Effect of Humidity on Constant Output and Breath Enhanced Nebulizer Designs When Tested in the EN 13544-1 EC Standard

摘要

Aqueous aerosols produced by nenulizers used in clinical situations can rapidly chane size as the patient inhales.This is caused by air with a relatibe humidity (RH) lower than inside the nebulizer being entrained and mixed with nebulized aerosol during the inhalation maneuver.A way toassess the changte in size is to measure the aerosol in a test method that reflecs the clinical situation.The EC standard,EN 13544-1,offers a first step towards this step towars this assessment.In thi spaper we have tested two nebulizer designs,one conventional constant output neulizer and one breath-enhanced nebulizer,using th eproposed standard in order to assess the effect of the relative humidity of entrained amninet air on nebulized aerosol size properties.The results indicate that aerosol size from the conventional nebulizer is greatly affected by the RH of the entrained air,while the reath-enhanced nebulizer is not affected.The results agree with theoretical expectations of how the entrained air interacts with neulized aerosol.In the breath-enhanced nebulizer,the air is passed through the nebulizer interior and becomes saturated with moisture drawn from the relatively large nebulizer,ambient air is drawn over the nebulizer and draws its moisture from the relatively small volume of nebulized aerosol released from the nebulizer.For the conventioanl nebulizer design,we found a large decrease in measured nebulized aerosol size with decreasing relative humidity-3.1mum MMAD at 75 RH fell to 1.9 mum MMAD was stale between a similar humidity range.The results indicate that aerosol size is dependent on relative humidity of the entrained air for the constnat output jet nebulizer design that has no air entrainment through te nebulizer.We found no significant effect of amibent humidity of entrained air on nebulized aerosol size from the breath-enhanced nebulizer design.