Effects of long-acting bronchodilators and prednisolone on inspiratory lung function parameters in stable COPD

In chronic obstructive pulmonary disease (COPD), there is a poor correlation between forced expiratory volume in 1 s (FEV1) and dyspnea following bronchodilator use. Better correlations have been observed between inspiratory lung function parameters (ILPs) and dyspnea, which drives our interest in ILPs. However, the acute and prolonged effects of long-acting bronchodilators and oral corticosteroids on ILPs have not been well investigated. Therefore, the aim of this study was to investigate the effects of these treatments on the ILPs, FEV1, dyspnea (visual analog scale (VAS)) and clinical COPD questionnaire (CCQ).

Twenty-eight stable COPD patients had their ILPs and FEV1 measured both before and 2 h after the use of a single dose of 18 mcg bronchodilator tiotropium and 50 mcg salmeterol. Thereafter, the patients were randomized to 2 weeks of treatment with 30 mg oral prednisolone once daily or oral placebo in combination with daily treatment with these two bronchodilators. Four weeks after the cessation of the randomized treatment, the ILPs and FEV1 were again measured. After each intervention, any change in the VAS score was assessed.

With both bronchodilators, significant improvements in ILPs were demonstrated (p < 0.005), with the exception of changes in ILPs inspiratory capacity (IC) and forced inspiratory flow at 50% of the vital capacity (FIF50) after tiotropium inhalation. After 2 weeks of treatment with prednisolone, significant differences were found for ILP forced inspiratory volume in 1 s (FIV1) and FEV1 compared with placebo. These differences were no longer present 4 weeks after the cessation of prednisolone. Significant relationships between ILPs and VAS scores were only found after 2 weeks of treatment with prednisolone or placebo.

After a single dose of long-acting bronchodilator salmeterol, significant improvements are observed in all ILPs and in FIV1 and PIF after tiotropium. Two weeks of oral corticosteroid treatment improved the FIV1 and FEV1. The dyspnea VAS score was only significantly correlated with the ILPs after 2 weeks of oral corticosteroid treatment.