Large and Small Airway Responses to Procaterol Hydrochloride Administered Through Different Extension Devices in Asthmatic Patients

Abstract

ABSTRACT

The effects of spacer devices on the magnitude and velocity of large and small airway bronchodilator responses in asthmatic patients who can correctly operate a metered dose inhaler (MDI) remain unclear. According to a double-blinded, randomized, crossover protocol, 14 asthmatic patients were studied on seven separate occasions. On each occasion, patients inhaled doubling methacholine concentrations until forced expiratory volume in 1 second (FEV₁) had fallen by 20% of baseline. Changes in forced expiratory flow between 25% and 75% of vital capacity (FEF_25–75) were also evaluated. Subsequently, patients were administered 20 or 50 μg of procaterol from an MDI either alone or in conjunction with a small- or large-volume spacer device. Changes in FEV₁ and FEF_25–75 corrected for baseline forced vital capacity (isoFEF_25–75) were assessed at 3-minute intervals for 15 minutes and at 30 minutes. Spontaneous recovery was similarly evaluated. The time required to attain significant increases in both FEV₁ and isoFEF_25–75 was calculated in bronchodilator trials. With 20 μg of procaterol, both spacers allowed larger and faster FEV₁ increases than the MDI alone (P < 0.01); with 50 μg, the velocity and magnitude of FEV₁ increases were further enhanced in trials with the MDI alone. The lower procaterol dose via the large-volume spacer determined larger and faster isoFEF_25–75 increases than the higher dose via both the small-volume spacer and the MDI alone (P < 0.01). Spacers enhance bronchodilation even in patients using MDIs optimally. Compared with both the small-volume device and the MDI alone, the large-volume spacer allows faster and larger small airway dilation with less than half of the procaterol dose.