Static lung volumes measured by plethysmography: does GLI fit well?

<bold>Introduction:</bold> Plethysmography is the gold standard for measuring lung volumes. The Global Lung Function Initiative (GLI) developed reference equations that facilitate interpretation of results and improve understanding of normal lung growth and development. <bold>Aim:</bold> to validate lung volumes GLI equation in pulmonary healthy individuals living at 2240m of altitude. <bold>Methods:</bold> cross-sectional, prospective study (IRB C39-22), in healthy individuals from Mexico City. Plethysmography results were loaded into the GLI calculator, the predicted values and z-scores were obtained. The concordance correlation coefficient (CCC) between results was calculated and the percentage of individuals < LLN and >ULN on plethysmograph variables were obtained. <bold>Results:</bold> 351 individuals were recruited, median (min-max) age was 35.6 (5-80) years, 56% females. CCC (95% limits of agreement) in liters =0.57 (−0.68-1.15), 0.88 (−0.78-1.54) and 0.61 (−0.23- 1.02) in FRC, TLC and RV respectively. RV and ERV z-score were higher in females than males (0.90 vs 0.67; p<0.01) in RV and (−0.18 vs 0.14; p<0.01) for ERV. RV/TLC was > ULN in 14% of subjects, ~ 70 % of volumes results were outside of ± 0.5 z-scores. <bold>(Figure 1)</bold>. <bold>Conclusions:</bold> GLI reference equation for lung volumes does not fit individuals living at 2240 m, this can overdiagnose pulmonary hyperinflation or underdiagnosed of restriction.