PEEP and Afterload

[slycaper]

Can anyone explain in simple terms (if possible) why PEEP decreases afterload?

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[jdh71]

"PEEP increases the pressure around structures in the thorax and, to a lesser extent, in the abdominal cavity, relative to atmospheric pressure. Because the rest of the circulation is at atmospheric pressure, this results in a pressure differential, with most of the systemic circulation being under lower pressure than the left ventricle and the thoracic aorta. Thus, increased ITP, at constant arterial pressure, decreases the force necessary to eject blood from the left ventricle in a manner exactly analogous to decreased arterial pressure, at constant ITP"

ITP = intrathoracic pressure

Though it's nuanced. Read the section on afterload: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1414045/