering and thermoregulatory responses during long-term cold exposure. The present model incorporates new knowledge on shivering thermogenesis, including the control and maximal limits of its intensity, inhibition due to a low core temperature, and prediction of endurance time. The model also takes into account individual characteristics of age, height, weight, % body fat, and maximum aerobic capacity. The model was validated against three different cold conditions i.e. water immersion up to 38 h and air exposure. The predictions were found to be in good agreement with the observations.

Predicting survival time for cold exposure

The prediction of survival time (ST) for cold exposure is speculative as reliable controlled data of deep hypothermia are unavailable. At best, guidance can be obtained from case histories of accidental exposure. This study describes the development of a mathematical model for the prediction of ST under sedentary conditions in the cold. The model is based on steady-state heat conduction in a single cylinder comprised of a core and two concentric annular shells representing the fat plus skin and the clothing plus still boundary layer, respectively. The ambient condition can be either air or water; the distinction is made by assigning different values of insulation to the still boundary layer. Metabolic heat production (M) is comprised of resting and shivering components with the latter predicted by temperature signals from the core and skin. Where the cold expousure is too severe for M to balance heat loss, ST is largely determined by the rate of heat loss from the body. Where a balance occurs, ST is govedrned by the endurance time for shivering. End of survival is marked by the deep core temperature reacing a value of 30 degrees C. Th emodel was calibrated against survival data of cold water (0 to 20 degrees C) immersion and then applied to cold air exposure. A sampling of ST predictions for the nude exposure of an average healthy male in relatively calm air (1 km/h wind speed) are the following: 1.8, 2.5, 4.1, 9.0, and > 24 h for -30, -20, -10, 0 and 10 degrees C, respectively. With two layers of loose clothing (average thickness of 1 mm each) in a 5 km/h wind, STs are 4.0, 5.6, 8.6, 15.4, and > 24 h for -50, -40, -30, -20, and -10 degrees C. The predicted STS must be weighted against the extrapolative nature of the model. At present, it would be prudent to use the predictions in a relative sense, that is, to compare or rank-order predicted STs for various combinations of ambient conditions and clothing protection.

The relationship between maximum breath hold time in air and the ventilatory responses to immersion in cold water

Eight subjects performed maximum breath holds in air and naked head-out immersions of 2 min duration in stirred water at 5, 10 and 15 degrees C. Analysis of the respiratory data collected in air and on immersion revealed a significant (P less than 0.05) inverse relationship between the maximum breath hold time (tbh,max) of subjects in air and their frequency of breathing and inspiratory volumes on immersion. No such relationship was identified between tbh,max in air and tidal volumes on immersion. It is concluded that the tbh,max of individuals in air may provide an indication of the magnitude of some of their respiratory responses to immersion. This information may be of use when personnel are being selected for activities with a high risk of immersion in cold water.