Developing A Total Consumption Inhaler

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Asthma and COPD (chronic obstructive pulmonary disease) are among the most occurring respiratory diseases, which present a significant public health burden to the global healthcare system. About 11% of Canadians suffer from respiratory diseases. Inhalers are a common drug delivery method for all respiratory problems. Many inhalers use a nebulizer to convert a solution type drug to an aerosol of droplets, which is inhaled by the patient. To successfully reach the patient's lungs, the aerosol droplet sizes should be less than 5 microns. Droplets larger than 5 microns are collected in the mouth and the upper respiratory tree. The currently available nebulizers generate a wide range of droplet sizes, usually between 1-30 microns, with 80-90% of the drug mass belonging to droplets with larger than 5 microns. Therefore, 80-90% of the drug is wasted. Since most medicines are costly, it is desired to have a nebulizer that every one of its droplets are used. In addition, when most of the medicine is lost in the mouth, the patient never knows if the right dosage is used. The objective of the present proposed research is to develop a nebulizer/inhaler that all of its droplets are less than 5 microns. This nebulizer would effectively transfer liquid medicine into a patient's lungs, ensuring proper dosage of medicine with minimal waste. The proposed inhaler would operate based on ultrasonic atomization of a small sessile droplet. A small liquid mass in the form of a sessile droplet is set on the surface of a piezoelectric transducer, and it is vibrated at Megahertz frequency ranges. Our preliminary results have shown that when the size of the sessile droplet goes below about 500 microns, small 2-5 micron droplets eject from its surface. We refer to this as a total consumption nebulizer since all the medicine that is generated is inhaled and used for the treatment of the patient. Before this concept is reduced to practice, we need to understand why it works and what are its limitations. Therefore, we propose a fundamental study of the ultrasonic atomization of a small (0.3-1 mm) sessile droplet, set on different types of surfaces (different coatings to change the surface contact angles) and vibrated at different frequencies (1-100 MHz). In addition, effect of liquid properties, including using rheological fluids of the type used in inhalers, as well as solutions containing particles (slurries) will be tested. The atomization process will also be studied theoretically (computationally) to reveal the physics involved in this process, and test out hypothesis for the formation of such small droplet. We plan to have two students on this project. One performing the experiments, and one on the theory. The proposed budget for this project is $73k a year, which will include the cost of two PhD students and the experimental tests.