The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

CAN A “HOLDING CHAMBER”IMPROVE NEBULIZER PERFORMANCE?

Michael McPeck BS RRT FAARC, Glenn Samford CNMT, Ross Potter CNMT and Russell King. Healthline Aerosol Medicine, Baldwin Park CA.

BACKGROUND: Holding chambers (HC) are now commonly used to increase the aerosol delivery performance of metered-dose inhalers (MDIs). One of the benefits conferred by using a HC is that it briefly stores aerosol and allows it to be inhaled on a subsequent breath. Similarly, the Healthline Medicator® Aerosol Maximizer is claimed to act like a HC for small volume medication nebulizers (SVNs). It uses a special manifold, unidirectional flow control valve and 1 L latex-free reservoir bag that stores most of the aerosol generated during the patient’s exhalation phase, which would otherwise be wasted, and allows it to be inhaled by the patient on the subsequent breath. We sought to determine whether the Medicator® increases aerosol delivery of various SVNs and, if so, by how much.

METHODS:
We tested 9 different models of plastic disposable jet SVNs that were available to us in our facility. Each SVN was loaded with ~3.2 mL of radiolabeled (99mTc) 0.083% unit-dose albuterol and run at 7 L/min with oxygen. A sine wave ventilator produced a simulated adult breathing pattern (VT = 600 mL; f = 12 BPM, I:E = 1:2) that was used to draw aerosol into a HEPA filter representing the mouth. SVNs were tested on both a Tee setup and when attached to the Medicator® manifold. Each SVN was run until it stopped producing aerosol (~ 9 mins). The SVNs and HEPA filters were measured in a radioisotope counter and the Inhaled Mass (IM) fraction (radioactivity on filter / radioactivity of initial nebulizer charge) was determined.

RESULTS:
The IM for the 9 SVNs varied from 7.3 to 14.8% (mean ±SD = 11.1 ±2.7%) on the Tee and from 20.3 to 34.1% (mean ±SD = 26.4 ±5.2%) on the Medicator® (the t-statistic was significant at the .025 critical level, p = .0000 by matched-pairs t-test).



DISCUSSION:
Bench studies of aerosol device performance in vitro are used to predict performance in vivo. In this study, we have shown in vitro that the Medicator® Aerosol Maximizer increases the delivery of aerosol to the mouth by an average of 2.4 times that of SVNs on conventional Tees.

CONCLUSION
: Because the Medicator® avoids aerosol waste by storing aerosol generated during exhalation in a 1 L reservoir bag (“holding chamber”) and returns it to the patient on the subsequent inhalation, this appears to significantly enhance the performance of a variety of typical SVNs much in the same way that a HC improves the performance of an MDI. However, in vivo confirmation of these predictive findings from the test bench is warranted.