Description of functions Servo-i Ventilator System
3 - 6 Service Manual Revision 02
3
Expiratory section
Functional Main Blocks diagram marking: 'E'
The main block Expiratory Section conveys the
breathing gas from the patient breathing system to
the Expiratory Outlet. It comprises:
• Measurement of expiratory flow
• Connection for measurement of expiratory
pressure.
• Controlling element for the regulation of expiratory
pressure.
Expiratory cassette
The expiratory gas conveying parts and PC 1786
Expiratory Channel Cassette are integrated into one
part – the Expiratory Cassette – which can be easily
removed for cleaning or exchange. See Servo-i
Ventilator System – User’s manual.
The expiratory cassette can be interchanged between
different Servo-i systems. A Pre-use check is always
required after exchanging the expiratory cassette.
Expiratory inlet
22 mm / 10 mm tube connector for the expiratory
tube of the patient breathing system. The inlet is
designed to make condensed water drip out and
allow use of a water trap for such water to be
collected. Expiratory inlet bacteria filter can be
connected to protect the cassette from
contamination.
Heating foil
An electrical Heating Foil applied on the outside of
the expiratory pipe where the Ultrasonic Flowmeter
is situated. The purpose of the Heating Foil to reduce
condensation and maintain a stable temperature in
the expiratory gas.
Ultrasonic flowmeter
The Ultrasonic Flowmeter is a measuring device for
the expiratory gas flow, using ultrasound technique
with two ultrasonic transducers/recievers.
The measuring process is controlled from the main
block PC 1784 Expiratory Channel.
SVX9018
The left hand side transducer is sending out
ultrasonic sound that is reflected against the inner
wall of the expiratory channel. The ultrasonic sound
is recieved by the right hand side transducer now
acting as a reciever. The time from sending to
recieving ultrasonic sound in downstream expiratory
gas flow is measured.
Then the right hand side transducer (earlier recieving)
is sending out ultrasonic sound upstream the
expiratory gas flow. The ultrasonic sound is recieved
by the left hand side transducer now acting as a
reciever. The time from sending to recieving
ultrasonic sound in upstream expiratory gas flow is
measured.
The time difference between the downstream and
the upstream time measurements provides flow
information.
A temperature sensor inside the cassette measures
the expiratory gas temperature. This temperature
measurement is also used when calculating the
expiratory flow.
SVX9017
Expiratory pressure
tube connector
Bacteria
filter
Heating
foil
PC 1786
Expiratory
channel cassette
Ultrasonic
transducer
Ultrasonic
transducer
Inlet
Outlet
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