Datex-Ohmeda S/5 Anesthesia Monitor
Document No. 800 1005-1
10
2.2.1
Gas sampling system
The gas sampling system samples the measured air to the module, and removes water and
impurities from it. A sampling line is connected to the water trap on the front panel. The pump
draws gas through the sampling line to gas measuring units. After the measurements, the gas is
exhausted from sample gas out connector on the rear panel of the module.
Water trap, D-fend
The gas sample enters the monitor through the water trap, where it is divided into two flows, main
flow and side flow (see Gas sampling system block diagram). The main flow goes into the
measuring system through a hydrophobic filter.
The side flow creates a slight sub-atmospheric pressure within the water trap container. This
facilitates gathering the fluid removed by the hydrophobic filter.
Sampling line
The sampling line is an integral part of the total sampling system. The resistance established by the
sampling line is significant when the software determines the occlusion and air-leak alarm limits
during the turn-on sequence.
The small inner diameter causes fluids such as blood or mucus not to propagate within the tube, so
that when the line is clogged, it is replaced.
The Nafion
TM
tube
1)
A nafion tube (tubes A or B, and C: see figure 5) is used to balance the sample gas humidity with
that of ambient air. The tube will prevent errors caused by the effect of water vapor on gas partial
pressure when humid gases are measured after calibration with dry gases. It is inserted between
the water trap and the zero valve (G-AiO/AiOV) or between the zero valve and ACX-200 measuring
unit (G-O/OV/AO/AOV). The tube is also inserted between the CO
2
absorber and the zero valve.
Zero valve
The main flow passes through a solenoid valve before proceeding to the ACX-200 measuring unit.
This valve is activated to establish the zero points for the ACX-200 and O
2
measuring units at start-
up, at 5 minutes, and after that at regular intervals. After 1-hour monitoring, the auto-zeroing is
performed once an hour. When the valve is activated, room air is drawn through the CO
2
absorber
into the internal system and the gas sensors.
1)
Nafion is a trademark of Du Pont
Summary of Contents for S/5 B-GAS
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