2006 OPEN FORUM Abstracts
SPECIAL CONCERNS RELATING TO THE ADMINISTRATION OF AEROSOLS
Terry Jones RRT,
Ashley Shuffit CRT, Brian Hoskins CRT, Adrian Lambeth RRT
Ozarks Technical Community College, Springfield, MO
Background: Over the past few months there has been
growing doubt among some members of our team that an aerosol treatment can be
effectively delivered when passed through a humidifier. We decided to perform an experiment to
determine what effect nebulizer placement within the ventilator circuit has
upon aerosol deposition.
Methods: We fabricated a test lung of rubber that
would be strong enough to simulate a mechanically ventilated lung and yet light
enough to allow us to accurately weigh and calculate the deposition of our
bronchodilator. The experiment began by
running the ventilator through a ten minute treatment cycle using an empty
nebulizer which was delivering 8 liters per minute of flow. This gave us a baseline weight for the water
that would be delivered to the patient during the treatment period. In order to obtain an average, we did the
experiment a total of 3 times with the nebulizer at the wye, and three times
with the nebulizer inline behind the humidifier. The water was collected in
test lung via a standard 4.0 micron filter connected in line at the circuit
wye, and was determined by weighing the filter and balloon both before and
after the test. Albuterol was then
added to the nebulizers at standard concentration of 0.5 mg/3ml. The test lung and filter was again weighed
after 10 minutes and the expected water subtracted to reveal the amount of
albuterol delivered. This was performed
3 times at the wye, and 3 times behind the humidifier. Ventilator settings were as follows: CMV, tidal volume 500 ml, peep 10 cmH20, rate
10 bpm, flow 30 lpm.
Results:
Test #1: Baseline water colleted during treatment
cycle. Nebulizer at wye.
| Init.Wt. filter | Init. Wt. lung | Final Wt. lung | Final Wt. filter | Water collected |
| 3.11g | 29.44g | 3.24g | 29.64g | 0.33g |
| 3.24g | 29.31g | 3.38g | 29.90g | 0.43g |
| 3.43g | 29.70g | 3.45g | 30.05g | 0.37g |
Test #2: Baseline water collected during treatment
cycle. Nebulizer behind humidifier.
| Init.Wt. filter | Init. Wt. lung | Final Wt. lung | Final Wt. filter | Water collected |
| 4.23g | 29.05g | 4.35g | 30.35g | *1.42g |
| 4.35g | 29.63g | 4.45g | 31.2g | *1.67g |
| 10.94g | 29.24g | 11.34g | 30.25g | *1.41g |
*Increased water collected
from this test is due to the added 8
liters of flow traveling through the humidifier.
Test #3: Nebulizer at wye with albuterol added.
| Init.Wt. filter | Init. Wt. lung | Final Wt. lung | Final Wt. filter | Alb. delivered |
| 3.52g | 30.26g | 3.61g | 31.6g | 1.11g |
| 3.61g | 29.12g | 3.7g | 30.39g | .98g |
| 3.68g | 29.27g | 3.75g | 30.57g | .99g |
Test #4: Nebulizer inline behind humidifier with
albuterol added.
| Init.Wt. filter | Init. Wt. lung | Final Wt. lung | Final Wt. filter | Alb. delivered |
| 3.9g | 29.67g | 4.23g | 32.19g | 2.85g |
| 3.7g | 31.57g | 3.96g | 33.7g | 2.39g |
| 3.8g | 30.52g | 4.09g | 32.96g | 2.53g |
Conclusion: The amount of albuterol delivered via the
nebulizer at the wye versus behind the humidifier was 1.03g and 1.09g
respectively. Findings suggest that nebulizer
placement in the ventilator circuit is statistically insignificant.
Ancillary findings: The total amount of albuterol that was
received through the nebulizer in the best case scenario was .16ml, or
approximately on third the dose given.
Also of note, is that the standard 4.0 micron filter allows
approximately 9 ml of water through every hour when set at a flow of 38
lpm. Further research on the effects of
using these filters to protect moisture sensitive components of the ventilator
by placing them in the circuit needs to be performed.