Particle Size Distribution for Jet Nebulizers Commonly Employed in the Pediatric Clinical Setting

Influence of formulation on jet nebulisation quality of alpha 1 protease inhibitor

As foam appears during solution constitution and nebulisation of alpha 1 protease inhibitor (alpha 1 PI), we selected in a previous work, antifoams likely to be associated with an alpha 1 PI solution to be nebulised: span 65 at a 0.025% concentration and cetyl alcohol at a 0.05% concentration associated with tyloxapol at 0.025% concentration. The purpose of this study was, on the one hand to study the influence of the formulation on nebulisation quality by relating physicochemical properties and nebulisation capacity, and on the other hand, to define the alpha 1 PI that will be retained for a clinical study. The properties of the different alpha 1 PI formulations are compared: surface tension, viscosity, time required to constitute the protein solution and pH. Nebulisation quality is evaluated under different operating conditions by measuring the droplet size, the quantity of alpha 1 PI nebulised, nebulisation time and the quantity of alpha 1 PI likely to reach the lungs which was subjected to statistical analysis. The statistical analysis of results indicates that the addition of the cetyl alcohol/tyloxapol mixture improves nebulisation effectiveness by significantly increasing the quantity of drug nebulised and therefore the quantity of alpha PI likely to reach the lungs. It is this formulation that will be retained for clinical trials. We check that the nebuliser and operating conditions influence all the parameters, that is to say the respirable fraction, the quantity nebulised and the nebulisation time. Although there is no interaction between the nebuliser and the formulation, nebulisation quality is the combined result of the formulation, the nebuliser and the operating conditions.

Aerosol deposition in infants with cystic fibrosis

Twenty asymptomatic infants with cystic fibrosis (CF) were studied to determine the amount of radiolabeled aerosol [99m technetium diethylenetriamine penta acetic acid (Tc99m DTPA)] deposited in the respiratory system and its distribution. Aerosols were generated by jet nebulization systems that were used in the wards and the laboratory. Subjects were studied in three groups: group A (n = 10) was sedated with chloral hydrate; children inhaled an aerosol of 7.7 microns mass median diameter (MMD); group B (n = 5) was not sedated, using the same nebulization system (same aerosol particle size as group A); and group C (n = 5) was not sedated; these children inhaled an aerosol with an MMD of 3.6 microns. Normal saline plus 4 mCi of Tc99m bound to DTPA was added to each nebulizer. A closed system was used to collect the expired aerosol. Radioactivity in each infant and in the equipment was measured with a gamma camera on completion of nebulization. In groups A and B, the percentages of the total dose deposited in the lung were 0.97 +/- 0.35% and 0.76 +/- 0.36%, respectively. In group C, 2.0 +/- 0.71% was deposited in the lung (P < 0.01). Deposition in the nose, mouth, and pharynx was least in group C (P < 0.01). In groups A and B, the intrathoracic deposition occurred predominantly in the trachea and main bronchi, whereas in group C, significantly more aerosol was deposited in the lung region. There was marked inter-subject variability in the percentage of aerosol deposition within the three groups. There was no correlation between percentage of aerosol deposited in the respiratory system and age, height, or weight. Sedation did not have a significant effect on deposition of aerosol in infants. This study indicates that only a small proportion of nebulized solution is deposited in the lungs of infants and that this proportion is influenced by the particle size of the aerosol. The smaller particle size (3.6 microns MMD) was deposited in the lung better than large particles.