Effect of bronchodilatation on single breath pulmonary uptake of carbon monoxide in chronic obstructive pulmonary disease

Simonetta Baldi¹, Claudio Fracchia¹, Claudio Bruschi¹, Roberto Dore², Roberto Maestri¹, Vito Brusasco³, Riccardo Pellegrino⁴

¹U.O di Riabilitazione Specialistica Pneumologia Riabilitativa, Istituto Scientifico di Montescano, Fondazione Salvatore Maugeri IRCCS, 27040 Montescano, Pavia; ²Istituto di Radiologia Medica, Policlinico S. Matteo IRCCS, 27100, Pavia; ³Dipartimento di Medicina Interna, Università di Genova, 16132 Genova; ⁴Centro di Fisiopatologia Respiratoria e di Studio della Dispnea, Azienda Ospedaliera S.Croce e Carle, 12100 Cuneo; Italy

Abstract: We studied 21 COPD patients in stable clinical conditions to evaluate whether changes in lung function induced by cumulative doses of salbutamol alter diffusing capacity for carbon monoxide (DL_CO), and whether this relates to the extent of emphysema as assessed by high resolution computed tomography (HRCT) quantitative analysis. Spirometry and DL_CO were measured before and after cumulative doses of inhaled salbutamol (from 200 µg to 1000 µg). Salbutamol caused significant increments of forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), and flows at 30% of control FVC taken from both partial and maximal forced expiratory maneuvers. Functional residual capacity and residual volume were reduced, while total lung capacity did not change significantly. DL_CO increased progressively with the incremental doses of salbutamol, but this became significant only at the highest dose (1000 µg) and was independent of the extent of emphysema, as assessed by radiological parameters. No significant changes were observed in CO transfer factor (DLCO/VA) and alveolar volume (VA). The results suggest that changes in lung function induced by cumulative doses of inhaled salbutamol are associated with a slight but significant increase in DL_CO irrespective of the presence and extent of emphysema.

Keywords: lung volumes, high resolution computed tomography, chronic obstructive bronchitis, emphysema