The central-venous pressure (CVP), which is located in the central vessels near the chest, is a pressure measurement. It is used to estimate right ventricular pressure. The central venous blood pressure is not a true measure of blood volume, but it’s often used as a rough estimate. The central blood pressure in the vein cava is affected by the right-heart function as well.
Central venous pressure can detect under-filling or over-distention before any clinical symptoms are evident. Normal circumstances result in an increased heart output from an increased venous returns, but without a significant change to central venous. In the case of a obstructed pulmonary circulatory system or poor right-ventricular function, the right atrial blood pressure will rise, which in turn causes a rise to central venous measurement pressure. In contrast, a patient suffering from hypovolemia may have a reading within the normal range of central venous due to reduced venous flow or widespread vasodilation. This will cause a decrease in right atrial blood pressure and central arterial pressure. The central venous level must be set at the same level as the right atria in both cases. The fourth intercostal space is typically the same level as the mid-axillary axillary ridge when the patient lies in a flat position. The same position should be used for each measurement of the central venous blood pressure. It is more useful to look at trends than just one reading. The trend of measurement is inaccurate if the central vein pressure is not measured consistently.
Pulmonary arterial pressure (PA) is the blood pressure measured in the pulmonary vein of the heart. The right ventricle releases blood into the lung circulation to create pulmonary artery pressure. This is an opposite force of production by the heart’s right ventricle. As the heart contracts during ventricular-systole and blood is ejected, the volume of pulmonary blood increases. This in turn stretches the walls of the artery. As the heart begins to relax, or ventricular dialole, blood continues flowing from the arterial pulmonary into the circulatory system. The smaller arteries (arterioles) are the main resistance vessels. They regulate pulmonary blood pressure by changing their diameter.
pulmonary artery catheters today are placed according to the individual patient’s needs and staff qualifications. Patients with severe cardiogenic lung edema and acute respiratory distress syndrome, who are hemodynamically unstable, as well as patients who have undergone major thoracic surgeries or who have septic shock, may be candidates for pulmonary catheters. A sensor is used to measure the heart rate and pulmonary blood pressure. The sensor has a size similar to a penny and two thin loops attached at either end. The sensor is inserted into the pulmonary artery. The sensor is usually not felt and will not interfere with daily activities, or any other implanted devices such as pacemakers or defibrillators” (Abbott n.d.).
Pulmonary wedge capillary pressure can be used to estimate left atrial pressur. It is possible to measure left atrial blood pressure by inserting a capillary into the right atria and then puncturing the interatrial septum. This method, however, is not commonly used because it can cause damage to this septum as well as harm to patients. “Measuring pulmonary capillary valve pressure is helpful in diagnosing the severity and degree of left ventricular dysfunction. Both conditions elevate left atrial tension, and consequently the pulmonary capillary-wedge pressure. Left atrial blood pressure is also elevated by mitral regurgitation or stenosis of the aortic valve. These pressures above 20 millimeters mercury can cause pulmonary edema, which could be fatal to the patient.
