Abstract
In vitro T½ (aerosol) was less than 10 sec in a polycarbonate holding chamber compared to a T½ (aerosol) of longer than 30 sec in a steel holding chamber. A prototype holding chamber of 220 mL was cast in steel, and was equipped with a two-way low-resistance valve with a small dead space to ensure a rectified inspiratory flow from the spacer and expiratory flow outside the spacer. This prototype was tested against a traditional 750 mL polycarbonate single-valved holding chamber for the delivery of budesonide aerosol from P-MDI to children in the age-range of 0-7 years suspected of asthma. The polycarbonate was primed with benzalkonium chloride prior to use to avoid the confounding effect of the material. Both holding chambers were equipped with closely fitted face masks for children less than 48 months old. One hundred and sixty five children suspected of asthma, equally distributed as regards age from 0 to 7 years, inhaled one dose of budesonide from one of the holding chambers for 60 seconds. A filter was interposed between the holding chamber and the face mask adsorbing all particles delivered to the child. The mean dose fraction inhaled from the prototype approximated 38% irrespective of age, whereas the large-volume holding chamber exhibited a highly significant age-related decrease from approximately 44% in the older children down to 19% in infants. The difference in the doses of aerosol delivered was significant among children less than 3 years of age.
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