Oxygen delivery in inspiration

Relation between oxygen delivery and dead space during tidal inspiration. Panel A) With a tidal volume of 450 mL, the first gas to arrive at the alveoli is the 150 mL of oxygen poor gas already occupying the dead space in the airways. This is followed by the first 300 mL of inspired gas expected to reach the alveoli. Panel B) The final 150 mL of inspired gas will fill the dead space at the end of inspiration but not reach the alveoli. Ideally, all oxygen delivery should occur prior to this last 150 mL.