Siemens Servo Ventilator 300, Service Manual

Page: 62 / 131

60 Siemens-Elema AB E382 E380E 061 01 03 01
Description of functions Servo Ventilator 300/300A
2
6.3 End inspiration indicator
During inspiration time when pressure
regulation is used, except in Pressure
Control mode or mandatory breaths in
SIMV(Press. Control) mode, the moment
when the inspiration is about to stop is
normally determined in this block (a
START EXP
signal is generated). Thus this block
determines when a signal,
INTERNAL START
EXP
.
H
, should be sent to the block 6.1
MODE
CPU
in order to start an expiration.
This output signal is depending on:
• Expiratory pressure (
EXP PRESSURE
).
• Inspiratory flow (
INSP FLOW
)
•
PRESSURE REGULATION PRESSURE REF
(N43:B3).
6.4 Pressure PID control
For pressure regulation the
INSP PRESSURE
signal from the pressure transducer in the
main block 12
INSPIRATORY PRESSURE
is used as
actual value in this controller block.
PRESSURE REGULATION PRESSURE REF
signal is
used by the
PRESSURE PID CONTROL
as
reference for the pressure. Additionally the
EXP PRESSURE
signal from the pressure
transducer in the main block 13
EXPIRATORY
PRESSURE
is used to adjust this reference
level for the pressure. This adjustment -a
compensation for pressure drop in the
inspiratory airway- is to achieve a resulting
pressure level in the patient system -
generated via the main blocks 8 and 9
(Inspiratory valve units) - equal to
PRESSURE
REGULATION PRESSURE REF
(= P
REF
) as measured
by the block 13.2
PRESSURE TRANSDUCER
for
Expiratory pressure. This normally results in
a pressure level at the Y-piece (= close to
the patient) which corresponds to settings
on the main block 1
FRONT PANEL
even if there
is a pressure drop in the inspiratory tubing
between the block 11.1
INSPIRATORY MIXING
PART
and the Y-piece (for example when
using an active humidifier). Such a pressure
drop up to 15 cm H
2
O is compensated in
this way.
The actuating signal from the
PRESSURE PID
CONTROL
output is used by the block 7.3
MIXER
as reference for the total flow (
PRESSURE
REGULATION FLOW REF
).
6.5 I/O
This block is an interface for the input and
output signals (to and from this PC-board).
Example of output:
Disabling signals for inspiratory valves
(
ZEROING INSP VALVES
).