IN-VITRO PERFORMANCE TESTING OF 3 SMALL VOLUME-HOLDING CHAMBERS UNDERCONDITIONS THAT CORRESPOND WITH USE BY INFANTS AND SMALL CHILDREN

The in vitro behavior of three types of small volume-holding chambers intended for use by infants and small children (child AeroChamber(R), Vent-170 and Space Chamber(TM)) has been compared with two pMDI-delive red aerosol formulations (salbutamol: 100 mu g unit dose and beclometh asone di-propionate (BDP): 50 mu g unit dose) widely prescribed for th is age group of patients. All devices were evaluated using a pediatric breathing simulator that created respiratory conditions likely to be encountered with infants and small children. The filter that collected aerosol delivered from the holding chamber on test was located at app roximately the position that the patient's lips would be in the mask, by means of an annular support plate glued into the mask itself. At th e lowest tidal volume (50 mi), no salbutamol or BDP was delivered by e ither the Vent-170 or Space Chamber(TM), whereas the unit doses from t he child AeroChamber(R) were 39.7 +/- 1.6 mu g and 11.8 +/- 1.2 mu g, respectively. The Vent-170 and Space Chamber(TM) delivered measurable doses of both drugs when the tidal volume was increased to 100 mi and again to 200 mi, however, the corresponding doses available from the A eroChamber(R) were always significantly greater. These findings emphas ize the importance of designing in vitro tests that mimic use by the p atient group for which the device is intended. In vitro measurements m ade at constant high flow rates in excess of 20 l/min do not reveal th ese differences in performance that are clinically significant, and ma y lead the physician to prescribe a device that under certain conditio ns may not deliver any drug to infants or small children.