alveolluften

Alveolluften is a term that appears to be nonstandard in English-language medical literature, but in some Scandinavian contexts it is used to refer to alveolar air—the gas mixture contained within the alveoli of the lungs. In that sense, alveolluften denotes the air actively involved in gas exchange between the lung and the bloodstream, as distinct from ambient or inspired air and from mixed venous blood.

Alveolar air has a characteristic composition shaped by ventilation and metabolism. At sea level, the inspired fraction of oxygen (FIO2) is about 0.21, and after humidification in the airways, the partial pressure of inspired oxygen (PIO2) is roughly 149–150 mmHg. Through the alveolar gas equation, PAO2 = PIO2 − (PACO2/R), alveolar oxygen in healthy individuals is around 100 mmHg, with alveolar CO2 (PACO2) near arterial CO2 (PaCO2) at about 40 mmHg and a respiratory quotient R of ~0.8. This alveolar composition underpins the gradient driving oxygen diffusion into blood and carbon dioxide diffusion out of blood.

Measurement and clinical relevance: alveolar gas composition can be estimated directly or inferred from end-tidal values. Alveolar ventilation, diffusing capacity, and ventilation–perfusion matching affect how closely PAO2 and PACO2 reflect systemic values. Abnormal alveolar air composition or impaired alveolar ventilation can indicate respiratory disorders such as hypoventilation, pneumonia, edema, or fibrosis.

See also: alveolar gas equation, alveolar ventilation, end-tidal CO2, gas exchange, ventilation–perfusion mismatch.