The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts

AIR FLOW RESISTANCE FOR THREE BRANDS OF MDI SPACER SYSTEMS.

Edwin M. Lybarger, RRT, CPFT, RCP, El Dorado Hospital & Medical Center, Tucson, Az.

An important aspect of MDI spacer performance is its air flow resistance characteristics. The air flow resistance affects the ease of use for a given spacer product. High flow resistance leads to the situation where the patient must work harder to exhale through the spacer system, and inhale through the spacer system. For the situation of low resistance, the patient will inhale and exhale through the spacer system with ease. These characteristics of a spacer system turn out to be very important for a patient suffering from some form of respiratory illness. Such a patient already has difficulty breathing. The added resistance of a spacer systems adds to the difficulty when inhaling or exhaling through the spacer system. METHOD: Ten devices each, for three different brands of spacer systems were tested for inhalation resistance and exhalation resistance. These brands are Baxter's Hand-Held MediSpacer, Diemolding Healthcare Division's Ace Aerosol Cloud Enhancer, and Monaghan's Aerochamber (new model with clear body). To test inhalation air flow resistance, the mouth piece of the spacer system is connected to 22mm diameter tubing connecting to a flow meter. The other end of the flow meter is connected to vacuum. The vacuum is adjusted so that it creates an inhalation flow rate of 30 L/min. A manometer is connected via a Tee adapter to the flow meter - spacer system tubing. The reading of this manometer is the difference in pressure for the atmosphere and the inside of the tubing. This represents the inhalation flow resistance. To test exhalation air flow resistance, the mouth piece of the spacer system is connected to 22mm diameter tubing connecting to a flow meter. The other end of the flow meter is connected to positive pressure source. The positive pressure source is adjusted so that it creates an exhalation flow rate of 30 L/min. A manometer is connected via a Tee adapter to the flow meter - spacer system tubing. The reading of this manometer is the difference in the inside of the tubing pressure for the atmosphere and the pressure for the atmosphere.

Results: There was a significant difference in the inhalation flow resistances for the three devices tested (Ace: 1.94±.20 cm H20, Aerochamber: 1.36±.11 cm H20, MediSpacer: .7±.1 cm H20: Average ± standard deviation). There also was a significant difference in the exhalation flow resistances for the devices tested (Ace: 8.2±.4 cm H20, Aerochamber: 36.4±10 cm H20, MediSpacer: .7±.1 cm H20: Average ± standard deviation).

Conclusions: The Hand Held MediSpacer exhibits the least amount of resistance during inspiration and expiration, therefore indicating that it is the spacer that would be easiest for the patient to breath through.

SEE ORIGINAL GRAPH

OF-95-110

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