Mindray SynoVent E5, Operator'S Manual

Page: 93 / 196

7-1
7
CO2 Monitoring
7.1 Introduction
CO2 monitoring is a continuous, non-invasive technique for determining the concentration of
CO2 in the patient’s airway by measuring the absorption of infrared (IR) light of specific
wavelengths. The CO2 has its own absorption characteristic and the amount of light passing
the gas probe depends on the concentration of the measured CO2. When a specific band of IR
light is passed through respiratory gas samples, some of IR light will be absorbed by the CO2
molecules. The amount of IR light transmitted after it has been passed through the respiratory
gas sample is measured with a photodetector. From the amount of IR light measured, the
concentration of CO2 is calculated. End tidal CO2 concentration reading is using the highest
values respectively of the temporal CO2-curve.
The measurement provides:
1. CO2 waveform;
2. End-tidal CO2 (EtCO2) value: the CO2 value measured at the end of the expiration
phase;
3. Fraction of inspired CO2 (FiCO2): the CO2 value measured during inspiration.
The rated respiration rate range of etCO2 module is 0 to 120 bpm, and the data sample rate is
50 Hz. The method used to determine the rated respiration rate range: Utilize a valve to
permit switching between the two sampling gases at different frequencies (simulating the
range of specified breath rates).Record the etCO2 value presented for each frequency. From a
diagram of end-tidal value over frequency, the frequency at which the gas analyzer is no
longer able to resolve etCO2 according to specification is identified.