Efficiency evaluation of nebulizers for inhalation therapy

Three types of aerosol nebulizers used in clinical practice, a jet type (JT), and IPPB (Bennett PR-2) and an ultrasonic nebulizer (Mistogen EN 142) (US) were studied regarding aerosol size distribution, efficiency in aerosol output, efficiency in lung deposition and deposition patterns in the lungs. The JT was operated both manually and mechanically. Tc-99m-albumin solution was the agent for aerosol generation. Aerosol size was measured by a cascade impactor, efficiency by measuring radioactivity in the lungs and nebulizers and deposition patterns by visual comparison. Mass median diameter (MMD) was the largest (4.18 μ) with its geometric standard deviation of 1.76 with the US, and the other nebulizers showed smaller MMD (2.00 - 2.35 μ) and broader geometric standard deviations. Aerosol output was 4 times more efficient with the US than with the others. Lung deposition was 8 times more efficient with the US, 7 times with the mechanically operated JT, and 6 times with the IPPB than the manually operated JT. Overall aerosol deposition in the lungs was the most efficient with the US, but the IPPB showed better penetration in normal subjects and patients with the least obstructive disturbance. Manually operated JT tended to produce the so-called central deposition pattern even in normal subjects. In conclusion, of the three nebulizers tested, the MMD of aerosol generated was the largest with the US, and the US was the most efficient in aerosol output and lung deposition. (author)