Radiographic determination of total lung capacity in patients with acromegaly

Total lung capacity (TLC) was measured from posteroanterior and lateral chest radiographs by the ellipsoid (TLCE) and planimetric (TLCp) radiographic methods in 16 acromegalic patients. These measurements were compared to the TLC measured by body plethysmography (TLCBP) in order to investigate the accuracy of the two radiographic methods. Our results showed that the mean value of TLCBP was 6.52 +/- 1.51 litres (mean +/- SD) or 120 +/- 13.3% of predicted values, statistically significantly increased from normal values (P less than 0.001). The mean value of TLCE was 7.09 +/- 1.8 litres and did not differ from the mean value of TLCBP (P greater than 0.125). The mean value of TLCP was 7.74 +/- 1.20 litres, statistically significantly increased from TLCBP (P less than 0.005). A statistically highly significant linear relationship was found between TLCE and TLCBP (r = 0.867, P less than 0.001) identical to the line of identity. Similarly a highly significant linear relationship was found between TLCP and TLCBP (r = 0.793, P less than 0.001) but to the left of the line of identity. It is concluded that both the ellipsoid and planimetric radiographic methods could be used to measure TLC in acromegalic patients but the planimetric method needed the appropriate correction.