THE OXYGEN CASCADE: HOW DOES OXYGEN GET FROM THE ATMOSPHERE TO OUR CELLS?

Abstract

By the time the air gets to the alveoli (the tiny air sacs where gas exchange takes place), the partial pressure of oxygen has dropped to approximately 100 mmHg, mainly because of dilution by carbon dioxide which is being transferred from the blood into the alveoli. There are a number of reasons for this gradient, including shunt (mixing of venous deoxygenated blood), mismatching of alveolar ventilation and blood flow, and diffusion problems.