alveolarvolym

Alveolar volume, often denoted V_A, is the portion of tidal air that reaches the alveoli and participates in gas exchange. It represents the air available for gas exchange after subtracting the air that remains in the conducting airways, known as the anatomical dead space, and, if present, any physiologic dead space where ventilation does not match perfusion. Thus V_A is the difference between tidal volume (VT) and dead space volume (V_D): V_A = VT − V_D.

In a typical healthy adult at rest, VT is about 500 mL and anatomical dead space is around 150 mL, giving an alveolar volume per breath of roughly 350 mL. Alveolar ventilation per minute is the product of V_A and the respiratory rate (f): VȦ = V_A × f. Physiologic dead space can differ from anatomical dead space, and it increases in several lung conditions, reducing the alveolar portion of ventilation even when VT is preserved.

Alveolar volume is not identical to total lung capacity and varies with breathing pattern. It is often estimated indirectly from VT and dead space and is conceptually distinct from the total gas that fills the alveolar region. In clinical settings, changes in alveolar volume and dead space influence CO2 elimination and oxygenation. Conditions that increase dead space (e.g., pulmonary embolism, emphysema) or decrease alveolar ventilation impair gas exchange and can lead to hypercapnia or hypoxemia, depending on overall respiratory function and compensatory responses.