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The partial pressure of oxygen (pO2) in the pulmonary alveoli is required to calculate both the alveolar-arterial gradient of oxygen and the amount of right-to-left cardiac shunt, which are both clinically useful quantities. However it is not practical to take a sample of gas from the alveoli in order to directly measure the partial pressure of oxygen. The alveolar gas equation allows the calculation of the alveolar partial pressure of oxygen from data that is practically measurable. It was first characterized in 1946. ==Assumptions== The equation relies on the following assumptions: * Inspired gas contains no carbon dioxide (CO2) or water * Nitrogen (and any other gases except oxygen) in the inspired gas are in equilibrium with their dissolved states in the blood * Inspired and alveolar gases obey the ideal gas law * Carbon dioxide (CO2) in the alveolar gas is in equilibrium with the arterial blood i.e. that the alveolar and arterial partial pressures are equal * The alveolar gas is saturated with water 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「alveolar gas equation」の詳細全文を読む スポンサード リンク
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