Mindray iPM-9800 - 17 Monitoring AG

17-1
17 Monitoring AG
17.1 Introduction
The anesthetic gas (AG) module measures the patient’s anesthetic and respiratory gases, and
can be integrated into the optional O
2
module.
The AG module determines the concentration of certain gases using the infrared (IR) light
absorption measurement. The gases that can be measured by the AG module absorb IR light.
Each gas has its own absorption characteristic. The gas is transported into a sample cell, and
an optical IR filter selects a specific band of IR light to pass through the gas. For multiple gas
measurement, there are multiple IR filters. The higher the concentration of gas in a given
volume the more IR light is absorbed. This means that higher concentration of IR absorbing
gas cause a lower transmission of IR light. The amount of IR light transmitted after it has
been passed though an IR absorbing gas is measured. From the amount of IR light measured,
the concentration of gas present can be calculated.
Oxygen does not absorb IR light as other breathing gases and is therefore measured relying
on its paramagnetic properties.Inside the O
2
sensor are two nitrogen-filled glass spheres
mounted on a strong rare metal taut-band suspension. This assembly is suspended in a
symmetrical non-uniform magnetic field. In the presence of paramagnetic oxygen, the glass
spheres are pushed further away from the strongest part of the magnetic field. The strength of
the torque acting on the suspension is proportional to the oxygen concentration. From the
strength of the torque, the concentration of oxygen is calculated.
There are two types of AG modules:
 AION 02 type, which cannot identify anesthetic gases automatically.
 AION 03 type, which can identify two anesthetic gases in a mixture automatically and
distinguish between them according to their proportion for display as the primary and
secondary anesthetis agent.
The AG module provides end tidal (Et) and inspired (Fi) values for the following gases:
 End tidal CO
2
value (EtCO
2
): the CO
2
value measured at the end of the expiration phase.
 N
2
O.
 O
2 :
optional.
 AA: represents Des (desflurane), Iso (isoflurane), Enf (enflurane), Sev (sevoflurane), or
Hal (halothane).
 Airway respiration rate (AwRR): the number of breaths per minute (rpm).