The first phase has no nitrogen, and is the air that entered the lung only as far as the conducting airways.

Particulate matter is trapped on the mucus that lines the conducting airways, allowing its removal by mucociliary transport.

Mammals breathe in and out of their lungs, wasting that part of the inspiration which remains in the conducting airways where no gas exchange can occur.

Despite the flexibility of the trachea and smaller conducting airways, their overall volume (i.e. the anatomic dead space) changes little with bronchoconstriction or when breathing hard during exercise.

The quantity of CO exhaled from the healthy alveoli will be diluted by the air in the conducting airways, and by air from alveoli that are poorly perfused.

Human lung tissue was obtained from mid-tremester abortuses (15-21 weeks old), dissected free from blood vessels and conducting airways, then minced with a sterile razor blade into 1 mm 3explants [ 6 ] .

In physiology, dead space is the volume of air which is inhaled that does not take part in the gas exchange, either because it (1) remains in the conducting airways, or (2) reaches alveoli that are not perfused or poorly perfused.