PiCCO原理以及计算过程课件.ppt

If the pulmonary thermal volume is now subtracted from the intrathoracic thermal volume, the total blood volume in all 4 cardiac chambers is obtained. This is also called the global end-diastolic volume. This is a volumetric parameter that gives information about the filling condition of the heart and thus about cardiac preload. If the blood volume present in the pulmonary circulation (pulmonary blood volume, PBV) is now added to the global end-diastolic volume, the intrathoracic blood volume is obtained. This thus represents the total blood volume present in the heart and pulmonary circulation. The intrathoracic blood volume can be measured either directly by double indicator dilution or – as with PiCCO technology – calculated reliably from the GEDV. The ITBV is usually 25% higher than the GEDV. The continuous pulse contour analysis is calibrated by transpulmonary thermodilution measurement. The stroke volume obtained with thermodilution is placed in relation to the area under the systolic part of the arterial pulse curve. Using this calibration, the cardiac output can then be determined continuously from the arterial pressure curve (pulse contour). Besides the area under the pressure curve and other factors, calculation of the continuous PiCCO pulse contour cardiac output also involves the aortic compliance measured by thermodilution, which represents an important advantage compared to systems that cannot be calibrated. The PiCCO pulse contour cardiac output has been validated in numerous studies against the gold standard of pulmonary artery thermodilution All of these studies demonstrate the accuracy of continuous CO measurement using the PiCCO pulse contour algorithm. Besides CO, the PiCCO also measures the dynamic parameters of volume responsiveness from the arterial pressure curve. To do this, the stroke volumes are measured over a period of 30 seconds and the stroke volume variation is calculated from this. This gives very reliable information on whether t