Asymmetric visual deficit at high sustained Gz.

Occasionally, acceleration research personnel see an individual who experiences consistent asymmetric visual deficits at high sustained Gz (HSG). Recently, one such centrifuge research subject from this laboratory was investigated with transcranial Doppler sonography. The results indicate an abnormal circle of Willis which could explain the asymmetric visual deficit at HSG.     

Centrifuge braking effects on cardiac arrhythmias occurring at high +Gz acceleration

Abrupt onset and offset of acceleration induces hemodynamic changes that activate a number of reflex cardiovascular responses. At high +Gz on a centrifuge, apparently healthy subjects occasionally develop a serious cardiac arrhythmia such as supraventricular tachycardia or asystole. We report on four such cases and examine the effect of rapid centrifuge braking (1 G x s(-1)) on the arrhythmia. It appears that the hemodynamic consequences and reflex responses produced by rapid deceleration may have a positive effect on paroxysmal supraventricular tachycardia, slowing the heart rate or terminating the arrhythmia. On the other hand, deceleration tends to intensify sinus bradycardia. If further study confirms these findings, medical monitors and centrifuge operators may want to consider using gradual braking in cases of bradycardia.     

Human gas exchange at +Gz with the use of various anti-g protectors]

Human respiration parameters were studied in subjects exposed to +Gz (6.0; 7.0, 8.0 and 9.0 g with a 15-s plateau and a g-gradient of 1.0 and 5.0 g/s) with the use of anti-g measures, i.e. a barber chair inclined at 30 or 45 degrees, anti-g suit VKK-15 with a pressure controller, and a positive oxygen pressure. The gas-exchange parameters were found to be indicative of the effectiveness of an anti-g protector. When used together, these protective methods (VKK-15 munitions, an oxygen respirator for positive-pressure breathing, and chair back inclination to 45 degrees) improved g-tolerance significantly.     

Bladder tumor detection at virtual cystoscopy

PURPOSE: To investigate the utility of computed tomographic (CT) virtual cystoscopy in the detection of bladder tumors. MATERIALS AND METHODS: Twenty-six patients suspected or known to have bladder neoplasms underwent CT virtual and conventional cystoscopy. The bladder was insufflated with carbon dioxide through a Foley catheter. Helical CT of the bladder was then performed. The data were downloaded to a workstation for interactive intraluminal navigation. Two radiologists blinded to the results of conventional cystoscopy independently reviewed the transverse and virtual images, with consensus readings for cases with discrepant results. RESULTS: Thirty-six (90%) of 40 bladder lesions proved at conventional cystoscopy were detected with a combination of transverse and virtual images. Four (10%) of 40 bladder lesions, all smaller than 5 mm, were undetected. Transverse and virtual images were complementary, since six polypoid lesions smaller than 5 mm depicted on the virtual images were not seen on the transverse images. In contrast, areas of wall thickening were more readily appreciated on transverse images. CT with patients in both supine and prone positions was necessary, since seven (19%) and five (14%) of 36 lesions were seen only on supine and prone images, respectively. CONCLUSION: CT virtual cystoscopy is a promising technique for use in bladder tumor detection of lesions larger than 5 mm. Optimal evaluation requires adequate bladder distention with the patient in both supine and prone positions and interpretation of both transverse and virtual images.     

飞行员加速度耐力与Gz暴露后眼房水蛋白含量变化的关系

目的查明飞行员离心机加速度负荷前后眼前房蛋白含量的变化与加速度耐力之间的关系。方法歼击机飞行员42例，男性，20－35岁。采用63型载人离心机检测其加速度耐力，耐受＋Gz值＞4．25G，峰值恒速时间＞10s为加速度耐力良好；低于此限者为加速度耐力不良。眼前房蛋白含量检测采用日本产KowaFC－1000型激光蛋白细胞检测仪。加速度负荷前后各检测一次。结果加速度耐力不良的飞行员，加速度负荷后房水蛋白含量（6．20±0．52Photoncount／ms）较加速度负荷前（4．36±0．65photoncount／ms）升高（P＜0．05）。而加速度耐力良好的飞行员，加速度负荷前后服房水蛋白含量无显著性差异（P＞0．05）。结论眼前房蛋白含量的变化，在加速度耐力检测中出现较早也较敏感，利用这项指标可能有助于客观判定加速度耐力。     

低+Gz重复暴露后对高+Gz致大鼠脑损伤的影响

目的：探讨低 Gz重复暴露后对高 Gz致脑损伤的影响。方法：SD大鼠40只,随机分为正常对照组（5只）, 10Gz/5min单次暴露组（5只）和 4Gz/3min暴露1次、3次和5次组（每组10只,每天暴露1次）,分别于暴露后1d和6d再暴露于 10Gz/5min,于 10Gz暴露后3d处死取脑,观察脑组织病理损伤情况。结果： 4Gz/3min锻炼1-5次,每天1次,大鼠脑组织未见病理性损伤。而 10Gz/5min单次暴露后,在皮层、海马、丘脑等部位均可见到变性的神经元,个别脑区出现神经细胞凝固性坏死。经过 4Gz/3min锻炼3次和5次后再暴露于 10Gz,变性神经元的数目在顶叶皮层、梨状皮层、海马和丘脑下部等部位明显减少。结论： 4Gz/3min反复锻炼3次和5次,再暴露于损伤强度的 10Gz/5min,其神经元损伤程度明显轻于 10Gz/5min单次暴露。 Gz作用下在脑部同样存在缺血耐受现象。     

Recovery to +1Gz and +2Gz following +Gz-induced loss of consciousness: operational considerations

With the development of aircraft autorecovery technology, the need to understand the effects of potential inflight recovery profiles on human physiology has become important. Eight male volunteer subjects were exposed to +7Gz with an onset rate of 6 G.s-1 until they were unconscious. The subjects did not wear anti-G suits and did not perform anti-G straining maneuvers. The subjects controlled the centrifuge utilizing an F-16A stick, thereby deliberately self-inducing their unconsciousness. Following +Gz-induced loss of consciousness (G-LOC), recovery to the usual +1Gz level was compared to recovery to a +2Gz level by comparing absolute, relative, and total incapacitation times. The mean (+/- S.D.) absolute incapacitation time (period of unconsciousness) was 11.9 +/- 2.9 s for recovery to a +1Gz level and 12.9 S (+/- 6.9 S.D.) for recovery to a +2Gz level. The mean relative incapacitation time (period of confusion/disorientation) was 3.6 +/- 2.3 s for recovery to a +1Gz level as compared to 2.9 +/- 0.8 s for recovery to a +2Gz level. The total incapacitation time (sum of the absolute and relative incapacitation) was 15.6 +/- 2.7 s for recovery to a +1Gz level and 16.0 s (+/- 6.8 S.D.) for recovery to a +2Gz level. No significant differences in any of the incapacitation times were found when comparing recovery to +1Gz and +2Gz. The mean time from the onset of +Gz-stress to the onset of unconsciousness was approximately 7 s.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproducibility of +Gz tolerance testing.

The +Gz tolerance of USAF aircrewmen undergoing medical evaluation has been tested at the USAF School of Aerospace Medicine since 1973. For various reasons, the test protocol can usually be carried out only once on these patients. Accurate determination of the +Gz tolerance of aircrewmen who fly high performance fighter aircraft is very important in assuring aero-medical safety, since loss of consciousness as a result of exceeding a pilot's G tolerance may result in loss of life and loss of aircraft. It is, therefore, necessary to estimate the variability associated with each profile of the test so that a more accurate assessment of +Gz tolerance can be made. Multiple repeat medical evaluation test protocols were performed on 17 centrifuge acceleration panel members. The standard deviations in the +Gz measurements for the four centrifuge profiles were GOR(1) = 0.38 Gz, ROR=0.22 Gz, GOR(2)=0.34 Gz, and GOR(S)=0.39 Gz. A statistically significant learning effect, which increases +Gz tolerance, was observed in both experienced and inexperienced subjects. Knowledge of the variability associated with each test profile will allow a more accurate definition of an individual +Gz tolerance when only a single centrifuge test protocol can be performed. In addition, possible future use of this centrifuge protocol in the selection of individuals with above- or below-average +Gz tolerance is facilitated with an accurate assessment of the variability associated with the test.     

G_z对大鼠血液流变学的影响

观察了＋10Gz重复暴露（G值增长率1G／s，持续3min，30min后重复暴露，共3次）。对大鼠血液流变学的影响。结果表明，＋Gz组大鼠全血粘度（ηb）、全血还原粘度、血浆纤维蛋白原含量、红细胞聚集指数（EAI）及屈服应力较对照组均有升高（P＜0．05），而血浆粕度、红细胞比积、Casson粘度及红细胞刚性指数则无明显改变；在各切变率时，ηb增加值与EAI增加值均呈显著正相关（P＜0．05）。提示＋10Gz重复暴露可引起大鼠血液流变学改变，全血粘度增高主要是红细胞聚集程度增加引起的。     

Errors in measurement of +Gz acceleration tolerance

Most acceleration studies estimate a subject's G-level tolerance by taking only one determination (test) for a given condition. The purpose of this study was to examine the error structure and reliability of an individual's acceleration tolerance and to provide design considerations for future experimentation. A hierarchical (nested) design was used to estimate the sources of variation in measuring G-level tolerance. Six males rode relaxed in the USAF School of Aerospace Medicine human-use centrifuge and were exposed to a 0.1 G/s onset rate profile until greyout. Each subject was tested on three randomly selected days with three repeated determinations within a day. This design allowed for an estimate of both day-to-day and measurement error within a testing session. A single +Gz tolerance determination was found to be moderately unreliable (reliability coefficient = 0.74). Under the best of circumstances a subject's G-level tolerance cannot be estimated with any more accuracy than about +/- 0.3 G with 95% confidence. This degree of accuracy can only be obtained with multiple measurements.     

高+Gz应激致脑损伤的分子机制与低+Gz预适应的保护作用

目的：筛选与高+Gz暴露和低+Gz预适应相关的差异表达基因,并进行生物信息学分析,加深对加速度应激致脑损伤分子机制的认识。方法将大鼠分为对照组、+10 Gz应激组和低+Gz预适应组,在+10 Gz暴露后24 h分别提取大鼠海马组织总RNA,利用基因芯片技术进行差异基因筛选,基于京都基因与基因组百科全书（kyoto encyclopedia of genes and genomes,KEGG）数据库进行Pathway分析。结果与对照组比较,+10 Gz应激组筛选出差异基因846个,涉及56个KEGG信号通路;低+Gz预适应组筛选出差异基因992个,涉及49个KEGG信号通路。结论对高+Gz应激和低+Gz预适应组的差异基因表达的分析发现,差异基因表达涉及多条信号通路,可为深入研究高+Gz应激致脑损伤的分子机制和探讨有关防护措施的效果提供实验依据。     

Interventional MR imaging at 1.5 T: quantification of sound exposure

Sound pressure levels (SPLs) during interventional magnetic resonance (MR) imaging may create an occupational hazard for the interventional radiologist (ie, the potential risk of hearing impairment). Therefore, A-weighted and linear continuous-equivalent SPLs were measured at the entrance of a 1.5-T MR imager during cardiovascular and real-time pulse sequences. The SPLs ranged from 81.5 to 99.3 dB (A-weighted scale), and frequencies were from 1 to 3 kHz. SPLs for the interventional radiologist exceeded a safe SPL of 80 dB (A-weighted scale) for all sequences; therefore, hearing protection is recommended.     

Change of voice characteristics during +3 Gz acceleration

BACKGROUND: This study was performed to test the feasibility of an experimental approach for assessing voice changes during exposure to increased +Gz acceleration. Such changes are probably due to mechanical alterations of the structures involved in voice production. This may be relevant to automatic speech analysis for flight control. Because voice control by means of auditory feedback may compensate for acceleration effects, the investigations included conditions with masked auditory feedback. METHOD: Four male subjects read standard speech test material while seated in a human centrifuge both during sustained +3 Gz acceleration and in a reference condition. Both test runs were repeated with masking of the auditory feedback by a white noise presented via headphones. Microphone and acceleration signals were recorded on a PC-based dynamic signal acquisition board. Long-time average spectra (LTAS), fundamental frequency (F0), and the frequency of the first, second, and third formant (F1, F2, F3) of the vowels /a/, /o/, and /i/ were extracted from the microphone signal for the different conditions. RESULTS: LTAS clearly differed between the masking conditions, but not between reference and +3 Gz conditions. F0 clearly rose with auditory masking and showed a small increase under +3 Gz acceleration. Several effects of +3 Gz acceleration on formant frequencies were found, all of rather small magnitude. Increased acceleration lowered F2 for the vowel /i/. A decrease of F3 was observed for vowels /i/ and /o/. CONCLUSION: This pilot study has shown the feasibility of an experimental approach to assessing voice changes during exposure to increased +Gz acceleration. Exposure to +3 Gz showed small effects on FO and several formant frequencies. A definitive forthcoming study should assess the significance of these effects by investigating a greater number of subjects during exposure to acceleration higher than +3 Gz.     

Responses of domestic fowl to repeated +Gz acceleration

The responses of domestic fowl to repeated exposures of 4 min to +6Gz (8 times daily, 5 d weekly) are reported. Survivorship curves for the test group of 48 birds divided into three response categories: mode I, highly susceptible, with all individuals dying on the first day; mode II, more tolerant, with mortality occurring within the first 20 d of treatment; and mode III, highly tolerant, with mortality occurring only after 20 d of treatment. Observations of lymphocyte frequency, an index of systemic stress, and postmortem observations indicate that this heterogeniety has a biological basis.     

一种新型囊式抗荷系统的+Gz防护作用

目的在离心机上,研究新型囊式抗荷系统的抗荷性能,评估其抗荷作用.方法6名男性被试者采用本囊式抗荷系统不做抗荷动作(AGSM),暴露于10～15 s的梯形+Gz曲线后,再暴露于+5～9Gz 模拟空战动作曲线(SACM) ,并伴随腿部适度收紧.结果得到了该先进囊式抗荷系统的+Gz防护作用和被试者的+Gz时间耐力.本抗荷系统的抗荷效果为5.33±0.26G,均顺利通过了+5～9 Gz SACM,且用力程度和疲劳程度均较低.结论本抗荷系统+Gz防护效果良好,其配套方案可行.     

高+Gz暴露对血小板功能的影响

目的 观察高 Gz暴露引起的人体血小板功能的变化并探讨其作用机制。方法 6名健康男性受试者进行 Gz暴露，用PFA-100血小板功能分析仪检测 Gz暴露前、暴露后即刻和暴露后24h血小板功能的变化。结果 受试者 Gz暴露后即刻及暴露后24h的血流停止时间大于 Gz暴露前， Gz暴露后24h与暴露后即刻相比则无显著差异。 Gz暴露对血小板计数无影响。结论高 Gz暴露可导致反映血小板功能的血流停止时间延长。     

Localization of pancreatic insulinomas with MR imaging at 0.5 T

OBJECTIVE: To determine the role of MR imaging in the localization of pancreatic insulinomas in patients with clinical and laboratory diagnosis of insulin-producing tumor. MATERIAL AND METHODS: Thirty-one patients presenting with signs and symptoms of pancreatic insulinomas were prospectively included in our study. Twenty-six patients underwent surgery, and pathologic specimens were examined: 5 patients, in whom the initial diagnosis of insulinoma was excluded, were also studied and then followed up. All patients were studied with a high gradient power 0.5 T magnet. Images were evaluated by 2 radiologists blinded to previous investigations, tests and results. RESULTS: MR imaging correctly localized 24 of the 26 insulinomas (2 were false-negative and 1 false-positive) and was correctly negative in the 5 control patients. The interobserver agreement had a kappa value of 0.89. CONCLUSION: MR imaging was accurate in localizing pancreatic insulinomas and as a consequence, patients in our institution are now submitted to surgery directly after the MR examination. Invasive methods are considered only in cases in which, despite clear biochemical results, MR imaging has not demonstrated a pancreatic focal lesion.     

膳食中蛋白质比例对小鼠加速度耐受性的影响

为探讨膳食中不同热源质比例与机体加速度耐受性的关系，观察了增加膳食中蛋白质比例对小鼠加速度耐受性的影响。将300只体重15～20巴雄性小鼠随机分为3组，每组100只。A组饲喂高蛋白质膳食（蛋白质热比47.6％），B组饲喂较高蛋白质膳食（蛋白质热比31．1％），C组饲喂适量蛋白质膳食（蛋白质热比15．0％）。饲养3周后分别从各组随机抽取小鼠60只暴露于 16Gz10min，另取20只暴露于 20Gz10min，记录死亡数，计算死亡率。另从各组未经 Gz暴露的动物中分别随机抽取12只测定总运动次数；再从各组暴露于 16Gz10min后存活的动物中分别随机抽取12只，于 Gz暴露后30min内测定总运动次数。结果表明，暴露于 16Gz10min的各组动物死亡率有随膳食中蛋白质比例增加而降低的趋势，膳食中蛋白质比例增加的小鼠 Gz暴露后30min内的总运动次数多于不增加者；暴露于 20Gz10min时三组小鼠死亡率无明显差别。饲养期间，膳食中蛋白质比例增加的小鼠生长较缓慢。结果揭示增加膳食中蛋白质比例对提高机体加速度耐受性有一定作用。