DRUG OUTPUT FROM NEBULIZERS IS DEPENDENT ON THE METHOD OF MEASUREMENT

The objective of this study was to determine whether current regulator y methods for assessing the output of nebulizers are appropriate for t he delivery of nebulized steroid suspensions to patients. We studied a conventional jet nebulizer (the Intersurgical Cirrus), an open-vent n ebulizer (the Medicaid Sidestream) and a breath enhanced nebulizer (th e Pari LC Plus), using a constant sampling flow or a sinusoidal pump t o represent the breathing pattern of children from 6 months to adultho od. Recovery of budesonide released from the nebulizers onto filters w as reduced when using breathing simulation compared with constant flow , and this reduction was greatest for the conventional nebulizer (Cirr us, 103 mu g with constant flow to 4.4 mu g with a 50 mL tidal volume; Pari, 176 mu g to 25 mu g). The open-vent nebulizer deposited very li ttle budesonide on the filter at lower tidal volumes (4.5 mu g with a 50 mL tidal volume), possibly because the enhanced flow of aerosol lad en air was greater than the inspiratory how from the breathing simulat or. The output of the LC plus was reduced at high flow, from 176 mu g at 20 L.min(-1) to 93 mu g at 60 L.min(-1). Overall, the measured outp ut varied by up to 700%,depending on the method used. These results su ggest that breathing patterns dramatically alter the measured output o f different nebulizers and that breathing simulation should be include d as part of their assessment.