Patient Monitor User’s manual
14-1
Chapter 14 Anesthetic Gas (AG)
14.1 Introduction
AG module is used to measure respiratory and anesthetic gases of a patient
during anesthesia, including CO
2
, N
2
O, O
2
, Halothane, Isoflurane, Enflurane,
Sevoflurane and Desflurane.
AG module is intended to be connected to a patient breathing circuit for
monitoring of inspired/expired gases during anesthesia, recovery and
respiratory care. It may be used in the operating suite, intensive care unit,
patient room and for applicable versions emergency medicine/emergency
transport settings for adult, pediatric and infant patients.
AG module is not intended to be used as the only means of monitoring a
patient. They shall always be used in combination with other vital signs
monitoring devices and/or professional human judgments of patient condition.
The measuring principle is that anesthetic gas can absorb infrared light.
Gases that can be measured by AG module are able to absorb infrared light.
Besides, each gas has its own absorption characteristic. First the gas is driven
into a sample cell. Then the optic infrared filter selects the infrared light with
special wavelength to penetrate this gas. For a given volume, the higher the gas
concentration is, the more infrared light is absorbed. We may measure the
quantity of the infrared light that have penetrated the gas and then calculate the
gas concentration via specialized formula. If you desire to measure multiple
gases, you should install various infrared filters in the AG module.
There are two methods for measuring anesthetic gas in the patient’s airway:
1. Mainstream: Uses an AG sensor attached to an airway adapter directly
inserted into the patient’s breathing system.
2. Sidestream: Takes a sample of the respiratory gas with a constant sample
flow from the patient’s airway and analyzes it with the AG module.
Note: This chapter describes the operation of IRMA multi-gas sensor
and ISA multi-gas module, if you use the IRMA CO
2
or ISA
CO
2
sensor, please refer to this chapter.
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