Tracheal size and distensibility in patients with cystic fibrosis

Retrospective studies have reported that tracheal enlargement is common in patients with cystic fibrosis (CF). To determine whether significant tracheal enlargement occurs in these patients, we used the acoustic reflection technique to prospectively measure the tracheal cross-sectional area near functional residual capacity (FRC) in 39 stable outpatients with CF and 39 age- and sex-matched normal control subjects. The patients with CF had a mean age of 19.0 yr with a mean percent predicted FEV1 of 69%. The mean +/- SEM tracheal area of the patients with CF was 1.99 +/- 0.13 cm2, compared with a mean tracheal area of 1.87 +/- 0.10 cm2 in the control subjects (t = 0.79, NS). CF tracheal area was not a function of age nor of disease severity, as assessed by percent predicted FEV1. To determine whether tracheomegaly might occur only in older patients, we examined the six patients with CF who were 28 yr of age or older. Mean tracheal area for these older patients with CF was 2.46 +/- 0.26 cm2, compared with 2.27 +/- 0.10 cm2 for the control subjects (t = 0.70, NS). Eleven patients with CF also had their tracheal area measured near TLC. At this high lung volume, the tracheal area of the patients with CF was 2.62 +/- 0.23 cm2, significantly larger than the 1.91 +/- 0.13 cm2 in 11 control subjects (t = 2.68, p less than 0.02). The increase in tracheal area per change in lung volume was also significantly greater in the patients with CF than in the control subjects (t = 3.33, p less than 0.01). We conclude that near FRC the tracheal size of patients with CF is not different from that of age- and sex-matched control subjects. The tracheas of patients with CF expand more than do the tracheas of control subjects when higher lung volumes are attained, suggesting increased airway distensibility.