The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts

PERFORMANCE OF DEMAND OXYGEN DELIVERY SYSTEMS IN A SIMULATION OF LOW FLOW OXYGEN USE:

Pete Bliss BME, Robert McCoy RRT, Alexander B. Adams RRT. Regions Hospital, St. Paul, MN.

Background: Demand oxygen delivery systems (DODS) are in widespread use in conjunction with oxygen cylinders or liquid oxygen reservoirs and nasal cannula. The interposed DODS are designed to deliver oxygen during all or portions of inspiration to provide a comparable FIO2 to low flow continuous oxygen and to conserve oxygen. Each model of device delivers oxygen in a different manner. We evaluated the FIO2 delivery capabilities and oxygen conservation of currently available models of DODS compared to continuous low flow oxygen. Methods: An apparatus was constructed to simulate the nares, conducting airways and an alveolar chamber with a nasal cap, flex tube (150 ml of deadspace) and one limb of a mechanical test lung (TTL-Michigan Instruments). A respiratory pattern of mild tachypnea (VT=505 ml, f=20/min, Ti/Ttot=0.33, decelerating flow wave) was generated in the "respirating" limb of the test lung as driven by a linked ventilator (Quantum - Healthdyne). The FIO2 delivery to the alveolar chamber was measured at 1,2 and 4 L/min settings for each DODS by a Ceramatec model OM-25A oxygen analyzer. Oxygen pulses from the DODS were measured by a pneumotachometer and extrapolated to O2 use per minute for cylinder duration calculations. Results: % oxygen measured and duration of cylinder use for DODS (actual FIO2 would be reduced by O2 consumption):

Flow Setting Hrs/M9 cylinder

Device 1 2 4 (at setting 4)

Continuous oxygen 26.3 29.9 35.7 1.0

Chad - Oxymatic 301 23.8 26.3 31.7 6.9

Devilbiss - EX2000D 24.5 27.7 33.0 3.7

Invacare - Venture 23.5 25.3 29.3 2.9

Nellcor PB - CR50 26.3 27.8 31.6 2.6

Transtracheal - DOC2000 23.5 25.3 29.0 4.7

Western - O2Advantage 25.0 26.3 29.2 5.6

All DODS triggered their oxygen pulses as anticipated. There is variability in FIO2 between devices at each setting. At each setting, continuous oxygen had higher FIO2 than DODS, probably due to jetting of oxygen during exhalation into our simulated conducting airways. For the condition tested, DODS allowed an extension of cylinder use ranging from 2.6 to 6.9 times that of continuous oxygen use. Conclusion: The DODS allow prolonged cylinder use but settings must be made to meet therapeutic goals rather than expected comparisons between devices or to continuous O2 use.

The 44th International Respiratory Congress Abstracts-On-DiskĀ®, November 7 - 10, 1998, Atlanta, Georgia.

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