![]() By these definitions, healthy subjects are those whose physiological dead space and shunt do not exceed their anatomical dead space and shunt. 7) that allow systemic blood to bypass the pulmonary circulation plus any pulmonary arterial blood flowing through alveoli with inadequate ventilation, that is, V̇ A/Q̇ <0.01 ( Table 8.1). 9 includes actual extra-pulmonary anatomical defects like PDA or PFO (Chap. Likewise, a calculated physiological shunt as detailed in Chap. 4) plus the volume of all alveoli whose ventilation vastly exceeds their blood flow, that is V̇ A/Q̇ >100 ( Table 8.1). Thus, a calculated physiological dead space includes the anatomical dead space of conducting zone airways (Chap. ![]() It is important to emphasize that such physiological estimates are made on living subjects and include any anatomical defects that are only quantifiable by autopsy. 9 present equations to calculate a patient’s physiological dead space and physiological shunt. This study evaluates the effects of increased alveolar dead-space (VDalv), pulmonary shunt, and abnormal ventilation perfusion ratio (V/Q) distributions.
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