Describe the oxygen cascade in a person breathing room air at sea level.

[Click here to toggle visibility of the answers]

College Answer

This question could be answered with a description or a diagram but required an ordered 
journey from the atmosphere to the mitochondria. This is commonly available in many texts 
and most candidates answered the question well. Most candidates said the alveolar PO2 fell 
solely because CO2 came out of the pulmonary capillary. Very few talked about oxygen 
uptake into the capillary. Another common omission was failure to state normal values for the 
A-a gradient.