Respiratory patterns in spirometric tests of adolescents and adults with cystic fibrosis.

Objective: To evaluate spirometric patterns of respiratory disorders and their relationship with functional severity and maximal expiratory flows at low lung volumes in patients with cystic fibrosis (CF).

Methods: A retrospective cross-sectional study including adolescents and adults with CF. All of the patients were submitted to spirometry. Patients were classified as having preserved respiratory function, obstructive lung disease (OLD), OLD with reduced FVC, presumptive restrictive lung disease (RLD) or mixed obstructive and restrictive lung disease (MORLD). Maximal expiratory flows at low lung volumes were assessed using FEF(25-75%), FEF(75%) and FEF(75%)/FVC. We included 65 normal subjects, also submitted to spirometry, as a control group.

Results: The study group included 65 patients: 8 (12.3%) with preserved lung function; 18 (27.7%) with OLD; 24 (36.9%) with OLD and reduced FVC; 5 (7.7%) with presumptive RLD; and 10 (15.4%) with MORLD. The FEV1 was significantly lower in the OLD with reduced FVC group and the MORLD group than in the other groups (p < 0.001). In the patients with preserved respiratory function, FEF(25-75%) and FEF(75%) were significantly reduced in 1 patient, as was FEF(75%)/FVC in 2 patients.

Conclusions: The respiratory pattern was impaired in 88% of the patients with CF. The most common pattern was OLD with reduced FVC. The degree of functional impairment was greater in the OLD with reduced FVC group and in the MORLD group than in the other groups. Maximal expiratory flows at low lung volumes were impaired in a low percentage of patients with preserved respiratory function.