Does the mode of inhalation affect the bronchodilator response in patients with severe COPD?

Spacing devices improve lung deposition of aerosols from metered dose inhalers (MDI) but it is sometimes difficult for dyspnoeic patients to perform maximal breaths with breath-holds needed to inhale the aerosols from them. Our aim was to determine whether the response to bronchodilators (BD) depended on the method of inhalation. We studied 20 patients with moderately severe chronic obstructive pulmonary disease (COPD) with a mean age of 68 years and a mean of forced expiratory volume in 1 sec (FEV1) of 41% predicted. In a randomized, cross-over fashion they inhaled terbutaline 1.5 mg (six puffs) followed by ipratropium 120 mug (six puffs) via MDI and nebuhaler with either two inspirations to total lung capacity and a 10-sec breath-held per puff or with six tidal breaths per puff. Before and after BDs we measured FEV1, forced vital capacity (FVC), airways resistance using interrupter method (R-int) and 6-min walking distance (6MWD). Subsequently, we re-tested nine of these patients with the two methods of inhalation, before and after conventional doses (terbutaline 500 mug+ipratropium 40 mug), then after terbutaline 1 mg and ipratropium 80 mug and finally after nebulized terbutaline 5 mg and ipratropium 500 mug to see whether there was a dose-dependent difference in effect between the two methods. Spirometry, slow vital capacity (SVC), inspiratory capacity and shuttle walking tests were monitored. In the original 20 patients there were highly significant improvements in all parameters after inhalers, with no significant difference between methods of inhalation. Median improvements after BDs were: FEV1 0.221 and 0.191, FVC 0.501 and 0.381 and 6MWD 40 m and 44 m, for maximal breaths and tidal breathing, respectively. For nine patients, tidal and maximal breaths produced similar effects on lung function and exercise tolerance at both doses of BDs. Nebulized BDs only improved shuttle distances slightly when compared with either method of inhalation from MDI and spacer but had no additional effect on lung function. In conclusion, in patients with moderately severe COPD, BDs given by metered dose inhaler via nebuhaler have similar effects whether given by six easy tidal breaths or the more difficult two maximal breaths with breath-hold. This holds true at small or larger doses of ED. Either method of inhaling six puffs of the BDs call be used as an effective alternative to nebulized aerosol.