Conference Proceedings
December 2002 / Volume 47 / Number 12 / Page 1406
Nebulizers That Use a Vibrating Mesh or Plate with Multiple Apertures to Generate Aerosol
IntroductionSeveral electronic nebulizer devices that use a vibrating mesh or plate with multiple apertures to generate a fine-particle, low-velocity aerosol have been marketed or will shortly become available for clinical use. These devices have a high efficiency of delivering aerosol to the lung, such that the nominal dose of drugs to be administered could be substantially reduced. Moreover, the volume of drug solution left in these new devices when the nebulization has ceased is negligible, so there is potential to improve the cost-effectiveness of administering expensive medications. Because these devices nebulize at a faster rate than conventional jet or ultrasonic nebulizers, the duration of each treatment could be shortened. These devices efficiently nebulize solutions and suspensions; they have been successfully used for aerosolizing insulin, other proteins and peptides, and fragments of DNA. They could be employed for a wide variety of clinical applications, including the delivery of aerosols for systemic therapy and gene transfer. These devices have overcome many of the limitations associated with conventional jet and ultrasonic nebulizers, and they offer the versatility to modify the aerosol characteristics according to the clinical application for which they are employed. With these devices clinicians will be able to precisely control drug delivery to the respiratory tract.
Design Features of Aerosol Generators That Use a Vibrating Mesh
or Plate with Multiple Apertures to Generate Aerosol
Aerogen's Aerosol Generator
Omron's Vibrating Mesh Technology
ODEM's TouchSpray Technology
Characteristics of Devices
Aerogen Devices
Omron Devices
ODEM TouchSpray Inhaler Devices
PARI eFlow
Comparison of Vibrating Mesh/Plate Devices and Conventional Jet
and Ultrasonic Nebulizers
In Vitro Comparisons of Efficiency in Aerosolizing Solutions
In Vitro Comparisons of Efficiency in Aerosolizing Suspensions
Scintigraphic Evaluation of Pulmonary Deposition of Aerosol
Clinical Evaluation of Devices
Aerosolization of Insulin
Aerosolization of Deoxyribonucleic Acid
Limitations/Drawbacks of Vibrating Plate/Mesh Devices
Summary
Introduction
Nebulizers convert liquids into aerosol particles for deposition in the lower respiratory tract. A pneumatic (jet) nebulizer uses the energy provided by compressed gas flow to generate an aerosol, whereas an ultrasonic nebulizer uses electricity to vibrate a piezoelectric crystal at high frequency. Standing waves are generated when the high-frequency vibrations are focused onto the surface of the medication solution. Liquid droplets break off from the wave crest to form an aerosol.
For several decades nebulizers have been employed to deliver medications via inhalation. Indications for aerosol therapy, however, are rapidly expanding. In the not-so-distant future, aerosols could be used to deliver drugs to the respiratory tract for systemic effects and to deliver genes to the respiratory tract. There is a need for better technology to improve the efficiency, precision, and consistency of aerosol deposition in the lung, to use new formulations, and to allow efficient aerosolization of suspensions and drugs with high lipid solubility. In addition, there needs to be a concerted effort to protect respiratory therapists and other health care workers from occupational exposure to aerosolized drugs.
This review discusses several new devices that have in common the ability to aerosolize a drug solution by using a vibrating mesh or plate with multiple apertures. These devices offer important advances in our ability to deliver aerosolized drugs to the respiratory tract.