Pulmonary function following mild respiratory tract infections ("common cold") in teenagers.

Ventilatory function--forced vital capacity (VC)--forced expiratory volume (in 1-sec forced expiratory flows) static lung volumes, closing volume, and phase III slope (single-breath N2 test) were compared in 94 children with and 436 children without a history of recent mild acute respiratory infection. Their age ranged from 10 to 16 years; subjects with symptoms on the day of the study were excluded. We found no difference in lung function between the two groups, with the exception of a slight (inconsistently significant) increase in closing volume (CV) and the CV/VC ratio. Although the influence of a persistent increase in interstitial lung pressure leading to early small airways closure cannot be ruled out, this isolated functional abnormality probably represents a spurious positive result, arising by chance when a large number of statistical tests are done.