Continuous cardiac output measurements using a newly developed pulmonary artery Doppler catheter combined with intravascular ultrasound tehnique.

心输出量是危重病人最重要的测量参数之一。目前用于测量心输出量的程序一直被称为推注热稀释，这是一种基于能量守恒定律的技术。尽管团注热稀释技术被广泛接受为临床标准，但该技术仅提供间歇性信息，且过程耗时。在危重病患者中，由于血流动力学状态可能会迅速改变，持续的心输出量监测将提供及时的信息，以便快速制定和调整治疗方案。连续监测心输出量的各种技术已经被许多研究人员和临床医生研究了十多年。使用连续热稀释技术测量心输出量是一种临床可用的技术。使用肺动脉导管的持续热稀释是一种无注射系统，它结合了一个热丝来提供间歇性的每…更多IOD的热量，这是由远端热敏电阻感应的。该系统提供几分钟内的平均心输出量，并提供30秒的更新。连续热稀释对临床情况提供了可接受的准确性，但它不能提供实时值。该值表示几分钟内的平均心输出量，不表示实时值。多普勒超声技术已被用于测量连续速度，从而测量心输出量。这些技术在实时基础上是优越的，然而，由于它们固有地依赖于超声波束和当前方向之间的角度(多普勒角)，它们存在不准确性。多普勒角将构成速度测量和心输出量测量的误差。用这些技术测量的心输出量在临床上并不可靠。因此，我们研制了一种新型的肺动脉多普勒导管，克服了这种角度依赖性，可以连续准确地监测心输出量。该导管有一个特殊的管腔，可用于血管内超声技术测量肺动脉横截面积。通过在导管末端安装2个超声换能器晶体对导管进行了改进。我们将多普勒超声技术与肺动脉导管相结合，将血管内超声技术与多普勒超声技术相结合。因此，心输出量可以用血流速度和肺动脉横截面积来测量。将一对超声换能器以固定角度放置在肺动脉导管的远端，定位于主肺动脉。用两个探头在主肺动脉间隔较近的两个点取样，检测多普勒频移(Δf1，Δf2)。用Δf1和Δf2的值计算两个速度测量值，用公式V=(V_1)^2(V_2)^2)^&lt；1/2&gt；其中V=真速度，V_1和V_2=探头1和2检测的速度。应用血管内超声技术，通过我们的肺动脉导管的特殊管腔，显示和测量了肺动脉横截面积。血管内超声测量肺动脉横截面积比经胸或经食道超声心动图更准确。在连续心输出量测量方面，在IRB批准后，我们评估了我们新开发的肺动脉多普勒导管在动物实验中的可用性。我们发现，我们新研制的肺动脉多普勒导管测量的心输出量给我们提供了准确的数值，适用于危重患者。这种实时连续测量心输出量的技术优于其他改进的热稀释技术。较少

Cardiac output is one of the most crucial parameters measured in critically ill patients. The current procedure used to measure cardiac output has been as bolus thermodilution, a technique based on the law of conservation of energy. Although the bolus thermodilution technique is widely accepted as the clinical standard, the technique provides only intermittent information, and the procedure is time-consuming. In critically ill patients, as hemodynamic status may change rapidly, continuous cardiac output monitoring would provide timely information to permit rapid institution and adjustment of therapy. Various technologies for continuous monitoring of cardiac output have been examined by many researchers and clinicians for overa decade.Measurement of cardiac output using continuous thermodilution technique is technology clinically available. Continuous-thermodilution using pulmonary artery catheter is an injectless system, which incorporates a thermal filament to provide intermittent per … More iods of heat, which is sensed by a distal thermistor. This system provides the average cardiac output over several minutes with a 30-second update. Continuous thermodilution provides acceptable accuracy for clinical situalion, however, it does not provide real-time values. The value indicates the average cardiac output over several minutes, it does not indicate real-time value. Doppler ultrasound techniques have been used for measurement of continuous velocity and, thus, of cardiac output. These techniques are superior in real time basis, however, they suffer from inaccuracy because of their inherent dependency on the angle between the ultrasound beam and the now direction(Doppler angle). Doppler angle would constitute the errors in velocity measurements and in cardiac output measurements. Cardiac output measured by these techniques would not be reliable clinically. So, We have devdoped a new pulmonary artery Doppler catheter, which overcomes this angle dependency, to accurately monitor cardiac output continuously.Our pulmonary artery Doppler catheter is a modified PA catheter. The catheter has a special lumen for measurement of cross sectional area of pulmonary artery using intravascular ultrasound technique. The catheter was also modified by mounting 2 ultrasound transducer crystals on its distal tip. We combined Doppler ultrasound technique with pulmonary artery catheter, and also combined intravascular ultrasound technique with Doppler ultrasound technique. Thus, cardiac output is able to measure using flow velocity and cross-sectional area of pulmonary artery. A pair of ultrasonic transducers positioned at a fixed angle was mounted on the distal section of pulmonary artery catheter to be positioned in the main pulmonary artery. The Doppler shifts(Δf1, Δf2)were detected by two transducers sampling at closely spaced two points in the main pulmonary artery. The values of Δf1 and Δf2 were used to compute two velocity measurements, and true flow velocity of pulmonary artery was calculated using following equation : V=(V1)^2+(V2)^2)^<1/2>, where V=true velocity, V1 and V2 =velocity detected by the transducer 1 and 2. The velocities were calculated using newly developed phase differential techniques. Cross-sectional area of pulmonary artery was revealed and measured using intravascular ultrasound technique through the special lumen of our pulmonary artery catheter. For the measurements of cross-sectional area of pulmonary artery, intravascular ultrasound technique is more accurate than transthoracic or transecophageal echocardiography. Regarding to continuous cardiac output measurements, after IRB approval, we evaluated the availability of our newly developed pulmonary artery Doppler catheter in animal experiments. We found that cardiac output measured by our newly developed pulmonary artery Doppler catheter gave us accurate value, which could applicable for critically ill patients.Using a newly developed pulmonary artery Doppler catheter, we are able to continuously measure cardiac output. This technique for continuously measuring cardiac output in real time is superior to other modified thermodilution techniques. Less