Clinical meaning
The pulmonary artery catheter (PAC/Swan-Ganz) is a flow-directed, balloon-tipped catheter inserted via central venous access (internal jugular or subclavian vein) and advanced through the right atrium, right ventricle, and into the pulmonary artery. The balloon at the catheter tip allows flow-directed advancement without fluoroscopy by following normal blood flow patterns. When the balloon is inflated in a branch pulmonary artery, it occludes forward flow, and the distal port measures pressure transmitted retrograde from the left atrium through the pulmonary capillary bed, yielding the pulmonary artery wedge pressure (PAWP or PCWP). PAWP approximates left atrial pressure (LAP), which in turn approximates left ventricular end-diastolic pressure (LVEDP) in the absence of mitral valve disease. This provides an indirect assessment of LV preload. The PAC also measures right atrial pressure (RAP/CVP), pulmonary artery systolic and diastolic pressures, and allows calculation of cardiac output (CO) via thermodilution (injection of cold saline bolus through the proximal port; the thermistor at the catheter tip detects temperature change; CO is calculated from the area under the thermodilution curve using the modified Stewart-Hamilton equation). From CO and pressure...