Responsiveness to bronchodilator procaterol in COPD as assessed by forced oscillation technique

The aim of this retrospective study was to assess responses to a bronchodilator by forced oscillation technique (FOT) and to relate the results of respiratory impedance (Zrs) to spirometric parameters in patients with chronic obstructive pulmonary disease (COPD). Zrs was measured as a function of frequency from 4 to 36 Hz before and after inhalation of procaterol, a short-acting β2-agonist (n = 60). Respiratory resistance (Rrs) and reactance (Xrs) were significantly frequency-dependent, and inspiratory and expiratory phases were different both before and after procaterol inhalation. The Rrs at 4 Hz and Xrs at 4-20 Hz during a whole breath were significantly improved after procaterol inhalation. The response to procaterol inhalation varied among patients, and changes in Xrs at 4 Hz significantly correlated with% change in forced expiratory volume in one second and changes in forced vital capacity. Taken together, Zrs, and specifically Xrs parameters, are sensitive to acute physiological responses to a bronchodilator in COPD.