breathe in, breathe out

We measure all hemodynamic variables (CVP, PAs, PAWP, CO/CI) at end-expiration, because exhalation is usually the longest period of the respiratory cycle. Inhalation increases systemic venous return, but also decreases pulmonary venous return, which in turn decreases flow to the left side of the heart.

Here is that mechanism at work with bolus thermodilution:

IMG_3191

This image demonstrates the high degree of variability from respiratory artifact. Trials 1, 3, 5 were performed at end-exhalation. Trials 2, 4, 6 were performed during inhalation.

Author: Mitochondrial Eve

CCRN-CMC/CSC I know less than half as much as I'd like to, and say more than half as much as I should.

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