Lung Volumes

Abstract

Lung volume measurement can provide invaluable information concerning the effects of lung disease. Indeed, the two basic patterns of pathophysiological derangement of the lung involve either increases (airflow limitation or obstruction) or decreases (restriction) in lung volumes. Of the various lung volumes and capacities, the three boundaries of lung volume-total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV)-provide the most useful information. The techniques used to measure lung volume include inert gas dilution, which measures communicating gas spaces; body plethysmography, which measures compressing gas spaces that may or may not be communicating; and x-ray, which measures physical space. The method used has an important impact on interpretation because lung volume results need to be considered in the light of the technique used and pertinent physiological principles.

Key Words:

lung volumes - total lung capacity - restriction - functional residual capacity - residual volume - airflow limitation