Alveolar gas equation

In order to evaluate the ventilatory status of a patient the alveolar oncygevL tension (Pj 02) must be known. It can be determined from the "alveolar gas equation" (equation 5),... 

The alveolar gas equation is used to estimate the Pao2 of a perfect alveolus with varying fractions of inspired oxygen and it states that... 

The value for Cc o2 cannot be calculated in this way very easily as a sample is technically difficult to take without a catheter in the pulmonary vein. It is, therefore, assumed to be in equilibrium with the Pao2, which, in turn, is given by the alveolar gas equation. 

State the first principles, for example the Bohr equation considers a single tidal exhalation comprising both dead space and alveolar gas. 

As arterial C02 tension is practically identical to alveolar C02 partial pressure, it can be used as a surrogate measurement. This is desirable as measuring arterial C02 tension involves only a simple blood gas analysis. The term Paco2, therefore, becomes Paco2 and so the equation is often written as... 

The level of carbon dioxide is itself proportional to the amount of gas passing in and out of the alveoli (alveolar ventilation) according to the following equation ... 

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