2004 OPEN FORUM Abstracts
Performance of a Heat & Moisture Exchanger Designed to Allow Aerosol Delivery
Richard
Branson, MS, RRT, Jay A. Johannigman MD. University of
Cincinnati, 231 Albert Sabin Way; Cincinnati, OH 45267-0558
Background:
The use of heat & moisture exchangers (HME) during mechanical
ventilation has become routine. One contraindication for HME use is
the need for aerosol therapy using a nebulizer and/or MDI during
mechanical ventilation. We evaluated a new prototype HME which
utilizes a bypass-valve to allow intermittent aerosol therapy and/or
in-line MDI.
Description:
The prototype HME (Thayer Medical) uses a traditional foam media.
A by-pass valve, which is controlled by the caregiver, can be open
(to allow aerosol through the center of the device) or closed
(forcing inspired and expired gases through the media).
Method:
Using the method described in ISO 9360
we evaluated moisture output, deadspace, and resistance of the HME
(one treated with hygroscopic material, the other untreated).
Moisture output was calculated using the gravimetric method at a VT
of 500 mL and 1000 mL. Resistance was measured prior to use and after
2 and 24 hours in the model. Resistance was determined by directing
flow at 1 L/s through the HME and measuring pressure drop (Timeter
RT-200) across the HME. Each device was tested twice. We also
evaluated resistance after 24 hrs of use in the model using a
neblulizer to deliver 0.5 mL/5 mL of albuterol/saline every 2h.
Results:
Data are shown I the table for a VT of 500 mL x 20 bpm.
| Device | Moisture Output 500/1000ml (mg H2O/L) | Dead space (mL) | Resistance (cm H2O/L/s) | |||
| Pre use | 2 hrs | 24 hrs | 24hrs (q 2h aerosol) | |||
| Untreated | 30.1/28.2 | 91±3 | 0.46 | 0.77 | 1.1* | 1.3* |
| Untreated | 30.9/28.6 | 90±2 | 0.55 | 0.80 | 1.4* | 1.5* |
| Treated | 33.1/30.1 | 90±2 | 0.54 | 0.93 | 1.3* | 1.6* |
| Treated | 32.7/29.8 | 89±1 | 0.61 | 0.99 | 1.5* | 1.6* |
All
data are raw or mean ±
SD, *p ≤ 0.05
compared to pre-use.
Conclusion:
The prototype HME performs comparatively to current HME’s
with respect to moisture output. Resistance is increased with
duration of use and with aerosol delivery q 2 hrs. The difference
between resistance with and without aerosol therapy was not
statistically significant. Deadspace must be considered when using
this HME during low VT ventilation.