Osmosis video - Alveolar gas equation

Alveolar gas equations are a set of mathematical equations used to calculate the alveolar oxygen partial pressure. It is used extensively in medicine and physiology and is considered to be one of the most important tools in understanding how the alveolar gas exchange works.

PAO2 = (Patm - PH2O) FiO2 - PaCO2/RQ

PAO2: oxygen partial pressure inside the alveoli; Patm: atmospheric pressure (at sea level 760 mm Hg); PH2O: partial pressure of water (approximately 45 mm Hg); FiO2: fraction of inspired oxygen; PaCO2: partial pressure of carbon dioxide in alveoli (in normal physiological conditions around 40 to 45 mmHg). RQ is the respiratory quotient (average value is around 0.82)