Drug output from nebulizers is dependent on the method of measurement

The objective of this study was to determine whether current regulatory methods for assessing the output of nebulizers are appropriate for the delivery of nebulized steroid suspensions to patients. We studied a conventional jet nebulizer (the Intersurgical Cirrus), an open-vent nebulizer (the Medicaid Sidestream) and a breath enhanced nebulizer (the Pari LC Plus), using a constant sampling flow or a sinusoidal pump to represent the breathing pattern of children from 6 months to adulthood. Recovery of budesonide released from the nebulizers onto filters was reduced when using breathing simulation compared with constant flow, and this reduction was greatest for the conventional nebulizer (Cirrus, 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 little 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 laden air was greater than the inspiratory how from the breathing simulator. 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 output varied by up to 700%,depending on the method used. These results suggest that breathing patterns dramatically alter the measured output of different nebulizers and that breathing simulation should be included as part of their assessment.