| Co-Investigator(Kenkyū-buntansha) |
SAI Takuji Gifu University School of Medicine, Research Associate, 医学部・附属病院, 助手 (30242720)
UEDA Norio Gifu University School of Medicine, Research Associate, 医学部・附属病院, 助手 (20223464)
DOHI Shuji Gifu University School of Medicine, Professor, 医学部, 教授 (40155627)
KONDO Yuji Aloka Co. Ltd., Senior Engineer, 技術部・課長(研究職)
MATSUNAKA Yoshiyuki Aloka Co. Ltd., Manager, 技術部・部長(研究職)
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| Research Abstract |
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
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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
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