Roentgenographic determination of total lung capacity in normal Chinese children

Roentgenographic determination of total lung capacity (TLC) in children, rarely mentioned in the past, differs from the determination of TLC using helium dilution method in that it does not need the measurement of functional residual capacity. Therefore, it is useful for hospitals where pulmonary function testing (PFT) is not available. In this study, 87 out of 125 normal children completed both chest radiographs and PFT. Ellipsoid method which divides the lung field into several sections was used to calculate TLC from chest radiographs. The correlation coefficient of TLC measured by both chest radiographs and PFT was 0.7680, and paired Student's t-test of the mean values of the two groups showed P value greater than 0.05. Among the variables of height, weight, age and body surface area, height alone was able to predict the normal reference value of TLC. Line of regression between TLC and height was expressed as "TLC = 52.776 x Height- 4404.998", and correlation coefficient was 0.8013. Intersubject reproducibility was also verified. It is concluded that chest radiographs can be used to determine TLC in children.