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Article ; Online: Dual-Lead 55 mm Impedance Pneumography

Klum Michael / Urban Mike / Pielmus Alexandru-Gabriel / Orglmeister Reinhold

Current Directions in Biomedical Engineering, Vol 6, Iss 3, Pp 205-

2020 Volume 208

Abstract: In recent years, respiratory monitoring has gained attention due to the high prevalence and severe consequences of sleep apnea, post-anesthesia respiratory instability and respiratory diseases. Nevertheless, respiratory monitoring oftentimes relies on ... ...

Abstract	In recent years, respiratory monitoring has gained attention due to the high prevalence and severe consequences of sleep apnea, post-anesthesia respiratory instability and respiratory diseases. Nevertheless, respiratory monitoring oftentimes relies on obtrusive masks and belts, which are unsuitable for wearable, long-term monitoring. Impedance pneumography (IP) is a bioimpedance method aiming to assess respiratory parameters unobtrusively. However, most IP configurations require far-spaced electrodes. Based on our recent work on wearable IP, we propose a dual-lead, wearable IP setup with 55 mm electrode spacing to estimate respiratory flow and rate (RR). Using our recently presented multimodal patch stethoscope as well as commercial systems, we conducted a study including 10 healthy subjects which were recorded in the supine, lateral and prone position. Using time-delay neural networks, we achieved RR estimation errors below 0.6 breaths per minute and flow correlations of 0.88 with relative errors of 25 % to a pneumotachometer reference. We conclude that dual-lead IP increases the performance of respiratory signal estimation compared to a single lead and recommend research in the area of subject position dependency and movement artefacts.
Keywords	multi-lead bioimpedance ; wearable impedance pneumography ; wearable respiratory monitoring ; respiratory rate ; respiratory flow ; sensor patch ; neural network ; Medicine ; R
Language	English
Publishing date	2020-09-01T00:00:00Z
Publisher	De Gruyter
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Wearable Impedance Pneumography

Klum Michael / Urban Mike / Pielmus Alexandru-Gabriel / Orglmeister Reinhold

Current Directions in Biomedical Engineering, Vol 6, Iss 3, Pp 233-

2020 Volume 236

Abstract: Respiratory diseases are a leading cause of death worldwide. The prevalence of sleep apnea, its cardiovascular consequences, postoperative respiratory instability and severe respiratory syndromes further highlight the importance of respiratory monitoring. ...

Abstract	Respiratory diseases are a leading cause of death worldwide. The prevalence of sleep apnea, its cardiovascular consequences, postoperative respiratory instability and severe respiratory syndromes further highlight the importance of respiratory monitoring. Typical methods, however, rely on obtrusive nasal cannulas and belts. Impedance pneumography (IP) is a promising bioimpedance application which aims to estimate respiratory parameters from the thorax impedance. Currently, IP configurations require large inter-electrode distances, diminishing its applicability in a wearable context. We propose an IP configuration with 55 mm spacing using our recently presented sensor patch. In a study including 10 healthy subjects, respiratory rate (RR) and flow are estimated in the supine, lateral and prone position. Using time-delay neural network regression, RR errors below 1 bpm, flow correlations of 0.81 and relative flow errors of 38 % with respect to a pneumotachometer reference were achieved. We conclude that high accuracy RR estimation is possible in a 55 mm IP configuration. Respiratory flow can be roughly estimated. Further research combining several biosignals for a more robust, wearable flow estimation is recommended.
Keywords	impedance pneumography ; wearable respiratory monitoring ; respiratory rate ; respiratory flow ; sensor patch ; neural network ; bioimpedance ; Medicine ; R
Language	English
Publishing date	2020-09-01T00:00:00Z
Publisher	De Gruyter
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Progressive Dynamic Time Warping for Noninvasive Blood Pressure Estimation

Pielmus Alexandru-Gabriel / Klum Michael / Tigges Timo / Orglmeister Reinhold / Urban Mike

Current Directions in Biomedical Engineering, Vol 6, Iss 3, Pp 579-

2020 Volume 582

Abstract: Arterial blood pressure is one of the most important cardiovascular parameters. Yet, current-generation devices for continuous, noninvasive acquisition are few, expensive and bulky. Novel signal processing applied to easily acquired unimodal signals can ... ...

Abstract	Arterial blood pressure is one of the most important cardiovascular parameters. Yet, current-generation devices for continuous, noninvasive acquisition are few, expensive and bulky. Novel signal processing applied to easily acquired unimodal signals can alleviate this issue, reducing size, cost and expanding the use of such devices to ambulatory, everyday settings. The features of pulse waves acquired by photo- or impedance-plethysmography can be used to estimate the underlying blood pressure. We present a progressive dynamic time warping algorithm, which implicitly parametrizes the morphological changes in these waves. This warping method is universally applicable to most pulse wave shapes, as it is largely independent of fiducial point detection or explicit parametrization. The algorithm performance is validated in a feature selection and regression framework against a continuous, noninvasive Finapres NOVA monitor, regarding systolic, mean and diastolic pressures during a light physical strain test protocol on four clinically healthy subjects (age18- 33, one female). The obtained mean error is 2.13 mmHg, the mean absolute error is 5.4 mmHg and the standard deviation is 5.6 mmHg. These results improve on our previous work on dynamic time warping. Using single-sensor, peripherally acquired pulse waves, progressive dynamic time warping can thus improve the flexibility of noninvasive, continuous blood pressure estimation.
Keywords	progressive dynamic time warping ; arterial blood pressure ; impedance ; photo plethysmography ; noninvasive ; continuous ; unobtrusive ; dtw ; ppg ; ipg ; Medicine ; R
Subject code	621
Language	English
Publishing date	2020-09-01T00:00:00Z
Publisher	De Gruyter
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: GRU Neural Network Improved Bioimpedance Based Stroke Volume Estimation during Ergometry Stress Test.

Urban, Mike / Klum, Michael / Pielmus, Alexandru-Gabriel / Liebrenz, Falk / Mann, Steffen / Tigges, Timo / Orglmeister, Reinhold

Sensors (Basel, Switzerland)

2022 Volume 22, Issue 20

Abstract: Cardiovascular diseases (CVDs) are one of the leading members of non-communicable diseases. An early diagnosis is essential for effective treatment, to reduce hospitalization time and health care costs. Nowadays, an exercise stress test on an ergometer ... ...

Abstract	Cardiovascular diseases (CVDs) are one of the leading members of non-communicable diseases. An early diagnosis is essential for effective treatment, to reduce hospitalization time and health care costs. Nowadays, an exercise stress test on an ergometer is used to identify CVDs. To improve the accuracy of diagnostics, the hemodynamic status and parameters of a person can be investigated. For hemodynamic management, thoracic electrical bioimpedance has recently been used. This technique offers beat-to-beat stroke volume calculation but suffers from an artifact-sensitive signal that makes such measurements difficult during movement. We propose a new method based on a gated recurrent unit (GRU) neural network and the ECG signal to improve the measurement of bioimpedance signals, reduce artifacts and calculate hemodynamic parameters. We conducted a study with 23 subjects. The new approach is compared to ensemble averaging, scaled Fourier linear combiner, adaptive filter, and simple neural networks. The GRU neural network performs better with single artifact events than shallow neural networks (mean error -0.0244, mean square error 0.0181 for normalized stroke volume). The GRU network is superior to other algorithms using time-correlated data for the exercise stress test.
MeSH term(s)	Humans ; Stroke Volume ; Cardiography, Impedance/methods ; Exercise Test ; Neural Networks, Computer ; Algorithms
Language	English
Publishing date	2022-10-17
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2052857-7
ISSN	1424-8220 ; 1424-8220
ISSN (online)	1424-8220
ISSN	1424-8220
DOI	10.3390/s22207883
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Detection of a Stroke Volume Decrease by Machine-Learning Algorithms Based on Thoracic Bioimpedance in Experimental Hypovolaemia.

Stetzuhn, Matthias / Tigges, Timo / Pielmus, Alexandru Gabriel / Spies, Claudia / Middel, Charlotte / Klum, Michael / Zaunseder, Sebastian / Orglmeister, Reinhold / Feldheiser, Aarne

Sensors (Basel, Switzerland)

2022 Volume 22, Issue 14

Abstract: Compensated shock and hypovolaemia are frequent conditions that remain clinically undetected and can quickly cause deterioration of perioperative and critically ill patients. Automated, accurate and non-invasive detection methods are needed to avoid such ...

Abstract	Compensated shock and hypovolaemia are frequent conditions that remain clinically undetected and can quickly cause deterioration of perioperative and critically ill patients. Automated, accurate and non-invasive detection methods are needed to avoid such critical situations. In this experimental study, we aimed to create a prediction model for stroke volume index (SVI) decrease based on electrical cardiometry (EC) measurements. Transthoracic echo served as reference for SVI assessment (SVI-TTE). In 30 healthy male volunteers, central hypovolaemia was simulated using a lower body negative pressure (LBNP) chamber. A machine-learning algorithm based on variables of EC was designed. During LBNP, SVI-TTE declined consecutively, whereas the vital signs (arterial pressures and heart rate) remained within normal ranges. Compared to heart rate (AUC: 0.83 (95% CI: 0.73-0.87)) and systolic arterial pressure (AUC: 0.82 (95% CI: 0.74-0.85)), a model integrating EC variables (AUC: 0.91 (0.83-0.94)) showed a superior ability to predict a decrease in SVI-TTE ≥ 20% (
MeSH term(s)	Algorithms ; Humans ; Hypovolemia/diagnosis ; Lower Body Negative Pressure/adverse effects ; Machine Learning ; Male ; Stroke Volume/physiology
Language	English
Publishing date	2022-07-06
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2052857-7
ISSN	1424-8220 ; 1424-8220
ISSN (online)	1424-8220
ISSN	1424-8220
DOI	10.3390/s22145066
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Article: Perioperative advanced haemodynamic monitoring of patients undergoing multivisceral debulking surgery: an observational pilot study.

Middel, Charlotte / Stetzuhn, Matthias / Sander, Nadine / Kalkbrenner, Björn / Tigges, Timo / Pielmus, Alexandru-Gabriel / Spies, Claudia / Pietzner, Klaus / Klum, Michael / von Haefen, Clarissa / Hunsicker, Oliver / Sehouli, Jalid / Konietschke, Frank / Feldheiser, Aarne

Intensive care medicine experimental

2023 Volume 11, Issue 1, Page(s) 61

Abstract: Background: Patients undergoing high-risk surgery show haemodynamic instability and an increased risk of morbidity. However, most of the available data concentrate on the intraoperative period. This study aims to characterise patients with advanced ... ...

Abstract	Background: Patients undergoing high-risk surgery show haemodynamic instability and an increased risk of morbidity. However, most of the available data concentrate on the intraoperative period. This study aims to characterise patients with advanced haemodynamic monitoring throughout the whole perioperative period using electrical cardiometry. Methods: In a prospective, observational, monocentric pilot study, electrical cardiometry measurements were obtained using an Osypka ICON™ monitor before surgery, during surgery, and repeatedly throughout the hospital stay for 30 patients with primary ovarian cancer undergoing multivisceral cytoreductive surgery. Severe postoperative complications according to the Clavien-Dindo classification were used as a grouping criterion. Results: The relative change from the baseline to the first intraoperative timepoint showed a reduced heart rate (HR, median - 19 [25-quartile - 26%; 75-quartile - 10%]%, p < 0.0001), stroke volume index (SVI, - 9.5 [- 15.3; 3.2]%, p = 0.0038), cardiac index (CI, - 24.5 [- 32; - 13]%, p < 0.0001) and index of contractility (- 17.5 [- 35.3; - 0.8]%, p < 0.0001). Throughout the perioperative course, patients had intraoperatively a reduced HR and CI (both p < 0.0001) and postoperatively an increased HR (p < 0.0001) and CI (p = 0.016), whereas SVI was unchanged. Thoracic fluid volume increased continuously versus preoperative values and did not normalise up to the day of discharge. Patients having postoperative complications showed a lower index of contractility (p = 0.0435) and a higher systolic time ratio (p = 0.0008) over the perioperative course in comparison to patients without complications, whereas the CI (p = 0.3337) was comparable between groups. One patient had to be excluded from data analysis for not receiving the planned surgery. Conclusions: Substantial decreases in HR, SVI, CI, and index of contractility occurred from the day before surgery to the first intraoperative timepoint. HR and CI were altered throughout the perioperative course. Patients with postoperative complications differed from patients without complications in the markers of cardiac function, a lower index of contractility and a lower SVI. The analyses of trends over the whole perioperative time course by using non-invasive technologies like EC seem to be useful to identify patients with altered haemodynamic parameters and therefore at an increased risk for postoperative complications after major surgery.
Language	English
Publishing date	2023-09-08
Publishing country	Germany
Document type	Journal Article
ZDB-ID	2740385-3
ISSN	2197-425X
ISSN	2197-425X
DOI	10.1186/s40635-023-00543-1
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Article ; Online: Balanced Adjustable Mirrored Current Source with Common Mode Feedback and Output Measurement for Bioimpedance Applications.

Klum, Michael / Schmidt, Malte / Klaproth, Joel / Pielmus, Alexandru-Gabriel / Tigges, Timo / Orglmeister, Reinhold

Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference

2019 Volume 2019, Page(s) 1278–1281

Abstract: Bioimpedance methods are used in a variety of applications such as impedance tomography, electrodermal activity detection and vascular disease assessment. Recent developments in portable and unobtrusive biosignal acquisition systems facilitate the ... ...

Abstract	Bioimpedance methods are used in a variety of applications such as impedance tomography, electrodermal activity detection and vascular disease assessment. Recent developments in portable and unobtrusive biosignal acquisition systems facilitate the integration of wearable bioimpedance applications including sleep monitoring, respiration estimation and fluid monitoring. However, the less stable measurement situation in a wearable scenario increases the requirements for the system's accuracy and adaptability. The current source of a bioimpedance system needs to drive large complex loads subject to vast variations over time while maintaining a high level of accuracy. The widely used improved Howland current source suffers from multiple disadvantages when considered for an adaptive bioimpedance system. We propose an optimized mirrored architecture which allows for a simple output current adjustment and current measurement without an additional shunt resistor in the load path. The system implements a common mode feedback system which includes balancing of the mirrored sources. Our design is validated by calculation, SPICE simulation and complex load measurements. We achieved output impedances in excess of 3 MΩ and derived a simplified transconductance function valid for frequencies up to 1 MHz. We conclude that the presented architecture is an important step forward towards accurate wearable bioimpedance acquisition. Employing generalized impedance converters, the output impedance could be further optimized.
MeSH term(s)	Electric Impedance ; Tomography ; Tomography, X-Ray Computed
Language	English
Publishing date	2019-12-30
Publishing country	United States
Document type	Journal Article
ISSN	2694-0604
ISSN (online)	2694-0604
DOI	10.1109/EMBC.2019.8856325
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Article ; Online: Heart Rate Variability Analysis During Lower Body Negative Pressure Test Induced Central Hypovolemia

Tigges Timo / Bajrami Lorik / Pielmuş Alexandru-Gabriel / Klum Michael / Orglmeister Reinhold / Wiegank Ludwig / Feldheiser Aarne

Current Directions in Biomedical Engineering, Vol 5, Iss 1, Pp 65-

2019 Volume 68

Abstract: In clinical patient monitoring scenarios, the detection of hemorrhage is still a major problem. Traditional vital signs like heart rate and blood pressure are insensitive to blood loss due to compensatory mechanisms in the body that can sustain these ... ...

Abstract	In clinical patient monitoring scenarios, the detection of hemorrhage is still a major problem. Traditional vital signs like heart rate and blood pressure are insensitive to blood loss due to compensatory mechanisms in the body that can sustain these parameters until shortly before cardiovascular collapse. These compensatory mechanisms during blood loss are primarily driven by the autonomic nervous system. Heart rate variability analysis is a viable tool in the quantitative analysis of the autonomic nervous system and shows promising results in the context of hypovolemia detection. In order to investigate if HRV parameters suitably reflect a mild to moderate blood volume reduction, we conducted a lower body negative pressure test study with 30 volunteering participants thereby simulating progressive central hypovolemia. Here, HRV parameters from the time domain (mean HR, SDNN, RMSSD, rSDRM, pNN50), the frequency domain (VLF, LF, HF, LF/HF), non-linear HRV parameters (SD1, SD2, SD1/SD2, SampEn, ApEn) and the respiratory rate (RR) were collected. The changes of the evaluated parameters as a consequence of the reduced blood volume were statistically evaluated. A statistically significant deviation from their baseline values could be found for RMSSD, rSDRM, pNN50, HF, LF/HF, SD1 and SD1/SD2 at a chamber pressures starting at −30 mmHg. Therefore, we support the proposition that heart rate variability analysis can help in detecting otherwise occult hypovolemia.
Keywords	hypovolemia detection ; heart rate variability ; respiration ; lower body negative pressure test ; Medicine ; R
Subject code	796
Language	English
Publishing date	2019-09-01T00:00:00Z
Publisher	De Gruyter
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Wearable Cardiorespiratory Monitoring Employing a Multimodal Digital Patch Stethoscope: Estimation of ECG, PEP, LVETand Respiration Using a 55 mm Single-Lead ECG and Phonocardiogram.

Klum, Michael / Urban, Mike / Tigges, Timo / Pielmus, Alexandru-Gabriel / Feldheiser, Aarne / Schmitt, Theresa / Orglmeister, Reinhold

Sensors (Basel, Switzerland)

2020 Volume 20, Issue 7

Abstract: Cardiovascular diseases are the main cause of death worldwide, with sleep disordered breathing being a further aggravating factor. Respiratory illnesses are the third leading cause of death amongst the noncommunicable diseases. The current COVID-19 ... ...

Abstract	Cardiovascular diseases are the main cause of death worldwide, with sleep disordered breathing being a further aggravating factor. Respiratory illnesses are the third leading cause of death amongst the noncommunicable diseases. The current COVID-19 pandemic, however, also highlights the impact of communicable respiratory syndromes. In the clinical routine, prolonged postanesthetic respiratory instability worsens the patient outcome. Even though early and continuous, long-term cardiorespiratory monitoring has been proposed or even proven to be beneficial in several situations, implementations thereof are sparse. We employed our recently presented, multimodal patch stethoscope to estimate Einthoven electrocardiogram (ECG) Lead I and II from a single 55 mm ECG lead. Using the stethoscope and ECG subsystems, the pre-ejection period (PEP) and left ventricular ejection time (LVET) were estimated. ECG-derived respiration techniques were used in conjunction with a novel, phonocardiogram-derived respiration approach to extract respiratory parameters. Medical-grade references were the SOMNOmedics SOMNO HD
MeSH term(s)	Electrocardiography/instrumentation ; Heart Ventricles ; Humans ; Phonocardiography/instrumentation ; Respiratory Rate ; Ventricular Function ; Wearable Electronic Devices
Keywords	covid19
Language	English
Publishing date	2020-04-04
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2052857-7
ISSN	1424-8220 ; 1424-8220
ISSN (online)	1424-8220
ISSN	1424-8220
DOI	10.3390/s20072033
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Article ; Online: Minimally spaced electrode positions for multi-functional chest sensors

Klum Michael / Minn Tobias / Tigges Timo / Pielmus Alexandru-Gabriel / Orglmeister Reinhold

Current Directions in Biomedical Engineering, Vol 2, Iss 1, Pp 695-

ECG and respiratory signal estimation

2016 Volume 699

Abstract: Unobtrusive medical instrumentation is a key in continuous patient monitoring. To increase compliance, multi-functional sensor concepts and measurement sites different from gold-standards are used. In this work, we aim to combine both approaches. We ... ...

Abstract	Unobtrusive medical instrumentation is a key in continuous patient monitoring. To increase compliance, multi-functional sensor concepts and measurement sites different from gold-standards are used. In this work, we aim to combine both approaches. We focus on minimally spaced electrode positions with high signal correlations to gold-standards. We present twofold experimental data from six and eleven healthy volunteers and provide chest positions with individual correlations up to 0.83 ± 0.06 for ECG and 0.73 ± 0.28 for the respiratory frequency. Using a performance index, we assess positions with correlations up to 0.77 ± 0.12 for ECG and 0.65 ± 0.35 for the respiratory frequency with 24 mm electrode distance.
Keywords	chest ; ecg derived respiration ; electrocardiogram ; minimally spaced ; multi-functional sensors ; respiratory signal estimation ; unobtrusive monitoring ; Medicine ; R
Language	English
Publishing date	2016-09-01T00:00:00Z
Publisher	De Gruyter
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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