The Central Venous Pressure (cvp)

The central venous pressure (CVP) is the pressure measured in the central veins located near the heart. It designates right mean atrial pressure and is recurrently used as a guesstimate of right ventricular preload. “The central venous pressure does not measure blood volume truthfully, although it is often used to estimate it. The central venous pressure value is determined by the pressure of venous blood in the vena cava and by the function of the right heart, and it is not only affected by intravascular volume and venous return, but also by venous tone and intrathoracic pressure, along with right heart function and myocardial compliance” (Department of Anaesthesiology The University of Hong Kong, n.d.).

“Under-filling and over-distention of the venous collecting system can be recognized by central venous pressure measurements before clinical signs and symptoms become evident. Under normal occurrences an increased venous return results in an augmented cardiac output, without significant changes in central venous pressure. However, with poor right ventricular function, or an obstructed pulmonary circulation, the right atrial pressure rises, therefore causing a subsequent rise in measures central venous pressure. Comparably, it is possible for a patient with hypovolemia to exhibit a central venous pressure reading in the normal range due to loss of blood volume or widespread vasodilation which will result in reduced venous return and a fall in right atrial pressure and central venous pressure” (Richard E. Klabunde, 2014).

“The central venous pressure can be measured either manually using a manometer or electronically using a transducer. In either case the central venous pressured must be zeroed at the level of the right atrium. This is usually the level of the fourth intercostal space in the mid-axillary line while the patient is lying in a supine position. Each measurement of central venous pressure should be taken at this same zero position. Trends in the sequential measurement of central venous pressure are much more informative than single readings. However, if the central venous pressure is measured at a different level each time then this renders the trend in measurement inaccurate” (Department of Anaesthesiology The University of Hong Kong, n.d.).

Pulmonary artery pressure (PA pressure) is a measurement of blood pressure found in the pulmonary artery of the heart. “Pulmonary artery pressure is generated by the right ventricle expelling blood into the pulmonary circulation, which acts as an opposition to the production from the right ventricle. With each ejection of blood during ventricular systole, the pulmonary arterial blood volume increases, which stretches the wall of the artery. As the heart relaxes also known as ventricular diastole, blood continues to flow from the pulmonary artery into the pulmonary circulation. The smaller arteries and arterioles serve as the chief resistance vessels, and through changes in their diameter, regulate pulmonary vascular resistance” (Richard E. Klabunde, The Pharmacologic Treatment of Pulmonary Hypertension, 2010).

Today, pulmonary artery catheters are placed on a case by case basis taking into consideration the patient’s condition and the staff qualification. Conditions for using a pulmonary catheter include severe cardiogenic pulmonary edema, patients with acute respiratory distress syndrome who are not hemodynamically stable, patients who have had major thoracic surgery, and patients with septic or sever cardiogenic shock. “A pulmonary artery pressure monitoring system uses a sensor to measure your pulmonary artery pressure and heart rate. The sensor is small, comparable to the size of a penny with two thin loops at each of the ends. The sensor is implanted in the pulmonary artery of the heart. Normally you will not feel the sensor, and it will not impede with your day to day activities or other devices that may be implanted such as a pacemaker or defibrillator” (Abbott, n.d.).

Pulmonary capillary wedge pressure provides an estimation of left atrial pressure. Left atrial pressure can be measured by insertion of a catheter into the right atrium then piercing through the interatrial septum, however, for apparent reasons, this is not usually accomplished because of the destruction to the septum and potential detriment to the patient. “It is helpful to measure pulmonary capillary wedge pressure to diagnose the severity of left ventricular Failure and to calculate the degree of mitral valve stenosis. Both conditions raise left atrial pressure and therefore raise pulmonary capillary wedge pressure. Aortic valve stenosis and regurgitation, and mitral regurgitation also elevate left atrial pressure. When these pressures are above twenty millimeters of mercury, pulmonary edema is probable to transpire, which is life threatening to the patient”