Show Summary Details
Page of

The Two Doctors Fick 

The Two Doctors Fick
The Two Doctors Fick

James R. Munis

Page of

PRINTED FROM OXFORD MEDICINE ONLINE ( © Oxford University Press, 2021. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy and Legal Notice).

date: 05 May 2021

We often confuse the ‘Fick principle’ with ‘Fick's law of diffusion.’ They are not the same. Ironically, Fick borrowed heavily from already known physical laws when he first described both his law of diffusion and his principle. Borrowing from Ohm's law of electricity, Fick applied concepts of diffusion and transfer across a resistance to formulate a law of diffusion that could be applied to gas or solute transfer across a membrane. Whether we are talking about transfer across the alveolar-capillary membrane or across a dialysis membrane, the concept is the same. The concept is similar to electricity—you have a transfer rate, resistance, and a gradient. Now let's consider the Fick principle. On the basis of another physical law he understood that, in the steady state, the difference between the amount of oxygen going into a tissue bed minus that leaving the tissue bed must be equal to the oxygen consumed. With a little reworking, this became the Fick principle: Cardiac output = O2 consumption / (arterial O2 - venous O2).

Access to the complete content on Oxford Medicine Online requires a subscription or purchase. Public users are able to search the site and view the abstracts for each book and chapter without a subscription.

Please subscribe or login to access full text content.

If you have purchased a print title that contains an access token, please see the token for information about how to register your code.

For questions on access or troubleshooting, please check our FAQs, and if you can't find the answer there, please contact us.