Evaluation of cutaneous insensible water loss during hyperbaric exposure in humans.

BACKGROUND: Water evaporation diminishes in high pressure environment, however it is unknown whether insensible water dissipation from the human skin falls as a function of the increased environmental pressure. We designed the present study to measure cutaneous insensible water loss at various pressures during exposure to a simulated saturation dive. METHODS: Four healthy male volunteers were exposed to eight different pressures between 1 and 18.4 atmospheres absolute (atm abs). Resting insensible water loss from the skin was measured as change in the body weight and corrected for the weight of the respiratory CO2 - O2 gas exchange and the respiratory water dissipation. RESULTS: We made an equation for the relationship between cutaneous insensible water loss and environmental pressure as: w = 14.5 X p(-0.48), where, w is cutaneous insensible water loss in g x m(-2) x h(-1), and P is the environmental pressure in atm abs. The average cutaneous insensible water loss (15.3 g x m(-2) x h(-1)) at normal atmosphere decreased (p < 0.01) to 4.2 g x m(-2) x h(-1) (reduced by 73%) during a saturation dive to 18.4 atm abs. CONCLUSION: The amount of insensible water loss estimated from the equation was comparable to that of reported observations.     

Metabolic and hormonal changes in moderate and intense long-term running exercises

The changes in selected muscle and blood metabolites - blood catecholamines, cyclic AMP, glucagon, growth hormone, insulin, and C-peptide--were measured in five male long-distance runners after moderate 90 min (4.3 min/km) and intense 45 min (3.3 min/km) of continuous running exercises. After the 45-min exercise, the mean concentrations of blood lactate and glucose were 2.8 and 8.8 mmol/l, respectively, and the muscle glycogen concentration had decreased by 31%. No changes could be found after the 90 min of running. The increase in blood glycerol concentration was greater after the 45-min exercise (5.8-fold) than after the 90-min exercise (3.9-fold), although the serum free fatty acid concentration increased significantly only during the 90-min exercise (1.6-fold). Plasma noradrenaline increases were 2.7-fold and 7.9-fold during the 90- and 45-min exercises, respectively, whereas the plasma adrenaline concentration was significantly elevated only after the 45-min exercise (4.7-fold). The respective changes of plasma cyclic AMP were 2.5- and 2.7-fold, and the increase in the concentration of plasma growth hormone was 5.8-fold after the 45-min exercise. The plasma insulin level decreased during the 90-min exercise, but was elevated after the 45-min exercise. The increase was greater than could be expected on the basis of the plasma C-peptide concentration. It is concluded that the hormonal and metabolic changes during submaximal long-term exercises are highly dependent on the intensity of exercise, even when the intensity of exercise is below the level of the anaerobic threshold.(ABSTRACT TRUNCATED AT 250 WORDS)     

Balance testing and Doppler monitoring during hyperbaric exposure

BACKGROUND: The effects on the postural system of saturation diving to shallow and medium depths have not previously been adequately tested. The purpose of this study was to investigate whether postural function is affected by a moderate hyperbaric exposure, and whether any deterioration is correlated with the presence of intravascular bubbles. HYPOTHESIS: Postural control and the vestibulo-ocular reflex are not affected during heliox saturation diving to 5 meters of seawater (msw). At greater depths, an effect may occur. METHODS: Postural control was tested with the subjects standing on a static balance platform before, during, and after onshore experimental saturation chamber dives to 5 msw heliox, 20 msw air, and to 100 msw heliox. Standard caloric testing with electronystagmography was performed before and after the heliox dives. Cardiac ultrasound and Doppler monitoring were used to detect possible venous gas emboli (VGE) during decompression in the heliox dives. RESULTS: During the heliox exposure to 5 msw, no significant change in body sway was found. However, a significant change in body sway was found during an air dive to 20 msw and during the 100 msw heliox exposure. Caloric responses were unchanged immediately post-dive. After decompression from 5 msw, VGE were detected in two divers. During the 100 msw exposure, one case of VGE was observed. CONCLUSIONS: Exposure to hyperbaric heliox conditions corresponding to 5 msw, did not influence postural control significantly, while exposure to 100 msw heliox, and air diving to 20 msw, did. Although VGE were detected in the heliox dives, we could not find any correlation between this observation and postural instability.     

Results of aromatherapeutic rehabilitation of women after extended exposure in altitude chamber for recompression treatment]

In recent years recreational diving has gained popularity among women. Occasional decompression sickness and pulmonary barotraumata are cured with the use of recompression tables. To evaluate factors in therapeutic recompression, experiment Rusalka-2004 (Mermaid) was performed with participation of a female crew "descended" at air pressure of 70 m H2O and maintained in hyperoxic (pO2 = 0.45-0.5 kgs/cm2) heliox at 40-0 m H2O for four days. On "ascent" the crew was given a course of aroma rehabilitation. To assess effects of this therapy, entries in a dedicated questionnaire were made and the Spilberger-Khanin SAM (self-appraisal-activity-mood) test and a modification of the Dembau--Rubinshtein self-appraisal method were fulfilled on the daily basis. The best result was achieved in the subjects who were particularly favourable to this sensory stimulation and made own choice of scents of 100% natural essences.     

Metabolic and hormonal responses to lipid and carbohydrate diets during exercise in man

Nine healthy subjects were studied to determine their performance and the metabolic and hormonal responses to prolonged exercise after ingestion of a carbohydrate or a lipid diet. Subjects exercised on a bicycle ergometer (60% VO2max) until exhaustion four times at weekly intervals. The exercise test was performed 1 h after ingestion of three different isocaloric meals (400 Kcal) containing either glucose, medium-chain triglycerides (MCTs) or long-chain triglycerides (LCTs). The fourth test was performed after a night fast. The metabolism of these nutriments was followed using [U-13C]glucose, [1-13C]octanoate, and [1-13C]palmitate added as tracers. The average work time was comparable whatever nutriment used (116 +/- 11 min). Oxidation of the ingested nutriment over this period was 80% for glucose, 45% for MCTs, and 9% for LCTs. Glucose ingestion produced an early insulin peak associated at the end of the exercise with a lower glycemia compared to the fat diets. After MCT ingestion, an increase in ketone bodies was observed. Catecholamine response to physical exercise was decreased by all the meals when compared to fasting. Thus, we conclude that a different lipid meal, MCTs, or LCTs, compared to glucose feeding, do not modify exhaustion time in spite of differences in hormonal and metabolic responses.     

高压氧治疗颅脑损伤的护理

高压氧治疗颅脑损伤有较好的疗效,它不仅对颅脑损伤昏迷有促醒作用,而且对恢复期的失语,偏瘫等后遗症有促进康复的作用。在高压氧治疗期间既能给病人合理的护理指导,又能缩短治疗时间及保证高压氧治疗的效果,促进病人的康复。1资料与方法1.1一般资料本组70例,全部为住本院病人,均已确诊。其中男40例,女30例,年龄19~70岁,较重30例,轻型颅脑损伤40例。1.2治疗方法采用多人氧舱加压吸氧,缓慢加压20min,使治疗压力达到0.25 MPa,稳压后给病人戴面罩吸纯氧,昏迷或气管切开病人改用急救吸氧头罩直接供氧。吸氧30 min,休息10 min,再吸氧30 min,然后…     

Results of the psychophysiological investigations of female test-subjects during long-term stay in pressurized chamber under the regime of therapeutic recompression]

IBMP has developed and applied protocols of therapeutic recompression of patients with delayed admission after the onset of decompression sickness or pulmonary barotraumas the occurrence of which increases among recreational divers including females. Experiment Rusalka-2004 was performed to validate a therapeutic recompression protocol with participation of female test-subjects subjected to experimental descents at air pressure of 40 and 80 m H2O (training) and of 70 m H2O (experimental) followed by 4 days at 40 to 0 m H2O in a hyperoxic (pO2 = 0.45-0.5 kgs/cm2) helium-oxygen-nitrogen atmosphere. Psychophysiological investigations during the experiment revealed only weak changes of the parameters evaluated by the well-being - activity - mood, Spilberg - Khanin, Luscher, and proof-read tests. Significant deviations in self-feeling (modified method by Dembaut - Rubinstein) and mental performance assessment (Krepelin's tables) were associated with the air pressure elevation to 40-80 m H2O both during the training and experimental descents, and symptoms of nitrogen narcosis. Based on these results, the therapeutic recompression protocol can be recommended for treatment of as males, so females.     

Hemodynamic effects of 10% dextrose and of dextran 70 on hemorrhagic shock during exposure to hyperbaric air and hyperbaric hyperoxia

Six groups of six conditioned dogs each were instrumented with an electromagnetic flow-meter transducer around the pulmonary artery, and indwelling silastic cannulae in the pulmonary artery, the left ventricle, the ascending aorta, and the right atrium. After allowing a minimum of 5 d for recovery, the dogs were studied under normobaric conditions, breathing air, at 2.8 atmospheres absolute (ATA), breathing 100% oxygen (PO2 2128 mm Hg) and at 6 ATA breathing air (PO2 960 mm Hg). Baseline recordings were made at 1 ATA and repeated after arrival at depth. The dogs were hemorrhaged until the mean aortic pressure fell to 40 mm Hg. Mean aortic pressure was maintained between 40-50 mm Hg for 30 min. This required a rather constant 40 +/- 4.5 ml X kg-1 body weight of total blood removed. Three groups, one at each depth perturbation, were then given Dextran 70, the other three groups 10% dextrose. Fluids were administered at a constant rate until the mean aortic pressure rose to within 90% of its original 1 ATA baseline value. At this point, the infusion was stopped and the total amount of fluid administered was recorded. Hemodynamic parameters were measured or calculated for eight different time periods during each experiment. The amount of Dextran 70 required did not change with hyperbaric exposure but only half as much 10% dextrose was required at depth. Dextran 70 held the cardiovascular parameters constant for 30 min following administration but after 10% dextrose, cardiac output tended to decrease at 15 and 30 min posttreatment. There were no significant differences in the cardiovascular effects of hemorrhage between or among the dogs exposed to the three different environmental conditions.     

Metabolic and cardiorespiratory parameters during three consecutive days of exhaustive running

The purpose of this study was to examine serum metabolites, cardiorespiratory parameters and creatine kinase during running on 3 consecutive days. Thirteen trained marathon runners exercised to exhaustion on a treadmill at 85 +/- 3% VO2max on each day. Expired gases and blood samples were obtained at rest, after 10 and 30 min of exercise and at exhaustion. There were no significant differences over days for glucose, insulin, lactate, free fatty acids, creatine kinase, oxygen uptake, minute ventilation, heart rate, rating of perceived exertion, respiratory exchange ratio or run times. Serum glycerol was elevated (p less than 0.05) both at rest and during exercise on each successive day. The findings suggested that, except for serum glycerol, acute metabolic and cardiorespiratory responses to exhaustive aerobic exercise are not altered by 3 days daily repetition by endurance trained individuals.     

Metabolic consequences of positive pressure respiration during exposure to acceleration

The purpose of this study was to identify metabolic changes in pilots exposed to linear acceleration with an onset rate of 0.1 G/sec. The exposure of +Gz increased the content of of lactate dehydrogenase and the concentration of lactate dehydrogenase and the concentration of potassium and phosphorus in plasma. Positive pressure breathing of 60 hPa during acceleration enhanced its tolerance by 2.2 G, producing no effect on metabolic changes.     

氢氧高压环境下小鼠脑电图功率谱和睡眠周期的变化

目的探讨高压氢氧环境对小鼠睡眠的影响。方法将小鼠暴露于2．1MPa．氢氧环境中10h，连续记录小鼠脑电图（EEG），进行EEG密度功率谱分析。结果在氢氧环境下，除了个别动物出现可逆的6段活动受抑制外，多数动物EEG密度谱中表示动物清醒和睡眠状态的密度疏密交替的特征始终存在。结论在2．1MPa氢氧环境下个别小鼠觉醒度提高，但总体上睡眠节律保持完好。同时，由于密度谱可以动态反映高压下动物EEG变化趋势和个体差异，提示用这一分析方法进行压力负荷监护的可能性。     

高压暴露条件下清醒大鼠脑电图和脑血流联合实时记录方法的建立

目的 探讨高压暴露条件下清醒大鼠脑电图和脑血流联合实时监测和记录的方法.方法 将激光多普勒光纤探头固定于大鼠颅骨上,并在大鼠颅骨上安装电极联合,再将光纤和导线引到加压舱外的生理记录仪上,对脑电图和脑血流进行监测.结果 用此方法可以清晰地记录到脑血流量和脑电图随暴露时间延长而出现的细微变化.结论 此方法可以用于需要对暴露于高压环境中的大鼠及其他动物的脑皮层局部血流量和脑电图进行实时监测和记录的实验研究.     

Thermal and metabolic responses of sleep deprivation of humans during acute cold exposure

PURPOSE: This investigation evaluated the effects of 33 h of sleep deprivation on the thermoregulation in 12 male and female subjects (26.6 +/- 6.4 yrs) during 180 min of cold exposure in 12 degrees C air. METHODS: Subjects underwent two cold air trials (CAT): one following a normal night of sleep (i.e., 6-8 h) (CON); and one following 33 h of sleep deprivation (SDEP). Rectal temperature (Tre), mean skin temperature (Tsk), heat production (HP), and tissue insulation (Iti), were measured at 5, 15, 30, and every 30 min thereafter. RESULTS: ANOVA revealed no significant differences (p > 0.05) between CON and SDEP for Tre, Tsk, HP, and Iti. A main effect for time was demonstrated for Tre, Iti, HP, and Tsk. A trial x time interaction for Tre and Tsk (p = 0.021) was demonstrated. DISCUSSION: Significant interactions were demonstrated for Tre and Tsk, but post hoc analysis determined no differences between SDEP and CON. This may have been due to the length of the sleep deprivation, cold stressor, or a combination of the two. There were also no overall differences in HP or Iti between SDEP and CON. Further research in this area is needed to evaluate the effects of sleep deprivation during acute cold exposure.     

Functional activity of serotonin- and histaminergic systems in humans during long-term antiorthostatic hypokinesia

The functional activity of serotonin- and histaminergic systems was investigated during 120-day head-down tilt. Serotonin excretion was increased until test day 70 and histamine excretion throughout the entire study. At the final stage of exposure (test days 100-120) the serotonin content decreased. Return to the normal motor activity stimulated the function of serotonin- and histaminergic systems.     

Early hormonal effects of head-down tilt (-10 degrees) in humans

The aim of this study was to determine the effects of a 5-h weightlessness simulation (using supine bed rest or head-down tilt at -10 degrees = HDT) on plasma renin activity (PRA), aldosterone (PA), and catecholamines (epinephrine-E, norepinephrine-NE, and dopamine-DA) and to compare the results with those obtained with horizontal bed rest (BR), which is often taken as a control situation for simulation studies. Ten healthy young volunteers submitted to the three following postural tests: 7 h sitting; 1 h sitting, 5 h supine, and 1 h sitting; 1 h sitting, 5 h HDT, and 1 h sitting. Our results show that a 5-h HDT or BR induced a significant progressive increase in plasma volume (14.5% for HDT and 7% for BR) and a decrease in diastolic blood pressure (18% for HDT and 17% for BR), PRA (60% for HDT and 40% for BR), PA (63% for HDT and 60% for BR), and NE (20% for HDT and 25% for BR) compared to the sitting position. E decreased only in HDT, and DA was unchanged. We concluded that the main part of the cephalad shift is achieved by bed rest as reflected by changes in hematocrit and plasma protein concentration. The decrease in diastolic blood pressure, the inhibition of the renin-angiotensin aldosterone system (in part explained by a decrease in NE) are similar in BR and HDT. We demonstrate that the use of a relevant body position as control is a major concern when investigating the hormonal effects of HDT. If recumbency is chosen as the control situation in HDT studies, it is not surprising to observe only few changes when HDT is applied.     

Study on hematological toxicity in irradiation and ICRF 159 combination treatment during experimentation on animals with particular consideration of long-term effects (author's transl)]

Experiments on animals are utilized for the control of hematological toxicity in sound NMRI mice during and after fractionated ICRF 159 therapy, fractionated whole-body irradiation and a combination of both. In the course of the 32-day therapeutic phase, and also during the total follow-up period lasting 196 days, continual determination of leukocytes and thrombocytes was performed. Leukocyte and thrombocyte depression is related to radiation effects during the phase of therapy and subsequently. In the later period of follow-up, however, hematological toxicity developed by ICRF 159 is higher than that produced by irradiation. Early and late effects of the preparation must be distinguished therefore. The thrombocytopenic effect is altogether less pronounced than the leukocytopenic effect. Here, too, the thrombocytopenic action of ICRF 159 appears in the course of the late phase only, but then more distinctly. The present results are discussed and compared to hitherto existing observations from animal experimentation and from clinical findings described in literature.