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Methane influences infrared technique anesthetic agent monitors
E Mortier1, G Rolly, L Versichelen
1Department of Anesthesia, University Hospital, Gent, Belgium.
Journal of Clinical Monitoring and Computing
|July 21, 1998
Summary
Methane accumulation during anesthesia can cause inaccurate readings from infrared anesthetic monitors. Devices not using the 3.3 microm wavelength are more reliable for potent inhalation anesthetics in low-flow systems.
Area of Science:
- Anesthesiology
- Analytical Chemistry
- Biomedical Engineering
Background:
- Infrared absorption at 3.3 microm is used for anesthetic vapor analysis.
- Methane accumulation in closed-circuit anesthesia can interfere with these measurements.
- Accurate anesthetic monitoring is crucial for patient safety.
Purpose of the Study:
- To investigate the impact of methane on anesthetic concentration readings.
- To evaluate different infrared anesthetic monitors under varying methane concentrations.
- To determine the reliability of 3.3 microm wavelength devices in the presence of methane.
Main Methods:
- Three gas mixtures with 100, 500, and 1000 ppm methane were tested.
- Four infrared anesthetic monitors (Ultima, Andros, Brüel & Kjaer 1304, Irina) were evaluated.
- Halothane or isoflurane concentrations were measured with and without added methane.
Main Results:
- Inaccurate anesthetic readings occurred at 500 and 1000 ppm methane for most devices using 3.3 microm wavelength.
- The interference was more significant with halothane than isoflurane.
- The Brüel & Kjaer 1304, operating at a different wavelength, remained accurate.
Conclusions:
- Infrared techniques relying on 3.3 microm wavelength are unreliable in the presence of methane.
- Anesthetic monitors using alternative wavelengths are preferable for closed-circuit or low-flow anesthesia.
- Careful consideration of monitor technology is needed in specific anesthetic setups.