Biomedical Engineering Reference
In-Depth Information
axm
1
:
MSR
∈
50
..
175
axm
2
:
acc
_
thr
∈ N
1
axm
3
:
MSR
=
URL
Two new variables
acler_sensed
and
acler_sensed_flag
are defined as to store
the measured value from the accelerometer and boolean stats of the accelerometer
sensor. Boolean state of the accelerometer sensor is used to synchronise with other
functionalities of the system. The accelerometer is used to measure the physical
activities of the body in the pacemaker system. Two invariants (
inv
3,
inv
4) provide
the safety margin and state that the heart rate never falls below the lower rate limit
(LRL) and never exceeds the maximum sensor rate (MSR) limit.
inv
1
:
acler
_
sensed
∈ N
inv
2
:
acler
_
sensed
_
flag
∈
BOOL
inv
3
:
HYT
_
State
=
FA L S E
∧
acler
_
sensed < acc
_
thr
∧
acler
_
sensed
_
flag
=
TRUE
⇒
Pace
_
Int
=
60000
/LRL
inv
4
:
HYT
_
State
=
FA L S E
∧
acler
_
sensed
=≥
acc
_
thr
∧
acler
_
sensed
_
flag
=
TRUE
⇒
Pace
_
Int
=
60000
/MSR
In this final refinement, we introduce two new events
Increase_Interval
and
De-
crease_Interval
, which are the refinements of the event
Change_Pace_Int
. These
new events are used to control the pacing rate of the one-electrode pacemaker in
the rate modulating operating modes. The new events
Increase_Interval
and
De-
crease_Interval
control the value of the pace interval variable
Pace_Int
, whenever a
measured value (
acler_sensed
) from the accelerometer sensor goes higher or lower
than the activity threshold
acc_thr
.
EVENT
Increase_Interval
Refines Change
_
Pace
_
Int
WHEN
grd1
:
Pace
_
Int
_
flag
=
TRUE
grd1
:
acler
_
sensed
≥
threshold
grd1
:
HYT
_
State
=
FA L S E
THEN
act1
:
Pace
_
Int
:=
60000
/MSR
act1
:
acler
_
sensed
_
flag
:=
TRUE
END
EVENT
Decrease_Interval
Refines Change
_
Pace
_
Int
WHEN
grd1
:
Pace
_
Int
_
flag
=
TRUE
grd1
:
acler
_
sensed < threshold
grd1
:
HYT
_
State
=
FA L S E
THEN
act1
:
Pace
_
Int
:=
60000
/LRL
act1
:
acler
_
sensed
_
flag
:=
TRUE
END
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