1. Alveolar dead space.
Alveolar dead space. A: An ideal unit (top) receives nearly equal amounts of ventilation and perfusion. B: When perfusion drops (and ventilation is kept constant) (top), a fraction of the ventilation the unit is receiving (gray area) does not adequately participate in gas exchange and behaves like parallel dead space (it leaves the lungs at the same time as alveolar ventilation [V̇A]). Bottom: histograms for ventilation and perfusion for each situation. For clarity, only units with V̇A/Q̇ > 0 and lower than infinite are plotted (neither shunt nor serial dead space is shown).
Gaston Murias et al. Respir Care 2014;59:
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