Air Trapping: A Cause of Heterogeneous Attenuation

Purpose: To investigate important factors affecting the frequency of air trapping through observation of normal lung attenuation, and propose a cause of heterogeneous attenuation. Materials and Methods: In this ethical committee-approved study, a total of 109 patients (30 males, 79 females;mean age, 58.2 years;range, 27 - 81 years) were included. All patients had undergone inspiratory and expiratory chest thin-section computed tomography (CT) examinations and pulmonary function tests. Air trapping on CT images was graded subjectively. Hounsfield units (HU) lung attenuation value and lung volume were measured on CT images. All variables (age, sex, indices of pulmonary function test results, air trapping score, HU value, and rate of change in lung volume) were compared by diagnoses and air trap- ping findings cohorts. The correlation between lung function test results and expiratory HU attenuation were analyzed. Results: Interstitial pneumonia showed higher and bronchiolitis obliterans showed lower HU attenuation at normal and air trapping regions. The variables affecting air trapping findings were age, a ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1.0/FVC), maximal expiratory flow at 50% of forced vital capacity (MEF50), HU attenuation at normal regions, and rate of change in lung volume. Compared with expiratory HU attenuation, significant positive correlation was shown to FEV1.0/FVC and negative correlation to single-breath diffusion capacity for carbon monoxide, which was confirmed by a simple regression analysis. Conclusion: It can be suggested that lung attenuation can increase when fibrosis is advanced, and this is exaggerated when lungs are compressed.

Quantitative Assessment of Air Trapping Using Inspiratory and Expiratory Low-Dose Computed Tomography

Objective: The purpose of this study was to evaluate the effect of radiation dose reduction on the quantification of air trapping on expiratory CT. Materials and methods: This study was conducted as a retrospective evaluation of inspiratory and expiratory CT studies performed in routine clinical practice before and after alteration of the scanning protocol for expiratory CT at our institute. Eighty-six patients who had a clinical diagnosis of chronic obstructive pulmonary disease (COPD) and underwent inspiratory and expiratory CT and pulmonary function testing (PFT) were included. For the quantitative analysis, CT scans were obtained at six evenly spaced levels from the lung apices to the bases. The area of segmented lung without emphysema between -500 to -950 HU was obtained from the summation of six slices. The relative area between -900 and -950 HU for the area of the segmented lung (RA900-950) was calculated on both the inspiratory and expiratory scans. Comparisons of the RA-change between the standard-dose group (200 mA) and the low-dose group (80 mA) were performed by Mann-Whitney U test. Results: There was no significant difference between the standard-dose group and the low-dose group in the mean RA-change, and RA-change in both the standard-dose and low-dose groups correlated significantly with the results of PFT. In addition, there were no prominent differences in the correlation coefficients between the two groups. Conclusions: Low-dose CT could evaluate air trapping objectively and was not inferior to standard-dose CT for this purpose.

Montelukast improves air trapping, not airway remodeling, in patients with moderate-to-severe asthma： a pilot study

Background Evidence has demonstrated that the distal lung,which includes airways of 〈2 mm in diameter and lung parenchyma,constitutes an important component of asthma pathology.Cysteinyl leukotrienes （CysLTs） are potent proinflammatory mediators and bronchoconstrictors involved in the asthmatic process.Guidelines recommend the leukotriene-modifying agents for asthma treatment.We hypothesized that a leukotriene receptor antagonist with an inhaled corticosteroid （ICS） and long-acting β2 agonist （LABA） combination would improve small airways function in moderate-tosevere asthmatics evaluated by physiological tests and high-resolution computed tomography （HRCT） analysis.This study was performed at a tertiary university hospital in Beijing.Methods This was a randomized,double-blind,parallel study performed in 38 patients with moderate-to-severe asthma treated with salmeterol/fluticasone （SFC） plus montelukast （SFC＋M） or SFC plus placebo over 24 weeks.Small airway function was assessed by physiological studies and HRCT image analysis.Results Montelukast significantly improved air trapping as expressed by the residual volume （RV）/total lung capacity （TLC）.Over 24 weeks of treatment,RV/TLC was improved by （15.41±6.67）% in patients receiving SFC＋M while RV/TLC was decreased by （8.57±10.26）% in patients receiving SFC alone,the difference between the two groups was significant （P=0.02）.There was a trend towards a significant difference in forced expiratory volume in the first second （FEV1）/forced vital capacity （FVC） in the SFC＋M group compared to that in the SFC group （（17.87±8.17）% vs.（12.28±9.20）%,P=0.056）.There was no significant change in percentage wall area （WA%） after 24 weeks of add-on treatment with montelukast.Patients receiving SFC＋M showed significant improvement in the ratio of CT-determined values at full expiration to those at full inspiration （E/I ratio） （0.894±0.005 vs.0.871±0.003,P=0.002）.Conclusion We have shown,using lung function tests and HRCT image technique,that add-on therapy with montelukast improves distal lung function reflected by air trapping,but not airway wall thickness in moderate-to-severe asthma.（ClinicalTrials.gov number,NCT00699062）

A new geometrical and mechanical relation in the respiratory system with airflow limitation—From the perspective of analytical respiratory mechanics

Classic respiratory mechanics is a branch of vectorial mechanics, which aims to recognize all forces acting on the respiratory system. Another branch of mechanics, analytical mechanics, has been used for analyzing the motions of complicated systems with constraints through equilibrium among scalar quantities such as kinetic energy and potential energy. However, until now, there have not been any studies concerning about analytical respiratory mechanics. In this paper, the author has obtained two types of motion equations (linear and nonlinear) for the airflow limitation from formulation of the analytical respiratory mechanics. Reconstructed flow-volume trajectories of the linear equation revealed a new relationship among the slope of the linear portion of trajectory, the coefficient of the dissipation function and the coefficient of the potential function. Reconstructed trajectories of the nonlinear equation suggested that a curved flow-volume trajectory would be caused by the emergence of regional hypoventilated clusters with airtrapped lobules. In conclusion, analytical respiratory mechanics will provide the basis for analyzing the mechanical properties of the respiratory system con cerning pulmonary functional images made by newly developed technologies.

准饱和细砂在圈闭气体溶解过程中渗透系数的变化

准饱和含水层的渗透系数会随着圈闭气体饱和度的增大而变小,但受限于试验操作和测量精度,通过传统驱替试验很难获得大量连续的圈闭气体饱和度数据,因此限制了小圈闭气体饱和度及其对应的准饱和渗透系数之间关系的准确刻画。研究设计了一个以氧气代替天然圈闭过程中空气的准饱和细砂圈闭气体溶解试验,通过精确测量溶解过程中水中可溶性氧和相应的渗透系数得到了大量连续的圈闭气体饱和度及其准饱和渗透系数的数据。试验结果表明,在小于5%圈闭气体饱和度的区间,圈闭气体进入到无效孔隙中,因此不影响渗透系数的大小;圈闭气体饱和度在5%~6%时会形成孔喉阻塞效应,对渗透系数的影响加剧。在此基础上,构建了预测准饱和渗透系数的van Genuchten模型。与传统Faybishenko幂律模型相比,新构建的模型很好地表征了小圈闭气体饱和度对渗透系数影响不大的特征;在其他圈闭气体饱和度时,新模型与传统模型的预测性能相当。新构建的准饱和渗透系数模型为深入研究准饱和水流和溶质运移奠定了基础。

Estimating Exposure to Traffic-Related Air Pollution and Its Consequences on Respiratory Health in Population Working or Living along the Trunk Road: A Systematic Review

Introduction: Urban Air pollution is increasingly becoming a major health and sustainable development issue. Several studies showed that Traffic-related air pollution (TRAP) is one of the main sources of urban air pollution and has serious consequences on respiratory health. As no systematic review focused on the traffic-related air pollution and respiratory health in the target population of individuals working in a shop or in an office or individuals living along the trunk road, the authors conducted the current study to try to fill this gap. Methods: A systematic review search was conducted using MEDLINE (PubMed), Scientific Research Publishing: SCIRP, Web of Science, Google scholar. Studies were included if they meet the following selection criteria: 1) focus on population working or living along a major/trunk road; 2) studies had reported clearly at least on the exposure variables related to TRAP; 3) the association between TRAP and development of respiratory symptoms or respiratory diseases was established. Results: 13 articles were selected on the 192 articles that were retrieved in the initial research. Exposure to traffic-related air pollution was determined by using distance to road, traffic intensity and pollutants measured. The main respiratory health problems found were cough, wheeze, asthma and bronchitis. No article discussed about roundabouts in characterizing exposure to traffic-related air pollution. Conclusion: Distance to road, traffic density and pollutants measured are the usual methods to characterize the exposure to traffic-related air pollution and its consequences on respiratory health. Regarding the context of area occupations in African cities, it is necessary to focus on population around roundabouts and see if they are not more exposed to TRAP.

冰中微尺度受陷气泡生长分布特性与宏观热力影响综述

结冰是传热传质流动耦合的非线性、变密度液固相变过程,在自然界与工业界广泛存在且多呈负面影响。溶解于液态水中的微量空气在结冰时因冰晶挤压而汇聚后成核,形成较大气泡后因界面黏附力而停留在冻结锋面处,最终形成冰中大小各异、分布不一的微尺度受陷气泡。形成于结冰过程的微尺度受陷气泡,不仅因改变冰的内部结构、密度分布、导热系数及冻结速率而影响后期动态结冰过程,亦会影响结冰过程和结束后冰体的整体导热系数、热阻分布、抗压强度、应力分布等宏观热学、力学物理特性。为精准预测及控制结冰过程,开发和优化各类防除冰技术,微尺度受陷气泡的生长分布特性与宏观热力影响研究在学术界和工业界均备受关注。首先,以冰中微尺度受陷气泡为研究对象,从微观与宏观尺度对其成核机制、生长过程、分布特性和静态稳定性等进行综述。结果显示:气泡形状与冻结速率直接相关,当冻结速率大于25μm/s时,冰中出现长短轴比小于5的蛋状受陷气泡;当冻结速率在5~25μm/s时,冰中出现长短轴比大于5的针状受陷气泡;当冰冻结速率小于3μm/s时,冰中未能发现任何受陷气泡。其次,通过对既有文献中各类研究成果的梳理分析,对受陷气泡全生命周期的影响因素及其对结冰时、成冰后热力物性的不同影响机制进行了梳理与解释。冰中受陷气泡因降低冰的密度及改变内部冰晶结构而会显著降低冰的有效导热系数。在融冰实验中,气泡体积分数为57%的冰比不含气泡的透明冰开始融化时间滞后约50%,相同时间内的融冰高度低36.81%。随气泡体积分数增加,冰的水平和竖直抗压强度均逐渐减小,当气泡体积分数由4%增加到34%时,水平和竖直方向抗压强度分别降低为原来的8.38%和8.10%。最后,基于既有受陷气泡研究成果,对目前存在的研究空白及发展趋势进行了预测与阐述。本综述对理清受陷气泡复杂特性、丰富结冰过程传质理论有较大帮助,亦可为既有防除冰技术的优化设计提供参考与借鉴。

抽吸式动态顶空固相萃取装置的开发

在前期搭建好的简易动态顶空固相萃取装置的基础上,将通气方式从吹扫式改为抽吸式,考察抽气流速、抽气时间、吸附介质、解析溶剂、脱附过程对分析结果的影响,并使用气相色谱-质谱联用仪对7种合成香料进行检测。最后将优化后的方法应用于天然金桂干花挥发性成分的检测中,检测出的物质数量和总峰面积皆优于前期吹扫式装置,表明此装置可为天然香料的香气成分的分析提供经济、便捷、有效的解决方案。

Moldflow在注塑模浇口优化设计中的应用

针对注塑模具中合理的浇口位置和数目在塑料制品设计中的重要性,以汽车的副仪表板装饰盖零件为例,借助模拟分析软件Moldflow对其浇口位置及数目进行计算机模拟分析。通过对单浇口和双浇口的对比,综合分析各种因素对注塑成型的影响,确定最佳浇口位置和浇口数目,优化模具浇口设计,并具有显著的经济效益。

多层螺旋CT体素指数评估慢性阻塞性肺病空气潴留的研究

目的探讨肺部多层螺旋CT(MSCT)体素指数(VI)在慢性阻塞性肺病(COPD)空气潴留定性、定量评估中的价值。方法选取43例拟行胸部HRCT受检者行MSCT-DPVI,检查后1周内行肺功能测试。图像经后处理,分别设定呼吸双相的阈值,得到相应VI。各VI与PFT指标FEV1(%)、FEV1/FVC作统计学相关性分析,并通过ROC曲线找出界值。结果所有VI与FEV1/FVC和FEV1(%)均具显著相关性(P<0.01)。与FEV1/FVC相关性最大的是呼气相VI-810(r=-0.606,P<0.01),其诊断界值是40%。与FEV1(%)相关性最大的是呼气相VI-790(r=-0.661,P<0.01)。结论MSCT呼气相VI-810和呼气相VI-790可分别作为评估COPD空气潴留的定性指标和半定量指标。

敦德冰芯过去800a来的甲烷记录

敦德冰芯上部９５ｍ的１２个样品记录了近８００ａ来冰内气泡包裹气体中甲烷的浓度变化，结果表明，最近２００ａ来该冰芯记录的甲烷浓度急剧上升，与南极及格棱兰的甲烷记录反映的趋势相一致，但与两极同时代样品相比，其浓度总体上要高出０．５×１００－６～０．６×１０－６ｍｏｌ／ｍｏｌ．在这之前，３者基本保持一致，在０７×１０－６～０．８×１０－６ｍｏｌ／ｍｏｌ之间波动．

支气管扩张的螺旋CT动态扫描——空气潴留与支气管扩张、肺功能指数相互关系

目的 评价空气潴留、支气管扩张与肺功能指数相关性。方法 对 33例临床和HRCT检查确诊的支气管扩张的病人 ,使用螺旋CT分别进行了不同呼吸时相的连续容积数据模式扫描。对支气管扩张和空气潴留分别进行评分。 2 8例病人做了肺功能检查。结果 支气管扩张和空气潴留分别在 98/ 198和 112 / 198个肺叶中见到 ,两者平均积分高度相关 (r =0 .94;P <0 .0 0 1)。空气潴留积分与肺功能指数相关性如下 :FEV1、FVC、FEV1/FVC不相关 ,FIF2 5相关 (r =- 0 .5 1;P <0 .0 5 ) ,FIF50 (r=- 0 .77;P <0 .0 1)、RV(r =0 .75 ;P <0 .0 1)高度相关。结论 在支气管扩张病人中空气潴留与支气管扩张。

无症状非吸烟者肺空气潴留的HRCT评估及其与肺功能的相关性研究

目的 分析不同年龄组无症状非吸烟者呼气相高分辨率CT(HRCT)空气潴留情况,探讨年龄对呼气相CT 空气潴留的影响以及空气潴留与肺功能的相关性。 资料与方法 对经严格选择的63名无症状非吸烟者进行肺 吸气末与呼气末HRCT扫描,其中32名进行肺功能测试。将所有受试者按年龄分为5组,对呼气相HRCT上空气潴 留进行定量分析并与肺功能指标进行相关性分析。 结果 所有受试者吸气相HRCT均未见异常,呼气相HRCT空 气潴留总的出现率为39．7％(25/63),其中Ⅰ型22．2％(14/63),Ⅱ型17．5％(11/63),各组均未出现Ⅲ型空气潴留。 以小叶型空气潴留为主者16例,以肺段型为主者9例,未出现肺叶型。空气潴留组与无空气潴留组之间的用力肺 活量(INC)和1s用力呼气容积(FEV1)/FVC平均值之间存在显著差异(P<0．05);FEV1/FVC更是与空气潴留的分 级有明显的相关性(r=-0．529,P<0．05)。结论元症状非吸烟者呼气相HRCT出现的空气潴留约40％,年龄 为其形成原因之一。空气潴留的面积分级与。FEV1/FVC呈明显的相关性。

CAE技术在解决胶带座注塑缺陷中的应用

介绍了CAE技术在注塑产品生产中的应用。针对胶带座在注塑成型过程中产生的缺陷,借助CAE软件验证了产生缺陷的位置,找出了产生缺陷的原因。并在工艺、模具和产品设计上进行了修改,从而解决了实际生产中遇到的问题,为实际生产提供了指导。

水流冲击管道内滞留气团现象的VOF模型仿真分析

针对复杂管道系统内水流冲击滞留气团现象,采用VOF模型(Volume of Fluid Model)进行了数值模拟计算,并与一维模型进行了比较计算分析,结果表明:系统的最大压力并不总是气团的最大压力,有可能还会叠加水体对管壁的撞击而形成的突然升高压力。与实验实测结果的比较分析表明:采用VOF模型,能够较精细地仿真水流冲击滞留气团现象的气团形态、流场结构以及压力分布等的变化过程,其压力数值计算结果与实验实测基本吻合,其计算误差明显小于现有一维模型的计算误差,是深入研究该复杂瞬变流现象的有效方法。

双相薄层MDCT诊断造血干细胞移植术后气体潴留

目的探讨双相薄层MDCT诊断造血干细胞移植术(HSCT)后闭塞性细支气管炎综合症(BOS)的价值。方法回顾性分析HSCT后29例疑似BOS患者双相薄层MDCT表现和肺功能检查(PFT)结果,对呼气相MDCT气体潴留情况、双相MDCT表现进行分级,并进行统计学分析。结果呼气相MDCT发现气体潴留23例,PFT分级在BOS-p(隐匿级)以上者12例,呼气相MDCT与PFT对气体潴留的检出阳性率差异无统计学意义(P>0.05);所有肺功能BOS-p级病例均有呼气相CT气体潴留表现;呼气相CT较PFT能筛查出更多异常病例;气体潴留常发生于双肺下叶和背侧。结论对于移植后出现BOS临床表现的患者,双相薄层MDCT可作为首选影像学检查方法。

儿童哮喘肺HRCT空气潴留与肺功能的相关性研究

目的:观察儿童哮喘患者呼气末HRCT空气潴留的表现;明确空气潴留的面积与肺功能阻塞性指标如FEV1、FEF25%～75%等的相关性。方法:选择21名哮喘儿童行呼气末HRCT扫描,并于同一天或第2天做肺功能检查。在HRCT上分别于上、中、下肺野选取2个可清晰显示空气潴留的层面。用一张规格为2mm×2mm的透明方格纸对空气潴留的面积进行评估。根据空气潴留面积占全肺面积的比例,将其分为3级:Ⅰ级<5%,Ⅱ级5%～25%,Ⅲ级>25%。然后将空气潴留的级别与肺功能的指标做相关性分析。结果:①哮喘儿童肺呼气末HRCT空气潴留出现率为90.5%(19/21);②下叶是空气潴留最好发的部位,占100%(19/19);③空气潴留级别与肺功能阻塞性指标FEV1、FEF25%～75%、FEF50%显著相关,相关系数分别为(r=-0.565,P<0.01;r=-0.499,P<0.05;r=-0.521,P<0.05)。④肺功能正常的哮喘儿童肺HRCT空气潴留出现率为87.5%(14/16)。肺功能正常的哮喘儿童在肺HRCT可观察到明显的空气潴留征,其空气潴留级别可达到Ⅱ、Ⅲ级。结论:肺呼气末HRCT空气潴留可直观显示气道病变的不均匀分布及病变的严重程度;空气潴留征比肺功能异常改变出现早,其敏感性明显高于肺功能检查,可用于评价肺功能正常的哮喘儿童的小气道病变。

注射成型模拟中气泡的分析与评价

对注射成型CAE软件分析气泡缺陷的评价方法进行了研究。基于CAE软件分析得出的气泡缺陷、熔体温度、熔体压力和熔体流动速度等结果的XML文件,以气泡的位置、体积、压力和温度等参数作为评价气泡严重性的主要指标,建立了气泡缺陷的质量评价体系。在分析气泡结果的XML文件结构基础上,讨论了从XML文件中提取气泡的算法和计算气泡体积的公式。利用理想气体状态方程计算气泡内空气的最高温度。经过实例分析证明此气泡的严重性评估方法具有有效性和充分性。

变特性长管道内水流冲击气团的刚性数学模型

导出了可模拟分析变特性长输水管道系统内有压水流冲击管道内滞留气团的瞬变流现象的实用刚性数学模型,并通过算例对比分析了该数学模型与现有针对单特性管道的几种简化刚性数学模型的差异,验证了该数学模型的有效性和合理性。

水流冲击管道内滞留气团的刚性数学模型

通过数学分析证明,在不计局部水头损失时,目前常用的几种简化刚性数学模型的最大气压计算结果相等,并与管道内初始充水段长度无关。但算例表明,对于初始充水段较短或滞留气团体积很小情况,这些简化模型的计算误差将达到不容忽视的程度,甚至导出错误结论。笔者导出的完整刚性数学模型,弥补了简化模型的不足,同时指出了刚性模型的理论缺陷和适用条件。