Study objectives: The aim of the present study was to evaluate the forced oscillation technique (FOT) in cystic fibrosis (CF) children and to participate in the discussion about the usefulness of β2-antagonists in CF.
Design: Pulmonary function was measured with spirometry, body plethysmography, and FOT before and after inhalation of 200 µg of albuterol (salbutamol). The following were collected: vital capacity (VC), FEV1, FEV1/VC, airway resistance (Raw), thoracic gas volume, respiratory system resistance (Rrs) and respiratory system reactance (Xrs) at 6 Hz (Rrs6 and Xrs6), and resonance frequency.
Setting: The study was set up at a university hospital with a CF population of 125 children and adolescents.
Patients: Data were collected on 20 patients in stable condition able to perform the three lung function tests.
Measurements and results: Mean baseline values (±SD) were 0.36±0.15 kPa/L/s for Raw, 0.5±0.15 kPa/L/s for Rrs6, and 61±22% predicted for FEV1. The relationship between FEV1 and Raw or Rrs6 was poor. Xrs6 and FEV1/VC correlated weakly (r=0.56; p<0.05). After bronchodilator administration, the mean changes ±SD in percent of baseline were +3±11% for FEV1, −16±22% for Raw, and −16±9% for Rrs6. In six patients, a paradoxical decrease in FEV1 was measured but an increase in Rrs6 was never found; in two patients, an increase of Raw of <10% was found. In 13 patients, the decrease of Rrs6 was >12%.
Conclusions: The results suggest that FOT measurements cannot replace baseline spirometric measurements in CF, but that the evaluation of the effect of β2-agonists on the airway diameter in CF should include an FOT measurement.