The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.

Monitoring Sleep and Hypercapnia with Near-Infrared Spectroscopy

Jaakko Virtanen

Doctoral dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the School of Science for public examination and debate in Auditorium F239a at the Aalto University School of Science (Espoo, Finland) on the 16th of September 2011 at 12 noon.

Overview in PDF format (ISBN 978-952-60-4231-2)   [1898 KB]
Dissertation is also available in print (ISBN 978-952-60-4230-5)


Near-infrared spectroscopy (NIRS) is a medical imaging modality that allows non-invasive estimation of tissue oxygenation and hemodynamics. NIRS has great potential in long-term monitoring of regional cerebral circulation due to its unique combination of excellent temporal resolution, safety and suitability for multimodal measurements, and low cost and portability. Such monitoring can provide valuable information on cerebral oxygenation during voluntary or involuntary cessation of breathing, and on slow changes in spontaneous cerebral activity. However, contribution from extracerebral tissue and motion artefacts hinder interpretation of the measured signals.

This thesis presents methodological improvements to NIRS that aid in separating the cerebral and extracerebral waveforms from NIRS signals measured during hypercapnia (elevated blood carbon dioxide level), and in removing motion artefacts that prevent tracking slow hemodynamic changes. It also describes the cerebrovascular and systemic responses to hypercapnia induced by voluntary breath hold, illustrates differences between voluntary breath hold and obstructive sleep apnea (OSA), and characterises spontaneous cerebral hemodynamic activity during different sleep stages.

The results show that extracerebral contribution to NIRS signals during hypercapnia can be greatly reduced in multi-distance measurements with a blind source separation method such as principal component analysis. In some cases, simply maximising the source–detector separation can provide high sensitivity to cerebral changes with minimal extracerebral interference. Evaluation of experimental data and literature allows identifying potentially clinically significant features of the breath hold and OSA responses. Finally, with the aid of a novel motion artefact reduction method, the slow-wave-sleep stage is shown to be characterised by a significant reduction in slow hemodynamic fluctuations compared to light and rapid-eye-movement sleep. This observation complements previous knowledge of the electrophysiological characteristics of slow-wave sleep, and can help in understanding the unique features and functions of different sleep stages.

This thesis consists of an overview and of the following 5 publications:

  1. Jaakko Virtanen, Tommi Noponen, and Pekka Meriläinen. 2009. Comparison of principal and independent component analysis in removing extracerebral interference from near-infrared spectroscopy signals. Journal of Biomedical Optics, volume 14, number 5, 054032, 10 pages. © 2009 Society of Photo-Optical Instrumentation Engineers (SPIE). By permission.
  2. Jaakko Virtanen, Tommi Noponen, Kalle Kotilahti, Juha Virtanen, and Risto J. Ilmoniemi. 2011. Accelerometer-based method for correcting signal baseline changes caused by motion artifacts in medical near-infrared spectroscopy. Journal of Biomedical Optics, volume 16, number 8, 087005, 9 pages. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). By permission.
  3. Jaakko Virtanen, Tommi Noponen, Tapani Salmi, Jussi Toppila, and Pekka Meriläinen. Impaired cerebral vasoreactivity may cause cerebral blood volume dip following obstructive sleep apnea termination. Sleep and Breathing, 4 pages, published online in May 2011. DOI 10.1007/s11325-011-0526-9.
  4. Jaakko Virtanen, Tommi Noponen, and Risto J. Ilmoniemi. 2011. Properties of end-expiratory breath hold responses measured with near-infrared spectroscopy. In: Bruce J. Tromberg, Arjun G. Yodh, Mamoru Tamura, Eva M. Sevick-Muraca, and Robert R. Alfano (editors). Optical Tomography and Spectroscopy of Tissue IX. SPIE Photonics West 2011 Conference: Biomedical Optics Symposium (BiOS 2011). San Francisco, California, USA. 23-26 January 2011. Bellingham, WA, USA. Society of Photo-Optical Instrumentation Engineers. Proceedings of SPIE, volume 7896, article 78960D, 10 pages. ISBN 978-0-8194-8433-8. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). By permission.
  5. Tiina Näsi, Jaakko Virtanen, Tommi Noponen, Jussi Toppila, Tapani Salmi, and Risto J. Ilmoniemi. 2011. Spontaneous hemodynamic oscillations during human sleep and sleep stage transitions characterized with near-infrared spectroscopy. PLoS ONE, volume 6, number 10, e25415, 9 pages. © 2011 by authors.

Keywords: near-infrared spectroscopy, monitoring, hemodynamics, sleep, hypercapnia, extracerebral contribution, motion artefact

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© 2011 Aalto University

Last update 2012-02-10