Markus Hülsbusch

In-Ear Vital Signs Monitoring Using a Novel Microoptic Reflective Sensor

Cardiovascular diseases are among the most common causes of death in industrial countries. In order to take preventive actions, it is of great interest, to both physicians and patients, to determine cardiovascular risk factors early. To address this problem, a wearable in-ear measuring system (IN-MONIT) for 24/7 monitoring of vital parameters has been developed. The central component is a microoptic reflective sensor located inside the auditory canal. From the measured photoplethysmographic curves, heart activity and heart rate can be derived. In this paper, we describe the optoelectronic sensor concept and the autonomous design of the IN-MONIT measurement system. For the assessment of heart rate, different algorithms are introduced and the performance of the developed sensor system is evaluated in relation to conventional systems. In addition, the robustness to external artifacts is evaluated and artifact reduction strategies are considered.

In-Ear Heart Rate Monitoring Using a Micro-Optic Reflective Sensor

Cardiovascular diseases are among the most common causes of death in western industrial nations. It is of great interest of both physician and patient to determine the cardiovascular risk factors early in order to take preventive measures. To assist the recognition of irregularities in a subjects cardiovascular system, we develop an optic 24/7 in-ear monitoring system (IN-MONIT). The central component is a micro-optic remission/reflection sensor (MORES), which is placed inside the auditory canal. There the pulsation of blood within the capillaries is measured by means of optical absorption. From the resulting photoplethysmographic curves (pulse plethysmogram, PPG), the heart rate, oxygen saturation (SpO2), respiratory rate and higher order moments can be derived. The optical absorption data are processed locally using a microcontroller and the results are transferred wirelessly to a personal digital assistant (PDA) or PC for sophisticated classification. This paper introduces the IN-MONIT system and two algorithms for heart rate determination from ECG or PPG data. The performance of these algorithms was tested using annotated ECG data from the ldquoMIT-BIH Normal Sinus Rhythm Databaserdquo, synchronously recorded ECG and pulse oximeter data, and data acquired by the MORES sensor.

A system for assessing motion artifacts in the signal of a micro-optic in-ear vital signs sensor

Cardiovascular diseases are among the most common causes of death in developed industrial nations. It is of great interest of both physician and patient to determine the cardiovascular risk factors early in order to take preventive measures. To assist these investigations we develop a wearable in-ear mesuring system (IN-MONIT) for 24/7 monitoring of heart rate and oxygen saturation (SpO2). The central component is a micro-optic remission/reflection sensor (MORES) located inside the auditory canal. From the measured photoplethysmographic curves the aforementioned vital signs can be derived. In the following we present a recording system for assessing motion artifact influence in the in-ear sensor data. Two accelerometer sensors record posture and motion while at the same time SpO2, heart rate and PPG are mesured using both a commercial sensor and the in-ear sensor. The data is transmitted wirelessly to a control PC for storage and further investigation. Using this system we assessed the influence of motion artifacts produced by daily life activities on infrared and red in-ear PPG data and on readings of the reference sensor.

Analysis of Heart Rate Variability with an In-Ear Micro-Optic Sensor in View of Motion Artifacts

The variability of the heart rate has emerged to a popular marker for the overall condition of the circulatory system. In this paper, a novel approach for determining the heart rate by pulseoxymetric measurements inside the ear (IN-MONIT) is presented. Pulse signals from the auditory canal are mainly influenced by jaw motions. This influence can complicate the precise determination of the pulse rate and may yield lacks in the derivated tachograms. Therefore, the correlation properties of heart beat intervals and the influence of possible lacks in the tachograms on the outcome of the analysis are studied. It is shown that the usage of advanced methods of statistical time series analysis (e.g. Lomb-periodograms) is suitable in order to analyse signals without further complex filter designs. Together with this mathematical approach, the IN-MONIT system offers the opportunity to perform a 24/7 monitoring without disturbing the normal life of the monitored subject.

Contactless measurement of dermal oxygen saturation with spatial resolution

Optoelectronic registration of dermal oxygen saturation can be done via photoplethysmographic (PPG) measurement of arterial perfusion or via measurement of the remission spectrum of vital skin. Due to their simple measurement principle and setup photoplethysmographic oxygen measurement systems have found their way to daily use in clinics and ambulances many years ago. The measured oxygen saturation is one of the most important parameters to evaluate the patient’s state of health. The used sensors consist just of two monochromatic light sources and one photo-detector and are either used in reflective or transmission mode. In the last years the Institute of High Frequency Technology (IHF), RWTH Aachen, has developed an enhancement of the PPG measurement called Photoplethysmography Imaging (PPGI) giving the possibility to measure skin perfusion contactless with a sensitive camera instead of the classical sensor. This system will also be used for the contactless measurement of dermal oxygen saturation. The concept and basic setup of this system will be described in this paper.