Final answer:
CVP, PAP, and PCWP are invasive measures of blood pressure in the venous, pulmonary artery, and left atrium of the heart, respectively, to assess cardiac function and are primarily used in critical care or during surgery.
Step-by-step explanation:
The Central Venous Pressure (CVP), Pulmonary Artery Pressure (PAP), and Pulmonary Artery Capillary Wedge Pressure (PAW or PCWP) are all measures of blood pressure within different areas of the cardiovascular system, expressed in millimeters of mercury (mm Hg). The CVP refers to the pressure in the large veins like the vena cava, which reflects right ventricular end-diastolic pressure and hence, the amount of blood returning to the heart which is typically low, approximately 2 to 8 mm Hg. The PAP measures the pressure within the pulmonary artery and provides insight into the function of the right side of the heart and status of the pulmonary circulation; normal values are between 25 mm Hg during systole and 8 mm Hg during diastole. Lastly, the PCWP measures the pressure that reflects left atrial pressure and is used to infer left ventricular end-diastolic pressure; normal PAW is between 6 to 12 mm Hg. These pressures are monitored in critically ill patients or during surgery, as the process is invasive, requiring a catheter being threaded to the location for the pressure to be transmitted to an external measuring device.