【作者】 熊华强；

【导师】 曹铁生； 袁丽君；

【作者基本信息】 第四军医大学 ， 影像医学与核医学， 2009， 硕士

【摘要】 目的应用超声心动图观察平静呼吸情况下胸压对三尖瓣反流速度的影响规律及机制,为超声心动图方法准确测定肺动脉压和验证呼吸影响心功能机制新假说提供实验依据。方法1、实验对象的筛选经多普勒超声检查证实三尖瓣口有稳定反流且频谱多普勒速度曲线清晰者,排除有明显心律不齐、中度以上心包积液、缩窄性心包炎、先天性心脏病疾病患者。2、实验数据采集采用Acuson Sequoia 512彩色电脑声像仪,探头频率2.5～4.0MHz。同步记录单向导联心电图,采用热敏式呼吸传感器(E99H450)记录呼吸曲线,其上升支为吸气相,下降支为呼气相。受检者取左斜卧位,平静呼吸。三尖瓣反流速度测定:清晰显示胸骨旁四腔切面观及心尖四腔切面观后,启动彩色多普勒功能,将连续多普勒聚焦区置于三尖瓣瓣口,调整探头部位使声束与血流方向尽可能平行,设置扫描速度(sweep)为50mm/s或25mm/s。显示轮廓完整、清晰的反流曲线后,连续测量5个吸气末的反流速度与其后相对应的呼气末反流速度,分别平均后作为不同呼吸相三尖瓣反流速度的平均值。跨三尖瓣压力阶差:利用简化伯努利方程,根据三尖瓣反流速度,计算跨三尖瓣压力阶差,即:△P=4V2。分别计算不同呼吸相跨瓣压差,取平均值。3、统计学分析使用SPSS 13.0统计软件,超声测量指标以均数±标准差表示,吸气相与呼气相之间的反流速度及跨瓣压差别进行配对t检验。P<0.05为差异有统计学意义。结果在平静呼吸条件下,三尖瓣反流速度吸气相与呼气相之间差异无统计学意义[(2.87±0.72)m/s对( 2.84±0.75)m/s, p=0.410],三尖瓣反流跨瓣压吸气相与呼气相之间差异无统计学意义[(35.01±20.65)mmHg对(34.51±19.84)mmHg,p=0.581]。呼吸对三尖瓣反流速度有明确的影响,反流速度与呼吸时相关系表现有三种类型:第一种为吸气相速度增加,呼气相速度减小;第二种表现与第一种相反;第三种为速度变化表现为随机性。结论呼吸性胸压变化对三尖瓣反流速度有明确影响,根据国内学者提出的新假说,呼吸性胸压变化导致了三尖瓣跨瓣压的变化,因而产生了呼吸影响三尖瓣反流速度的现象。表现为:吸气使跨瓣压减小,反流速度减小。同时,吸气又使外周回到右心的血液增加,右室于舒张期得到相对较多的充盈,使得收缩力增大,构成了增大反流速度的因素。正常人的呼吸和心动周期并无固定的时相关系,心脏收缩可能落到呼气周期的任何时相,使得这两个对抗因素出现较为复杂的配对而表现为呼吸性胸压变化对三尖瓣反流速度的影响具有复杂性,不规律性。因此提示用多普勒法无创测定肺动脉压时,需要将呼吸停止在呼吸时相的中期,并保持测定过程中胸压稳定,以提高测定准确性,研究为呼吸影响心功能新假说提供了更多的依据。更多还原

【Abstract】 ObjectiveTo study the mechanism of the effects of the intrathoracic pressure variation on the velocity of tricuspid regurgitation in quiet respiration, to accurately estimate the pulmonary artery systolic pressure, and to verify the new proposed mechanism of respiratory effects on hemodynamics using echocardiography.Methods1、Experiment subjects screened The patients with stable tricuspid regurgitation and clear Doppler spectral envelopes were selected for the study. Regurgitations were confirmed by continuous-wave Doppler method and apparent arrhythmia, moderate pericardial effusion, constrictive pericarditis, congenital heart disease were ruled out.2、Experimental data acquisition Together with Electro-cardiogram and respiratory curve recorded simultaneously, continuous-wave Doppler spectra of tricuspid regurgitation were recorded with the Siemens Sequoia 512 system using a 2.5-4.0MHz probe.Breathing thermal sensors (E99H450) were used to record respiratory curve in which the ascending branch represented the inspiratory phase and the decreasing branch represented the expiratory phase. The left lateral decubitus was adopted in all subjects with calm breathing. Followed with clear graphics got in parasternal four chamber view or apical four chamber view and focus area set under tricuspid valve, the tricuspid regurgitation velocity was detected by using color Doppler function. The probe position was adjusted to make the sound beam and the blood flow in the same direction as far as possible. The scan rate (sweep) set to 50mm/s (or 25mm/s) simultaneously. And the tricuspid regurgitation spectra recorded at the end-inspiration and end-expiration. According to tricuspid regurgitation velocity by using of simplified Bernoulli equation(△P = 4V2), the cross-tricuspid pressure gradients were acquired. The 5 continuous measurements were averaged in each phase.3、Statistical analysis Using SPSS 13.0 statistical software, all the ultrasound measurements were respectively compared between the inspiratory phase and expiratory phase of the regurgitation velocity and the pressure gradient. All the demographic data were expressed as mean±standard deviation. P values of <0.05 were considered as statistically significant.ResultsIn the calming-breath conditions, there was no significant difference between the inspiratory phase and expiratory phase of the tricuspid regurgitation velocity [(2.87±0.72) m / s of (2.84±0.75) m / s, p = 0.410] and the pressure gradients [(35.01±20.65) mmHg to (34.51±19.84) mmHg, p = 0.581].The tricuspid regurgitation velocity were affected by the respiration variation apparently, and showed three patterns:①The velocity increased in the inspiratory phase.②T he velocity decreased in the inspiratory phase.③The velocity changed randomly.ConclusionAccording to the new hypothesis by Chinese scholars, the thoracic pressure changes have a clear impact on the tricuspid regurgitation velocity, and the respiratory changes in pleural pressure has led to inter-tricuspid valve pressure changes, which results tricuspid regurgitation velocity varies with the respiratory changes. The former theory shows that the regurgitation velocity decreases followed the inter-tricuspid valve pressure decreases in inspiratory phase. And at the same time the peripheral blood return to right heart increases in right ventricular diastolic filling phase followed the increased contractility, which become the factors to lead to the regurgitation velocity increase. But there is no fixed relation between the normal respiratory and the cardiac cycle. So the heart contraction cycle can be occurred in any respiratory phase, which leads to the complex effects on the tricuspid regurgitation velocity. The regularity of the variations of the tricuspid regurgitation velocity affected by the respiratory pleural pressure shows two characteristics: complexity and non-regularity. So it is essential to keep respiratory movement in the medium-term during estimating pulmonary arterial pressure by using the tricuspid regurgitation velocity method, which can keep the intrathoracic pressure stability to improve the accuracy of the determination. This study provides more evidences for the new hypothesis that the cardiac function affected by the respiratory movement.更多还原