Chest
Volume 111, Issue 5, May 1997, Pages 1200-1205
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Clinical Investigations: Nebulizers
Aerosol Delivery During Continuous Nebulization

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Background and objectives

Continuous administration of aerosolized β2-agonists has been suggested as an effective treatment for severe reversible airways disease. To facilitate continuous therapy and avoid a feed system for small-volume nebulizers (SVNs), a large-volume medication nebulizer (Vortran HEART) was developed. The goal of this study was to determine actual drug delivery of the HEART and conventional SVNs for both adult and pediatric breathing patterns.

Design

Output studies were conducted on comparable samples of CIS-US AeroTech II and Hospitak PowerMist SVNs and Vortran HEART large-volume continuous nebulizers. To duplicate clinical aerosol delivery via an aerosol mask, drug particles were inhaled through the mouth of a model of a human face for two test breathing patterns (adult=tidal volume (VT) of 500 mL, 20 breaths/min, duty cycle of 40%; pediatric=VT of 100 mL, 35 breaths/min, duty cycle of 40%), generated by a ventilator. Radiolabeled particles of saline solution, confirmed to behave identically to albuterol, were collected on absolute filters at the mouth of the face to measure the actual mass of albuterol particles delivered to the airway opening.

Results

The AeroTech II and PowerMist SVNs delivered 5.14 and 3.74 mg/h, respectively, for the adult breathing pattern and 2.97 and 2.48 mg/h, respectively, for the pediatric breathing pattern. Drug delivery rates of the HEART were a function of drug concentration and ranged from 0.87 to 3.48 mg/h for the adult breathing pattern. For the pediatric breathing pattern, drug delivery rate was a function of drug concentration and inspired minute ventilation and ranged from 0.41 to 1.83 mg/h.

Conclusion

Our data demonstrate that drug delivery to the patient, expressed as inhaled mass over time, is similar for continuous nebulization (HEART system) and intermittently filled SVNs. In addition, for all nebulizers, the influence of the pediatric breathing pattern needs to be considered. Continuous nebulization permits the redistribution of health-care personnel and may reduce the costs of therapy.

Section snippets

Selection of Nebulizers

Because our group has previously reported that disposable plastic nebulizers may vary significantly in output within the same manufacturing lot,10,11 we used the “standing cloud” technique12, 13, 14 to pretest 12 HEART, six AeroTech II (No. CA-1200A; CIS-US; Bedford, Mass), and six PowerMist nebulizers (No. 3759; Hospitak; Lindenhurst, NY), all from the same manufacturer’s lot, to determine their comparability and to enable selection of similar nebulizers for subsequent experiments. The

Output Studies (Albuterol Delivery)

The AeroTech II and PowerMist nebulizers nebulized a 3-mL charge in a mean time of 10 min. The HEART nebulizers with a 120-mL charge ran dry in a mean of 240 min in the adult breathing pattern and 270 min in the pediatric breathing pattern.

Table 1 summarizes the measured data. The two SVNs, AeroTech II and PowerMist, both emptied in 10 min and delivered an inhaled mass of 0.86 mg and 0.62 mg, respectively, for the adult breathing pattern. Significant differences were noted for the pediatric

DISCUSSION

Our studies, as summarized in Table 1 and Figure 4, demonstrate that, under conditions simulating patient therapy with both adult and pediatric breathing patterns, a wide range in aerosolized albuterol can be inhaled over time with different nebulizers. But, with some attention paid to the drug concentration in the nebulizer, similar quantities will be inhaled using all devices. Further, as shown in Figure 4 for the adult breathing pattern, the HEART CN approaches a typical SVN at its highest

ACKNOWLEDGMENT

Lorraine Morra, BS, performed the albuterol assay.

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    Supported by University Hospital Operational Grant 371318. The authors have no financial interest in any of the products or companies mentioned herein.

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