Topical delivery of nebulizedantibiotics to the paranasal sinuses has been shown to improve clinicaloutcomes in patients with chronic sinus disease after functional endoscopicsinus surgery (FESS). This is according to a study on the differential deposition ofaerosols in the maxillary sinus of human cadavers by particle sizeposted on the American Journal of Rhinology. The study also stated that themost efficient method for delivering nebulized particles, to the sinuses,however, has not been established.

Inhaled pharmaceutical aerosols(IPAs) are one type of the more common methods for delivering medication to thesinuses. Scientists and engineers must cope with several factors that makedesigning an IPA device quite difficult. Some of these challenges are asfollows:

• Producing such small particles - it is not easy to produce drug particles that have a mass between 1 and 100 trillionths of a gram in a device that can be carried around conveniently. Even if a process is developed for one particular drug, it may work differently for a different drug. The research and development process must be revisited for each drug under consideration, a time-consuming and labor intensive process.
• Everyone inhales differently. The speed of the air that an IPA is exposed to is different for everyone. That is why for example, for certain dry powder inhalers, this requires trying to design the powder so that people inhaling either slowly or quickly can both inhale similar amounts of powder from the device. Inhaled air speed can also affect where particles deposit in the respiratory tract.
• Differences in the geometry of people's mouth-throat airway passages - Some people have sudden bends that cause particles to deposit in the mouth-throat. Others have a relatively "smooth" mouth-throat passage, causing less mouth-throat deposition. This can cause variability in the dose reaching the lung or sinuses among various patients.
• Differing effects of device mouthpieces on mouth-throat geometry and their effect on the fluid mechanics in the mouth-throat - Small diameter mouthpieces that have been commonly used in the past have been shown to cause high mouth-throat deposition due to a high speed jet of air impacting in the mouth. There are also differences in the lung geometry between individuals.
• Humidity - For medication carried by inhaled water droplets (such as those produced by nebulizers), the humidity of the air being inhaled can cause differing amounts of droplet evaporation and also give rise to variations in where the drug deposits in the lung. In fact, evaporation of nebulized aerosols leads to one of the most commonly made mistakes when measuring nebulized aerosols with a measurement device called a cascade impactor. Users unfamiliar with nebulized aerosols often mistakenly mix the nebulized aerosol with room air during sizing, or else allow the nebulized aerosol to be warmed to room temperature inside the cascade impactor, both of which can lead to significant undersizing of the aerosol (and incorrect assumptions regarding where in the lung the aerosol will deposit).

These are just a few of thechallenges that need to be considered with IPAs. Much research goes intoovercoming these, as well as other challenges not mentioned here. The AerosolResearch Laboratory of Alberta is one of several laboratories that is helpingto explore this interesting and important area.

To read the complete study on DifferentialDeposition of Aerosols in the Maxillary Sinus, please refer to .

To learn more about inhaledmedication for sinusitis, please click here: .