Modelling and Control in Anaesthesia From Design to Validation

237 Pages·2008·12.18 MB·English

ETH Library
Modelling and control in
anaesthesia
from design to validation
Doctoral Thesis
Author(s):
Stadler, Konrad Shedden
Publication date:
2003
Permanent link:
https://doi.org/10.3929/ethz-a-004624343
Rights / license:
In Copyright - Non-Commercial Use Permitted
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Diss. ETHNo. 15222
Modelling and Control in Anaesthesia
From Design to Validation
- -
A dissertation submitted to the
Swiss Federal Institute ofTechnology Zurich
for the degree of
Doctor ofTechnical Sciences
presented by
Konrad Shedden Stadler
Dipl. El.-Ing. ETH
Swiss Federal Institute ofTechnology, Zurich
born November 24th, 1971
citizen ofDavos (GR)
accepted on the recommendation of
Prof. Dr. AdolfH. Glattfelder, examiner
Prof. Dr. Peter Niederer, co-examiner
Prof. Dr. Alex M. Zbinden, co-examiner
September 2003

Acknowledgments
I am greatly thankful to my advisors Prof. A. H. Glattfelder and Prof. A. M. Zbinden fortheir
support, experience and knowledge they generously provided. I am not only grateful for their
project specificbut alsofortheirpersonal advice andhelp. All the fruitful discussions held over
the pastyears have helpedtremendously in guidingthethesisto a successful end. Furthermore,
I would like to thank Prof. P. Niederer forjoining the committee ofreferees.
This thesis is influenced by the work conducted during previous projects andby the experience
collected by the anaesthesia group. My special thanks go to the group members both in Berne
andinZurichwhohave contributedin one orthe otherway: ThomasBohlen, ThomasBouillon,
Christian Frei, Andrea Gentilini, Pascal Hänzi, Volker Hartwich, Sibylle Hirter, Jürg Imober-
steg, Alexandra Kruisheer, RolfLauber, Stefan Locher, Emilie Martinoni, Bertram Möhrlein,
Christoph Pfister, Sibylle Rohrbach, Valentina Sartori, Thomas Sieber, Robert Wessendorf,
Reto Wirz, RolfWymann and EleonoraZanderigo.
Especially thankful I am to Daniel Leibundgut for his support throughoutthe last years and to
Peter Schumacherwho's advice grewmore and more importantin avery shorttime. Moreover,
I am thankful fortheirfriendship.
The significant contributions provided by Raimundo Sierra, David Hausheer, Christian Aebi
and Michael Wyss while working on term projects is greatly appreciated. I would also like to
thankRalfKahlerfor coming to Zurich and forthe resulting stimulating discussions.
Further I would like to thank the members ofthe automatic control laboratory for their help,
especially Marco Sanvido for the patience in sharing an office and in explaining the hidden
secrets ofOberon.
l
The generous support received from the Swiss National Science Foundation (Grant SNSF 32-
55479.98) and DrägerMedizintechnik AG, Lübeck, Germany is greatly appreciated.
Last but not least I would like to thank my family for their manifold support throughout the
manyyears ofeducation and especially mywife Christi whohas endured somany "controlling"
discussions and for sharing the future.
Thank you!
Summary
Patientsafetyand costreductionas acauseofminimizeddrug consumption and shortened post¬
operative recovery phases are part ofthe main issues to motivate automation in anaesthesia.
The anaesthetist has four main objectives while maintaining anaesthesia, these are to provide
hypnosis, analgesia, skeletal muscle relaxation and artificial ventilation. For all objectives a
solution to automate these routine tasks is described including the clinical tests on patients
undergoing general anaesthesia for elective surgery.
A first focus is on the development of a framework for the design of closed-loop controllers.
This includes a modelling framework based on a physiologically based model. With the same
model structure the patient's reaction to different anaesthetic drugs can be estimated, which
allows to design artefact and robust controllers. A crucial part in introducing any automatic
system is the appropriate testing ofthe system prior to the application in the actual environ¬
ment. Therefore, a simulation tool was developed, which allows strict closed-loop testing and
moreover, allows the involved anaesthetistto "train" on the system.
A second focus arethe descriptions ofthe single controllers forthe main fourobjectives, which
includes many details on the specific implementation. All controllers were tested during pilot
studies and with one exception also tested during a clinical study. The results are described
in detail. The clinical studies are partially designed to compare the performance ofthe con¬
trollers to the performance of an anaesthetist. The results suggest that the automatic system
outperforms the anaesthetist and indications are found that patient safety may be improved.
in

Zusammenfassung
Die Motivation zurAutomation vonRoutineprozessen in derAnästhesie dienenunter anderem
derPatientensicherheitund dem Sparpotential aufgrund möglicherMedikamentenminimierung
sowie den daraus folgenden kürzeren postoperativen Erholungsphasen der Patienten. Der
Anästhesist hat vier Hauptaufgaben während der Anästhesie, die Erhaltung der Hypnosetiefe,
der Schmerzunempfindlichkeit, derRelaxierung und der künstlichen Beatmung. Für alle diese
wurde eine Automationslösung erarbeitet, welche klinisch erprobtwurde.
Einen ersten Schwerpunkt bildet die Erarbeitung von Grundlagen zum Entwurf von Regel¬
kreisen in der Anästhesie. Dabei spielt die Modellierung des Verhaltens des Patienten auf
die Verabreichung von Anästhetika eine wichtige Rolle. Basierend auf einem physiologis¬
chen Modell kann die Reaktion aufverschiedene Medikamente vorausgesagtwerden wodurch
das Verhalten der Regler wesentlich verbessert werden kann. Ein wesentlicher Teil bei der
Entwickelung automatischer Systeme im allgemeinen und im speziellen in einer klinischen
Umgebung ist die gründliche Erprobung der Systeme, bevor diese am Menschen eingesetzt
werden. Daherwurde eine Testumgebung entwickelt, womit die geschlossenen Regelsysteme
erprobtund die involvierten Anästhesisten ausgebildetwerden können.
Einen zweiten SchwerpunktbildetdieBeschreibung dervierwesentlichenRegelkreise. Fürdie
klinische Anwendbarkeitwichtige Details derImplementierungwerden erklärtund diejeweili¬
gen klinischen Tests beschrieben. Bis aufeinen Regelkreis wurden alle in einer ausgedehnten
klinischen Studie eingesetzt. Diese sind teilweise ausgelegt um die Regelgüte des automa¬
tischen Systems mit der eines Anästhesisten zu vergleichen. Die Resultate zeigen, dass das
automatische System eine genauere Anästhesie führen kann und dass dadurch die Patienten¬
sicherheit eherverbessertwird.
v

Contents
1 Introduction 1
1.1 Anaesthesia 2
1.2 Motivation 4
1.3 Automation 5
1.3.1 DevelopmentPhases 6
1.3.2 Development Cycle 8
1.4 Previous Work 8
1.4.1 Literature 8
1.4.2 Basis Provided by the Research Group 9
1.5 Scope 11
2 Concepts and Methods 15
2.1 Modelling in Anaesthesia 16
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