isce2003 alarm detection

8/6/2019 Isce2003 Alarm Detection

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Alarm Detection Methods for Physiological Variables

Sandra Ramos, Isabel Silva 1,

M. Eduarda Silva Teresa Mendon a

ICSE 2003

Departamento de Matemtica Aplicada,

Faculdade de Cincias da Universidade do Porto

1 Departamento de Engenharia Civil,

Faculdade de Engenharia da Universidade do Porto

This research is part of the Ph.D. work of Isabel Silva, financially supported by PRODEP III


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Summary

Motivation

Purpose

Designing an adaptive reference trajectory

ICSE 2003

Alarm system for neuromuscular blockade

Walsh-Fourier spectral analysis

Simulations results

Final remarks


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Motivation

Design of automatic control systems for neuromuscular blockade

Nonlinear dynamical relationship between the muscle relaxant dose and theinduced muscle paralysis

Lar e variabilit of the individual res onses to the infusion of muscle relaxant

ICSE 2003

Individual tuning of

the controller

according to the

characteristics of the

patient

0 1 2 3 4 5 6 7 8 9 100

20

40

60

80

100

120

time (minutes)

r(t)%


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Motivation

Reference profile

induce total muscle relaxation in a very short period of time ( < 5)Initial bolus

control action starts 10 after bolusadministration

ICSE 2003

variability of theresponse

expected noiselevel

clinicalrequirements


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Motivation

( ) :tr level of muscle relaxation, normalized between 0 (full paralysis) and 100 (fullmuscular activity)

Longer effect of100

ICSE 2003

the initial bolus

0 50 100 1500

50end of infusion%

r(t)

t (minutes)

initial overshoot

and oscillatory

behaviour


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Purpose

Propose and evaluate an adaptive controller incorporating

a varying beginning for automatic control action

an individual reference profile

ICSE 2003

Alarm system for the control of the neuromuscular blockade

Forecasting techniques

Walsh-Fourier spectral analysis (WFA)


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Alarm systems for neuromuscular blockade

Predict the neuromuscular blockade upcrossing of a specified critical level, %

Estimate of the recovery time, P, at an critical neuromuscular blockade level, . P

100

ICSE 2003

0 30 600

20

40

60

80

%

P

t(minutes)

r

(t+5)%

^


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Linear prediction of the neuromuscular blockade response, r( t)

( ) ( ) ( ) ( )[ ]ts;su,sr|mtrEmtr+=+

Alarm systems for neuromuscular blockade

r( t) is modelled using an ARX( 4, 4)

ICSE 2003

On-line identification of the ARX model parameters Kalman Filter

4141 3041 +++++= tubtubtratratr LL

( ) 5alarm""5 +=>+

tPtr


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Walsh Function: complete, ordered and orthonormed set of rectangular

wavestaking the values -1 and 1.

Sequential or Walsh order

t: time

( ) [ [ K,,,n,,t,t,nW 21010 =

Walsh-Fourier Spectral Analysis

ICSE 2003

Walsh periodogram: x0, x1, ..., xN-1 observations

where =j / N, 0 < j < N, is the sequency.

n: sequency num er o sw c es s gns

( ) ( ) ( )2

1

0

1

=

=

N

n

jjW ,nWnx

N

I

j

One can plot versus to inspect the peaks, that indicate a switch

each time points. The average periodsare defined byj

j

j/

1

(jW

I


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Walsh-Fourier Spectral Analysis

is highly correlated with r(14.0)

Relaxation level at the WFA average periods

High predictive power for the parameters of the controller

Robustness of the parameters prediction in the presence of noiseP

ICSE 2003

r(14.0) 0.87 0.75 0.63 0.72 0.67 0.53

r(28.0) 0.85 0.88 0.87 0.76 0.84 0.84r(1.6)+r(3.0)+r(7.0)+r(12.0)+r(14.0) 0.89 0.83 0.77 0.77 0.72 0.60

r(1.6)+r(3.0)+r(7.0)+r(12.0)+r(14.0)+r(28.0) 0.92 0.91 0.89 0.83 0.86 0.84

Without noise With noise

5P 10P52.P 52.P5P 10P

: near regress on us ng as pre c ors e re axa on eve s o average per o s

Correlation coefficient


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Choosing P

= PPe

( ) ( ) ( ) ( ) ( ) ( ){ }02801401207036128

.r,.r,.r,.r,.r,.rW =

Comparision of ARX and WFA predictors of by calculatingP

P

P

True value for 5%, 10%

ARX( 4, 4) process

linear regression with

=

Estimated value

ICSE 2003

ARX WFA-10

-5

0

5

10

15

e10 Boxplots of e10 for simulated

responses with P10 > 28.0 minutes


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Final Remarks

Design of an adaptive controller for neuromuscular blockade incorporating an

alarm system

Robust on-line prediction of the beginning of the patients recovery from the

initial bolusby

ICSE 2003

WFA methodology

Improvement of the reference pursuit

Adaptation of the automatic control system to individual requirements

The alarm system can easily be adapted to deal with other related situations,

namely the detection of eventual changes in the dynamics of the system.

isce2003 alarm detection

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