Reproducibility of hyperventilation of cold dry air in children with cystic fibrosis.

Abstract

Wheezing is a significant problem in some patients with cystic fibrosis. Currently available tests are not reliable at determining whether this wheezing is due to co-existent asthma or to the underlying pulmonary disease. The reproducibility of hyperventilation of cold dry air (HVCDA) was studied over eight days in 11 children with cystic fibrosis. A group with mild lung disease were selected to minimize the variability due to underlying pulmonary disease. Fifty-six per cent of subjects had consistent responses to HVCDA. A test of reproducibility was performed on the respiratory heat exchange, the percentage fall in FEV1 after HVCDA and the ratio of these two (R). Respiratory heat exchange was found to be highly reproducible with a reproducibility co-efficient of 0.97. The percentage fall in FEV1 after HVCDA and R were not reproducible over the eight-day period. Hyperventilation of cold dry air did not give reproducible results in children with cystic fibrosis, suggesting that a single test may not be suitable for judging bronchial liability.