2006 OPEN FORUM Abstracts
methodology of the determInation of actuations remaining in a metered dose inhaler
-Cristin Bridgefarmer, RRT, David Mussetter, BA, RRT, Tim Frymyer, BS, RRT, Vic
Brewer, RRT, Larry West RPh, Michael
Trevino, MS, RRT, Gary Weinstein, MD, FCCP, Presbyterian Hospital of Dallas,
Dallas, Texas.
Background: We
are a 903 bed hospital in a major metropolitan area that utilizes a common
canister protocol. Metered dose inhalers (MDIs), which are stored in the Pyxis,
are administered to the patient using their own spacer. While performing a
literature search regarding inhaled medication, we came across data questioning
how the practitioner or patient would know when an MDI was empty. Unlike dry
powder inhalers, which have a mechanism to signal when the level of medication
is near depletion, MDIs have no such indicator. When presented to our staff
therapists, their responses included: 1) float the inhaler in water, 2) shake
it, or 3) perform a test puff; none of which have been supported within the
literature. Our challenge is to provide accurate medication delivery regardless
of the medication delivery device. The management team proposed using a clicker
counter to keep track of how many puffs have been actuated per inhaler in use.
This idea was brought to our key therapists, where it received less than
favorable feedback. One proposed solution was to weigh the canisters to
determine if that was an effective mechanism to determine when the MDI was
empty. This study seeks to determine the utility of such an approach.
Method: We
weighed 30 Andrx Pharmaceuticals, Inc., 17g Albuterol Inhalers from a common
lot number. Using a digital scale (The Mettler Toledo PG802-s), the average
weight per inhaler was 28.97 grams when full. Two inhalers were randomly
selected from this lot and used for this study. The canister was shaken for
approximately 20 seconds between each actuation. After each puff we placed the
canister on the scale and documented its weight until no visible cloud was
discerned.
Results:
| Number of total actuations | Avg. weight per puff | Final weight | |
| Inhaler A | 227 | 0.083 g ± 0.008 | 10.10 g |
| Inhaler B | 222 | 0.086 g ± 0.007 | 10.01 g |
| Weight after 100 actuations | Weight after 150 actuations | Weight after 200 actuations | |
| Inhaler A | 20.55 g | 16.42 g | 12.27 g |
| Inhaler B | 20.38 g | 16.05g | 11.73 g |
Conclusion: It is
apparent that an inhaler which has been actuated greater than 200 times may
still dispense a cloud. The composition of this cloud, however, is unknown. We
propose that weighing inhalers can be used as a reliable indicator to ascertain
when the inhaler should no longer be used. After weighing larger numbers of
inhalers, reference cards will be produced detailing a specific weight at which
the therapist would discard the canister. These cards would then be kept with
scales which would be located near each PYXIS medstation. The therapist would
then weigh the canister prior to patient rounds. Once the inhaler achieved the
critical weight indicated on the card, it would be thrown away.
methodology of the determInation of actuations remaining in a metered dose inhaler