Pulmonary ventilation is quantified by two related measures: minute (total) ventilation, the product of breathing frequency and tidal volume, and alveolar ventilation, the product of breathing frequency and the tidal volume remaining after subtracting anatomic dead space — the portion of each breath that never reaches gas-exchanging surface. Because only alveolar ventilation delivers gas to where exchange occurs, it is necessarily smaller than minute ventilation and is the physiologically and clinically decisive quantity, standing in a strict inverse relationship with arterial carbon dioxide, so that either variable predicts the other. Ventilation is further distributed within the lung according to regional compliance — the inverse of stiffness — with airflow preferentially entering more compliant regions, a principle that belongs to respiratory physiology within systems physiology and underlies the pathophysiology of restrictive and obstructive lung disease.
Pulmonary ventilation is quantified by two related measures: minute (total) ventilation, the product of breathing frequency and tidal volume, and alveolar ventilation, the product of breathing freque…