Evaluation of Lung diffusing capacity for Carbonmonoxide (DLco) in healthy adolescents


In pulmonary function tests (PFT), the selection of prediction equation for lung diffusing capacity for carbonmonoxide (DLco), remains a problem. If a single equation is selected and used by all laboratories, the variation in percent predicted values would be large enough to cause numerous diagnostic errors. The present study involved 36 healthy adolescents (20 boys and 16 girls aged 13-19 years) with body height (157-170 cm) and body weight (38-63 Kg). Normal values were reported for lung volumes, ventilation and diffusing capacity using spirographic, helium dilution and carbon monoxide single-breath techniques. Values observed in the present study were comparable to Asians studies but lower than those of Westerns. All pulmonary function parameters were significantly higher in boys, mainly due to larger lung volume, in addition to differences in the level of physical activity and social patterns of life. Regardless to sex, indices of lung volume and diffusion increased with age, body height, and surface area, however, best correlation was observed with body height. Gender specific prediction equations were generated for lung diffusing capacity. Lung diffusion corrected for volume (DLco/VA) seemed independent to sex or body size. In conclusion, it is not appropriate to rely on prediction equations derived from western populations who had higher levels of normality for DLco. Furthermore, height was the best single predictor for lung diffusion in adolescence age group.