Datex-Ohmeda Anesthesia Delivery Unit S/5, Technical Reference Manual

Page: 31 / 494

System description
Document No. 8502852
3-9
Fresh Gas Control Unit (A-FGC1)
The wall gas unit is connected to the gas inlets of the fresh gas control unit inside the gas distribution
block. The fresh gas control unit includes the flow controls and the vaporizer gas flow circuit.
Flow controls
The O
2
, N
2
O and Air flows are adjusted by means of mechanical needle valves.
The N
2
O flow may be adjusted up to 75% of total flow. This assures a minimum of 25% O
2
. Air may be
adjusted independently of O
2
flow.
Flow transducers electronically measure the O
2
, N
2
O and Air flows.
With the N
2
O/Air switch, the user may select either N
2
O or Air to be mixed with O
2
.
The mixed gas from the flow controls flows to the vaporizer gas flow circuit.
Electronically controlled vaporizer
The ADU is equipped with an electronically controlled vaporizer. The vaporizer gas flow circuitry and
agent concentration control system has been integrated within the delivery unit.
The gas flow from the flow controls is divided into bypass flow and liquid chamber flow. The gas
concentration is, through the control system, adjusted by changing the ratio between these two flows.
Aladin Cassette
The liquid chamber flow goes into the Aladin Cassette. This cassette is the only agent specific part of
the vaporizer. The agent cassette contains liquid agent, which is vaporized when the gas flow passes
through the cassette. The liquid chamber flow is then mixed with the bypass flow and conducted to
the fresh gas outlet.
There are keyed systems for filling the cassette with anesthetic agent. A level window indicates the
amount of liquid in the cassette. Changing the cassette, simply by pulling it out and inserting another
one, changes the agent.
Electronic Ventilator (A-EV1)
The ventilator consists of a control unit and a bellows unit.
The user may select the patient ventilation from two different modes of operation: Auto or Manual.
The selection is made by turning the Auto/Man. switch.
Auto mode
In Auto mode, driving pressure from the ventilator control unit, drives the bellows which ventilates the
patient via the patient circuit. It is possible to run the electronic ventilator in three ventilation modes:
VCV: Volume Controlled Ventilation
SIMV: Synchronized Intermittent Mandatory Ventilation
PCV: Pressure Controlled Ventilation
There are two sources of driving gas, primary (Air/O
2
) and secondary (O
2
/Air). If the pressure of the
primary gas is lower than 250 kPa (2.5 bar), the driving gas selecting unit automatically selects the
secondary gas for driving the ventilator.