Determinants of Cardiac Output and Principles of Oxygen

Determinants of Cardiac Output and Principles of Oxygen -...

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Determinants of Cardiac Output and Principles of Oxygen Delivery Scott V Perryman, MD PGY-III
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Principle of Continuity: Conservation of mass in a closed hydraulic system Blood is an incompressible fluid Vascular system is a closed hydraulic loop Vol ejected from left heart = vol received in R heart
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Preload Preload: load imposed on a muscle before the onset of contraction Muscle stretches to new length Stretch in cardiac muscle determined by end diastolic volume
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Preload
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Preload At bedside, use EDP as surrogate for ventricular preload i.e. assume EDV = EDP
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Preload How can we measure EDP? Pulmonary Capillary Wedge Pressure
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PCWP How does wedge pressure work? A balloon catheter is advanced into PA Balloon at the tip is inflated Creates static column of blood between catheter tip and left atrium Thus, pressure at tip = pressure in LA
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PCWP Only valid in Zone 3 of lung where: – P c > P A Catheter tip should be above left atrium Not usually a problem since most flow in Zone 3 Can check with lateral x-ray Will get high respiratory variation if in Zone 1 or 2
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Determinants of Cardiac Output and Principles of Oxygen -...

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