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52.
长骨内开口效应对其力学性能影响的理论模型研究 总被引:3,自引:0,他引:3
建立一个股骨中段的外侧皮质带有矩形开口的力学模型,采用有限元方法,计算骨开口区的尺寸改变时,股骨的扭转刚度和应力分布的变化。结果表明:骨开口长度为骨外径的1倍时(1OD),对股骨扭转刚度和剪应力分布的影响较小;开口长度从2OD增至4OD时扭转刚度急剧减小,而且剪应力的最大值位于开口区中心。本结论对临床骨科的手术治疗方法和骨开口尺寸的控制提供了重要的理论依据。 相似文献
53.
H. Seibold U. Roth R. Lippert J. Kohler S. Wieshammer E. Henze M. Stauch 《Journal of molecular medicine (Berlin, Germany)》1986,64(9):433-441
Summary In patients with varying degrees of chronic obstructive pulmonary disease (COPD), simultaneous measurements of central hemodynamics and left ventricular radionuclide ventriculograms at rest and during exercise were made. In 21 of these patients, satisfactory echocardiograms could be performed. In seven of the patients, arterial blood pressure at rest was increased. Decreased compliance of the left ventricle was thought to be present in patients with COPD and additional arterial hypertension. The left ventricular ejection fraction (LVEF) at rest was in the high normal range in all patients. During exercise, no further increase was observed. This pattern of LVEF response seems to be typical in patients with COPD. Because the highest values were observed in the more severe COPD and right ventricular hypertrophy, it is unlikely that an impairment of left ventricular function is caused by COPD. In five of 27 patients, an abnormal decrease of LVEF and regional hypokinesis occurred during exercise, thus suggesting additional coronary heart disease. The fact that at least 30% of the patients with COPD suffered from arterial hypertension and 20% of the patients exhibited unexpected ischemia detected by regional hypokinesis in RNV during exercise, but not in the ECG, may be of practical relevance. Coronary angiography was not indicated because most of these patients were over 65 and the factor limiting the working capacity was ventilatory impairment and not angina pectoris, in all patients. For this reason, a diagnostic uncertainty remains with regard to additional coronary heart disease in the older patients with advanced chronic obstructive pulmonary disease.Lung Function Parameters VC (1)
inspiratory vital capacity
- FEV1 (1)
forced exspiratory volume in 1 sec
- Raw (cmH20/l/s)
airways resistance
- RV/TLC (%)
residual volume/total lung capacity
- paO2 (mm Hg)
O2 partial pressure
Hemodynamic Parameters CI (1/min/sqm)
cardiac index
- SVI (ml/sqm)
stroke volume index
- PAP (mm Hg)
pulmonary artery mean pressure
- PwP (mm Hg)
pulmonary capillary wedge pressure
- RRs (mm Hg)
systolic arterial pressure
- RRd (mm Hg)
diastolic arterial pressure (at the time of catheterization)
- RR(WHO) (mm Hg)
mean values measured at different days (at least 3 values).
Parameters Derived from Combined Radionuclide Ventriculography and Central Hemodynamics LVEF (%)
left ventricular ejection fraction
- LVESVI (ml/sqm)
left ventricular endsystolic volume index
- P/V (mm Hg/ml/sqm)
peak systolic pressure/endsystolic volume index
- PFR (1/sec)
peak filling rate: endsystolic volume/sec
Echocardiographic Parameters RV d wth (mm)
right ventricular enddiastolic wall thickness
- LV d wth (mm)
left ventricular enddiastolic wall thickness
In honor to Prof. W.E. Adam's 60th birthday 相似文献
54.
M. Eriksen 《Medical & biological engineering & computing》1987,25(2):189-194
A system for the direct measurement of the inner diameters of selected human arteriesin situ has been developed. Ultrasound pulses are emitted perdendicular to the vessel axis, and reflected from the wall material
interfaces. Improved depth resolution is achieved by using a high-frequency transducer, and by inverse filtering of the signal.
This is performed by emitting a waveform calculated beforehand to give an optimum time resolution in the received echo. Echoes
from both innerand outer surfaces of the vessel walls are discriminated, and the inter-echo time intervals can be measured
with an accuracy of 33ns, corresponding to approximately 26μm. By repeating the measurements through the cardiac cycle, the
diameter variations can be accurately described. 相似文献
55.
Influence of vascular parameters on the effectiveness of intra-aortic balloon pumping: A model study
The intra-aortic balloon pump has been widely used as a temporary heart-assist device. In this investigation, a nonlinear
mathematical model of the arterial system and intra-aortic balloon pump was studied analytically. Thus, the influences of
a number of vascular parameters on the effectiveness of intra-aortic balloon pumping (IABP) were determined. The effects of
changes in vascular parameters of the model on a number of performance indexes were investigated. These performance indexes
(aortic mean diastolic pressure, aortic end diastolic pressure, cardiac output, coronary flow and phase differences between
the fundamental Fourier components of aortic root pressure and flow) were used as the criterion for an evaluation of the effectiveness
of the assist pump. The following vascular parameters were perturbed by four steps (±10%, ±20%) from the values in the standard
model: heart rate, peripheral resistance, left ventricular pressure, aortic elastance, aortic radius, arterial wall thickness,
and aortic length. This model was evaluated for a wide range of balloon-pump phase-control settings (assisted case) and for
the unassisted case (when the pump is disabled). It is concluded that changes in heart rate, peripheral resistance and left
ventricular pressure cause the most significant changes in pump performance.
Dr. Ohley is with the Datascope Corporation
Dr. Kao is with the Technicare Corporation 相似文献
56.
Dr. P. R. Hoskins P. J. Fish W. N. McDicken C. Moran 《Medical & biological engineering & computing》1998,36(3):259-269
Many of the changes resulting from arterial disease can be measured, using Doppler ultrasound for measurement of blood velocity
and B-scan imaging for measurement of tissue structure and composition. Wall thickness, the degree of arterial narrowing and
plaque volume can be measured using B-scan imaging, and 3D ultrasound can be used to improve the accuracy of measurements
of plaque volume and for improved visualisation of complex arterial geometries. Measurement of the dynamic properties of the
arterial wall permits estimation of wall elasticity and plaque motion. From the Doppler signal, measurements of blood velocity
are used to estimate the degree of arterial narrowing and volumetric flow, although measurement errors can be large. Wall
shear stress can be estimated by measuring the velocity gradient at the vessel wall. The problems of inadequate spatial resolution
and interference from overlying tissue are largely removed when intravascular systems are used, and these have superior capability
in the assessment of arterial structure and tissue composition. However, measurement of quantities relating to blood flow
is more difficult using the intravascular approach, as the indwelling cather disturbs the blood flow pattern, and currently,
assessment of flow and vessel cross-section are not performed at the same site. 相似文献
57.
由于人体组织中存在血液对流传热和代谢产热,当皮肤表面绝热后,皮肤表面的温度将上升,体表温升值是人体组织中血液灌注率和动脉血温度的函数,根据实际测量的体表温升与时间的关系就可以测出活体组织的血液灌注率和动脉血温度。根据一维Pennes生物传热方程,推导出了体表绝热后人体组织中及皮肤表面温度分布的解析解,并对人体组织中的血液灌注率及动脉血温度进行了实验测量。由于测量过程中利用的只是皮肤表面的温度信息,无须引入外加热源,对人体组织完全不会造成损伤,亦避免了干扰人体组织的正常生理状态,整个测量系统也比较简单。 相似文献
58.
Summary Twelve patients with borderline hypertension [⩽21.33/12.6, ⩾18.6/12.0 kPa (⩽160/ 95; ⩾ 140/90 mm Hg)] participated in an experiment
aimed at testing whether they could learn to attenuate heart rate while exercising on a cycle ergometer. Six experimental
(E) subjects received beat-to-beat heart-rate feedback and were asked to slow heart rate while exercising; six control (C)
subjects received no feedback. Averaged over 5 days (25 training trials) the exercise heart-rate of the E group was 97.8 bt
min−1, whereas the C group averaged 107 bt min−1 (P=0.03). Systolic blood pressure was unaffected by feedback training. Generally, changes in rate-pressure product reflected
changes in heart-rate. Oxygen consumption was lower in the E than in the C group late in training. We conclude that neurally
mediated changes associated with exercise in patients with borderline hypertension can be brought under behavioral control
through feedback training. 相似文献
59.
R. Busse U. Förstermann H. Matsuda U. Pohl 《Pflügers Archiv : European journal of physiology》1984,401(1):77-83
The effect of intraluminal hypoxia on vascular tone and the release of prostaglandins (PG) I2 and E2 were investigated in intact isolated segments of canine femoral and coronary arteries as well as in the rat tail artery. Perfusion with hypoxic Tyrode's solution (pO2 20–40 mm Hg) evoked a marked vasodilation of the segments, precontracted with norepinephrine or serotonin. Simultaneously, a 2–3-fold increase in the release of 6-keto-PGF1 (the stable hydrolysis product of PGI2) could be observed. In parallel to 6-keto-PGF1, smaller quantities of PGE2 were released. Removal of the endothelium as well as pretreatment with indomethacin abolished both, the dilatory response and the PG-release. After administration of verapamil as well as 3,4,5-trimethoxybenzoic acid 8-diethyl-aminooctylester (TMB-8) (which binds intracellular calcium) the PG-increase was abolished and hypoxic dilatation could no longer be elicited, although the vessel had still a capacity to dilate. Exogenous administration of PGI2 and PGE2 showed that in canine femoral and coronary arteries PGI2 was the most effective vasodilating prostaglandin, while in the rat tail artery PGE2 had a 10-fold higher dilating potency compared to PGI2. At very high concentrations both PGI2 and PGE2 caused vasoconstriction. Our experiments suggest that the hypoxic endothelium-dependent dilatation may be mediated by an increased PG-release. Hypoxia-induced transmembrane calcium influx into the endothelial cells seems to be the trigger reaction.Supported by the Deutsche Forschungsgemeinschaft (Bu 436/2-1) 相似文献
60.
Olufsen MS Peskin CS Kim WY Pedersen EM Nadim A Larsen J 《Annals of biomedical engineering》2000,28(11):1281-1299
Blood flow in the large systemic arteries is modeled using one-dimensional equations derived from the axisymmetric Navier–Stokes equations for flow in compliant and tapering vessels. The arterial tree is truncated after the first few generations of large arteries with the remaining small arteries and arterioles providing outflow boundary conditions for the large arteries. By modeling the small arteries and arterioles as a structured tree, a semi-analytical approach based on a linearized version of the governing equations can be used to derive an expression for the root impedance of the structured tree in the frequency domain. In the time domain, this provides the proper outflow boundary condition. The structured tree is a binary asymmetric tree in which the radii of the daughter vessels are scaled linearly with the radius of the parent vessel. Blood flow and pressure in the large vessels are computed as functions of time and axial distance within each of the arteries. Comparison between the simulations and magnetic resonance measurements in the ascending aorta and nine peripheral locations in one individual shows excellent agreement between the two. © 2000 Biomedical Engineering Society.
PAC00: 8719Uv 相似文献