流固耦合作用下人体上呼吸道内气流运动特性数值仿真研究

分析人体上呼吸道内流固耦合现象,深入认识上呼吸道内气流运动特性,对于研究气溶胶在人体上呼吸道内的扩散、转捩及沉积模式具有重要作用。运用流固耦合力学数值仿真方法,在呼吸流量为30 L/min的状态下,对人体上呼吸道内稳态气流运动特性进行数值模拟,系统分析流固耦合作用下上呼吸道壁面的形变特点、壁面剪切应力分布以及呼吸道内的气流运动特点。结果表明:在低强度稳态呼吸模式下,人体上呼吸道整体向后运动,三级支气管位移最大为4.99 mm,气管前壁面受到拉伸,后壁面受到压缩;口喉模型中受到的壁面剪应力较大,最大处可达30.34 Pa,气管支气管受到的壁面剪切应力较小;气流速度在声门处达到最大值7.85 m/s,在咽部外壁、气管外壁发生分离现象,气流在气管内壁形成局部高速区,支气管内气流在分叉处分离,靠近支气管内壁速度较高。     

不同运动状态下慢性阻塞性肺疾病患者下呼吸道内的气流特性

目的 运用计算流体动力学方法探究不同运动状态下慢性阻塞性肺疾病(chronic obstructive pulmonary disease, COPD)患者下呼吸道内气流特性。方法 收集稳定期COPD患者肺部CT扫描数据与肺功能数据,重建下呼吸道三维模型,通过施加个体化边界条件进行数值模拟,分析患者下呼吸道壁面压力、壁面剪切应力(wall shear stress, WSS)、气流速度以及压降等参数。结果 随着运动强度增加,COPD患者下呼吸道壁面压力、WSS、流速及压降呈逐渐上升趋势。静息状态与低强度运动状态各参数相差较小,高强度运动状态各参数显著增加。其中,WSS是一个较敏感的力学指标,3种运动状态下WSS>1.0 Pa所占面积分别为272.35、438.24、4 369.48 mm²。结论 运动状态下,COPD患者气道壁面压力、WSS、流速以及压降显著增加,增大患者气道黏膜损伤以及炎症的可能性。研究结果从力学角度解释COPD患者发生支气管炎症机制以及患者无法长时间运动的原因。     

高流量经鼻氧疗影响呼吸窘迫综合征患者呼吸力学参数的实验研究

目的 基于通气实验，分析高流量经鼻氧疗（high flow nasal cannula，HFNC）流量对呼吸窘迫综合征（acute respiratory distress syndrom，ARDS）患者呼吸力学参数的影响，探讨HFNC对ARDS患者的通气效果和副作用。方法 分别设计基于Matlab的HFNC通气系统模型和基于主动模拟肺ASL5000的物理实验平台，模拟不同肺顺应的ARDS患者呼吸运动，进行HFNC通气实验，并将两者实验结果进行比较分析。结果 基于Matlab模型的仿真实验和基于物理平台的物理实验结果一致表明，增大HFNC的通气流量，将减小患者的呼吸气流流量、潮气量，提高患者肺内压、功能残气量等。在实验中，HFNC所提供的气流有时低于患者呼吸道内的吸气气流，从而需要得到一定的吸气补偿气流来满足患者吸气需求。结论 充分的吸气补偿气流来填补HFNC所提供气流不足是通气安全的保障措施之一。明确HFNC下ARDS患者呼吸力学参数的变化将有助于采取通气措施，提高通气疗效，降低通气风险。     

上气道内流动现象与压力分布模拟

目的用计算流体力学模拟的方法和体外模型实验的手段,研究呼吸时真实结构的上气道内的流动状态和压力分布,同时验证数值模拟模型的准确性。方法首先基于磁共振图像,借助Mimics软件重建上气道三维结构。在此真实几何结构基础上,建立上呼吸道内流动的有限元分析模型,以及制作相应的实体模型。模拟并测量呼吸流量为200、400和600 m L/s时的情况,并将数值模型预测的壁面压力分布与实测结果比较。结果如果气道内气流流量相同,吸气时气道两端的压差比呼气时大,即吸气时气道阻力比呼气时大。不同点压力分布的数值计算结果与实体模型测量结果一致。数值模拟结果表明,吸气时气道悬雍垂以及会厌后的舌后区域流动速度较高,悬雍垂下舌后区有涡旋产生。呼气时矢状位鼻咽顶端靠近后壁处,冠状位鼻咽、会厌下口咽处均有涡旋产生。结论数值模型可以准确地模拟上气道的流动状态和压力分布,直观地反映上气道内流动特点。作为非侵入式的工具,气道模型和数值模拟可以在探索阻塞性睡眠呼吸暂停(obstructive sleep apnea,OSA)的发病机制和有效治疗方法的过程中发挥重要作用。     

基于3D打印和CT三维重构数值模拟上呼吸道气流状态的研究方法

目的建立物理模型实验和数值模拟相结合的方法,用于研究上呼吸道气流状态。方法基于网上公开CT医学图像,重建人体上呼吸道三维模型。基于3D打印技术,建立上呼吸道实验模型,进行呼吸的流量过程测量实验;通过对上呼吸道三维模型进行网格划分,采用湍流Realizable k-ε数值模型进行计算。结果首先进行与实验工况对应的数值模拟对比研究,得到与实验吻合的结果。数值模拟结果表明,呼吸过程中的气流的流动轨迹呈抛物线形状,呼气和吸气阶段的流场、壁面压力和涡结构分布很大区别,呼吸交换过程中上下鼻道有空气残留。另外,通过脉线、压力分布和涡结构分布情况,初步分析气流对上呼吸道生理环境的影响。结论该方法具有针对性、快速性和准确性的特点,充分发挥了物理实验可靠和数值模拟精细的优点,适用于不同个案上呼吸道不同问题的研究,对临床个性化诊疗具有价值。     

典型男性OSAHS患者上气道气流运动特性的数值模拟

目的 研究典型男性阻塞性睡眠呼吸暂停低通气综合症（OSAHS）患者在平静呼吸时上气道气流运动特性,以及气流对软腭和悬雍垂作用的动力特点。方法 基于患者CT影像数据建立可靠的上气道流场几何模型,以临床睡眠监测数据作为数值模拟边界条件的依据,采用低雷诺数的湍流模型计算获得一个完整呼吸周期内上气道气流运动规律。结果OSAHS患者在呼吸过程中,上气道气流流动形式有显著差异。在吸气阶段,上气道腔内流速可达9.808 m/s,最大负压可达-78.856 Pa,鼻腔顶部出现局部回流,软腭受到的最大气流压力为-10.884 Pa,悬雍垂受到的最大气流压力为-51.946 Pa,气流对软腭和悬雍垂造成的最大剪切应力分别为78和311 mPa。在呼气阶段,上气道腔内最大流速为10.330 m/s,最大负压为-51.921 Pa,口咽部和鼻腔顶部均出现局部回流,且口咽部顺时针回流现象显著,软腭受到的最大气流压力为2.603 Pa,悬雍垂受到的最大气流压力为-18.222 Pa,软腭和悬雍垂受到的最大剪切应力分别为51和508 mPa。结论 口咽部是易塌陷的部位,一个呼吸循环过程的数值模拟可以捕捉到上气道流场显著的回流特征,上气道回流直接影响软腭和悬雍垂所受的力,同时也关系到患者呼吸的流畅程度。     

法洛四联症根治术后对左肺动脉狭窄影响机理的数值分析

目的 利用计算流体力学(CFD)方法分析法洛四联症(TOF)根治术后不同的左肺动脉狭窄率（50%,20%,0%）模型的局部血流动力学改变。方法 通过对患者CT数据处理,完成3组左肺肺动脉狭窄几何的全三维数字化重构;结合主肺动脉血流量等临床数据,对3组模型中肺动脉分叉区的血液流动速度场、压力、壁面剪切应力等进行记录。结果 在3组模型的非定常模拟中,左肺动脉起始端均存在与狭窄率相关的反流和血流分布,右肺动脉血流分布规则。3组模型的静态压力、压力损失、壁面剪切力等也不同。结论 肺动脉分支的合理扩大在TOF根治术中有重要意义;术后左肺动脉狭窄是造成肺动脉反流的早期和重要因素;通过CFD模拟术后患者的三维模型可以对手术的效果提供早期参考。     

基于Matlab无创正压通气下呼吸道气阻与顺应性的在线测算方法研究

目的 在无创正压通气下,避免对呼吸道内部进行操作以及自主呼吸和漏气的干扰等,研究有效在线动态测算呼吸道气阻（resistance, R）和顺应性（compliance, C）的方法。方法 在呼气末气流为0时,控制呼气支持压（expiration positive airway pressure,EPAP）跃降1个幅度为Δp和时间宽度为Δt的负脉冲气压;在该负脉冲气压作用下,呼吸道出现短暂释放气流;通过获得Δt时间段的释放气流计算R和C。另外,基于Matlab建立通气模型,模拟正常成人、急性呼吸窘迫综合征（acute respiratory distress syndrome, ARDS)患者和慢性阻塞性肺疾病（chronic obstructive pulmonary disease, COPD）患者的呼吸,进行仿真实验,获取仿真数据并计算验证。结果 根据仿真数据计算得到正常成人、ARDS患者、COPD患者R和C与实践赋值的误差分别为1.6%和-1.6%、1.21%和-1.19%、-12.53%和14.32%。结论 该算法测算呼吸道R和C具有可行性和适应性。仿真研究结果有助于智能通气、比例辅助通气模式的研究与实现。     

基于三维医学影像的脑动脉瘤内血液流动的数值模拟

目的 利用数值模拟研究具有病人特异性的脑动脉瘤内的血液流动,为脑动脉瘤的破裂风险的评价和动脉瘤介入栓塞后复发风险的评价提供帮助。方法 从两例脑动脉瘤病人的3D-RA数据中重建动脉瘤几何模型,血液流变学模型选择假塑性非牛顿流体模型,利用商用CFD软件Fluent对两例动脉瘤内的血液流动进行数值模拟。结果 数值模拟给出了动脉瘤内的流线图、重要截面上的速度分布图、壁面上的切应力分布和压力分布图。并且绘制了在收缩期时刻动脉瘤颈部和瘤顶部各20个点上的壁面切应力和压力的变化情况。结论 血流动力学因素如流速、压力、壁面切应力、流动对壁面的冲击状况等因素与动脉瘤的生长和破裂密切相关,而由于脑动脉瘤形态各异、载瘤动脉与动脉瘤体的几何关系复杂,所以具有病人特异性的数值模拟对于研究动脉瘤破裂和复发风险具有重要价值。动脉瘤颈部的壁面切应力和壁面切应力的波动的变化规律并不相同,需要进一步研究壁面切应力的波动与脑动脉瘤生长与破裂之间的定量关系。     

颅内动脉瘤夹闭手术的血流动力学数值分析

本文利用计算流体力学(CFD)方法对颅内动脉瘤夹闭手术前后血液流场进行三维数值模拟,根据血流动力学对手术方案的可行性进行预估。采用逆向工程软件Mimics对临床CT图像进行三维数字化重构,结合相关脉动血流量,模拟心动周期不同时刻的血流动力学细节。通过计算得到了模型手术前后在心动周期不同时刻的速度场、壁面剪切应力场、压力场的分布特征,对比分析手术前后分叉处的血流速度、壁面剪切应力、壁面压力变化,结果显示术后的血流速度与壁面剪切力显著提高,而壁面压强则明显降低。     

基于体域网的动态呼吸监测系统设计

为了实现日常生活的动态呼吸监测,本研究设计了一种电子健康腰带。利用"体域网"的穿戴式人体生理参数动态监测技术和呼吸感应体积描记术(RIP),将电感传感器嵌入织物中,设计了动态呼吸监测穿戴式微系统。对22位被测试者进行了不同日常生活活动(坐-走-跑-恢复)和连续6 h的睡眠呼吸监测实验。结果表明:在不同日常生活中,呼吸率的平均测量精度约为95%。所设计的基于体域网和RIP技术的呼吸波监测腰带,可用于日常生活和睡眠呼吸监测。     

Organ-protective effect of angiotensin-converting enzyme 2 and its effect on the prognosis of COVID-19

This article reviews the correlation between angiotensin-converting enzyme 2 (ACE2) and severe risk factors for coronavirus disease 2019 (COVID-19) and the possible mechanisms. ACE2 is a crucial component of the renin-angiotensin system (RAS). The classical RAS ACE-Ang II-AT1R regulatory axis and the ACE2-Ang 1-7-MasR counter-regulatory axis play an essential role in maintaining homeostasis in humans. ACE2 is widely distributed in the heart, kidneys, lungs, and testes. ACE2 antagonizes the activation of the classical RAS system and protects against organ damage, protecting against hypertension, diabetes, and cardiovascular disease. Similar to SARS-CoV, SARS-CoV-2 also uses the ACE2 receptor to invade human alveolar epithelial cells. Acute respiratory distress syndrome (ARDS) is a clinical high-mortality disease, and ACE2 has a protective effect on this type of acute lung injury. Current research shows that the poor prognosis of patients with COVID-19 is related to factors such as sex (male), age (>60 years), underlying diseases (hypertension, diabetes, and cardiovascular disease), secondary ARDS, and other relevant factors. Because of these protective effects of ACE2 on chronic underlying diseases and ARDS, the development of spike protein-based vaccine and drugs enhancing ACE2 activity may become one of the most promising approaches for the treatment of COVID-19 in the future.     

严重急性呼吸综合征(SARS)患者血清白介素-8测定及其评价

为观察SARS患者血清白介素-8(IL-8)含量变化, 用放射免疫法检测了66例SARS患者血清IL-8含量, 并与对照组作了比较.结果显示, SARS患者IL-8含量明显高于对照组, 恢复期血清IL-8含量变化多样.结论: SARS患者存在免疫反应异常, 血清IL-8含量变化可能在SARS发病机制中起重要作用.     

Development and evaluation of a panel of multiplex one-tube nested real time PCR assay for simultaneous detection of 14 respiratory viruses in five reactions

Multiplex real-time quantitative polymerase chain reaction (mRT-qPCR) assay is commonly used to detect respiratory viruses, however, the sensitivity is limited for most reports. A panel of locked nucleic acid based multiplex closed one-tube nested real-time PCR (mOTNRT-PCR) assay consisting of five separate internally controlled RT-qPCR assays was developed for detection of 14 respiratory viruses. The sensitivity and reproducibility of mOTNRT-PCR panel were evaluated using plasmid standards and the specificity was evaluated using clinical samples. The clinical performance of mOTNRT-PCR panel was further evaluated with 468 samples collected from patients with an acute respiratory infection and compared with individual real-time PCR (RT-qPCR) assay. The analytical sensitivities of mOTNRT-PCR panel ranged from 2 to 20 copies/reaction, and no cross-reaction with common respiratory viruses was observed. The coefficients of variation of intra-assay and inter-assay were between 0.35% and 8.29%. Totally 35 clinical samples detected by mOTNRT-PCR assay panel were missed by RT-qPCR and confirmed true positive by sequencing of nested PCR products. The mOTNRT-PCR assay panel provides a more sensitive and high-throughput method for the detection of 14 respiratory viruses.     

有创机械通气治疗重症SARS

为探讨有创机械通气治疗严重急性呼吸综合征(severe acute respiratory syndrome，SARS)的优缺点及适应症，本文分析我院SARS ICU2003年5月15日到6月18日收治的4例应用有创通气治疗的重症SARS患者的资料。4例患者中有1例痊愈，3例死亡，其中2例死于SARS所致缺氧，另外1例死于缺氧及继发的室性心律失常、感染性休克和肾功能衰竭。结果显示有创机械通气对于改善重症SARS患者的氧合是一种有效方法，但患者存活率不高，并可能增加医护人员的交叉感染，故应用时需权衡利弊。     

Prevention and treatment of reactions to NSAIDs

Avoidance of ASA and other NSAIDs prevents the reactions and careful attention to clinical history along with patient education are important. However, blanked advice to avoid all NSAIDs is no longer reasonable. Except for AERD and chronic urticaria, cross-reactivity with other NSAIDs does not occur. A physician can definitively prove this by giving the patient another NSAID in their office and observing no reaction. Furthermore, for patients with AERD and chronic urticaria, they can be given the new selective COX-2 inhibitors (rofecoxib and celecoxib) without any cross-reactivity. All AERD patients can be desensitized to ASA and treated with ASA indefinitely. However, ASA desensitization in chronic urticaria is not possible. Underlying mild and moderate AERD responds well to topical and systemic corticoster-oids and leukotriene modifiers. However, the severe forms of the disease should be desensitized to ASA and treated with this drug on a long term basis. In the future, new drugs that prevent eosinophil activation and chemotaxis or enhance eosinophil apoptosis are likely to be useful. Specific blockers of the second cystLT receptor would also be useful. Ultimately as the genetics of these heterogeneous disorders are unraveled, gene substitution therapy may be the ultimate answer.     

Tissue and cellular tropism of the coronavirus associated with severe acute respiratory syndrome: an in-situ hybridization study of fatal cases

Severe acute respiratory syndrome (SARS) is a new human infectious disease with significant morbidity and mortality. The disease has been shown to be associated with a new coronavirus (SARS-CoV). The clinical and epidemiological aspects of SARS have been described. Moreover, the viral genome of SARS-CoV has been fully sequenced. However, much of the biological behaviour of the virus is not known and data on the tissue and cellular tropism of SARS-CoV are limited. In this study, six fatal cases of SARS were investigated for the tissue and cellular tropism of SARS-CoV using an in-situ hybridization (ISH) technique. Among all the tissues studied, positive signals were seen in pneumocytes in the lungs and surface enterocytes in the small bowel. Infected pneumocytes were further confirmed by immunofluorescence-fluorescence in-situ hybridization (FISH) analysis. These results provide important information concerning the tissue tropism of SARS-CoV, which is distinct from previously identified human coronaviruses, and suggest the possible involvement of novel receptors in this infection. Whereas the lung pathology was dominated by diffuse alveolar damage, the gut was relatively intact. These findings indicated that tissue responses to SARS-CoV infection are distinct in different organs.