Variability of aerosol delivery via spacer devices in young asthmatic children in daily life

Pressurized metered dose inhalers (pMDI) are widely used together with spac ers for the treatment of asthma in children, However, the variability of da ily medication dose for pMDI/spacer combinations is not known. Electrostati c charge is a potential source of dose variability. Metal spacers have no s tatic charge, This study assessed and compared within-subject variability o f aerosol delivery of metal and plastic spacers, This was a randomized, cro ssover study in children with stable asthma aged 1-4 (group I, n=17) and 5- 8 (group II, n=16) yrs, In both groups the amount of drug delivered to the mouth by a metal spacer (Nebuchamber(R)) and one of two plastic (polycarbon ate) spacers, i.e. Babyhaler(R) in group I and Volumatici(R) in group II wa s measured, The metal and plastic spacers mere tested at home in a randomiz ed order for 7 days each, using budesonide (200 mu g b.i.d.). Aerosol was c ollected on a filter positioned between spacer and facemask or mouth. Budes onide on the filter was assessed by high performance liquid chromatography. The mean filter dose for each child (mean+/-SD) during the 7 days was expr essed as a percentage of the nominal dose. Within-subject variability was e xpressed as coefficient of variation (CV). Mean filter dose in group I was 41.7+/-10.1% for Nebuchamber and 26.0+/-4.0 % for Babyhaler (p<0.001), Mean filter dose in group II was 50.2+/-9.2% for Nebuchamber and 19.4+/-7.2% for Volumatic (p<0.001). Mean CV in group I wa s 34% for Nebuchamber and 37% for Babyhaler (p=0.44), Mean CV in group II w as 23% for Nebuchamber and 34% for Volumatic (p=0.003), There was substantial within-subject dose variability in aerosol delivery i n children using a pMDI/spacer at home. This variability was lower for the metal than for the plastic spacer in children 5-8 yrs of age, The dose deli vered to the mouth was about two-fold higher for the metal than the plastic spacer independent of age.