Mindray A5 - Introduction

Introduction AG and O2 Concentration Monitoring (Optional)
8 - 2 046-003777-00 A5/A3™ Operating Instructions
8.1 Introduction
The Anaesthetic Gas (AG) module measures the patient's anesthetic and respiratory gases, and
incorporates the features of the O
2
module as well.
The AG (anesthesia gas) module determines the concentrations 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. This means that higher concentration of IR absorbing gas
causes 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.
The measurement provides:
1. An EtCO
2
waveform;
2. Measured parameters: O
2
, EtCO
2
, FiCO
2
, EtN
2
O, FiN
2
O, EtAA, FiAA and MAC,
where, AA stands for any of the five anesthetic agents: Des (desflurane), Iso (isoflurane), Enf
(enflurane), Sev (sevoflurane), or Hal (halothane)
.