Vol. 20 •Issue 5 • Page 21
Trends in Nebulizers
Greet the New Wave of Aerosol Delivery Devices on the Market
When technophiles carried home the first iPods in 2001, they were thrilled by their ability to carry 1,000 songs right in their pocket. Less savvy music fans stayed true to vinyl and CDs—at first anyway.
Now, fifth generation iPods are smaller, play videos and store far more songs than older versions. The recently unveiled iPhone combines all of those capabilities with mobile phone and wireless access technology. Even traditional music fans have flocked to the new formats, uploading their whole music collection to a device the size of a pack of cigarettes.
Nebulizers may not have the appeal of iPods or be able to phone home yet, but they have progressed just as dramatically over the past several years. And novel designs ensure the future will see the technology leap forward even more.
After all, aerosol therapy remains an important method of drug delivery, providing a direct application of medication to patients’ airways with a high therapeutic index and low side effects. Like iPods, nebulizers rock.
But let’s face it: Traditional jet nebulizers could be much more efficient. Only about 10 percent of the medication they deliver makes it into the patient’s lower respiratory tract on average. Effectiveness depends on the patient’s technique and device, and the actual dose delivered varies widely, according to Dean R. Hess, PhD, RRT, who spoke at the AARC International Congress in December about improving aerosol therapy and offering glimpses of new designs under development.
“Newer, novel nebulizers are, by and large, designed to decrease the amount of drug lost during exhalation, decrease the amount of dead volume and have a more precise control over the size of the particles which are generated,” said Hess, this year’s Jimmy A. Young medal winner.
Nebulizers will increasingly become dosimetric, delivering a metered dose of drug and releasing the aerosol only during the inspiratory phase. As a result, dose precision will be much improved. “This may allow delivery of increased drug concentrations and shorter treatment time,” he said.
As far as jet nebulizers are concerned, there are two approaches to improving this long-established drug delivery method. The breath-enhanced nebulizer increases the output of drug during inhalation and decreases loss during exhalation. Breath-actuated nebulizers, on the other hand, turn on only when the patient breathes in and shut off when the patient breathes out. “This should reduce the amount of aerosol lost during exhalation to zero,” he explained.
Then there are novel nebulizers which don’t use the jet technology at all. One utilizes a new ultrasonic innovation called focal point technology. A concave electric element drives the drug particles while a chimney-like design separates large and small particles, improving the particle size delivered to the patient.
In another design arena, several manufacturers have turned to using vibrating mesh technology. Essentially their devices use a membrane or mesh with small holes. The solution is placed on one side and the membrane vibrates, directing the solution through the membrane’s holes and into the patient’s respiratory system. The size of the holes can be changed to offer some control over the size of particles.
Vibrating mesh models have virtually no dead volume, require no external gas flow and offer flexibility for different therapeutic applications through their adjustable hole sizes. “These devices require no hand/lung coordination or special technique,” Hess said.
Another model, an adaptive aerosol delivery system, employs vibrating mesh technology but matches drug delivery to the breathing pattern of the patient. Essentially it pulses aerosol at the very beginning of inhalation, front-loading the dose. This action increases the likelihood of the drug being delivered deep into the respiratory tract.
Finally, Hess previewed a device designed to administer aerosols via catheter directly into the trachea of patients on mechanical ventilation. It offers breath-actuated delivery, reducing the amount of drug lost in the circuit.
“It requires relatively high head pressure in order to push the solution through the catheter,” he noted of the device not yet approved for human use. “There is also the potential that it could cause coughing—and this is something that will need to be worked out.”
Despite the wide range of new designs moving toward the market, Hess believes the technologies will eventually merge into a single, universal device for aerosol delivery.
There is, likewise, another possible trend to watch. As new drugs become available, they may be married to specific nebulizers as part of a kit. “They will be approved by the FDA as a package.”
Shawn Proctor, associate editor and Web editor, can be reached at [email protected].