Service manual

Servo Ventilator 300/300A Description of functions
E382 E380E 061 01 03 01 Siemens-Elema AB 51
2
A calculation is made at the end of inspiration
n to achieve a new calculated pressure value
P
CALC (n)
using one of the formulas (1) or (2) or
(3) below.
P
CALC (n)
= P
in use (n)
X
TV
P
TV
M
(1)
P
CALC (n)
= P
in use (n)
X
MV
P
MV
M
(2)
P
CALC (n)
= P
in use (n)
X X 150%
TV
P
TV
M
(3)
TV
P
= Preset Tidal Volume
TV
M
= Measured Inspiratory Tidal Volume
MV
P
= Preset Minute Volume
MV
M
= Measured Inspiratory Minute Volume
The following choise is made between
formulas (1), (2) and (3):
(1) if the calculated breathing frequency f
CALC
fulfills:
f
CMV
= f
CALC
or
f
CMV
< f
CALC
Applicable both for the PRVC mode and for
the VS mode.
(2) if the calculated breathing frequency
f
CALC
fulfills:
2/3 x f
CMV
< f
CALC
< f
CMV
Only applicable for the VS mode.
(3) if the calculated breathing frequency
f
CALC
fulfills:
f
CALC
< 2/3 x f
CMV
Only applicable for the VS mode.
The value f
CMV
is the CMV frequency
according to front panel setting.
The parameter f
CALC
is calculated every breath
(in VS mode). In breath number n the value is
f
CALC (n)
=
1
T
(n)
T
(n)
is the measured time from end of
inspiration number n  1 to end of inspiration
number n.
The result of the above choise of formula, (1)
or (2) or (3) is that the target Tidal Volume
(TV) depends on the calculated Breathing
frequency (f
CMV
) as illustrated in the diagram:
150% x TV
P
TV
P
2/3 x f
CMV
f
CMV
f
CMV
A
B
C
Diagram: Target Tidal Volume vs calculated
Breathing frequency
A: Const. Tidal Volume TV = 150% x TV
P
(3)
B: Const. Minute volume MV = MV
P
(2)
C: Const. Tidal Volume TV = TV
P
(1)
The calculated pressure value P
CALC (n)
is used
to calculate the pressure difference value:
P
DIFF (n)
= P
CALC (n)
 P
IN USE (n)
(4)
The parameter P
DIFF
is thus updated once
every breath. P
DIFF
is used to assign a new
value to the parameter P
REF
to be used during
the next breath (during inspiration number
n+1):
P
REF (n + 1)
= P
REF (n)
+ F
(n)
(P
DIFF
) (5)
The value of F depends on the value of P
DIFF
.