Swan-Ganz导管应用技巧与临床解读-课件，幻灯，ppt精选.pptVIP

* * * * * * * * The major components of oxygen delivery (DO2) are depicted on this slide. DO2 reflects the amount of oxygen leaving the heart to be delivered to the tissues. It is determined by multiplying cardiac output (CO) by arterial oxygen content (CaO2). One of the most important goals in managing the critically ill patient is to maximize the delivery of oxygen to prevent the occurrence of tissue hypoxia. * * Historically, it has been very difficult to actually measure fiber length or volume at the bedside. Clinically, it has been acceptable to measure preload as a pressure. Preload has been indirectly measured for both the right and left ventricle. The central venous pressure (CVP) and right atrial pressure (RAP) are used to evaluate right ventricular preload. Left ventricular preload is evaluated by assessing pulmonary artery diastolic pressure (PAD), pulmonary artery wedge pressure (PAWP) and left atrial pressure (LAP). * Contractility is the inherent property of the myocardial fibers to shorten and therefore contract. This allows the heart to increase its extent and force of muscle shortening. The degree of inherent contractility is referred to as the inotropic state of the myocardium. Several different parameters are used to reflect contractility. These include stroke volume (SV), stroke volume index (SVI), left ventricular stroke work index (LVSWI) and right ventricular stroke work index (RVSWI). The normal values and formulas for each of the measures is found on this slide. * Afterload refers to the resistance or pressure that the ventricles must overcome to eject their contents into the systemic and pulmonary circulations. Subsequently, afterload is the pressure against which the contractile force of the ventricles is exerted. Afterload is determined by many factors including the wall thickness of the ventricle, volume and mass of blood in the pulmonary or systemic circulation, and the impedance of the vasculature. * * The Fran