Design and Verification of a COPD Screening Equipment Based on Dual-differential Pressure Throttling Technique / 中国医疗器械杂志

This study was to design a chronic obstructive pulmonary disease (COPD) screening equipment, based on the dual-differential pressure throttling technique. The technique combined a wide range, but low-resolution ratio sensor and a narrow range, but high-resolution ratio one. It can accurately detect the indexes of forced vital capacity (FVC), forced expiratory volume in one second (FEV), one second rate(FEV/FVC (%)), and achieve them in a low-cost way. The new designed machine will be compared with a British machine, named ML-3500. The correlations of FVC and FEV between new machine and ML-3500 were 0.998 and 0.999, respectively. The P values of paired test of these two indexes were over 0.05. Bland-Altman analysis of FVC, FEV and FEV/FVC (%) showed that more than 90% of the scatter points of the three parameters fell within the consistency interval. This machine can be used to accurately screen COPD and its low-cost would be advantage to promote in large population.

Numerical Simulation of Hemodynamics in Three Kinds of Convertible Vena Cava Filters / 医用生物力学

Objective To study the hemodynamic effect of the convertible vena cava filters on treating pulmonary embolism with different thrombus diameters and contents. Methods Three kinds of simulated filter models with the same diameter but different filtering structures (L-style, S-style and W-style) were built and then the hemodynamics of the filter after its implantation into the vessels was analyzed by using computational fluid dynamic (CFD) method. Results Without thrombus in the vessels, three kinds of filters in blood had some obstructive effects and increased the average outlet velocity. While the L-style filter caused the maximum average outlet velocity, the S-style filter was in the middle, and the W-style filter was the lowest. Under the condition of thrombus, the structures of the filter rods had no obvious effect on the average outlet velocity of blood flow and thrombus, and differential pressure of blood flow and thrombus between inlet and outlet. With the increase of thrombus’s diameter and content, the hemodynamic factors showed varying degrees of decreasing tendency. The wall shear stresses (WSS) on three kinds of filter rods caused by blood flow were in normal ranges, and WSS on the lower end of filter supports, the joints of supports and filter rods were below the minimum value, where thrombosis was easy to occur. Conclusions The hemodynamic effect of three kinds of convertible vena cava filters with different filtering structures, different thrombus diameters and contents in vessels were analyzed by using CFD method, which would provide theoretical references for the design and development of novel filters.

Effectiveness of Serial Measurement of Differential Pressure in Closed Tibial Diaphyseal Fractures in Diagnosing Acute Compartment Syndrome using Whiteside's Technique

Acute Compartment Syndrome is a limb-threatening emergency and it occurs most commonly after fractures. The aim of our study is to find out the effectiveness of serial measurement of differential pressure in closed tibial diaphyseal fractures, in diagnosing acute compartment syndrome, using Whiteside’s technique. A total of 52 cases in the age group of 15 to 55 years admitted with closed fractures were studied for serial compartment pressure as well as serial differential pressure. Eight patients had persistent compartment pressure > 40mmHg, out of which only two patients had persistent differential pressure < 30mmHg and these two patients underwent fasciotomy. Thus, by measuring the compartment pressure serially and calculating differential pressure serially, acute compartment syndrome can be diagnosed or ruled out with higher precision, so that unnecessary fasciotomies can be avoided.

Comparative Study with Flow Regulated Valve and Differential Pressure Valve in Ventriculo-Peritoneal Shunt

In the management of hydrocephalus by shunts, two valve types are currently available:1) differential pressure valves(DPV) which provide a constant resistance and allow CSF flow when the proximal hydrostatic pressure exceeds the valve's present closing pressure, and 2) the newer variable resistance flow regulated valve(FRV). Eighty one cases of hydrocephalus were reviewed in this study to compare the two devices. Forty two patients were operated with FRV and 39 patients were operated with DPV. This study compared the preoperative and postoperative KPS score, ventricular size, periventricular low densities, and the frequency of complications. We have conclude that 1) In group 1(KPS score 50-70), FRV is useful and in group 2(KPS score 20-40), DPV is useful, 2) FRV is useful in dealing with excessively reduced ICP caused by over-drainage of a ventricular shunt;it can prevent postshunt subdural hygroma and symptomatic slit ventricles. 3) For evaluation of the effectiveness of FRV, the decrease of periventricular low densities is a more valuable index than the change of ventricle size(Hydrocephalus index).

Surgical Treatment of Hydrocephalus: Characteristics and Selection of Shunt System

Most patients suffering from hydrocephalus have been treated by insertion of differential pressure valves that have fairly constant resistance. The number of shunting procedures for hydrocephalus has increased significantly with the advent of more sophisticated diagnostic tools such as computed tomographic scanning and with rapid technical advances in shunt equidment. Since intracranial pressure is a variable parameter depending on the factors as patients position and since cerebrospinal fluid(CSF) secretion is almost constant, it may be assumed that some shunt complication are related to too much or too little CSF drainage. As a result, there has been a proliferation of shunt systems that differ in their component parts, particularly their valve mechanisms. To minimize complications and to maintain proper shunt functions, the shunt system optimal to each pathological condition must be selected out of variety of systems. To effect this, it is imperative to have an accurate knowledge of the structure and characteristics of each shunt is currently available. The author reviews some of the devices currently in use for the purposes of clarification and comparison. Also clinical results of 33 padiatric patients shunted with a valve which was selected out of a variety of shunt system, are reported.