2000 OPEN FORUM Abstracts
PERFORMANCE OF NEW DEMAND OXYGEN DELIVERY SYSTEMS IN A SIMULATION OF LOW FLOW OXYGEN USE
Peter Bliss BME, Robert McCoy RRT. Valley Inspired Products, Savage MN
Background: Demand oxygen delivery systems (DODS) are in widespread use in conjunction with oxygen cylinders or liquid oxygen portable devices via nasal cannula. DODS are designed to deliver oxygen during all or portions of inspiration to provide a comparable FIO2 to continuous flow oxygen (CFO) and to conserve oxygen. Each model of device delivers oxygen in a different manner. We evaluated the FIO2 delivery capabilities and oxygen conservation of new DODS compared to continuous flow oxygen and one currently available model.
Methods: An apparatus was constructed to simulate the nares, conducting airways and an alveolar chamber with a machined 'nose', flex tube (150 ml of deadspace) and one limb of a mechanical test lung (TTL-Michigan Instruments). Three respiratory patterns (VT=520 ml, f=15,20,26/min, I:E=1:2, decelerating flow wave) were generated in the "respirating" limb of the test lung as driven by a linked ventilator (7200 -- Puritan Bennett). The FIO2 delivery to the alveolar chamber was measured at 1,2 and 4 L/min settings by a Ceramatec model OM-25A oxygen analyzer. Oxygen pulses from the DODS were measured by a mass flowmeter (Model 4040 - TSI). Devices tested were Mallinckrodt CR-50, Mallinckrodt Helios, Victor O2N Demand II. The ratio of oxygen delivery (increase over 21%) to CFO was calculated for each device.
Results: FIO2 measured (%) at each respiratory pattern and device setting. Also, the ratio or oxygen delivery to CFO is shown (mean of all settings and respiratory patterns) for each device.
|Device||Del. Ratio Mean||FIO2, %|
|15 bpm||20 bpm||26 bpm|
|O2N Demand II||.91||25.1||27.4||32.1||24.6||26.3||29.6||24.1||25.2||27.8|
All DODS triggered their oxygen delivery as anticipated. There is variability in FIO2 between devices at each setting and with each respiratory pattern. Although these three DODS operate in a similar manner, there is a difference of +19% to -14% in the amount of oxygen entering the lung, relative to CFO.
Conclusion: DODS settings must be made to meet therapeutic goals rather than expected comparisons between devices or to continuous O2 use.