physiologic dead spaces

Noun

physiologic dead space (countable and uncountable, plural physiologic dead spaces)

1. (obsolete) The volume of the conducting airways of the lung. This definition became inadequate once the alveolar dead space was described.
   • 1948. Ward S. Fowler, Lung Function Studies. II. The Respiratory Dead Space., J. Physiology. Vol. 154. p 406.
     Throughout this paper, the term physiological dead space will be used to refer to the volume of the conducting airway down to the location at which a large change in gas composition occurs.
2. That volume of air in the lung which does not partake in gas exchange.
3. That volume of air in the lung that does not eliminate carbon dioxide, as defined functionally by the Bohr equation.
   • 2011. John B. West, Respiratory Physiology: The Essentials. Lippincott Williams & Wilkins; Ninth edition.
     Bohr's method measures the volume of the lung which does not eliminate CO₂. Because this is a functional measurement, the volume is called the physiologic dead space.
4. The sum of the anatomic plus the alveolar dead spaces.
5. The sum of the parallel and the serial dead spaces.
   • ...the effective respiratory dead space is made up of two principal components. The first component is associated with the volume of the respiratory passages leading to the lung.... A second component is the ... well ventilated, but poorly perfused alveoli are in parallel with the respiratory...1955, B. Folkow, J. R. Pappenheimer, Components of the Respiratory Dead Space and Their Variation With Pressure Breathing and With Bronchoactive Drugs J Appl Physiol 8:102-110