11/14/2023 0 Comments Lung apex dead spaceTherefore, physiologic dead space is equivalent to anatomical. In a healthy adult, alveolar dead space can be considered negligible. The respiratory zone is comprised of respiratory bronchioles, alveolar duct, alveolar sac, and alveoli. Physiologic or total dead space is equal to anatomic plus alveolar dead space which is the volume of air in the respiratory zone that does not take part in gas exchange. This volume is considered to be 30% of normal tidal volume (500 mL) therefore, the value of anatomic dead space is 150 mL. Anatomical dead space is represented by the volume of air that fills the conducting zone of respiration made up by the nose, trachea, and bronchi. The two types of dead space are anatomical dead space and physiologic dead space. By these definitions, healthy subjects are those whose physiological dead space and shunt do not exceed their anatomical dead space and shunt.Dead space represents the volume of ventilated air that does not participate in gas exchange. 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.
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