Harkins
Wood
The presence of alveolar dead space is due to alveoli that are ventilated, but not perfused with blood. This acts like anatomical dead space in that the ventilation does no good ("wasted ventilation"). This can occur at the top of the lung during diastole (no blood flows to the top), during continuous pressure ventilation (CPAP), and as a result of blood clots blocking arteries.
The converse is wasted perfusion (shunt) which is blood flowing to regions of the lung that are not ventilated; e.g., bronchospasm, mucous plug, aspirated foreign body.
Paul
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