From: Textbook of Arterial Stiffness and Pulsatile Hemodynamics in Health and Disease, 2022. The authors state that this observation supports the concept of the recruitment of previously atelectatic lung areas leading to an increase in compliance and a decrease in alveolar dead space, whereas overdistension of alveoli decreases compliance and increases alveolar dead space 4. The ratio of physiologic dead space to tidal volume is usually about 1/3. Respiratory dead-space is often increased in lung disease. Pulmonary dead space (VD) is the volume that does not participate in gas exchange, and the sum of anatomical dead space (conduit airways such as the mouth and trachea) and alveolar dead space. Alveolar dead space is the volume of gas within unperfused alveoli (and thus not participating in gas exchange either) it is usually negligible in the healthy, awake patient. Anatomic dead space is the volume of gas within the conducting zone (as opposed to the transitional and respiratory zones) and includes the trachea, bronchus, bronchioles, and terminal bronchioles it is approximately 2 mL/kg in the upright position. Physiologic or total dead space is the sum of anatomic dead space and alveolar dead space. Dead space is the volume of a breath that does not participate in gas exchange.
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