When studied quantitatively, how will changes in pulse pressure throughout the respiratory cycle during a positive-pressure breath predict improvements in cardiac output?

A. The predictive value is minimal.
B. The predictive value is not related at all to changes in pulse pressure.
C. Changes in pulse pressure are equally predictive as left ventricular end-diastolic pressure.
D. Changes in pulse pressure are better predictors than pulmonary artery wedge pressure.

?ANS: D
A. Incorrect response: See explanation D.
B. Incorrect response: See explanation D.
C. Incorrect response: See explanation D.
D. Correct response: In patients who are relatively hypovolemic, the negative and positive effects on left ventricular stroke volume predominate during separate phases of the respiratory cycle during a PPV breath. This condition exaggerates the changes in pulse pressure. When studied quantitatively, the change in pulse pressure across the respiratory cycle have been shown to predict the improvements in cardiac output following a fluid bolus. The positive and negative predictive values of changes in pulse pressure during a PPV breath exceed other traditional indexes of volume status, including the pulmonary artery wedge pressure.