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

心输出量是危重患者最重要的参数之一。目前用于测量心输出量的程序是团注热稀释法，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，并且该过程耗时。在危重患者中，由于血流动力学状态可能迅速变化，连续心输出量监测将提供及时的信息，以允许快速建立和调整治疗。十多年来，许多研究人员和临床医生研究了各种连续监测心输出量的技术，使用连续热稀释技术测量心输出量是临床可用的技术。使用肺动脉导管的连续热稀释是一种无需注射的系统，它包含一个热灯丝，以提供间歇性的热稀释。 关于我们 热量的IODs，其由远端热敏电阻感测。该系统提供了几分钟内的平均心输出量，更新时间为30秒。连续热稀释法为临床情况提供了可接受的准确度，但是，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。多普勒超声技术已用于测量连续速度，从而测量心输出量。这些技术在真实的时间基础上是上级的，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），所以它们遭受不准确性。多普勒角度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是不可靠的。因此，我们研制了一种新的肺动脉多普勒导管，克服了这种角度依赖性，以准确地连续监测心输出量，我们的肺动脉多普勒导管是一种改进的PA导管。该导管有一个特殊的管腔，用于使用血管内超声技术测量肺动脉的横截面积。还通过在其远端头端安装2个超声换能器晶体对导管进行了修改。我们将多普勒超声技术与肺动脉导管技术相结合，将血管内超声技术与多普勒超声技术相结合。因此，心输出量能够使用肺动脉的流速和横截面积来测量。将一对以固定角度定位的超声换能器安装在肺动脉导管的远端部分上，以定位在主肺动脉中。多普勒频移（Δf1，Δf2）由两个探头在主肺动脉近距离两点采样检测。Δf1和Δf2的值用于计算两个速度测量值，并使用以下公式计算肺动脉的真实流速：V=（V1）^2+（V2）^2）^<1/2>，其中V=真实流速，V1和V2 =换能器1和2检测到的流速。使用新开发的相位微分技术的速度计算。通过特制的肺动脉导管管腔，采用血管内超声技术显示和测量肺动脉横截面积。血管内超声技术测量肺动脉截面积较经胸或经食管超声心动图准确。关于连续心输出量测量，在IRB批准后，我们在动物实验中评估了我们新开发的肺动脉多普勒导管的可用性。我们发现，我们新开发的肺动脉多普勒导管测量心输出量给我们提供了准确的值，这可以适用于危重患者。使用新开发的肺动脉多普勒导管，我们能够连续测量心输出量。这种用于连续测量心输出量的真实的时间的技术上级于其他改进的热稀释技术。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