The aim of the present study was to compare the output of a breath-synchronized jet nebulizer to a conventional constant output nebulizer over a fixed period of time in terms of inhaled mass of budesonide, i.e., the amount of budesonide deposited on a filter interposed between the nebulizer and the face mask. One hundred and sixty-five asthmatic children (103 boys) were enrolled in this open, randomized, crossover trial. Their age ranged from 6 months to 7.9 years, height from 69 to 132 cm, and weight from 8.2 to 31.3 kg. Their duration of asthma ranged from less than 1 to 7 years. Budesonide suspension, 0.5 mg mL−1, 2 mL, was used. With 5 min of constant output nebulization, the mean inhaled mass of budesonide in percent of the nominal dose was 11.4% in the youngest children and 14.9% in the 7-year-old children. Expressed in percent of the total output of budesonide, i.e., the amount that left the nebulizer as an aerosol, the inhaled mass ranged from 34.6–48.6%. Thus, 51.4–65.4% of the total output was deposited on the expiratory filter. With 5 min of breath-synchronized nebulization, the mean inhaled mass ranged from 10.5–14.9% of the nominal dose. For the youngest patients less than 3–4 years of age, it was approximately 80–90% of the total output. For the older patients the inhaled mass was approximately 95% of the total output, i.e., only small amounts of budesonide were deposited on the expiratory filter. For both modes of nebulization the between-subject variation in inhaled mass was large: up to 6-fold in the young children, and 3–4-fold in the older ones
1. Inhaled Mass
There was no statistically significant difference between the inhaled masses generated by the two modes of nebulization (Fig.1a,b). The mean inhaled mass for each age class indicated age dependency for both modes of nebulization (Table 1). The plot of the individual inhaled mass of budesonide in percent of the nominal dose against the age of the patients showed statistically significant relationships between inhaled mass and age for both modes of nebulization (P < 0.01, Fig. 1a,b).
2. Inhaled Mass in Percent of Total Output The inhaled mass of budesonide in percent of the total output of budesonide, plotted against the age of the patient, reflects how effectively the nebulizer system was used by the patients. When using the nebulizer in COmode, the mean inhaled mass of budesonide in percent of the total ouput was 34.6% (SD 7.6, range 22.1–48.0) in the children below 1 year of age, and 48.6% (7.4, 36.8– 62.3) in the 7-year-old children (Fig. 2. Thus, 51.4– 65.4% of the total output was deposited on the expiratory filter. The correlation coefficient was 0.48, with confidence intervals 0.36 and 0.59. Nebulization in BS-mode showed (Fig. 2)
The inhaled mass of budesonide in percent of the total output of budesonide plotted against the age of the patients for both modes of nebulization.
The results of the present study showed that the inhaled mass of budesonide was significantly age-dependent with both modes of nebulization, i.e., the inhaled mass was less in younger children. Breath-synchronized nebulization resulted in reduced waste of drug during expiration.