The Science Journal of the American Association for Respiratory Care

1997 OPEN FORUM Abstracts

COMPARISON OF THE MINISPACER^{TM} WITH A SINGLE-SPRAY MDI DISPENSER IN AN HCH CIRCUIT

Paul D. McGowen RRT, Columbia El Dorado Hospital and Thayer Medical Corporation, Tucson AZ; Scott A. Foss BS, Thayer Medical Corporation, Tucson AZ

Background: The Airlife^{TM} Dual Spray MiniSpacer is designed to deliver MDI drugs in a ventilator circuit by splitting the aerosol spray into two plumes. The purpose of this laboratory experiment was to determine the dose output of the MiniSpacer in comparison with the single-spray Airlife^{TM} Metered Dose Inhaler Dispenser/Adapter ("Standard MDI"), when used in conjunction with a Baxter Adult Filtered Hygroscopic Condenser Humidifier (HCH). Method: In the experimental setup, a Harvard Breathing Machine was attached to a patient wye, which was followed by the HCH. The MDI delivery device was placed immediately downstream from the HCH; the Standard MDI spray was directed downstream, away from the HCH. Proventil(R) (albuterol) was the MDI drug used. The delivery device fed into an ET tube, and at the end of the ET tube a filter trapped the drug particles from each dose. A humidifier (at 33 C) after the filter mimicked the high humidity of a patient's breath. The total mass dose output (MDO) was measured for each device with proper timing for the actuation; that is, the canister was actuated immediately after the start of inhalation of the breathing machine. The breathing machine was set for six cycles/minute, 800 cc/cycle. Ten sample devices of each type (MiniSpacer and Standard MDI) were tested. In the sequence of trials, one MiniSpacer was tested, then one Standard MDI, and so on, to avoid any systematic bias. For each sample device a uniform procedure was followed:

1. The device was set into a clean circuit (with a new HCH) and left for ten minutes, to allow the RH in the ET tube to reach equilibrium.

2. The canister of Proventil was shaken vigorously and the nozzle was inserted into the MDI port of the delivery device.

3. The canister was actuated at the start of inspiration.

4. Steps 2 and 3 were repeated nine more times.

5. The filter was removed from the circuit, capped, and labeled.

When all 20 trials were completed, each filter was analyzed as follows:

1. 20.0 mL of phosphate buffer was pipetted into the filter.

2. The filter was shaken for about a minute to dissolve the albuterol into the phosphate buffer, and the solution was then poured into a flask.

3. The solution was analyzed spectrophotometrically to determine the amount of albuterol collected on the filter (that is, the total MDO).

Results: The table below gives the average total MDO for each type of device.

Device Total MDO One standard deviation

(micrograms/dose) (micrograms/dose)

MiniSpacer 20 3

Standard MDI 14 1

Conclusion: With placement immediately downstream from an HCH, the MiniSpacer delivered approximately 40% more Proventil than the Standard MDI. A t-test shows that the difference is statistically significant, since the p-value is 6.8 x 10^{-5}. As always, laboratory results do not necessarily indicate what clinical results would be.

OF-97-046

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