Metered dose inhaler add-on devices: Is the inhaled mass of drug dependenton the size of the infant?

Limited cooperation and low tidal volumes in infants make aerosol therapy d ifficult. We measured the amount of drug delivered from two baby spacer dev ices especially developed for use in infants. Designed as a randomized cros sover study, aerolized budesonide from a pressurized metered dose inhaler ( pMDI) was collected in the inspiratory filter interposed between the face m ask and the spacer in 13 infants aged from 2 to 19 months old. The study wa s performed in connection with pulmonary function testing with a plethysmog raph, and the children were sedated with cloral hydrate. Two small-volume b aby spacer devices were used: a Babyhaler(R) spacer (GlaxoWellcome, Hertfor dshire, UK) made of polycarbonate with a volume of 350 mt and a built-in de ad space of 40 mt and a NebuChamber(R) spacer (AstraZeneca, Lund, Sweden) m ade of stainless steel with a volume of 250 mt and no dead space. Budesonid e delivery from the NebuChamber was significantly higher than from the Baby haler: 38.2% (range, 28.3%-47.5%) of the nominal dose versus 12% (range, 3. 3%-21.25%) of the nominal dose of 400 mu g of budesonide (P = 0.002). The i nhaled mass of budesonide from the Babyhaler correlated significantly with skin surface area (r = 0.68, P = 0.018), weight (r = 0.66, P = 0.019), heig ht (r = 0.69; P - 0.017), tidal volume (r = 0.82; P = 0.004), and minute vo lume (r = 0.67; P = 0.019). No correlations were found between these variab les and the inhaled mass of budesonide from the NebuChamber. The results in dicate that the design of the NebuChamber spacer affords stable drug delive ry in infants and that a large variability in the inhaled mass of drug may be found when infants are inhaling from different baby spacers.