McCaughey, Euan James (2014) Abdominal functional electrical stimulation to improve respiratory ...

215 Pages·2014·3.22 MB·English

McCaughey, Euan James (2014) Abdominal functional electrical
stimulation to improve respiratory function in acute and sub-acute
tetraplegia. PhD thesis.

http://theses.gla.ac.uk/5471/

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ABDOMINAL FUNCTIONAL ELECTRICAL
STIMULATION TO IMPROVE RESPIRATORY
FUNCTION IN ACUTE AND SUB-ACUTE
TETRAPLEGIA
Euan James McCaughey, MEng
Submitted in fulfilment of the requirements for the Degree of Doctor of
Philosophy (PhD)
Submitted to the School of Engineering,
College of Science and Engineering,
University of Glasgow
August 2014
.
(cid:13)c Copyright 2014 by Euan James McCaughey, MEng. All Rights
Reserved.
i
Abstract
An injury to the cervical region of the spinal cord can cause paralysis affecting all four
limbs, termed tetraplegia. People with tetraplegia also have paralysis or impaired function
of the major respiratory muscles, namely the diaphragm and intercostal and abdominal
muscles. This often reduces respiratory function, with associated respiratory complications a
leadingcauseofmorbidityandmortalityforthispopulation. AbdominalFunctionalElectrical
Stimulation (AFES), the application of electrical pulses to the abdominal muscles causing
themtocontract,hasbeenshowntoimproverespiratoryfunctionintetraplegia. Despitethese
positive results, further work is needed to establish AFES as a standard clinical treatment.
The aim of this thesis is to support the clinical introduction of AFES. This was achieved
by addressing two primary objectives. Firstly, the development of new technologies and
protocols to optimise AFES for use in a clinical setting. Secondly, the clinical evaluation of
these technologies and protocols with tetraplegic patients.
For research purposes, AFES has typically been applied manually, requiring an operator
to synchronise stimulation with respiratory activity. One important step necessary for the
clinical introduction of AFES is the development of an automated AFES device that can
apply stimulation in synchrony with the users respiratory activity, with different stimulation
parameters applied for different breath types such as a quiet breath and a cough. In this
thesis, the signal from a non-intrusive respiratory effort belt, worn around the chest, was
used to develop a statistical classification algorithm capable of classifying respiratory activity
in real-time, and applying AFES in synchrony with the user’s respiratory activity. The
effectiveness of AFES can also be enhanced by stimulating at the abdominal muscle motor
points. Inthis thesis the positionsof the abdominal motorpoints were locatedsystematically
for the first time, in ten able bodied and five tetraplegic participants.
To aid the clinical introduction of AFES it is necessary to establish the patient groups who
would benefit most from this intervention, and to develop appropriate clinical protocols.
This is addressed in two clinical studies, where the feasibility and effectiveness of AFES to
improve the respiratory function of the acute ventilator dependant and sub-acute tetraplegic
populations was demonstrated. In the first study, conducted with 10 acute ventilator
dependant tetraplegics, AFES was applied on alternate weeks for a total duration of eight
weeks. This resulted in acute improvements in breathing and led to a longitudinal increase
ii
in respiratory function over the study duration. It was found that participants weaned from
mechanical ventilation on average 11 days faster than matched historic controls.
Previous work, which investigated the effect of a three week AFES training programme on
the respiratory function of people with sub-acute tetraplegia, suggested that an extended
AFES training programme may be more effective. In the second clinical study in this thesis,
a continuous eight week AFES training protocol (combined with a six week control period)
was evaluated with three sub-acute tetraplegic participants. The application of AFES led
to an acute increase in respiratory function, with a longitudinal improvement in respiratory
function observed throughout the study. In a single participant case study, the feasibility
of combining AFES with assisted coughing delivered by mechanical insufflation-exsufflation
was demonstrated for the first time. This was shown to lead to an acute improvement in
respiratory function at six of the eight assessment sessions, indicating that this technique
could be used to aid secretion removal.
This thesis highlights the feasibility and effectiveness of AFES to improve the respiratory
functionoftheacuteventilatordependantandsub-acutetetraplegicpopulations. Theclinical
protocols that enable AFES to be used with these patient groups, and the technological
developmentsdetailedthroughoutthisthesis, areanimportantsteptowardstheintroduction
of AFES as a regular treatment modality.
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Acknowledgements
The list of people who have helped me get to this stage is too long to be covered in this
acknowledgments section. However, the following people have played a major part in helping
me get to the stage of completing this thesis.
Firstly, I would like to thank Dr. Henrik Gollee for his supervision throughout my PhD. His
support, encouragement and ideas have helped to guide me through this process. Much of
what I have learned over the past few years is attributed to you and for this you have my
sincere thanks.
At the Queen Elizabeth National Spinal Injuries Unit (QENSIU) I would like to thank the
consultants Alan McLean, Mariel Purcell and Matthew Fraser, as well as the director David
Allan, for providing the knowledge, support and facilities to undertake cutting edge research
with the spinal cord injured population. For a mechanical engineer to come into a clinical
researchsettingwasachallenge,butitwasonethatIthoroughlyenjoyedandtookagreatdeal
of fulfilment from. The research driven environment that has been created at the QENSIU
provides an excellent platform for researchers to transfer knowledge gained in the lab to the
clinical setting, with a great benefit for the spinal cord injured population. I would like to
thank all at the QENSIU for helping create and maintain this unique research environment
andIhopethecollaborationwiththeUniversityofGlasgowcontinuesformanyyearstocome.
I would also like to acknowledge the various colleagues I have worked with within the Centre
for Rehabilitation Engineering over the course of my PhD. Every one of you was a source of
knowledge and encouragement and I will continue to offer you my whole hearted support at
all times. A special thanks goes to Angus McLachlan who acted as a mentor through my
masters project and the first year of my PhD. The knowledge and advice you passed on, even
when you had left the group, played a major role in the success of this project. I wish you
every success with your career in America and hope that maybe we can work together again
at some point in the future.
To all the volunteers who took part in the various studies outlined in this thesis I would like
to extend my thanks. Thank you for your patience and understanding when things were not
going to plan. I only hope you got the same amount of enjoyment out of taking part in the
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studies as I got from working with you.
I would like to acknowledge the EPSRC for the financial support provided to allow me to
conduct this PhD.
The unfaltering support of my friends and family throughout this PhD has meant a lot to
me. Spending time with those close to me has helped me to overcome the stressful periods,
of which there were many, and helped me to unwind. Finally, I would like to thank my wife
Laura. Your support, mainly in the form of putting up with me, has meant so much over
the last few years and will be rewarded with many cups of tea during your write up period!
Thank You!
“We must not forget that when radium was discovered no one knew that it would prove
useful in hospitals. The work was one of pure science. And this is a proof that scientific
work must not be considered from the point of view of the direct usefulness of it. It must be
done for itself, for the beauty of science, and then there is always the chance that a
scientific discovery may become like the radium a benefit for humanity.” Marie Curie
v
Author’s Declaration
I declare that, except where explicit reference is made to the contribution of others, that this
thesis is the result of my own work and has not been submitted for any other degree at he
University of Glasgow or any other institution.
All of the analysis and data collection techniques presented in this thesis were created by the
author.
E.J. McCaughey
August 2014
vi
Abbreviations
SCI: Spinal cord injury
FES: Functional electrical stimulation
AFES: Abdominal functional electrical stimulation
QENSIU: Queen Elizabeth National Spinal Injuries Unit
RTAs: Road traffic accidents
ASIA: American Spinal Injuries Association
AIS: ASIA impairment scale
UMN: Upper motor neuron
LMN: Lower motor neuron
V : Tidal volume
T
V /kg: Weight corrected tidal volume
T
CPF: Cough peak flow
MEP: Maximum expiratory pressure
MIP: Maximum inspiratory pressure
V : Vital capacity
C
FVC: Forced vital capacity
FVC/kg: Weight corrected forced vital capacity
V /kg: Weight corrected vital capacity
C
ATS: American Thoracic Society
ERS: European Respiratory Society
FEV : Forced exhaled volume in one second
1
NMES: Neuromuscular electrical stimulation
TENS: Transcutaneous electrical nerve stimulation
IMV: Intermittent mandatory ventilation
SBT: Spontaneous breathing trial
MI-E: Mechanical insufflation-exsufflation
RMT: Respiratory muscle training
PNP: Phrenic nerve pacing
DP: Intramuscular diaphragm pacing
SCS: Spinal cord stimulation
iSCS: Intercostal spinal cord stimulation
aSCS: Abdominal spinal cord stimulation
vii
EMG: Electromyograph
SVM: Support vector machine
RBF: Radial basis function
IMU: Inertial measurement unit
SaPO : Oxygen saturation level
2
GUI: Graphical user interface
PCC: Pearson product-moment correlation coefficient
ANOVA: Analysis of variance
FFT: Fast fourier transform
MP: Motor point
RA: Rectus abdominis
EO: External oblique
CoR: Coefficient of repeatability
BoTN-A: Botulinum toxin A
EV: Exhaled volume
PF: Peak flow
RCT: Randomised control trial
viii
Contributions
• In this thesis novel Abdominal Functional Electrical Stimulation (AFES) protocols and
technologiesaredevelopedandimplemented,anditisshownthattheycanhelpimprove
the respiratory function of the acute ventilator dependant and sub-acute tetraplegic
population. Demonstration of the feasibility and effectiveness of these technologies
and protocols is a necessary step towards the implementation of AFES as a clinical
treatment modality. As such, a key contribution of this thesis is proof of feasibility.
• By using the respiratory data recorded from 10 able bodied participants a novel
algorithm for non-intrusive real-time breathing pattern detection and classification has
been designed and tested. The use of a non-intrusive sensor, coupled with an improved
and less operator reliant classification algorithm, makes this method more suited to a
clinical setting than previous work where the signal from an intrusive spirometer was
used for breathing pattern classification.
• Neuromuscular electrical stimulation has been used for the first time to systematically
detect the position of the motor points of the abdominal muscles. By applying single
pulse electrical stimulation to the rectus abdominis and external oblique muscles, the
positionofthemotorpointsofthesemusclesweresuccessfullylocatedin10ablebodied
and five tetraplegic participants. The position of the motor points of these muscles,
along with the repeatability and uniformity of the position, is presented. The results
of this study suggest that this method could be used to accurately detect the position
of the abdominal muscle motor points to select the optimum electrode location for the
application of AFES.
• In the main clinical study of this thesis the feasibility of using AFES to improve the
respiratory function of acute ventilator dependant tetraplegics is shown. To use AFES
with this patient group a number of adaptations to standard AFES protocols were
required. NovelengineeringsolutionstoallowAFEStobesynchronisedwithmechanical
ventilation, or with the user’s own breathing, are presented. A novel training protocol,
designed to improve respiratory function while allowing the effectiveness of AFES to be
evaluated, was also developed. The gains in respiratory function achieved using these