Undersea biomedical research最新文献_第4页

Respiratory effects of warm and dry air at increased ambient pressure. 在环境压力增加的情况下，温暖和干燥空气对呼吸的影响。

Undersea biomedical research Pub Date : 1992-03-01

E Thorsen, I Rønnestad, K Segadal, A Hope

{"title":"Respiratory effects of warm and dry air at increased ambient pressure.","authors":"E Thorsen, I Rønnestad, K Segadal, A Hope","doi":"","DOIUrl":"","url":null,"abstract":"We have measured in 7 divers forced vital capacity (FVC), forced expired volume in 1 s (FEV1), and forced midexpiratory flow rate (FEF25-75%) before and after exposure to dry or humid breathing gas of 35.3 degrees-36.8 degrees C (air) when diving to pressures of 117-600 kPa. The response was compared with the subjects' reactivity to pharmacologic bronchoprovocation with methacholine. Baseline FEV1 and FEF25-75% decreased in accordance with increasing gas density. Relative to baseline, there was a significant reduction after the dives in FEV1 of 4.0 +/- 6.1% (P less than 0.05) and in FEF25-75% of 8.6 +/- 9.7% (P less than 0.01) with exposure to dry breathing gas. By analysis of variance the reduction in the lung function variables below baseline were related to the breathing gas characteristic (dry/humid) (P less than 0.01), bronchial hyperreactivity (P less than 0.02), and ambient pressure (P less than 0.02) independently of each other. There was no significant change in FVC after the exposures. Humid breathing gas was considered more comfortable than dry breathing gas, and the upper comfort limit for breathing gas temperature was higher with humid breathing gas. Convective respiratory heat loss was negligible in these experiments, indicating that dry gas itself had a significant bronchoconstrictive effect. Bronchial hyperreactivity may cause increased risk of development of bronchial obstruction and air trapping during diving.","PeriodicalId":76778,"journal":{"name":"Undersea biomedical research","volume":"19 2","pages":"73-83"},"PeriodicalIF":0.0,"publicationDate":"1992-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12729975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Cardiovascular responses to upright tilt in man during acute exposure to 3 atm abs air. 急性暴露于3atm腹肌空气中的人对直立倾斜的心血管反应。

Undersea biomedical research Pub Date : 1992-03-01

S Sagawa, K Miki, F Tajima, K Shiraki

{"title":"Cardiovascular responses to upright tilt in man during acute exposure to 3 atm abs air.","authors":"S Sagawa, K Miki, F Tajima, K Shiraki","doi":"","DOIUrl":"","url":null,"abstract":"To examine the effect of acute hyperbaric exposure on cardiovascular response to orthostasis, a passive 70 degrees head-up tilt (HUT) test was performed for 15 min in a simulated compressed-air hyperbaric environment of 3 atm abs at ambient temperature of 31 degrees C (thermoneutral) on 8 male subjects. Heart rate (HR), blood pressure, cardiac output (CO) by impedance cardiography, forearm blood flow (FBF) by the occlusion plethysmography, and laser-Doppler skin blood flow (BFLD) on the thigh were measured for 15 min before, during, and after HUT. Esophageal temperature and HR data were recorded continuously. An identical test was performed in a 29 degrees C (thermoneutral) normal atmospheric condition. None of the subjects showed signs of syncope during HUT in either environment. Baseline HR was significantly lower (P less than 0.05) at 3 atm abs, and the increase in HR (delta HR) during HUT was of the same magnitude (15 beats/min) at both atmospheric pressures. The reduction of systolic blood pressure (delta SBP) was identical in both environments. Thus, the chronotropic response to HUT (delta HR/delta SBP) was the same. A marked reduction in CO (P less than 0.05) was attributed to a reduction of stroke volume during HUT, and the reduction was greater (P less than 0.05) at 3 atm abs. There were no pressure-dependent changes during HUT in FBF, forearm vascular resistance, and BFLD except for a greater increase (P less than 0.05) in total peripheral resistance at 3 atm abs. These observations suggest that orthostatic tolerance was maintained in the presence of lower CO at 3 atm abs, probably by a greater vasoconstrictor response in the splanchnic areas. We conclude that the substantial bradycardia which occurred at 3 atm abs did not interfere with a normal response to orthostasis in humans because of a peripheral vasoconstriction caused by the elevated oxygen pressure and an enhanced increase in total peripheral resistance which occurred during HUT in 3 atm abs.","PeriodicalId":76778,"journal":{"name":"Undersea biomedical research","volume":"19 2","pages":"97-106"},"PeriodicalIF":0.0,"publicationDate":"1992-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12729977","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Relationship between physique and rectal temperature cooling rate. 体质与直肠温度降温速率的关系。

Undersea biomedical research Pub Date : 1992-03-01

M D White, W D Ross, I B Mekjavić

{"title":"Relationship between physique and rectal temperature cooling rate.","authors":"M D White, W D Ross, I B Mekjavić","doi":"","DOIUrl":"","url":null,"abstract":"Despite many attempts to relate components of physique to core temperature cooling rate, no consistent relationship has emerged. The inconsistencies among the reported findings may arise from unaccounted thermoregulatory responses or incomplete physique assessment or both. A study was designed to examine this relationship in the range of rectal temperatures (Tre) within which shivering and sweating are absent, defined as the null zone, thus minimizing the contribution of these effector responses. Twenty healthy subjects (10 male and 10 female), representing a variety of physiques, participated in the study. The anthropometric protocol included 5 heights, body mass, 8 skinfolds, 10 girths, and 4 breadths. This permitted derivation of a body surface-area-to-mass ratio and estimates of adipose and muscle tissue masses using a cadaver-validated mass fractionation model. Subjects were heated in a 40 degrees C bath followed immediately by cooling in a 30.6 degrees C bath. During the cooling, forehead sweating rate and oxygen uptake were monitored to establish the boundaries of the Tre null zone. In addition, on-line recordings were made of Tre, skin temperature, and surface heat flux at six sites. The rate of cooling of Tre (Tre), in the range of temperatures between thresholds for sweating and shivering, was correlated to the components of physique. Estimates of adipose and skeletal muscle tissue masses did not correlate to Tre in the range of core temperatures investigated. However, total mass exhibited a significant correlation (r = 0.5, P less than or equal to 0.05) with Tre, but gender seemed to distort this relationship, possibly due to differences in adipose tissue distribution.","PeriodicalId":76778,"journal":{"name":"Undersea biomedical research","volume":"19 2","pages":"121-30"},"PeriodicalIF":0.0,"publicationDate":"1992-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12729972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Delayed occurrence of dysbaric osteonecrosis: 17 cases. 迟发性不稳定骨坏死17例。

Undersea biomedical research Pub Date : 1992-03-01

J F Kang, L D Zhang, H Zhang

引用次数: 0

Static lung load and posture effects on pulmonary mechanics and comfort in underwater exercise. 静态肺负荷和姿势对水下运动中肺力学和舒适性的影响。

Undersea biomedical research Pub Date : 1992-03-01

T Derion, W G Reddan, E H Lanphier

{"title":"Static lung load and posture effects on pulmonary mechanics and comfort in underwater exercise.","authors":"T Derion, W G Reddan, E H Lanphier","doi":"","DOIUrl":"","url":null,"abstract":"Static lung load (SLL), or transrespiratory pressure gradient, imposed by underwater breathing apparatus can affect breathing comfort and mechanics, especially during exertion. We examined the effects of body position and SLL on two factors known to affect or limit exertion: a) tidal flow-volume limitation, i.e., the percentage of the tidal volume that meets the boundary of the maximum expiratory flow-volume curve; and b) breathing discomfort. Eight healthy male scuba divers (28 +/- 4 yr) performed cycle ergometry to exhaustion during immersion in each of four combinations of body position and SLL: upright, prone, +10 cmH2O, -10 cmH2O. SLL was referenced to the sternal notch. Tidal flow-volume limitation was significantly greater with the negative SLL (P less than 0.05). In the prone position, higher expiratory flows were achieved (P less than 0.01) and flow limitation was not significantly increased. Respiratory discomfort was quantified with a psychophysical rating scale and increased significantly as exercise intensity increased (P less than 0.01). No effect of posture or SLL on discomfort was found. We conclude that, although respiratory comfort is unaffected, positive static lung loading and the prone body position minimize adverse changes in respiratory mechanics during exercise in immersion.","PeriodicalId":76778,"journal":{"name":"Undersea biomedical research","volume":"19 2","pages":"85-96"},"PeriodicalIF":0.0,"publicationDate":"1992-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12729976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effects of treatment with dexamethasone on recovery from experimental cerebral arterial gas embolism. 地塞米松对实验性脑动脉气栓塞患者康复的影响。

Undersea biomedical research Pub Date : 1992-03-01

A J Dutka, R B Mink, R R Pearson, J M Hallenbeck

{"title":"Effects of treatment with dexamethasone on recovery from experimental cerebral arterial gas embolism.","authors":"A J Dutka, R B Mink, R R Pearson, J M Hallenbeck","doi":"","DOIUrl":"","url":null,"abstract":"Dexamethasone is often recommended as an adjunct to recompression in the treatment of serious central nervous system decompression accidents. We studied the effects of prophylactic and therapeutic administration of dexamethasone combined with hyperbaric treatment in anesthetized dogs that were subjected to carotid air embolism and a brief episode of arterial hypertension. To assess recovery we measured somatosensory evoked potential (SSEP) amplitude, intracranial pressure, brain water, and cerebral blood flow. Three groups were studied: pre-air treatment (dexamethasone 1 mg/kg 3-4 h before carotid air embolism, and 1 mg/kg immediately after air embolism); post-air treatment (2 mg/kg immediately after air embolism); and control (equivalent volumes of saline pre- and post-air). There was a slight improvement in SSEP early in the course of hyperbaric therapy in the pre-air treated group; the post-air group never differed from control. No differences in intracranial pressure or brain water were found among groups. No blood flows below those lethal to neurons occurred in treated animals but 4 of 7 control animals had low flows. Although prophylactic treatment with dexamethasone produces some improvement in recovery, we cannot confirm that dexamethasone is an effective adjunct to recompression when administered therapeutically.","PeriodicalId":76778,"journal":{"name":"Undersea biomedical research","volume":"19 2","pages":"131-41"},"PeriodicalIF":0.0,"publicationDate":"1992-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12729974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of inspiratory-phase negative pressure breathing on urine flow in man. 吸气相负压呼吸对人体尿流的影响。

Undersea biomedical research Pub Date : 1992-01-01

R A Hebden, B J Freund, J R Claybaugh, W M Ichimura, G M Hashiro

引用次数: 0

Susceptibility of divers in open water to motion sickness. 开放水域潜水员易患晕动病。

Undersea biomedical research Pub Date : 1992-01-01

W T Norfleet, R E Peterson, R W Hamilton, C S Olstad

引用次数: 0

Effect of pressure on the release of endogenous dopamine from rat striatum and the role of sodium-calcium exchange. 压力对大鼠纹状体内源性多巴胺释放的影响及钠钙交换的作用。

Undersea biomedical research Pub Date : 1992-01-01

M L Paul, R B Philp

{"title":"Effect of pressure on the release of endogenous dopamine from rat striatum and the role of sodium-calcium exchange.","authors":"M L Paul, R B Philp","doi":"","DOIUrl":"","url":null,"abstract":"Exposure to environmental pressures in excess of 20 atm abs can precipitate a hyperexcitability state known as high pressure neurologic syndrome (HPNS). Little is known about the underlying neurochemical basis of this syndrome. An in vitro model of the synthesis and release of endogenous dopamine (DA) from rat striatal slices has been used to examine the mechanism underlying the effects of high pressures of He. He at 100 atm abs produced changes in DA release which were strikingly similar to those of the cardiac glycoside, ouabain. Neither pressure nor ouabain (1-10 microM) had any significant effects on the spontaneous (nonevoked) release of DA or its metabolite 3,4-dihydroxyphenylacetic acid, but both pressure and ouabain significantly enhanced the stimulated release of DA which was evoked by a 6-min exposure to 35 mM KCl (P less than 0.05 and P less than 0.001). In both cases, this effect was dependent on the presence of extracellular Ca2+. Augmentation of evoked DA release by both ouabain and He pressure was reversed (P less than 0.05) by 3,4-dichlorobenzamil, a selective antagonist of the membrane Na+/Ca2+ exchange mechanism. The results suggest that pressure exerts its effects on DA release by increasing intracellular-free Ca2+ exchange after pressure-inhibition of the activity of the membrane Na,K-ATPase.","PeriodicalId":76778,"journal":{"name":"Undersea biomedical research","volume":"19 1","pages":"1-12"},"PeriodicalIF":0.0,"publicationDate":"1992-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"12705127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effects of four common anticonvulsants on the high pressure nervous syndrome in the rat. 四种常用抗惊厥药对大鼠高血压神经综合征的影响。

Undersea biomedical research Pub Date : 1992-01-01

B Wardley-Smith, C Doré, S Hudson, K Wann

引用次数: 0