Accuracy in measuring inspiratory and expiratory volatile anesthetic concentrations is especially important in low-flow anesthesia. Sampling lines and other accessories validated by device manufacturers can optimize anesthesia gas monitor function. Tests conducted by GE Healthcare show that a dedicated gas sampling line is preferred for patient safety and to avoid nuisance monitor alarms.
Tests confirm that common PVC tubing is appropriate and cost-effective for use in CO2, O2 and N2O sampling lines, but if PVC tubing directly contacts anesthetic agents, measurement accuracy may be compromised. For example, PVC absorbs anesthetics onto its surface, and therefore a PVC sampling line can act as a temporary collector or supplier of agent flow, causing underestimation of FiAA monitored values and overestimation of EtAA values. In addition, Anesthetic agents can dissolve the plasticizers that soften PVC, making the tubing hard and brittle.
For this reason, it is strongly recommended to use PVC tubing with an interior coating of polyethylene (PE), which provides strong chemical resistance against volatile agents. In addition, GE Healthcare respiratory airway monitors should be used with gas sampling lines of 1.2 mm inner diameter, for which the measurements are optimized.
Selection of the appropriate sampling line material and inner diameter, along with correct deployment and handling of the sampling line and water traps, can help support measurement accuracy, prevent nuisance alarms and maximize patient safety.
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