Metabohc rate approach

Pulmonary ventilation, i.e., the rate at which fresh air (and solvent vapor) enters the lungs. This is determined by the metabohc rate and therefore depends on physical exertion. The concentration in alveolar air approaches that in inhaled air when the physical exertion is great. When exertion is low, flic alveolar air concentration approaches the concentration in mixed venous blood. 

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