«PEKKA TIIHONEN Novel Portable Devices for Recording Sleep Apnea and Evaluating Altered Consciousness Doctoral dissertation To be presented by ...»
KUOPION YLIOPISTON JULKAISUJA C. LUONNONTIETEET JA YMPÄRISTÖTIETEET 261
KUOPIO UNIVERSITY PUBLICATIONS C. NATURAL AND ENVIRONMENTAL SCIENCES 261
Novel Portable Devices for Recording
Sleep Apnea and Evaluating
To be presented by permission of the Faculty of Natural and Environmental Sciences of the University of Kuopio for public examination in Auditorium L3, Canthia building, University of Kuopio, on Friday 27 th November 2009, at 12 noon Department of Physics University of Kuopio Department of Clinical Neurophysiology Kuopio University Hospital JOKA KUOPIO 2009 Distributor : Kuopio University Library P.O. Box 1627 FI-70211 KUOPIO
FINLANDTel. +358 40 355 3430 Fax +358 17 163 410 http://www.uku.fi/kirjasto/julkaisutoiminta/julkmyyn.shtml Series Editor : Professor Pertti Pasanen, Ph.D.
Department of Environmental Science Author’s address: Department of Clinical Neurophysiology Kuopio University Hospital P.O. Box 1777 FI-70211 KUOPIO
FINLANDTel. +358 17 173 233 Fax +358 17 173 244 E-mail: firstname.lastname@example.org http://kotisivu.dnainternet.net/tiihone/index.htm Supervisors: Docent Juha Töyräs, Ph.D.
Department of Physics University of Kuopio Deputy Chief Physicist Ari Pääkkönen, Ph.D.
Department of Clinical Neurophysiology Kuopio University Hospital Reviewers: Professor Thomas Penzel, Ph.D.
Charité Universitätsmedizin Berlin Germany Professor Sari-Leena Himanen, M.D., Ph.D.
Department of Clinical Neurophysiology Tampere University Hospital Opponent: Professor Hannu Eskola, Dr.Tech.
Tampere University of Technology ISBN 978-951-27-1199-4 ISBN 978-951-27-1294-6 (PDF) ISSN 1235-0486 Kopijyvä Kuopio 2009 Finland Tiihonen, Pekka. Novel Portable Devices for Recording Sleep Apnea and Evaluating Altered Consciousness. Kuopio University Publications C. Natural and Environmental Sciences 261.
2009. 79 p.
ISBN 978-951-27-1199-4 ISBN 978-951-27-1294-6 (PDF) ISSN 1235-0486 ABSTRACT Sleep apnea is defined as a repetitive cessation of airflow in spite of breathing efforts. In the middle-aged population, the prevalence of sleep apnea is 9 – 24%. Sleep apnea increases significantly the risk of cardiovascular disease, stroke, high blood pressure, diabetes and accidents. For example, untreated severe sleep apnea was found to increase fatal cardiovascular events by more than 500% in a 12 year follow-up. Traditionally, overnight polysomnography has been the primary method for diagnosing the disease and only recently have portable devices been accepted as alternative tools for diagnostics of sleep apnea.
The aim of the first study of this work was to design, construct and evaluate a portable device (Venla) suitable for recording of sleep apnea. In the second study, the clinical potential of a successor (APV2) of the device developed in the first study was evaluated. The device dependence of the reliability of an automatic analysis of sleep apnea events was investigated in the third study. In the fourth study, a portable device (Emma) was developed for monitoring of the level of consciousness in the intensive care unit (ICU); this device is based on recording of auditory evoked potentials.
Technical and clinical evaluation of the novel portable monitoring devices (Venla and APV2) revealed that they possessed similar diagnostic capabilities as a reference laboratory instrument (Embla) in detecting sleep apnea. No statistical differences were found in the apnea hypopnea index (AHI) or oxygen desaturation index (ODI) recorded with Venla and APV2 when compared to those recorded with the reference laboratory instrument. Furthermore, the AHI and ODI values determined with the novel devices and the reference instrument were highly correlated. Importantly, the novel devices showed better technical reliability, with fewer failed recordings (Venla 6.7% and APV2 4.0%) than the widely used commercial device (Embletta, 19.2%).
The results of the third study indicate that an exclusion of obstructive sleep apnea (OSA) should never be done based on automated analysis alone. The diagnosis of mild OSA should always be based on manual analysis of the recording, but if the result of the automatic analysis is detection of moderate or severe sleep apnea, it may be accepted without further manual confirmation of the validity of the analysis. Importantly, classifying the disease further into the obstructive, mixed or central types should always be done manually.
In the fourth study a compact portable battery operated device for measuring event-related potentials, somatosensory evoked potentials, as well as the electroencephalogram and electrocardiogram was designed, constructed and programmed for off-line monitoring of the level of consciousness or depth of sedation. The device is intended to be used in intensive care units and emergency rooms, which places special requirements on the robustness and simplicity of the use of the instrumentation. Technical evaluation and in vivo recordings revealed that the device can be reliably and safely used for clinical diagnostics.
National Library of Medicine Classification: QT 36, WB 142, WF 143, WM 188, WL 341, WL 705 Medical Subject Headings: Sleep Disorders/diagnosis; Sleep Apnea Syndromes/diagnosis;
Sleep Apnea, Obstructive/diagnosis; Consciousness; Consciousness Disorders; Monitoring, Ambulatory/instrumentation; Polysomnography; Evoked Potentials, Auditory; Electroencephalography; Intensive Care Units; Equipment Design; Biomedical Engineering To my family: Leena, Timo and Tiina
ACKNOWLEDGEMENTSThis study was carried out during the years 2006-2009 in the Department of Clinical Neurophysiology, Kuopio University Hospital. However, the technical development of the devices and transducers begun already in 1985 in Vaajasalo Hospital. The study was made possible by many important people and grant-giving organizations.
I sincerely thank my supervisors for guidance during this thesis work, for sharing their expertise and for setting such a brilliant example as true scientists. I am grateful to my tireless principal supervisor, Docent Juha Töyräs, Ph.D. from Biophysics of Bone and Cartilage group at the University of Kuopio, for guiding me on the long journey of planning and executing scientific studies and writing scientific papers. His competence in managing difficult scientific problems during this study has been astonishing. He is a positive example of a man who illustrates what “sisu” means in solving difficult problems. I am grateful to my second supervisor, deputy chief physicist Ari Pääkkönen, Ph.D., for placing at my disposal his extensive knowledge of neurophysiology, especially in the field of event-related potentials. His English writing skills have been a great help in preparing the manuscripts.
I thank my official reviewers Professor Thomas Penzel, Ph.D., and Professor SariLeena Himanen, M.D., Ph.D., for constructive criticism and valuable suggestions. I am also grateful to Ewen MacDonald, D. Pharm. for carrying out the linguistic review.
I owe my sincere gratitude to my co-authors: Professor, chief physician Esa Mervaala, M.D., Ph.D., Docent Henri Tuomilehto, M.D., Ph.D., and Taina Hukkanen, B.Sc. for their contributions during the measurements and the preparation of the manuscripts. In particular, I wish to thank my colleague physicist Jukka Kinnunen, M.Sc., for his valuable contribution in writing the measurement and analysis software for the Emma device. He provided valuable contributions during the many years we developed several new piece of equipment to be used in clinical neurophysiology.
Chief physician, Docent Juhani Partanen, M.D., Ph.D. is acknowledged for guiding me to concentrate on long-term recording of neurophysiological signals at the beginning of my career in Vaajasalo Hospital. In addition, his support in the development of event-related potential recording device (Emma) was important.
I am grateful to chief physician Sara Määttä, M.D., Ph.D., for her constructive suggestions on the thesis.
I sincerely thank my colleague physicists in the Department of Clinical Neurophysiology: Mervi Könönen, M.Sc., Petro Julkunen, Ph.D., Mikko Nissi, Ph.D., Docent Simo Saarakkala, Ph.D., and Eini Niskanen, M.Sc., for their highly intelligent and motivated support. I have greatly enjoyed working in the warm and inspiring atmosphere you produce.
I want to thank the staff of the Department of Clinical Neurophysiology for tolerating my sometimes curious way for solving problems. I appreciate the honest feedback I have received during the years I have been developing new devices for recording long-term signals from patients. Especially, I wish to thank instrumentation technician Pertti Knuutinen for his skillful mechanical construction work during the many years when we have been developing equipment (e.g., Emma) for clinical neurophysiology.
I want to acknowledge my radio amateur colleagues for keeping me in touch with I am grateful to my younger brother Aimo, for long lasting information exchange and innovative support concerning the development of electronical and mechanical equipments from the early 70s to the current days. Among other things, he showed me in practice how to do a proper soldering. I acknowledge my youngest brother Ossi, for taking a personal economical risk to set up a company to develop the Venla device further.
My dearest thanks go to my beloved parents Vieno and Pentti, for their loving and wonderful life long support in spite of poor starting circumstances only eight years after World War II.
I am deeply grateful to my dear children Timo and Tiina, for providing me twice with the opportunity to follow the growth and development of a human being from an infant into an adult. It has been a great privilege to be a proud father for almost three decades. You have stimulated me to work harder and get things done.
I owe my deepest thanks to my beloved wife Leena, for her love and understanding support during these projects and our family life. You have been my firm anchor to real life.
This study was financially supported by the Foundation for Advanced Technology of Eastern Finland, Kuopio University Hospital (EVO-grant) and the Finnish Cultural Foundation of Northern Savo, which I gratefully acknowledge. Finally, I would like to thank Remote Analysis Ltd, Kuopio, Finland, for technical support in studies related to the APV2 and Venla devices.
Kuopio, November 2009 Pekka Tiihonen
ABBREVIATIONSAASM American Academy of Sleep Medicine AD Analogue-to-digital ADC Analogue-to-digital converter AEP Auditory evoked potential AHI Apnea-hypopnea index AI Apnea index BAEP Brainstem auditory evoked potential BIS Bispectral BPM Beats per minute CF Compact flash CMRR Common mode rejection ratio CNS Central nervous system CVS Cardiovascular DC Direct current EDS Excessive daytime sleepiness ECG Electrocardiogram EEG Electroencephalogram EMC Electro magnetic compatibility EMG Electromyogram EOG Electrooculogram ERP Event-related potential ESS Epworth sleepiness scale HR Heart rate ICU Intensive care unit LCD Liquid crystal display LED Light emitting diode LLAEP Long-latency evoked potential MLAEP Middle-latency evoked potential MMN Mismatch negativity NTC Negative temperature coefficient ODI Oxygen desaturation index OSA Obstructive sleep apnea OSAS Obstructive sleep apnea syndrome PM Portable monitoring PSG Polysomnography PVDF Polyvinylidene fluoride RAM Random access memory RDI Respiratory-disturbance index RERA Respiratory effort-related arousal RMS Root mean square RP Respiratory polygraphy SAS Sleep apnea syndrome SEP Somatosensory evoked potential SpO2 Oxygen saturation UARS Upper airway resistance syndrome USB Universal serial bus VEP Visual evoked potential
LIST OF ORIGINAL PUBLICATIONSThis thesis is based on the following original articles, which are referred to in the text
by their Roman numerals:
I Design, construction and evaluation of an ambulatory device for screening of sleep apnea.
Tiihonen P, Pääkkönen A, Mervaala E, Hukkanen T, Töyräs J.
Medical & Biological Engineering & Computing (2009), volume 47, number 1, pages 59-66, DOI: 10.1007/s11517-008-0418-8.
II Evaluation of a novel ambulatory device for screening of sleep apnea.
Tiihonen P, Hukkanen T, Tuomilehto H, Mervaala E, Töyräs J.
Telemedicine and e-Health (2009), volume 15, number 3, pages 283-289, DOI:
III Accuracy of automatic analysis of ambulatory recordings of nocturnal breathing disorders is significantly instrumentation dependent.
Tiihonen P, Hukkanen T, Tuomilehto H, Mervaala E, Pääkkönen A, Töyräs J.
Journal of Medical Engineering & Technology (2009), volume 33, number 5, pages 386-393, DOI: 10.1080/03091900902739999.
IV A portable device for intensive care brain function monitoring with event-related potentials.
Tiihonen P, Kinnunen J, Töyräs J, Mervaala E, Pääkkönen A.
Computer Methods and Programs in Biomedicine (2008), volume 89, number 1, pages 83-92, DOI: 10.1016/j.cmpb.2007.10.010.
More than 70 different types of sleep disorders have been described. They are classified into eight major categories: insomnia, sleep related breathing disorders, hypersomnias of central origin, circadian rhythm sleep disorders, parasomnias, sleep related movement disorders, isolated symptoms and normal variants, and other sleep disorders (AASM 2005). The most common sleep related breathing disorders are obstructive sleep apnea (OSA), upper airway resistance syndrome (UARS) and long lasting partial obstruction. The most prevalent sleep disorders (with sufferers in USA presented in brackets) are insomnia (about 60 million), sleep apnea (18 million), restless legs syndrome (12 million) and narcolepsy (250000) (NIH 2007). This thesis concentrates on sleep related breathing disorders, mostly on obstructive sleep apnea.