Belgrade, Serbia
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Jovanovic D.,Technical Testing Center | Karkalic R.,Technical Testing Center | Zeba S.,University of Belgrade | Pavlovic M.,University of Belgrade | Radakovic S.S.,Military Medical Academy
Vojnosanitetski Pregled | Year: 2014

Background/Aim. In military services, emergency situations when soldiers are exposed to a combination of nuclear, biological and chemical (NBC) contamination combined with heat stress, are frequent and complex. In these specific conditions, usage of personal body cooling systems may be effective in reducing heat stress. The present study was conducted in order to evaluate the efficiency of four various types of contemporary personal body cooling systems based on the "Phase Change Material" (PCM), and its effects on soldiers' subjective comfort and physiological performance during exertional heat stress in hot environments. Methods. Ten male soldiers were voluntarily subjected to exertional heat stress tests (EHSTs) consisted of walking on a treadmill (5.5 km/h) in hot conditions (40°C) in climatic chamber, wearing NBC isolating impermeable protective suits. One of the tests was performed without any additional cooling solution (NOCOOL), and four tests were performed while using different types of cooling systems: three in a form of vests and one as underwear. Physiological strain was determined by the mean skin temperature (Tsk), tympanic temperature (Tty), and heart rate values (HR), while sweat rates (SwR) indicated changes in hydration status. Results. In all the cases EHST induced physiological response manifested through increasing Tty, HR and SwR. Compared to NOCOOL tests, when using cooling vests, Tty and Tsk were significantly lower (on 35th min, for 0.44 ± 0.03 and 0.49 ± 0.05°C, respectively; p < 0.05), as well as the average SwR (0.17 ± 0.03 L/m2/h). When using underwear, the values of given parameters were not significantly different compared to NOCOOL tests. Conclusions. Using a body cooling system based on PCM in the form of vest under NBC protective clothes during physical activity in hot conditions, reduces sweating and alleviates heat stress manifested by increased core and skin temperatures and heart rate values. These effects directly improve heat tolerance, hydration state, decrease in the risk of heat illness, and extends the duration of soldiers' exposure to extreme conditions.

Jovanovic D.B.,Technical Testing Center | Karkalic R.M.,Technical Testing Center | Tomic L.D.,Technical Testing Center | VelicKovic Z.S.,University of Belgrade | Radakovic S.S.,University of Belgrade
Thermal Science | Year: 2014

The present study was conducted in order to evaluate the efficiency of personal body microclimate cooling systems based on a phase change materials and its effects on physiological strain in soldiers during exertional heat stress in hot environment. The results are obtained in the experiment conducted in the climatic chamber in the Institute of Hygiene, Military Medical Academy in Belgrade. Ten male soldiers were voluntarily subjected to exertional heat stress tests consisted of walking on treadmill (5.5 km/h) in hot conditions (40 °C) in climatic chamber. The subjects performed first test while wearing a field camouflage uniform without any cooling system (CONTROL group) and in second test they used additional microclimate cooling system with paraffin wax consist of n-hexadecane (C16H34), in a form of cooling packs (COOL group). As indicators of thermal strain, mean skin (Tsk) and tympanic (Tty) temperature were determined. Simultaneously, thermal effects of phase change materials were measured by thermal imaging camera. The exercise in hot conditions induced a physiological response to heat stress, manifested through increased body core and skin temperatures. The results confirmed that the cooling vest worn over the field uniform was able to attenuate the physiological strain during exercise, compared to the identical exposure in the "control" group. The results of thermal imaging also indicate that heat generated inside the body is the main factor that will affect the phase change material melting time.

Tomic L.D.,Technical Testing Center | Jovanovic D.B.,Technical Testing Center | Karkalic R.M.,University of Belgrade | Damnjanovic V.M.,University of Belgrade | And 3 more authors.
Thermal Science | Year: 2015

Non-destructive thermal examination can uncover the presence of defects via temperature distribution profile anomalies that are created on the surface as a result of a defect. There are many factors that affect the temperature distribution map of the surface being tested by infrared thermography. Internal defect properties such as thermal conductivity, heat capacity, and defect depth play an important role in the temperature behavior of the pixels or regions being analyzed. Also, it is well known that other external factors such as the convection heat transfer, variations on the surface emissivity, and ambient radiation reflectivity can affect the thermographic signal received by the infrared camera. In this paper, we considered a simple structure in the form of flat plate covered with several defects, whose surface we heated with a uniform heat flux impulse. We conducted a theoretical analysis and experimental test of the method for case of defects on an aluminum surface. First, experiments were conducted on surfaces with intentionally created defects in order to determine conditions and boundaries for application of the method. Experimental testing of the pulsed flash thermography method was performed on simulated defects on an aluminum test plate filled with air and organic compound n-hexadecane, hydrocarbon that belongs to the phase change materials. Study results indicate that it is possible, using the pulsed flash thermography method, to detect the type of material inside defect holes, whose presence disturbs the homogeneous structure of aluminum.

Zeba S.,University of Belgrade | Surbatovic M.,University of Belgrade | Marjanovic M.,Galenika | Jevdjic J.,University of Kragujevac | And 4 more authors.
Vojnosanitetski Pregled | Year: 2016

Background/Aim. Hypothermia in surgical patients can be the consequence of long duration of surgical intervention, general anaesthesia and low temperature in operating room. Postoperative hypothermia contributes to a number of postoperative complications such as arrhythmia, myocardial ischemia, hypertension, bleeding, wound infection, coagulopathy, and prolonged effect of muscle relaxants. External heating procedures are used to prevent this condition. The aim of this study was to evaluate the efficiency of external warming system in alleviation of cold stress and hypothermia in patients who underwent major surgical procedures. Methods. The study was conducted in the Military Medical Academy in Belgrade. A total of 30 patients of both genders underwent abdominal surgical procedures, randomly divided into two equal groups: the one was externally warmed using warm air mattress (W), while in the control group (C) surgical procedure was performed in regular conditions, without additional warming. Oesophageal temperature (Te) was used as indicator of changes in core temperature, during surgery and awakening postoperative period, and temperature of control sites on the right hand (Th) and the right foot (Tf) reflected the changes in skin temperatures during surgery. Te and skin temperatures were monitored during the intraoperative period, with continuous measurement of Te during the following 90 minutes of the postoperative period. Heart rates and blood pressures were monitored continuously during the intraoperative and awakening period. Results. In the W group, the average Te, Tf and Th did not change significantly during the intraoperative as well as the postoperative period. In the controls, the average Te significantly decreased during the intraoperative period (from 35.61 ± 0.35ºC at 0 minute to 33.86 ± 0.51ºC at 120th minute). Compared to the W group, Te in the C group was significantly lower in all the observed periods. Average values of Tf and Th significantly decreased in the C group (from 30.83 ± 1.85 at 20th minute to 29.0 ± 1.39ºC at 120th minute, and from 32.75 ± 0.96 to 31.05 ± 1.09ºC, respectively). Conclusion. The obtained results confirm that the external warming using warm air mattress was able to attenuate hypothermia, i.e. substantial decrease in core temperature, compared with the similar exposure to cold stress in the control group. © 2016, Institut za Vojnomedicinske Naucne Informacije/Documentaciju. All rights reserved.

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