title: The alveolar air equation abbreviated.
abstract: The alveolar air equation is not widely used in clinical medicine, probably because of the complicated appearance of its classic forms. The following shorter form has been derived: formula: see text (where PAO2, PEO2, and PIO2 are the partial pressures of oxygen in alveolar, expired, and inspired, gas, respectively, and VD/VT is the ratio of physiologic dead space over tidal volume). This shorter form is an algebraic identity of the classic equation. The shorter form involves the same assumptions and requires the same measurements as the traditional expressions but is more compact and easier to use in circumstances where VD/VT is measured routinely.
mesh_terms: D000388:Air; D001158:Arteries / Q000378:metabolism; D002245:Carbon Dioxide / Q000032:analysis; D006801:Humans; D007320:Inspiratory Capacity; D008173:Lung Diseases, Obstructive / Q000503:physiopathology; D008176:Lung Volume Measurements; D008433:Mathematics; D010100:Oxygen / Q000032:analysis; D010101:Oxygen Consumption; D011650:Pulmonary Alveoli / Q000378:metabolism / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen