Portable Oxygen Monitor Operating
Instructions
Teledyne
Analytical
Instruments
19
When a ventilator is a part of the breathing system, the alternating “breath-
ing” pressure cycles generated by the ventilator will be sensed as pressure pulses
by the sensor, and over time, such pulses manifest as pressure increases in the
fast-reacting sensors such as R17MED. This perceived pressure increase results
in correspondingly higher oxygen reading. While the concentration of oxygen is
not changing, it is the total pressure that is increasing producing a corresponding
increase in the partial pressure of oxygen.
2.3.4 Discrepancy in Readings
When a discrepancy in oxygen readings is detected, the Monitor’s readings
should be verified by checking the MX300-I battery condition and calibration
using 100% oxygen. If the Monitor can be calibrated, the unit is assumed to be in
good working order. If, after reinstalling the unit, the discrepancy in oxygen
readings persists, the problem is most likely elsewhere in the breathing system.
Resolve the cause(s) for the discrepancy before using the Monitor. The trouble-
shooting section of this manual may provide additional assistance in locating the
problem.
2.3.5 Anesthetic Gases
2.3.5.1 Gases That MAY INDUCE Reading Error
When using the R17MED sensor in the presence of anesthetic gases, the
oxygen reading may fall (see Table below). The magnitude of this error will de-
pend 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%
oxygen / 70% nitrous oxide, and the resulting drops in oxygen level after an ex-
posure of approximately two hours were noted.
Exposures in excess of two hours may produce slightly greater errors. The er-
rors listed are typical for all oxygen sensors such as the R17MED. Exposing the
sensor to air or gases that do not contain anesthetic agents for a period of time
equal to or greater than the exposure interval will eliminate the reading error in
most cases.
Table 2-1: Oxygen Reading Error in a Mixture of Anesthetic Gas
Gas or Vapor Level
(Balance: Mixture of 30% O2 / 70% N2O, except where noted)
Gas or Vapor
Test Level
Oxygen Reading