Objectives: To evaluate the evolution pattern of dynamic pulmonary flow and volume in cystic fibrosis patients and analyze the relation between the severity of ventilatory attacks and age, gender, genotype and pulmonary colonization. Methods: At the Pediatric Pulmonary Unit and Pulmonary Service of Hospital de Clínicas of Porto Alegre, 243 spirometries performed between 1987 and 1999 in 52 cystic fibrosis patients older than four years of age were reviewed. From the patients' medical records the following informations were extracted: age at diagnosis, genetic data, bronchial colonization and absolute as well as percent values of the flows and volumes of the best annual spirometry. Results: The age of the patients ranged from four to 26 years (mean = 13.04 ± 4.82). Out of the 52 patients, 49 (94%) had at least one sputum culture with P. aeruginosa, 45 (86%) with S. aureus and 13 (25%) with B. cepacia. At initial evaluation, that included patients four to six years old (n = 40), mean values for FVC and FEV1 were 114.24% and 112.25%, respectively. Mean FVC remained above baseline until 18 years of age, when it abruptly dropped to 67.2% (p = 0.0002). Mean FEV1 values dropped to less than 80% at ten years and was 50% at 18 years (p < 0.00001). The FEV1/FVC% relationship, the most obstruction sensitive index, was observed to be reduced as early as initial evaluation. It was 85% between four and six years and gradually decreased to 63% at 18 years. The mean values of FEF50, FEF75 and FMEF were initially normal (94%, 80% and 90%, respectively), showed a greater and earlier statistically significant decline, and reached to 37%, 12.5% and 19%, respectively, at 18 years. Although a tendency to lower terminal flow was seen in the girls, the differences were not statistically significant. Significant correlations between pulmonary function and the airway colonizator or genotype were not detected statistic. Conclusion: The evolution pattern of pulmonary function alterations found in these patients is consistent with those reported in the literature, where obstructive ventilatory disorders with early terminal flow reduction and late FVC onset predominate.

Keywords: Spirometry. Cystic fibrosis. Pulmonary ventilatory.