Shivering heat production and core cooling during head-in and head-out immersion in 17 degrees C water

INTRODUCTION: Many cold-water scenarios cause the head to be partially or fully immersed (e.g., ship wreck survival, scuba diving, cold-water adventure swim racing, cold-water drowning, etc.). However, the specific effects of head cold exposure are minimally understood. This study isolated the effect of whole-head submersion in cold water on surface heat loss and body core cooling when the protective shivering mechanism was intact. METHODS: Eight healthy men were studied in 17 degrees C water under four conditions: the body was either insulated or exposed, with the head either out of the water or completely submersed under the water within each insulated/exposed subcondition. RESULTS: Submersion of the head (7% of the body surface area) in the body-exposed condition increased total heat loss by 11% (P < 0.05). After 45 min, head-submersion increased core cooling by 343% in the body-insulated subcondition (head-out: 0.13 +/- 0.2 degree C, head-in: 0.47 +/- 0.3 degree C; P < 0.05) and by 56% in the body-exposed subcondition (head-out: 0.40 +/- 0.3 degree C and head-in: 0.73 +/- 0.6 degree C; P < 0.05). DISCUSSION: In both body-exposed and body-insulated subconditions, head submersion increased the rate of core cooling disproportionally more than the relative increase in total heat loss. This exaggerated core-cooling effect is consistent with a head cooling induced reduction of the thermal core, which could be stimulated by cooling of thermosensitive and/or trigeminal receptors in the scalp, neck, and face. These cooling effects of head submersion are not prevented by shivering heat production.     

Cooling hyperthermic firefighters by immersing forearms and hands in 10 degrees C and 20 degrees C water

INTRODUCTION: Firefighters experience significant heat stress while working with heavy gear in a hot, humid environment. This study compared the cooling effectiveness of immersing the forearms and hands in 10 and 20 degrees C water. METHODS: Six men (33 +/- 10 yr; 180 +/- 4 cm; 78 +/- 9 kg; 19 +/- 5% body fat) wore firefighter 'turn-out gear' (heavy clothing and breathing apparatus weighing 27 kg) in a protocol including three 20-min exercise bouts (step test, 78 W, 40 degrees C air, 40% RH) each followed by a 20-min rest/cooling (21 degrees C air); i.e., 60 min of exercise, 60 min of cooling. Turn-out gear was removed during rest/cooling periods and subjects either rested (Control), immersed their hands in 10 or 20 degrees C water (H-10, H-20), or immersed their hands and forearms in 10 or 20 degrees C water (HF-10, HF-20). RESULTS: In 20 degrees C water, hand immersion did not reduce core temperature compared with Control; however, including forearm immersion decreased core temperature below Control values after both the second and final exercise periods (p < 0.001). In 10 degrees C water, adding forearm with hand immersion produced a lower core temperature (0.8 degrees C above baseline) than all other conditions (1.1 to 1.4 degrees C above baseline) after the final exercise period (p < 0.001). Sweat loss during Control (1458 g) was greater than all active cooling protocols (1146 g) (p < 0.001), which were not different from each other. DISCUSSION: Hand and forearm immersion in cool water is simple, reduces heat strain, and may increase work performance in a hot, humid environment. With 20 degrees C water, forearms should be immersed with the hands to be effective. At lower water temperatures, forearm and/or hand immersion will be effective, although forearm immersion will decrease core temperature further.     

Changes in manual dexterity following short-term hand and forearm immersion in 10 degrees C water

BACKGROUND: Following accidental immersion in cold water, the chance of survival through the initial short-term period may depend on manual dexterity for survival tasks. We aimed to study the time course of impairment of manual dexterity during the initial stages of immersion. METHODS: We investigated gross (manipulating harness buckles) and fine (Purdue Pegboard Assembly) manual dexterity of 11 male and 15 female subjects with either no immersion (Control) or after immersion of right and left hand and forearm in 10 degrees C water for 30, 120, and 300 s. Exposure lengths were presented in a counter-balanced order in a single session. RESULTS: Mean local skin temperature decreased significantly with cold-water immersion, with the amount of cooling proportional to the length of exposure. Buckle test times increased significantly from 9.1 +/- 3.0 s during Control to similar values of 19.5 +/- 11.1 s and 18.14 +/- 12.1 s after 120 and 300 s of immersion. Pegboard scores were significantly lower at 40.2 +/- 7.6 pieces following 300 s of immersion compared with Control and 30 s values of 49.0 +/- 6.4 and 47.2 +/- 6.9 pieces, respectively. CONCLUSIONS: It is concluded that fine and gross manual dexterity were rapidly and progressively impaired with short-term cold-water immersion. Therefore, efforts must be made to protect the hands/forearms from cold and to ensure survival equipment manipulation requires as little dexterity as possible.     

Prediction of human thermoregulatory responses and endurance time in water at 20 and 24 degrees C

A multi-compartmental mathematical model for predicting human thermoregulatory responses was applied to immersion in moderately cold water. Data were used from experiments where eight healthy male volunteers were immersed nude and up to the neck for 1 h in water at 20 and 24 degrees C under conditions of rest and exercise. Rectal temperature and metabolic rate were measured before and during immersion. Once agreement between the model prediction and experimental observation was obtained, the model was used for prediction beyond the duration of the experiment. Stabilization of core temperature was predicted after 4-5 h of immersion for rest and after 2-4 h for exercise. Stabilization for resting individuals has been observed in other experiments under similar conditions. These results suggest that linear extrapolations based on linear body cooling rates are inadequate for predicting endurance times in moderately cold water. In this study, predicted endurance times were based on the concept of relative exercise intensity and are in agreement with the limited data available.     

Head and neck cooling by air, water, or air plus water in hyperthermia.

The effects of air, water, and air plus water head cooling on thermoregulatory responses and human operator performance were studied in nonacclimatized, heat-exposed men. Forty chamber exposures (46 degrees C, 30 mm Hg water vapor pressure) were conducted under noncooled and the aforementioned subconditions of head cooling. Five subjects, exposed for 80 min, were monitored for mean skin and rectal temperatures, heart rate, sweat loss, and compensatory tracking performance. A modified Air Force helmet shell provided facial air ventilation (24 degrees C) at 8 cfm. Eight interconnected neoprene modules fastened beneath a helmet linear provided water cooling (20 degrees C at 0.9 l/min). Tracking performances was unchanged across conditions. Elevation of rectal temperature and heart rate, sweat loss, and Physiological Index of Strain were significantly reduced by each condition of head cooling. Air is as effective as water as a cooling agent. Air ventilation acts synergistically with water cooling in reducing physiological strain. Relative merits of each approach to head cooling, in an operational context, are discussed.     

Muscle metabolism, temperature, and function during prolonged, intermittent, high-intensity running in air temperatures of 33 degrees and 17 degrees C

Nine unacclimatized university sportsmen performed a prolonged, intermittent, high-intensity shuttle running test in hot (HT) (33 degrees C, dry bulb temperature, approximately 28 %, relative humidity) and moderate (MT) (17 degrees C, 63 %) environmental conditions. Subjects performed 60 m of walking, a 15-m sprint, 60 m of cruising ( approximately 85 % V.O (2max)), and 60 m of jogging ( approximately 45 %V.O (2max)) for 14.8 +/- 0.1 min followed by a 3-min rest, repeated until volitional exhaustion. The hot trial was performed first followed, 14 days later, by the moderate trial. During exercise subjects drank water ad libitum. Subjects ran almost twice as far in the moderate as in the hot trial (HT 11216 +/- 1411, MT 21644 +/- 1629, m, p < 0.01), and the decline in average 15-m sprint performance was greater in the heat (HT, 0.17 +/- 0.05, MT, 0.09 +/- 0.03, s, p < 0.05). Average heart rates, blood lactate and glucose, and plasma adrenaline and noradrenaline concentrations were greater in the HT (main effect trial, p < 0.01), as were serum cortisol concentration (main effect trial p < 0.05, n = 5) and muscle temperature (HT exhaustion vs. same time point in MT, 40.2 +/- 0.3 vs. 39.3 +/- 0.2, degrees C, p < 0.01). Peak torque during knee flexion and extension was not different pre-and post-exercise in the HT. Muscle glycogen utilization tended to be greater in the heat (HT 193.2 +/- 19.5, MT 143.8 +/- 23.9, mmol . kg dry wt (-1), p = 0.055, n = 8). In 7 out of the 8 subjects the increase in utilization was between 19 and just over 200 % greater in the HT. Glycogen remaining in the muscle at exhaustion was greater in the hot than moderate trial (HT 207.4 +/- 34.3, MT 126.5 +/- 46.8, mmol . kg dry wt (-1), p < 0.01, n = 8). Rectal temperature (T (rec)) was higher in the HT at exhaustion than at the same point in time in the moderate trial (HT, 39.60 +/- 0.15 vs. MT 38.75 +/- 0.10, degrees C, interaction trial-time, p < 0.01). There was a very strong negative relationship between rate of rise in T (rec) and distance completed in the HT (HT r = - 0.90, p < 0.01, MT r = - 0.76, p < 0.05). Thus, the earlier onset of exhaustion during prolonged intermittent shuttle running in the heat is associated with hyperthermia. However, while muscle glycogen utilization may be elevated by heat stress, low whole muscle glycogen concentrations would not seem to be the cause of this earlier exhaustion.     

Cognitive, psychomotor, and physical performance in cold air after cooling by exercise in cold water

INTRODUCTION: This study evaluated performance after lowering core temperature at different rates while local tissues were either cooled (lower body) or not cooled (upper body). METHODS: There were 10 men who volunteered to perform up to 8 cold water immersions (CWI) at combinations of 2 water temperatures (10 degrees C and 15 degrees C), 2 depths [waist (W), chest (C)], and 2 walking speeds (0.44 or 0.88 m x s(-1)) until their core temperature fell to 35.5 degrees C, stabilized above that temperature, or they requested to stop. They also completed a control trial (120 min rest in 19 degrees C air). Immediately following each CWI and control, cognitive and physical performance tests were performed in cold air (10 degrees C; CAE). RESULTS: Overall, the CWI protocol lowered rectal temperature by 0.3-1.0 degrees C. Mean skin temperature was approximately 26 degrees C and finger temperature was approximately 15 degrees C during CAE. No statistical differences were observed across trials for any cognitive test. On the physical performance tests, step test performance was degraded approximately 12% on CWI trials compared with control, but there were no differences in manual dexterity, hand grip strength, marksmanship, or pull-ups. CONCLUSIONS: These results indicate that cognitive performance can be maintained despite mild hypothermia, and that physical performance is related to local tissue temperature, not a moderately reduced core temperature.     

Dose reduction in CT while maintaining diagnostic confidence: diagnostic reference levels at routine head, chest, and abdominal CT--IAEA-coordinated research project

PURPOSE: To measure radiation doses for computed tomography (CT) of the head, chest, and abdomen and compare them with the diagnostic reference levels, as part of the International Atomic Energy Agency Research coordination project. MATERIALS AND METHODS: The local ethics committees of all participating institutions approved the study protocol. Written informed consent was obtained from all patients. All scanners were helical single-section or multi-detector row CT systems. Six hundred thirty-three patients undergoing head (n = 97), chest (n = 243), or abdominal (n = 293) CT were included. Collected data included patient height, weight, sex, and age; tube voltage and tube current-time product settings; pitch; section thickness; number of sections; weighted or volumetric CT dose index; and dose-length product (DLP). The effective dose was also estimated and served as collective dose estimation data. RESULTS: Mean volumetric CT dose index and DLP values were below the European diagnostic reference levels: 39 mGy and 544 mGy . cm, respectively, at head CT; 9.3 mGy and 348 mGy . cm, respectively, at chest CT; and 10.4 mGy and 549 mGy . cm, respectively, at abdominal CT. Estimated effective doses were 1.2, 5.9, and 8.2 mSv, respectively. CONCLUSION: Comparison of CT results with diagnostic reference levels revealed the need for revisions, partly because the newer scanners have improved technology that facilitates lower patient doses.     

Life raft entry from water: effect of strength, tallness, and weight burden in men and women

BACKGROUND: The recurring failure of survivors of accidental water immersion to self-board a life raft prompted us to quantify the requisite physical attributes for successful self-boarding for predictive purposes. METHODS: There were 24 men and 24 women (18 to 52 yr) who attempted to self-board an inflated double-tube life raft using ladder, ramp, and over-the-side (OTS) entry methods while wearing a lifejacket in warm, calm water. The OTS method was also tested under weight-bearing conditions to determine the subject's 'reserve' capacity (i.e., maximum additional load capacity). RESULTS: Out of the 24 men, 22 successfully boarded the life raft, as did 17 out of the 24 women, using all methods of entry, and their reserve capacities ranged from 2 to 23% of body mass. Men reported lower efforts of exertion and were faster than women when using the ladder or boarding OTS without weights. There were no gender differences in these measures for the ramp and weighted OTS methods of entry. Strength and tallness were positive attributes for boarding the life raft using the ladder and OTS methods of entry, but not when using the ramp, which was the easiest and fastest entry method to execute. CONCLUSIONS: Men were more successful in boarding the life raft OTS (approximately 90%) compared with women (approximately 70%), but the difference was less pronounced for the ladder and ramp entry methods. The subjects' limited reserve capacities suggest that heavy layers of wet clothing and/or loss of muscle strength can easily compromise an individual's ability to self-board a life raft.     

The influence of tube voltage,X-ray exposure rate and thickness of filter material on image quality with dual-energy subtraction imaging in chest diagnostics

Digital luminescent radiography enables dual-energy subtraction imaging, because this computed system allows susbtraction of imaging data and image post processing, as for example special windowing or edge enhancement. In a special cassette a copper filter is placed between two imaging plates for energy separation by a single X-ray exposure. Image post-processing with subtraction of imaging data permits the elimination of either skeleton or soft tissue structures. The influence of filter thickness, tube voltage and the X-ray exposure dosage on image quality is examined by the use of an anthropomorphic quality is examined by the use of an anthropomorphic phantom of the chest. According to our initial results dual energy subtraction imaging in one-shot-technique seems to be useful in the diagnostics of skeletal lesions and especially pulmonary nodules.     

Signal-to-noise ratio and absorbed power as functions of main magnetic field strength, and definition of "90 degrees " RF pulse for the head in the birdcage coil.

Calculations of the RF magnetic (B(1)) field as a function of frequency between 64 and 345 MHz were performed for a head model in an idealized birdcage coil. Absorbed power (P(abs)) and SNR were calculated at each frequency with three different methods of defining excitation pulse amplitude: maintaining 90 degrees flip angle at the coil center (center alpha = pi/2), maximizing FID amplitude (Max. A(FID)), and maximizing total signal amplitude in a reconstructed image (Max. A(image)). For center alpha = pi/2 and Max. A(image), SNR increases linearly with increasing field strength until 260 MHz, where it begins to increase at a greater rate. For these two methods, P(abs) increases continually, but at a lower rate at higher field strengths. Above 215 MHz in MRI of the human head, the use of FID amplitude to set B(1) excitation pulses may result in apparent decreases in SNR and power requirements with increasing static field strength. Magn Reson Med 45:684-691, 2001.     

Identification and quantification of diphenhydramine,haloperidol, and its metabolite,reduced haloperidol in a saponified brain specimen that was immersed in the sea water for more than 10 years

In forensic toxicology, blood and urine specimens are commonly used for detecting and quantifying drugs and their metabolites. When the cadaver is so damaged or decomposed such that the specimens mentioned above cannot be collected, it is necessary to perform drug analysis using alternative specimens such as hair, nails, oral fluids and meconium. Adipocere is resistant to further degradation; it is thus possible to be used as an alternative specimen to analyze drugs and their metabolites. Some researchers indeed have reported drug concentrations in saponified samples that were collected years after decedents’ deaths.In this study, we subjected saponified brain, which remained under sea for over 10 years after death, to forensic toxicological analysis using liquid chromatography/tandem mass spectrometry (LC/MS/MS). Using product ion scan analysis, we confirmed the presence of diphenhydramine, haloperidol, and reduced haloperidol, a metabolite of haloperidol. In addition, drugs and metabolite quantification were performed using the standard addition method. Correlation coefficients of the calibration curves were over 0.98. Analyte concentrations in the saponified brain were as follows: diphenhydramine was 1.84 ng/g, haloperidol was 1.30 ng/g, and reduced haloperidol was 3.02 ng/g. Our results suggest that it can be possible to quantify not only parent drugs but also their metabolites in saponified brain. These findings indicate that saponified tissues could be applied as alternative specimens for forensic toxicology, and could be useful as supporting information for victim identification.     

Effect of contrast material on image noise and radiation dose in adult chest computed tomography using automatic exposure control: a comparative study between 16-, 64- and 128-slice CT

Purpose

To determine the difference in radiation dose between non-enhanced (NECT) and contrast-enhanced (CECT) chest CT examinations contributed by contrast material with different scanner generations with automatic exposure control (AEC).

Methods & materials

Each 42 adult patients received a NECT and CECT of the chest in one session on a 16-, 64- or 128-slice CT scanner with the same scan protocol settings. However, AEC technology (Care Dose 4D, Siemens) underwent upgrades in each of the three scanner generations. DLP, CTDIvol and image noise were compared.

Results

Although absolute differences in image noise were very small and ranged between 10 and 13 HU for NECT and CECT in median, the differences in image noise and dose (DLP: 16-slice:+2.8%; 64-slice:+3.9%; 128-slice:+5.6%) between NECT and CECT were statistically significant in all groups. Image noise and dose parameters were significantly lower in the most recent 128-slice CT generation for both NECT and CECT (DLP: 16-slice:+35.5-39.2%; 64-slice:+6.8-8.5%).

Conclusion

The presence of contrast material lead to an increase in dose for chest examinations in three CT generations with AEC. Although image noise values were significantly higher for CECT, the absolute differences were in a range of 3 HU. This can be regarded as negligible, thus indicating that AEC is able to fulfill its purpose of maintaining image quality. However, technological developments lead to a significant reduction of dose and image noise with the latest CT generation.     

Inhibition of cyclooxygenase-2 with NS-398 and the prevention of radiation-induced transformation, micronuclei formation and clonogenic cell death in C3H 10T1/2 cells

PURPOSE: Abnormally high levels of the cyclooxygenase (COX)-2 isozyme as well as the prostaglandin metabolites produced by the COX pathway have been observed in a variety of malignancies, including cancers of the skin, pancreas, colon, breast, cervix, prostate, and head and neck. Furthermore, exogenous genotoxic agents, including ionizing radiation (IR), have been shown to induce cellular transformation and to elevate COX-2 activity, whereas exposure to agents that specifically inhibit COX-2 activity have been shown to inhibit transformation. These data suggest a possible role of COX-2 both in IR-mediated cellular transformation processes and cell death. MATERIALS AND METHODS: C3H 10T1/2 and/or HeLa cells were treated with N-[2-(cyclohexyloxy)-4-nitrophenyl]-methanesulfonamide (NS-398) and/or exposed to IR. Following treatment, cells were assayed for neoplastic transformation, clonogenicity, growth rates, cell cycle distribution, micronuclei formation and DNA damage by established methodologies. Statistical tests were performed on data as described. RESULTS: In the present study, experiments in normal murine fibroblast C3H 10T1/2 cells demonstrated that the chemical inhibition of COX-2 activity with moderate doses of NS-398 abrogated IR-induced transformation events by fourfold and protected irradiated C3H 10T1/2 cells from clonogenic cell death. Considering that these doses of NS-398 had no significant effect on cellular proliferation or cell cycle distribution in C3H 10T1/2 cells, the results suggest that inhibition of COX-2 either increases DNA repair or prevents the accumulation of DNA damage. In supplemental experiments, treatment with NS-398 caused a 1.5-fold reduction in IR-induced micronuclei formation and a significant decrease in DNA damage. CONCLUSIONS: These results suggest a role for COX-2 inhibitors in the normal tissue response to IR when administered at therapeutically achievable doses and therefore may have clinical implications for radiation oncology patients in the prevention of IR-induced malignancy.