Pharmaceutical stability as it relates to climatic exposure

Manufacturers' recommended temperatures for pharmaceuticals were compared with actual field temperatures that the medications were exposed to during the winter months of December and February in the Republic of Korea. Two daily temperatures of field pharmaceuticals were taken in a M577 armored aid station. These temperatures were then averaged and compared with the ambient high and low for that day. The total data collected during the month of December yielded a mean pharmaceutical temperature of 57.50 degrees F with a standard deviation of 5.37. This result showed that the heating unit in the M577 was able to keep the medications 15.07 degrees F warmer than the mean high and 30.77 degrees F warmer than the mean low for the temperatures collected. For February, the mean temperature of pharmaceuticals was 49.25 degrees F with a standard deviation of 5.89. This temperature was 11.37 degrees F higher than the mean high and 33.00 degrees F higher than the mean low. For both the months of December and February, the heating unit in the vehicle tested was not able to meet manufacturer's specifications for more than 90% of the medications reviewed.     

Controlled trial of an intravenous fluid warmer

INTRODUCTION: In critically ill patients (e.g., trauma victims) prevention of hypothermia is an important goal. Infusion of warm fluids has been addressed in the hospital setting, but not in the air medical transport setting. PURPOSE: The purpose of this study was to test the efficacy of an intravenous (IV) fluid warming device that is well-suited for the air medical transport environment. METHOD: The warmer studied was used with IV fluid heated to approximately 38 degrees C (100 degrees F) and evaluated in environmental temperatures of -16 degrees C (3 degrees F), 2 degrees C (36 degrees F), and 22 degrees C (72 degrees F). The warmer group was compared to a control group of similarly treated IV fluids without a warming device. Temperatures were measured at baseline, 15, 30 and 60 minutes. RESULTS: The 30- and 60-minute fluid temperatures were higher in the warmer than in the control group for all three environmental temperature settings. At 15 minutes, fluid temperatures were higher in the warmer group for the 2 degrees C and -16 degrees C, but not the 22 degrees C, environments. There was no significant drop in temperature in the warmer group in the 22 degrees C and 2 degrees C settings, but a decrease was noted in the -16 degrees C environment. There was a significant drop in the control group at all temperatures tested. CONCLUSION: The IV fluid warmer tested effectively maintains the temperature of warmed IV fluids in temperatures above 2 degrees C. At -16 degrees C there was significant heat loss, but the loss was significantly less when compared to the control group.     

Heat strain during at-sea helicopter operations and the effect of passive microclimate cooling.

Twelve Navy H-3 helicopter aircrew members were monitored (heart rate, skin and rectal temperatures) in both microclimate cooling (ice) vest and non-vest conditions during at-sea operations in the high heat environment of the Persian Gulf. During all flights and flight phases, ambient dry bulb temperatures ranged from 31.0 degrees C (in-flight) to 48.6 degrees C (hover). Heart rate was greatest during hover and on-deck (range: 89.9 to 145.0 beats/min) without an ice vest, yet was significantly reduced with ice (range: 79.7 to 86.0 beats/min) (p less than 0.05). Rectal temperature was not found to be different between vest and non-vest conditions; however, change across flight phases in both conditions was significant (p less than 0.05). Analysis of variance demonstrated significantly lower mean weighted skin temperatures (p less than 0.05) when wearing the ice vest. These data suggest that wearing a protective cooling vest can reduce the heat strain associated with helicopter flight in high heat environments.     

Heat stress on helicopter pilots during ground standby.

We attempted to use measurements of ambient thermal conditions to characterize and then predict thermal conditions in the cockpit before takeoff and during an hour standby period in Bell 206 and Bell 212 helicopters with a crew of two and with the cockpit doors opened. Dry bulb, wet bulb, and globe temperatures were measured on 28 separate summer days. The wet bulb globe temperature index (WBGT) was used to estimate heat stress. Ambient WBGT at time 0 ranged from 13 degrees C to 31 degrees C. There was a 2.9 +/- 3.7 degree difference in WBGT between ambient and cockpit conditions at time 0 which increased to 7.2 +/- 3.5 degrees after 1 h. Because of the cooling effect of opening the helicopter cockpit doors, the cockpit WBGT actually decreased over the standby period when cockpit WBGT values were 30 degrees C or more at time 0. Thus, there was an inverse correlation between cockpit WBGT at time 0 and the change in cockpit WBGT over the 1-h period (r = -0.767, p less than 0.001). The mean WBGT in the cockpit over the 1-h standby period was positively correlated with the ambient WBGT at time 0 (r = 0.783, p less than 0.001). We conclude that the greenhouse effect results in a cockpit WBGT which is significantly higher than ambient conditions. Subsequent changes in cockpit WBGT depend on the balance between heat transfer from the pilot's bodies to the cockpit and the loss of heat after the doors of the helicopters are opened. Ambient thermal conditions can be used to predict heat stress during the ground standby period.     

Finger and toe temperatures on exposure to cold water and cold air

INTRODUCTION: Subjects with a weak cold-induced vasodilatation response (CIVD) to experimental cold-water immersion of the fingers in a laboratory setting have been shown to have a higher risk for local cold injuries when exposed to cold in real life. Most of the cold injuries in real life, however, occur in the foot in cold air rather than in the hand in cold water. Therefore, an experiment was conducted to investigate the within-subject relation between CIVD in the fingers and toes exposed to cold water and cold air. METHODS: In 4 experimental sessions, 11 healthy male subjects immersed their toes and fingers in 5 degrees C water and exposed the fingers and toes to -18 degrees C cold air for 30 min. The pad temperature of the middle three digits was measured. RESULTS: CIVD in water was more pronounced in the fingers (onset time 5.1 +/- 1.8 min; amplitude 5.0 +/- 2.1 degrees C) than in the toes (onset time 10.6 +/- 6.0 min; amplitude 3.0 +/- 1.0 degrees C). Out of 22 skin temperature responses to cold air, 13 were not identifiable as CIVD. The mean skin temperatures for fingers and toes during the last 20 min of cold exposure were 25.6 +/- 7.1 degrees C and 20.9 +/- 6.8 degrees C, respectively, for air and 9.3 +/- 1.9 degrees C and 7.1 +/- 1.3 degrees C for water immersion. There was a strong relation between the mean temperature of the fingers during cold-water immersion and toes during cold air exposure (r = 0.83, P < 0.01), showing that a weak CIVD response in the hand is related to a weak response in the foot. DISCUSSION: We conclude that the cold-water finger immersion test is related to the temperature response in the toes and may thus continue to serve as a valid indicator for the risk of local cold injuries.     

The effect of the UK aircrew chemical defence assembly on thermal strain

The thermal strain imposed on helicopter aircrew by chemical protective (NBC) clothing in summer in Germany has been assessed in a laboratory simulation. The environmental conditions used were dry bulb temperature 35 degrees C, wet bulb temperature 19 degrees C and a wind speed of 2.0 m X s-1. The NBC equipment imposed a significant thermal strain on the crewman when compared with standard summer flying clothing, but not on the pilot whose tasks involve lower energy expenditures. Deep body temperature exceeded 37.6 degrees C and a significant degree of dehydration (1% of body weight) also occurred, despite the availability of a drinking facility in the respirator. It is recommended that the only practical way of preventing thermal strain in helicopter crewmen under NBC conditions is by providing personal conditioning.     

Insidious hypothermia during raft use

It is commonly thought that increasing protection against cold water results in greater physiological efficiency in maintaining core temperature. To examine the relationship of physiological changes resulting from cold exposures as a function of increased insulation, five subjects (4 males, 1 female) wearing anti-exposure ensembles covering the entire body and head were exposed in a pool to water temperatures (Twater) = 4.4 degrees C and air temperatures (Tair) = 5.6 degrees C. Trials consisted of subjects undergoing either head-out immersions with mean exposure time (t = 150 +/- 9 S.E.M. min) or enclosed within a raft (t = 398 +/- 126 min). Rectal temperatures were higher, and their relative change from baseline (delta Tre) smaller, for 3 of the 5 subjects at minute 122 in the water than in the raft. While no correlation was found between mean weighted skin temperature (Tsk), hand temperature (Thand), or foot temperature (Tfoot) with Tre, close correlation was found between delta Tre and forehead temperature (Tfore) (r = 0.97, p less than 0.05) and change in forehead temperature (r = 0.97, p less than 0.05). The results suggest that, during cold exposure, increased insulation, under specific conditions, may result in a lower Tre.     

Is oral endotracheal intubation efficacy impaired in the helicopter environment?

INTRODUCTION: Patients transported by helicopter often require advanced airway management. The purpose of this study was to determine whether or not the in-flight environment of air medical transport in a BO-105 helicopter impairs the ability of flight nurses to perform oral endotracheal intubation. SETTING: The study was conducted in an MBB BO-105 helicopter. METHODS: Flight nurses performed three manikin intubations in each of the two study environments: on an emergency department stretcher and in-flight in the BO-105 helicopter. RESULTS: The mean time required for in-flight intubation (25.9 +/- 10.9 seconds) was significantly longer than the corresponding time (13.2 +/- 2.8 seconds) required for intubation in the control setting (ANOVA, F = 38.7, p < .001). All intubations performed in the control setting were placed correctly in the trachea; there were two (6.7%) esophageal intubations in the in-flight setting. The difference in appropriate endotracheal intubation between the two settings was not significant (chi 2 = 0.3; p > 0.05). CONCLUSION: Oral endotracheal intubation in the in-flight setting of the BO-105 helicopter takes approximately twice as long as intubation in a ground setting. The results support pre-flight intubation of patients who appear likely to require urgent intubation during air medical transport in the BO-105 helicopter.     

Physiological and behavioral temperature regulation of men in simulated nonuniform thermal environments between 18 and 30 degrees C

Human thermoregulatory responses to nonuniform thermal environments was studied by simulating the situation with altered clothing distribution. Clothing was symmetrically or asymmetrically distributed over the body surface. Esophageal and local skin temperatures, metabolism, skin heat flux, evaporative heat loss and subjective responses of six sedentary men were measured at air temperatures between 18 and 30 degrees C. Clothing distribution significantly (p less than 0.05) influenced thermoregulatory responses only at 18 degrees C. At 18 degrees C, the bilaterally asymmetric clothing resulted in a higher (p less than 0.05) esophageal temperature compared to the symmetric condition. Mean skin temperatures did not differ with clothing distribution over the range of air temperatures studied, but at 18 degrees C whole body thermal sensation was warmer (p less than 0.05) for the asymmetric compared to the symmetric group. This increased perception of warm thermal sensation was significantly correlated to the difference in skin temperature across the body.     

Immersion suit insulation: the effect of dampening on survival estimates

Immersion suit leakage values were obtained from realistic testing of helicopter passenger immersion suits using eight subjects. Simulated helicopter underwater escape resulted in mean leakages of 198 +/- 103, 283 +/- 127, 203 +/- 179, and 45.7 +/- 31.6 g (mean +/- S.D.) when wearing four different immersion suits. Suit leakages obtained from a 20-min swim test to simulate vital in-water survival actions produced leakages of 213 +/- 224, 1398 +/- 691, 145 +/- 96.5, and 177 +/- 139 g (mean +/- S.D.). Dampening of undergarments during simulated helicopter travel at an elevated cabin temperature of 30 degrees C was 115 +/- 47.3 (mean +/- S.D.; n = 4) when wearing an impermeable suit and 19 +/- 16.7 g (mean +/- S.D.; n = 4) when wearing a vapour-permeable suit. The commensurate loss of insulation with the impermeable suit at the upper level of temperature could reduce clothing insulation by 17%. A reduction of less than 5% may result under similar conditions when wearing the permeable suit. The combined dampening effect of sweating, helicopter underwater escape, and performance of vital survival actions could result in a total dampening of 247-1712 g, depending on the type of suit worn. The respective loss of insulation would be 15% and 50% respectively. This could reduce, for the 10th percentile thin man, his survival time in water at 5 degrees C from 3.5 h to between 2.4 h and 1.1 h, respectively.     

Fall in skin temperature of exercising man.

Fall in skin temperature during initial muscular work was investigated in ten healthy men. Bicycle exercise was performed at workloads of 50-150 W in a climatic chamber at ambient temperatures of 10-40 degrees C (relative humidity 45-55%). Skin temperatures at seven or eight points over the body surface were measured using thermography and thermocouple recording systems. Sweat rates were significantly higher at 40 degrees C than at 30 degrees C, whereas the fall in skin temperature was almost equal. The reduction of skin temperature during exercise was the same throughout the year, although sweat rate was significantly higher in summer than in winter. In coloured thermographics of the skin temperature distribution during exercise of both 50 and 150 W at 10 or 20 degrees C, the skin temperature began to decline immediately at the onset of the exercise. Increased work intensities reduced skin temperature. The results suggest that fall in skin temperature during initial exercise was not due to increased evaporative cooling but to vasoconstriction, probably caused by non-thermal factors.     

Effects of environmental heat stress (35 degrees C) with simulated air movement on the thermoregulatory responses during a 4-km cycling time trial

The aim of the present investigation was to examine the influence of environmental heat stress (35 degrees C) on 4-km cycling time trial performance using simulated environmental conditions and facing air velocities that closely reflect competitive situations. Nine competitive cyclists (age 34 +/- 5 years, maximal oxygen uptake 61.7 +/- 8.6 ml . kg (-1) . min (-1)) completed a simulated 4-km cycling time trial in laboratory ambient temperatures (dry bulb temperatures) of 35 degrees C and 13 degrees C (relative humidity 60 %, air velocity 5.6 m/s). Mean performance time was reduced in 35 degrees C (390.1 +/- 19.6 s) compared to 13 degrees C (382.8 +/- 18.2 s) (95 % CI of difference = 4.0 to 10.6 s; p < 0.01). This was consistent with a decline in mean power output throughout the duration of exercise in 35 degrees C compared with 13 degrees C (p < 0.01). Mean skin temperature and mean body temperatures were elevated at rest and throughout the duration of exercise in 35 degrees C (p < 0.01). A higher level of muscle temperature was also observed at the onset and cessation of exercise in 35 degrees C (p < 0.01). The rate of heat storage (35 degrees C, 413.6 +/- 130.8 W . m (-2); 13 degrees C, 153.1 +/- 112.5 W . m (-2)) representative of the entire 4-km time trial was greater in the heat (p < 0.01). When expressed per kilometre, however, difference in the rate of heat storage between conditions declined during the final kilometre of exercise (p = 0.06). We conclude that the current decrements in self-selected work-rate in the heat are mediated to some extent through afferent feedback arising from changes in heat storage at rest and during the early stages of exercise which serve to regulate the subsequent exercise intensity in attempt to preserve thermal homeostasis.     

Wheel-well and cargo compartment temperatures of large aircraft in flight: implications for stowaways

BACKGROUND: Desperate people sometimes risk journeys as stowaways in aircraft wheel-wells. Some of them survive, despite the risks of being crushed by retracting landing gear, falling when the gear deploys for landing, or experiencing severe hypoxia and hypobaria in-flight. This study evaluates the level of hypothermia to which stowaways in aircraft may be exposed. METHODS: Miniature dataloggers were used to record in-flight temperatures in aircraft wheel-wells and cargo compartments. Temperatures were measured for front and side wheel-wells (FW and SW, respectively) on 36 flights by C-130 aircraft (mean duration 3.3 h, mean cruise altitude 5588 m (18,333 ft)) and 11 flights by C-141 aircraft (6.7 h and 10,744 m (35,250 ft)). RESULTS: Mean minimum temperatures for the C-130 remained above freezing and averaged 5.1 degrees C for FW and 11.9 degrees C for SW. The higher, longer C-141 flights produced temperatures below freezing with mean minimum temperatures of -18.0 degrees C for FW and -12.4 degrees C for SW. In general, temperatures in wheel-wells remained about 20 degrees C above outside air temperature (OAT) at all altitudes. This increase reflects the fact that wheel-wells are closed spaces within the aircraft body, in addition to which they contain sources of heat such as hydraulic lines and electrical equipment. Cargo compartment minimum temperature was relatively high (mean = 18.6 degrees C for commercial airline). A search of the medical literature and lay press produced information on 46 incidents of people found in wheel-wells after landing where there was no evidence of trauma. The 15 survivors had stowed away on relatively short flights (mean = 4.8 h, maximum = 10 h) compared with fatalities (mean = 7.5 h, range = 3-12 h). CONCLUSIONS: Temperatures in wheel-wells during short flights may sustain life. Long flights add severe hypothermia to acute hypoxia and hypobaria as potentially fatal environmental factors faced by wheel-well stowaways.     

载人航天器预冷温度的热生理学探讨

目的探讨载人舱室适宜的预冷温度 ,以预防或减缓发射、返回段航天器内高温对人体的不利影响。方法 5名健康男性青年按着航天服时不通风和以通风流率 1 0 0L/min(STPD)通风等不同着装条件 ,在舱温 1 5、l0、5℃环境中进行 2 5人次实验。测量直肠温度 (Tr)、平均皮温 (Tsk)和平均体温 (Tb)等热生理指标。结果在舱温 1 5℃航天服通风和不通风状态 ,实验 2h内人体直肠温度降低不显著 (从初始值 37.0± 0 .2℃降为 36.7± 0 .3℃ ) ,平均体温、平均皮温显著降低 (P <0 .0 5) ,受试者有局部的冷紧张 ;而在舱温和通风温度 1 0℃时 ,受试者热生理指标随时间延长不断降低 ,直肠温度从 37.0± 0 .3℃显著下降至 36.3± 0 .3℃ ,Tsk、Tb 显著低于初始值 (P <0 .0 5) ,受试者有全身性冷紧张。结论按人体热舒适状态无显著改变的要求 ,航天器座舱预冷后维持 1 5℃气温对人体较为适宜。     

Heating of the scrotum by high-field-strength MR imaging

Sterility can occur in mammals if spermatogenic tissue is acutely or chronically heated to levels equal to or greater than body temperature. High-field-strength MR imaging has been shown to elevate tissue temperatures, particularly if high levels of RF radiation are used. To determine if MR imaging above the recommended level for RF radiation is associated with heating of the scrotum, scrotal skin temperatures were measured in eight subjects immediately before and after MR imaging of the scrotum with a 1.5-T, 64-MHz MR scanner at mean whole-body average specific absorption rates ranging from 0.56 to 0.84 W/kg (mean, 0.72 W/kg). The average imaging time was 23 min. A statistically significant (p less than .01) increase in average scrotal skin temperature was associated with MR imaging (before MR imaging, 30.8 degrees C; after MR imaging, 32.3 degrees C). The largest change in temperature was 3.0 degrees C, and the highest temperature measured was 34.1 degrees C. MR imaging at relatively high specific absorption rates produced a statistically significant increase in average scrotal skin temperature. However, the recorded temperatures were below the threshold known to affect spermatogenesis in mammals.     

Evaluation of warmed intravenous fluids in the prehospital setting

INTRODUCTION: This study was designed to determine if warmed intravenous fluid (IVF) in the prehospital setting improves core body temperature and patient comfort. METHODS: Data were collected in a controlled, nonblinded, prospective study during the winter months of 2 consecutive years. Prehospital adult patients qualified if they received a bolus of 250 mL of fluid (20 mL/kg for pediatrics). Patient and IVF temperatures were measured on arrival at the ED. If the patient's condition allowed, a visual analog survey was completed. RESULTS: Twenty adult patients were enrolled. The warmed IVUF demonstrated an average temperature of 32.5 degrees C (90.1 degrees F) versus 23.5 degrees C (74.3 degrees F) for nonwarmed fluids. The patients with warmed IVF demonstrated a higher core body temperature than the nonwarmed-36.8 degrees C (98.2 degrees F) versus 35.5 degrees C (95.9 degrees F). Overall, patient surveys showed increased comfort with warmed IVF. CONCLUSION: Prehospital IVF can be warmed in the field and should help prevent the adverse effects of hypothermia. Although this study shows a trend in favor of warmed IVF, the population is too small to justify any broad statements. This matter warrants further investigation with a larger group of patients.     

Radiofrequency energy induced heating of bovine capsular tissue: in vitro assessment of newly developed, temperature-controlled monopolar and bipolar radiofrequency electrodes

This in vitro investigation characterized temperature changes associated with radiofrequency (RF) energy induced heating of bovine capsular tissue using newly developed, temperature-controlled monopolar (Vulcan RF system and Vulcan, TAC-S Electrothermal Probe) and bipolar (VAPR II RF system and VAPR TC RF electrode) RF systems and electrodes. Bovine capsular tissue samples were placed in a saline bath maintained at room temperature. Both RF generators were used at settings of 75 degrees C and 40 W. The RF electrodes were placed in stationary positions on the tissue samples and activated for 1- to 10-s. A fluoroptic thermometry system was utilized to record temperatures at the RF electrode-tissue interface at 1-s intervals. The results indicated that the mean tissue temperatures for the monopolar RF electrode tended to be higher than those produced by the bipolar RF electrode, especially during the 2- to 10-s RF delivery time intervals (P<0.05). Notably, during the 2- to 10-s time intervals the monopolar RF electrode produced mean tissue temperatures that exceeded the set temperature of 75 degrees C (range of differences +1.2 to +15.7 degrees C highest mean temperature 90.7 degrees C). By comparison, the bipolar RF electrode maintained tissue temperatures relatively close to the set temperature(range of differences -3.2 to +2.7 degrees C; highest mean temperature 77.7 degrees C). These findings provide basic temperature profiles for the two new temperature-controlled RF devices.     

Heat and cold: what does the environment do to marathon injury?

The medical work load seems to increase both with heat and humidity, and with cold and rainy conditions. Heat tolerance during exercise is variable and heat intolerance may contribute to collapse and increase medical encounters. Exposure to cold, wet conditions results in increasing incidence of hypothermia in exhausted marathon runners. Finish-line encounters and course dropouts increase as conditions cool and warm away from the most advantageous conditions in the 4.4-15 degrees C (40-59 degrees F) wet bulb globe temperature (WBGT) range. The risk of requiring medical attention and not finishing rises considerably when the WBGT is >15.5 degrees C (60 degrees F). Comparing the correlation coefficients of the Boston Marathon and Twin Cities Marathon data suggests that the risks of medical problems and not finishing are associated with the warmest temperature of the race and not the start temperature. The community consequences of races conducted in hot and humid conditions can be significant, particularly when the WBGT is >15.5 degrees C. The emergency medical systems can be overwhelmed with a surge of patients, some very ill, and the emergency call response times drop to unacceptable levels blocking access for the citizens of the community. With respect to marathon encounters, heat stress increases both the finish-line medical encounter rate and the on course drop-out rate, and seems to increase the incidence of hyponatraemia and heat stroke. Cold conditions increase the drop-out rate along the course and, if associated with wet conditions, also increase the encounter rate.     

Temporal changes of 7 Be and 210 Pb concentrations in surface air at temperate latitudes 40 degrees N.

Atmospheric concentrations of (7)Be and (210)Pb were measured for 15 years (1987--2001) in ground-level air at Thessaloniki, Northern Greece (40 degrees 38'N, 22 degrees 58'E). Mean activity concentrations of (7)Be and (210)Pb were 5.02 mBqm(-3) and 664 microBqm(-3), respectively, characteristic of the latitude of 40 degrees N. Monthly atmospheric concentrations of (7)Be showed a strong seasonal trend with the highest values being observed in the summer and the lowest in the winter period. Multiple regression analysis of the data of (7)Be concentrations and a number of meteorological parameters revealed that the sunspot number and temperature are the most significant parameters affecting the concentrations of (7)Be in surface air. The observed strong positive correlation between the mean monthly concentrations of (7)Be and the temperature confirms that the increased rate of vertical transport within the troposphere, especially during the warm months, has as a result to carry down to the surface layer air masses enriched in (7)Be. Highest values of the mean monthly atmospheric concentrations of (210)Pb were observed in the autumn and lowest in the spring period. The positive correlation that was observed between (210)Pb and (7)Be concentrations during the summer months suggests that these two radionuclides could be used together as tracers of environmental processes.     

Toe temperatures during arctic training

The surface toe temperature of 10 subjects was monitored in the field in Arctic Norway (minimum air temperature -27 degrees C). The lowest skin temperature recorded was 1.9 degrees C. The mean estimated time for the toe temperature to cool from 25 degrees C to 5 degrees C was 109 minutes (SD, 10.2) at an ambient temperature of -21 degrees C. One subject experienced a toe temperature below 5 degrees C for 2.9 hours during a 27-hour period. Surprisingly none of the subjects demonstrated clinical signs of cold injury, but this does not mean that this exposure was without risk. Cold sensitization could have occurred.