Abstract

Objective: Thoracic gas compression (TGC) has a negative effect on expiratory flow. In patients with chronic obstructive pulmonary disease (COPD), TGC is high. Bronchodilators may affect thoracic gas compression by reducing airway resistance and improve maximal expiratory flow. The aim of this study was to investigate the effects of long-acting bronchodilators (formoterol 12 μg and tiotropium 18 μg) on thoracic gas compression, forced expiratory volumes measured at the mouth and in a plethysmograph in patients with COPD.

Material and Method: Bronchodilator response to formoterol and tiotropium was assessed in 40 COPD patients using maximum expiratory flow-volume curve values measured at the mouth (m) and plethysmograph (p). Volume of compression (V Comp= ΔV lung - ΔV mouth) was obtained.

Results: The repeated measurements were performed at baseline, 30., 60. and 120. minutes. Formoterol and tiotropium had significant bronchodilator effects, and formoterol produced a higher increase in FEV1 m (p<0,001) compared to tiotropium. Thoracic gas compression volumes did not change significantly after either long-acting bronchodilator administration in patients with COPD. With regard to thoracic gas compression volume at 25, 50 and 75 % of VC (Vcomp25, Vcomp50, Vcomp75, no relevant difference was found between the two drugs. The thoracic gas compression volumes did not differ between stage II–III and stage IV COPD patients.

Conclusion: The results of this study suggest that thoracic gas compression volume did not change significantly after administration of long-acting bronchodilators, even if both study drugs elicited significant bronchodilation in spirometric measurements, and the disease severity did not influence the effect of the long acting bronchodilator agents on thoracic gas compression volumes.