![]() Residual volume cannot be measured by spirometry.įirst, the subject is asked to breathe quietly. Respiratory exchange quotient (CO2 production/O2 consumption)įigure 5–2 Lung volumes and capacities. Measurements of lung volumes and capacities are made by spirometry. Volume of forced vital capacity expired in 1 second Partial pressure of CO2 in dry inspired air Partial pressure of O2 in dry inspired air ![]() Partial pressure of CO2 in arterial blood Table 5–1 Abbreviations and Normal Values Associated with Respiratory Physiology The volume displaced is recorded on calibrated paper ( Fig. Typically, the subject is sitting and breathes into and out of the spirometer, displacing a bell. Static volumes of the lung are measured with a spirometer ( Table 5-1). However, differences in the exact way of measuring this space result in clinically significant different results and, therefore, debate remains about the true value of this measured parameter.Ĭopyright © 2023, StatPearls Publishing LLC.Physiology 5th Ed. Indeed, it may serve as a prognostic factor in patients with acute repository distress syndrome (ARDS) who require ventilation. This phenomenon has clinical significance because, both in healthy and impaired lungs, properly calculating and accounting for this non-physiological space is important for the proper respiratory care of ventilated patients. This is therefore termed anatomical dead space as it serves no respiratory function. Anatomic dead space is an important phenomenon in respiratory physiology whereby, owing to the fact that upper airways do not function as locations for gas exchange, and because of the tidal nature of ventilation, there is always a fraction of the inspired air that does not perform a physiologic function of exchanging carbon dioxide for oxygen.
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