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Afterload is the mean tension produced by a chamber of the heart in order to contract. It can also be considered as the ‘load’ that the heart must eject blood against. Afterload is, therefore, a consequence of aortic large vessel compliance, wave reflection, and small vessel resistance (LV afterload) or similar pulmonary artery parameters (RV afterload
The tendency of the arteries and veins to stretch in response to pressure has a large effect on perfusion and blood pressure. This physically means that blood vessels with a higher compliance deform easier than lower compliance blood vessels under the same pressure and volume conditions. [ 1 ]
Consequently the vessels wall are more stretched so the caliber of the vessels increases causing an increase in flow due to lower resistance. Zone 4 can be seen at the lung bases at low lung volumes or in pulmonary edema. Pulmonary interstitial pressure (Pi) rises as lung volume decreases due to reduced radial tethering of the lung parenchyma ...
Immediately following the arterioles are the capillaries. Following the logic observed in the arterioles, we expect the blood pressure to be lower in the capillaries compared to the arterioles. Since pressure is a function of force per unit area, (P = F/A), the larger the surface area, the lesser the pressure when an external force acts on it ...
The next addition to the historical understanding of pulmonary circulation arrived with the Ancient Greeks. Physician Alcmaeon (520 – 450 BCE) proposed that the brain, not the heart, was the connection point for all of the vessels in the body. He believed that the function of these vessels was to bring the "spirit" ("pneuma") and air to the ...
The pulmonary artery pressure (PA pressure) is a measure of the blood pressure found in the main pulmonary artery. This is measured by inserting a catheter into the main pulmonary artery. [ 13 ] : 190–191 The mean pressure is typically 9–18 mmHg, [ 14 ] and the wedge pressure measured in the left atrium may be 6–12 mmHg.
When both the heart and lungs are healthy, pulmonary wedge pressure is equal to left ventricle diastolic pressure and can be used as a surrogate for preload. [3] Pulmonary wedge pressure will overestimate left ventricle pressure in people with mitral valve stenosis, pulmonary hypertension and other heart and lung conditions. [4]
Diagram of a pulmonary artery catheter in position. The pulmonary wedge pressure (PWP) (also called pulmonary arterial wedge pressure (PAWP), pulmonary capillary wedge pressure (PCWP), pulmonary artery occlusion pressure (PAOP), or cross-sectional pressure) is the pressure measured by wedging a pulmonary artery catheter with an inflated balloon into a small pulmonary arterial branch. [1]