The biomechanics of vibration and low back pain

This work is a review of the mechanical factors related to low back pain production in a vibration environment. The sitting posture is an extreme orientation for the lumbar intervertebral disc that 1) increases its internal pressure, 2) increases its anteroposterior shear flexibility, while: 3) decreasing its resistance to buckling instability and 4) stressing the posterior region of the disc. Vibration is an additional mechanical stressor. Several studies suggest that the following preventive measures be taken to reduce the risk of low back pain due to driving: 1) minimize the vibration reaching the driver, 2) avoid lifting or bending immediately following driving, and 3) walk around for a few minutes following driving. © 1993 Wiley-Liss, Inc.     

屈膝过程中的胫股运动特性分析

本文采用三维位移测量方法，测试１０例离体人膝标本的胫股关节三维运动特性。发现屈膝过程中，胫股运动也具有典型的三维运动特点。其中在屈膝初期的３０°内，胫骨内旋最明显并伴有胫骨内翻现象，平均内旋８°，内翻６－７ｍｍ，膝关节完全伸直时胫股扣锁使膝关节稳定，屈曲时胫股“解锁”使膝关节松弛，具重要的临床意义，同时提示，在解释传统的胫股扣锁现象时不应遗漏伴随发生的胫骨内／外翻现象。     

老年卧床病人鼻饲并发症的护理干预

目的　通过护理干预 (增加置入胃管深度、抬高床头、适宜鼻饲量及鼻饲速度 )预防鼻饲时出现的呛咳、食物反流、胃潴留以及吸入性肺炎。方法　将 16例老年卧床鼻饲患者随机分成四组 ,对照组给予教科书上常规的置管深度及鼻饲方法 ;实验一组 (A)给予常规置管深度 ,鼻饲时抬高床头 30～ 80cm ;实验二组 (B)置管深度延长 8～ 10cm ,实验三组 (C)置管深度延长8～ 10cm ,鼻饲时抬高床头 30～ 80cm(坐位或半坐位 ) ,保持该体位 30min。结果　四组病人比较呛咳 ,对照组与实验组 (A、B、C)P <0 .0 1,差异有统计学意义 ;食物返流率P <0 .0 5 ;胃潴留对照组与实验组P >0 .0 5 ,差异无统计学意义 ;吸入性肺炎对照组 2例 ,A、B组各 1例 ,C组无发生。结论　护理干预可以减少与预防鼻饲并发症的发生。     

Changes in cardiovascular function induced by verapamil in healthy subjects and in patients with ischemic heart disease

Alterations in cardiovascular function induced by the acute intravenous administration of verapamil (5 or 10 mg) in 52 patients (29 with ischemic heart disease and 23 without heart disease) were evaluated with use of invasive techniques (right and left heart catheterization, left ventricular cineangiography, and coronary arteriography). The most significant changes were represented by a decrease in systemic vascular resistance and systemic arterial pressure, and an increase in heart rate and cardiac output. Contractility indexes were not depressed in either group, and altered ventricular wall motion tended to improve to a slightly smaller degree than in patients treated with nitroglycerin. The use of verapamil in patients with ischemic heart disease appears to be safe, and concern about the negative inotropic influences in humans no longer seems justified.     

The effect of naloxone on the preoperative gastric volume and pH

The effect of 4 mg oral naloxone on preoperative gastric volume and pH of gastric aspirate was studied in a double-blind, randomized study. Twenty patients received 10 ml of naloxone (4 mg) mixed with 10 ml of orange juice, and 20 patients received 10 ml of isotonic saline mixed with 10 ml of orange juice, 2 h before surgery. Gastric content was obtained immediately after intubation of the trachea. No significant difference in gastric volume and pH of gastric aspirate was found between the two groups. It is concluded that naloxone does not affect gastric emptying and gastric acid secretion to a degree great enough to protect against aspiration of gastric contents into the lungs.     

Factor analysis of bowel symptoms in US and Italian populations

BACKGROUND AND AIMS: Functional gastrointestinal disorders are diagnosed by the presence of a characteristic set of symptoms. Aims of this study were to validate the Rome symptom criteria by factor analysis and to determine whether symptoms cluster in the same way in different cultures. METHODS: One thousand forty-one gastroenterology clinic patients in the US (response rate 53%) and 228 family members accompanying clinic patients in Italy (84%) completed a previously validated symptom questionnaire. Factor analysis identified clusters of symptoms which are highly correlated with each other, and these were compared to the Rome diagnostic criteria. RESULTS: In the US, 13 factors were identified. The irritable bowel factor was composed of three core symptoms corresponding to the Rome II classification system. Two dyspepsia factors were identified which correspond to the ulcer- and motility-like subtypes proposed in the Rome I classification system. All symptoms of constipation formed a single cluster as proposed in the Rome II classification system. Symptom clusters in the US agreed well with symptom clusters identified in Italian subjects. CONCLUSIONS: Empirically derived symptom clusters agree in most respects with the Rome II classification system and support their validity. These symptom clusters are independent of cultural differences in diet and behaviour.     

Effect of artifacts due to flowing blood on the reproducibility of phase-contrast measurements of myocardial motion

The reproducibility of myocardial motion trajectories calculated from cine phase-contrast (PC) velocity data is reduced by artifacts due to the inconsistent motion of intracardiac blood. Spatial presaturation reduces these artifacts but requires a longer sequence TR, with a potentially negative effect on trajectory accuracy and reproducibility. We investigated the effect of spatial presaturation on trajectory reproducibility. A midventricular transaxial slice was imaged in five normal volunteers. The same slice was imaged three times each with sequences using spatial presaturation or not. Because the most serious artifacts originate in the heart chambers and propagate in the phase-encoded direction, myocardial regions that were in line with the heart chambers (in the phase-encode direction) had the highest artifact level in the scans without spatial presaturation. The reproducibility of trajectories for regions placed in these areas (the anterior wall, septum and posterior wall in the transaxial scans with phase encoding in the anterior-posterior direction) improved by a factor of two when presaturation was used (P < .001). In areas that were not in line with the heart chambers (eg, the anterior aspect of the lateral wall in the transaxial scans), the effect of presaturation was not significant. These results correlate well with the measured reduction in artifact level. The reproducibility of myocardial motion trajectories over large areas of the heart is improved to approximately 1 mm when presaturation is used. Therefore, use of presaturation is recommended for myocardial motion studies using cine PC velocity data.     

Sclerosed liver hemangioma mimicking malignant tumor at MR imaging: Pathologic correlation

This case report illustrates atypical magnetic resonance (MR) imaging findings in a liver hemangioma mimicking a malignant lesion—lower signal intensity than cerebrospinal fluid on T2-weighted spin-echo images and lack of early enhancement on dynamic contrast material—enhanced gradient-echo images. Pathologic analysis demonstrated nearly total replacement of the vascular cavities by dense fibrous tissue. In this rare, sclerosed form, this lesion could not be defined as a hemangioma with MR imaging.     

电动秋千的研制及其在前庭功能研究中的应用

本文介绍了带转椅的电动秋千的研制及其使用,包括其工作原理、结构与控制系统的设计、主要技术性能及其在前庭功能与空间运动病研究中的应用。多年的实验证明,这台电动秋千设计合理,技术指标先进,使用性能良好,是研究前庭功能和空间运动病的实用设备。