Development of an Orientation-independent Handheld Nebulizer

ABSTRACT

This work aims to develop and characterize a miniaturized handheld vibrating mesh nebulizer (MHVMN) that can be operated equally well in any orientation. The MHVMN developed and tested in the present study comprises a power supply-frequency generator unit, a vibrating mesh plate, and a liquid reservoir equipped with a flat end orifice tube (FEOT) or a traditional wick for liquid delivery. Since the study focused on optimizing the dimensions of the FEOT which is a unique application of capillary force for solution delivery, the operating parameters including gap between reservoir wall and FEOT (L_LR-FEOT), diameter of orifice on FEOT (D_orifice), nebulizer orientation, and aperture size were examined to investigate their effects on the performance of the MHVMN. The output rate and residual of a nebulizer were determined gravimetrically. An aerosol size spectrometer (Welas 3000) and a Micro orifice uniform deposit impactor (MOUDI) were employed to measure both aerosol concentration and mass distribution of the generated particles. The developed nebulizer was mainly evaluated with deionized water and 0.9% sodium chloride solution. The results showed that the L_LR-FEOT of 0.225 mm was the optimal design because of the output rate and residual were similar for different orientations. The D_orifice needed to be larger than 0.8 mm, to guarantee the continuity of nebulization, and residual less than 4%. The FEOT-based MHVMN had significant advantage over the wick-based one, for much lower residual, which was important when the drug or solution was precious. The most significant and unique feature of the optimized MHVMN was the performance almost orientation independent. This made it ideal for aerosol medications, especially for patients lying on bed.