A recent estimate for the normal range of forced expiratory tracheal collapse differs substantially from that in an earlier study performed with comparable measurement methods. Given differences in subject characteristics between the two samples, we hypothesized that these discrepant findings may reflect a heretofore unrecognized association between forced expiratory tracheal collapse and age or sex.
We enrolled 40 female and 41 male healthy volunteers between 25 and 75 years of age who were without respiratory symptoms or known risk factors for tracheomalacia. Subjects underwent low-dose CT scanning at total lung capacity (TLC) and during forced exhalation (Expdyn) with spirometric monitoring and coaching. Percentage forced expiratory collapse was regressed on age for the total sample and separately within sex.
Mean tracheal cross-sectional area (CSA) was 2.54 cm2 ± 0.57 cm2 at TLC and 1.15 cm2 ± 0.53 cm2 at Expdyn. Mean percentage forced expiratory collapse (%collapse) was 54% ± 20%. Men aged 24 to 31 years (n = 12) had mean %collapse of 36% ± 19%, comparable to results previously reported for similarly aged men (35% ± 18%). Men, but not women, showed a significant positive correlation (R2 = 0.40, P < .001) between %collapse and age. Older men had both greater CSA at TLC (P = .02) and smaller CSA at Expdyn (P = .001) than younger men.
Men exhibit positive age dependence of forced expiratory tracheal collapse. The influence of age and sex on forced expiratory tracheal collapse should be considered in the diagnostic evaluation of expiratory dynamic airway collapse and/or tracheomalacia.