Lung volume and emphysema

Total lung volume at full inspiration was used as a radiological measure of total lung capacity (TLC_CT) and was expressed as a percentage of predicted values [12]. Emphysema was measured as the percentage of low-attenuation areas below −950 Hounsfield units (%LAA₋₉₅₀) [13]. %LAA₋₉₅₀ is reported for the whole lung and upper and lower lobes of combined lungs. Subjects were defined as having emphysematous or nonemphysematous lungs when %LAA₋₉₅₀ of the lower third was ≥5% or <5%, respectively [14].