Pulmonary capillary wedge pressure
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` Cardiovascular Physiology Concepts
` Richard E. Klabunde, Ph.D.
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`Pulmonary Capillary Wedge Pressure
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`on Cardiovascular
`Physiology Concepts,
`published by Lippincott
`Williams & Wilkins (2005)
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`What does it measure?
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`Pulmonary capillary wedge pressure (PCWP) provides an indirect estimate of left atrial pressure
`(LAP). Although left ventricular pressure can be directly measured by placing a catheter into the left
`ventricle by feeding it through a peripheral artery, into the aorta, and then into the ventricle, it is not
`feasible to advance this catheter back into the left atrium. LAP can be measured by placing a special
`catheter into the right atrium then punching through the interatrial septum; however, for obvious
`reasons, this is not usually performed because of damage to the septum and potential harm to the
`patient.
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`How is it measured?
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`PCWP is measured by inserting balloon-tipped, multi-lumen
`catheter (Swan-Ganz catheter) into a peripheral vein, then
`advancing the catheter into the right atrium, right ventricle,
`pulmonary artery, and then into a branch of the pulmonary
`artery. Just behind the tip of the catheter is a small balloon
`that can be inflated with air (~1 cc). The catheter has one
`opening (port) at the tip (distal to the balloon) and a second
`port several centimeters proximal to the balloon. These ports
`are connected to pressure transducers. When properly
`positioned in a branch of the pulmonary artery, the distal port
`measures pulmonary artery pressure (~ 25/10 mmHg) and the
`proximal port measures right atrial pressure (~ 0-3 mmHg).
`The balloon is then inflated, which occludes the branch of the
`pulmonary artery. When this occurs, the pressure in the distal
`port rapidly falls, and after several seconds, reaches a stable
`lower value that is very similar to left atrial pressure
`(normally about 8-10 mmHg). The balloon is then deflated.
`The same catheter can be used to measure cardiac output by
`the thermodilution technique.
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`The pressure recorded during balloon inflation is similar to left atrial pressure because the occluded
`vessel, along with its distal branches that eventually form the pulmonary veins, acts as a long catheter
`that measures the blood pressures within the pulmonary veins and left atrium.
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`Why is it measured?
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`It is important to measure PCWP to diagnose the severity of left ventricular failure and to quantify
`the degree of mitral valve stenosis. Both of these conditions elevate LAP and therefore PCWP. These
`pressures are normally 8-10 mmHg. Aortic valve stenosis and regurgitation, and mitral regurgitation
`also elevate LAP. When these pressures are above 20 mmHg, pulmonary edema are likely to be
`present, which is a life-threatening condition. Note that LAP is the outflow or venous pressure for the
`pulmonary circulation and increases in LAP are transmitted almost fully back to the pulmonary
`capillaries thereby increasing their filtration. By measuring PCWP, the physician can titrate the dose
`of diuretic drugs and other drugs that are used to reduce pulmonary venous venous and capillary
`pressure, and thereby reduce the pulmonary edema. Therefore, measurement of PCWP can help
`guide therapeutic efficacy.
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`PCWP is also necessary to measure when evaluating pulmonary hypertension. Pulmonary
`hypertension is often caused by an increase in pulmonary vascular resistance. To calculate this,
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`http://web.archive.org/web/20090602211655/http://www.cvphysiology.com/Heart%20Failu...
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`Pulmonary capillary wedge pressure
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`Page 2 of 2
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`pulmonary blood flow (usually measured by the thermodilution technique), pulmonary artery
`pressure and pulmonary venous pressure (PCWP) measurements are required. Pulmonary
`hypertension can also result from increases in pulmonary venous pressure and pulmonary blood
`volume secondary to left ventricular failure or mitral or aortic valve disease.
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`PCWP is also useful in evaluating blood volume status when fluids are administered during
`hypotensive shock. One practice is to administer fluids at a rate that maintains PCWP between 12-14
`mmHg.
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`RK Revised 04/07/07
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`DISCLAIMER: These materials are for educational purposes only, and are not a source of medical decision-making
`advice.
`© 1999-2008 Richard E. Klabunde, all rights reserved.
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