The Science Journal of the American Association for Respiratory Care

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.

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