Purpose: We recently reported a high prevalence of expiratory flow limitation (EFL) independent of sex in prepubescent children that exceeds the prevalence reported in adults. It is unknown how transpubertal maturation and growth affect pulmonary function, specifically EFL, during exercise. The purpose of this longitudinal study was to investigate the changes in EFL, including sex differences, from pre- to postpuberty.
Methods: Twenty-one children (age 12-16 yr, 11 boys and 10 girls) were recruited from 40 prepubescent children who completed testing in our laboratory ∼5 yr ago. Subjects completed pulmonary function tests before and after an incremental exercise test to exhaustion on a cycle ergometer. EFL was determined using the percent tidal volume overlap method.
Results: Nineteen of 21 subjects (10 boys and 9 girls, ∼90%) exhibited EFL prepuberty, whereas only 7 of 21 subjects (5 boys and 2 girls, 33%) exhibited EFL postpuberty. Boys had a significantly greater forced vital capacity (FVC) than girls both pre- (∼15%) and postpuberty (boys: 4.73 ± 0.53 L; girls: 3.80 ± 0.29 L). Maximal aerobic capacity (V˙O2max) significantly increased (boys: ∼120%; girls: ∼110%) from pre- to postpuberty and was greater (P < 0.05) in boys postpuberty (boys: 2.76 ± 0.43 L·min; girls: 1.94 ± 0.35 L·min). V˙E/V˙CO2 significantly decreased (∼13%) in boys and girls during maximal exercise. Postpuberty, subjects regulated tidal breathing at significantly higher lung volumes (greater expiratory reserve volume/FVC and lower inspiratory reserve volume/FVC) during exercise compared with prepuberty.
Conclusion: Our findings suggest that the prevalence of EFL declines as children mature from pre- to postpuberty, likely because of increases in lung size, decreases in V˙E/V˙CO2, and/or changes in breathing mechanics that are greater than increases in maximal ventilation that occur with increased pulmonary gas exchange.