Changes in cross-sectional area of the lungs on end expiratory computed tomography in normal individuals.

With the increasing use of expiratory computed tomography (CT) for the detection of air-trapping, and specifically the diagnosis of small airways disease, information about the range of excursion of the chest wall in normal individuals is needed. CT was performed, in full inspiration and end expiration, in 78 individuals (age range 17-70 years) with no demonstrable lung disease. The area of the lungs was measured at the level of the carina, in inspiration and end expiration, and the percentage change in area was calculated. In normal subjects there is, on average, a 55% (SD 8.7%) change in cross-sectional area of the lungs at the level of the carina. Awareness of the normal change in area is of value in assessing the severity of air-trapping in patients undergoing CT for suspected obstructive lung disease.