label: Decreased RV/TLC ratio
label_lc: decreased rv/tlc ratio
description: "An abnormally low ratio of residual volume (RV) to total lung capacity (TLC) on pulmonary function testing. RV is the amount of air remaining after maximal expiration and TLC is the total amount of air in the lungs at full inspiration. These volumes cannot be determined by spirometry, but can be measured by inert gas dilution, nitrogen washout, and body plethysmography."