Service Manual AX300-I
Teledyne Analytical Instruments 34
When the sensor is connected to a ventilator circuit, the alternating
“breathing” pressure cycles generated by the ventilator will be sensed as an
increase in the oxygen percentage (especially if the sensor is fast enough to sense
the changes, as is the R17MED). In reality, the percentage of oxygen is not
changing; it is the total pressure that is increasing producing a corresponding
increase in the partial pressure of oxygen. A hundred centimeter of water
pressure pulse will produce a 0.11 atmosphere, or an 11% increase in the total
and therefore partial pressure of oxygen. Assuming that the sensor is fast enough
to track this pressure pulse, an un-pressurized reading of 50% oxygen will
increase to 55.3% if the sensor is subjected to a pressure cycle of 100cm H2O.
The reading will rise proportionally less for smaller pressures.
3.6.4 Discrepancy in Readings The AX300-I instrument should be used to measure the oxygen
concentration exiting another oxygen mixing device or life support system (i.e., a
blender, incubator or anesthesia machine). The information obtained from the
AX300-I should never be used to adjust a life-support system, but should only be
used as an indication that the life support system or device may require service
and/or calibration.
When a discrepancy in oxygen readings is detected, the oxygen analyzers
readings should be verified by checking the AX300-I battery condition and
calibration using 100% oxygen. If the analyzer can be calibrated, the unit can be
assumed to be in good working order and capable of providing readings to
specification. If, after reinstalling the unit, the discrepancy in oxygen readings
persists, the problem is most likely elsewhere (i.e., flow blockage, primary
device error, etc.). Further investigation should be made until the discrepancy in
readings is resolved. The troubleshooting section of this manual may provide
additional assistance in locating the problem.
Note: The MSDS on this material is available upon request through the
Teledyne Environmental, Health and Safety Coordinator. Contact
at (626) 934-1592
3.6.5 Anesthetic Gases 3.6.5.1 GASES THAT INDUCE READING ERROR
When using the R17MED sensor in the presence of anesthetic gases such as
Halothane, the oxygen reading may fall (see Table below). The magnitude of this
error will depend upon the level of oxygen and the duration of exposure.
The anesthetic agents listed in the following table (Halothane, Enflurane,
Isoflurane, Sevoflurane, and Desflurane) were vaporized into a stream of 30%