#### Constanzo physiology - cardiovascular physiology - cardiac muscle contraction - measurement of cardiac output-Fick Principle

There is conservation of mass

Fick principle states that?

In steady state, cardiac output of left and right ventricles is equal

Fundamental assumption of Fick principle's application in measurement of cardiac output

In stead state, rate of O2 consumption by body must equal amount of O2 leaving lungs in pulmonary vein minus amount of O2 returning to lungs in pulmonary artery

Fick principle's application in measurement of cardiac output is?

Oxygen consumption = amount of oxygen leaving lungs in pulmonary vein - amount of oxygen returning to lungs in pulmonary artery

Calculation for oxygen consumption

Pulmonary blood flow × oxygen content of pulmonary venous blood

Calculation for amount of oxygen in pulmonary veins

Pulmonary blood flow × oxygen content of pulmonary arterial blood

Calculation for amount of oxygen in pulmonary artery

The assumption is that pulmonary blood flow = cardiac output of right heart = cardiac output of left heart

Why is pulmonary blood flow the same?

Cardiac output × [O2 ]pulmonary vein − Cardiac output × [O2 ]pulmonary artery

Calculation for oxygen consumption in terms of cardiac output

...

Calculation for cardiac output using oxygen consumption

mL/min

Unit for cardiac output

mL O2/min

Unit for oxygen consumption

mL O2/mL blood

Unit for [O2]pulmonary vein and [O2]pulmonary artery

250 mL/min

Total oxygen consumption of body in a 70kg man

By sampling blood from a peripheral artery (because none of the O2 added to blood in lungs has been consumed by the tissues yet)

How to measure oxygen content of pulmonary venous blood?

Can be sampled either in pulmonary artery itself or in right ventricle

How to measure oxygen content of pulmonary arterial blood?

Individual organs

Fick principle can be applied to measurement of blood flow to ____

Renal blood flow can be measured by dividing O2 consumption of kidneys by difference in O2 content of renal arterial blood and renal venous blood

Example of calculating renal blood flow by using Fick principle