Thomas Penzel, Ph.D.

Signal recording and non-linear processing in sleep research

Sleep disorders are found to be more prevalent than previously realized. This may be a consequence of a modern society which optimizes work and social activities up to the edge.

In order to investigate normal and disturbed sleep, we record biosignals both in the sleep laboratory and at home. Signals may be recorded directly, such as EEG, EOG, EMG from the head of the sleeping person, or indirectly, such as ECG, heart rate, respiration, pulse wave. Signals may be recorded with little contact or no contact systems such as actigraphy, body movement, bed sensors or bedside radiofrequency sensors. Some signals are new in sleep research and require new technology and analysis concepts.

Always biosignals were recorded with an appropriate time and amplitude resolution, and then we derive physiological functions. We can identify wakefulness and sleep, we can derive details about sleep, such as light sleep, deep sleep, and REM sleep, arousals and sleep fragmentation. Not only classical methods in the time and frequency domain are used, but also more recent methods using statistical approaches are applied.

This allows recognizing normal and restorative sleep and identifying sleep disorders as well. Some sleep disorders imply cardiovascular consequences and require treatment. Sleep disordered breathing is the disorder with most cardiovascular consequences. Many diagnostic tools focus on this group of disorders [1]. Diagnostic methods and perspectives are presented in this communication.

[1] IEEE Engineering in Biology and Medicine Society: “The Science of Sleep”. Pulse Magazine. Sept. / Oct. issue 2014.


Dr. Thomas Penzel graduated from physics (1986), human biology (1991), and physiology (1995) at the University Marburg, Germany. In 1997 he received a certificate for sleep medicine and for medical informatics. In 2001 became extra-ordinate Professor at the University of Marburg. At the University hospital Marburg he started in 1982 and installed the first sleep lab in a Department for Internal Medicine in Germany. This lab initiated many activities in the field of sleep medicine like home sleep apnea testing, deriving sleep apnea and sleep stages from ECG and heart rate, sleep center accreditation, cardio respiratory coupling analysis, sleep physician training and certification, and conferences with engineers and physicians on sleep medicine. In 2006 he moved to Berlin to join the interdisciplinary sleep medicine center at the Charité University hospital. He received the Bial award for clinical medicine in Portugal 2001, the Bill Gruen Award for Innovations in Sleep Research by the Sleep Research Society in 2008, the Somnus Award by Sleep apnea patient groups in Germany 2012, and the distinguished development award by the Chinese sleep research society in 2014. He is treasurer of the World Sleep Society (WSS), secretary of the German Sleep Society (DGSM), and board member of other societies. He authored more than 250 papers, book chapters and books. He is an editorial board member on journals in sleep research and biomedical engineering. His research focus is on new methods in sleep recording and cardiovascular consequences of sleep disorders. He is chair of the German IEEE EMB chapter and past chair of EMB TC cardiopulmonary systems.