What's the difference between Cardiac Output and Blood Flow Rate?

[manohman]

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Cardiac Output = Change in Pressure / Total Peripheral Resistance

Blood flow Rate = Change in Pressure / Resistance

Are they equivalent? Why not?

 

[NextStepTutor_1]

Hi @manohman ,

Great question, and it seems like part of what spurred you to ask it may have been an analysis of the units. Analyzing units is definitely a great habit to get into for the MCAT (and in general)! Basically, "blood flow" is the more general term. You can analyze blood flow within a single vessel, a given organ, or for a certain part of the circulation (i.e., pulmonary vs. systemic circulation), whereas cardiac output refers more specifically to the blood passing through the heart. It can also be defined as the heart rate (beats per minute) multiplied by the stroke volume (volume per beat). Note that those two sets of units (beats per minute and volume per beat) cancel out to give volume per minute (as appropriate for a rate).

Hope this clarifies things & best of luck as you study!