Home Medicine Classification of morphologic changes in photoplethysmographic waveforms
Article Open Access

Classification of morphologic changes in photoplethysmographic waveforms

  • Timo Tigges EMAIL logo , Zenit Music , Alexandru Pielmus , Michael Klum , Aarne Feldheiser , Oliver Hunsicker and Reinhold Orglmeister
Published/Copyright: September 30, 2016
Download Article (PDF)
Become an author with De Gruyter Brill
Author Information Explore this Subject
Current Directions in Biomedical Engineering
From the journal Current Directions in Biomedical Engineering Volume 2 Issue 1

Abstract

An ever increasing number of research is examining the question to what extent physiological information beyond the blood oxygen saturation could be drawn from the photoplethysmogram. One important approach to elicit that information from the photoplethysmogram is the analysis of its waveform. One prominent example for the value of photoplethysmographic waveform analysis in cardiovascular monitoring that has emerged is hemodynamic compensation assessment in the peri-operative setting or trauma situations, as digital pulse waveform dynamically changes with alterations in vascular tone or pulse wave velocity. In this work, we present an algorithm based on modern machine learning techniques that automatically finds individual digital volume pulses in photoplethysmographic signals and sorts them into one of the pulse classes defined by Dawber et al. We evaluate our approach based on two major datasets – a measurement study that we conducted ourselves as well as data from the PhysioNet MIMIC II database. As the results are satisfying we could demonstrate the capabilities of classification algorithms in the automated assessment of the digital volume pulse waveform measured by photoplethysmographic devices.

Keywords: cardiovascular monitoring; machine learning; photoplethysmography; pulse waveform analysis

1 Introduction

Despite the fact that the photoplethysmography (PPG) has been one of the standard monitoring modalities for vital parameters for many years, the waveform of the PPG is ignored in the clinical daily routine. That kind of attitude towards the PPG waveform changed in recent years, and is still changing. An ever increasing number of research is examining the question to what extent physiological information beyond the blood oxygen saturation could be drawn from the PPG. One important approach to elicit that information from the PPG is the analysis of its waveform.

One prominent example for the value of PPG waveform analysis that has emerged is that of hemodynamic compensation assessment in the peri-operative setting or trauma situations. It could be shown that the width of the digital volume pulse measured by a photoplethysmographic device on the index finger is sensitive to changes in the systemic vascular resistance and thus allows for early detection of active compensatory mechanisms during hemorrhage [1]. Recently Convertino et al. [2] demonstrated how modern machine learning techniques can be beneficially utilized to reveal subtle waveform features that trend the compensatory phase of hemorrhage.

Digital pulse waveform dynamically changes, among others, with alterations in vascular tone or changes in pulse wave velocity induced for example by blood pressure variations or medication. The aim of this work is the development of a classification algorithm that automatically groups individual digital volume pulses measured with photoplethysmographic devices based on their specific waveform.

This paper is organized as follows. In Section 2, the class definitions for grouping of the pulses are given. Also, the developed approach for automated pulse classification is outlined. The results are presented in Section 3. Finally, concluding remarks are given in Section 4.

2 Methods

2.1 Class definitions for digital volume pulses

In their pioneering paper about pulse waveform analysis [3], Dawber et al. defined four classes for the categorization of arterial pulse waves:

  • Class 1: A dicrotic notch (i.e. an incisura) is apparent on the downward slope of the pulse wave.

  • Class 2: No distinct dicrotic notch is visible, but the downward slope becomes horizontal.

  • Class 3: No distinct dicrotic notch is visible, but a well-defined change in the angle of descent is observed.

  • Class 4: No evidence of a dicrotic notch is visible.

An example waveform for each class is presented in Figure 1. Under the most simple assumptions digital volume pulses can be thought of as a superposition of two Gaussian shaped waves, where the leading (systolic) wave is the direct wave that travels from the heart to the finger after coronary contraction and the lagging (diastolic) wave results from reflections mainly at the Iliac arteries in the lower body.

Figure 1 Periphal pulse wave classes as defined by Dawber.
Figure 1

Periphal pulse wave classes as defined by Dawber.

Although Dawber et al. based their definitions on the assessment of arterial pressure pulses measured with a pressure cuff on the finger, these classes are equally applicable to digital volume pulse signals recorded by a photoplethysmographic device, as Millasseau et al. have shown that a simple transfer function can be found to transform the volume pulses into pressure pulses [4].

2.2 Automated classification of pulse waves

In this work, we present an algorithm based on modern machine learning techniques that automatically finds individual pulses in photoplethysmographic signals and sorts them into one of the pulse classes defined by Dawber et al. The main steps of our approach is outlined in Figure 2.

Figure 2 Outline of the automated pulse waveform classification algorithm. Employed classifiers are artificial neural network (ANN), support vector machine (SVM) and bagged tree classifier (BTC).
Figure 2

Outline of the automated pulse waveform classification algorithm. Employed classifiers are artificial neural network (ANN), support vector machine (SVM) and bagged tree classifier (BTC).

At first, in the pre-processing stage, the raw signals are filtered by an 8th order, zero-phase Butterworth filter with cut-off frequencies of 0.2 Hz and 16 Hz, respectively, in order to remove noise and baseline variations. The high-pass cut-off frequency was chosen because for higher cut-off frequencies, not neglegible pulse shape distortions can be observed. The low-pass cut-off frequency was found empirically and constitutes a good trade-off between shape distortions and high-frequent noise rejection.

In the pulse detection state, individual pulses are found by means of an open-source peak-detection algorithm presented by Zong et al. [5].

In the next stage, a set of features that facilitates separating the pulse waveform classes is calculated for every single pulse. Initially, we designed 24 features with the goal to map the information on class affiliation, that is easily visible for the human eye, onto numerical values that the classification algorithms can utilize for model training and subsequent classification. We identified a subset of 13 features that showed a positive interaction with respect to the classification problem by means of the INTERACT [6] feature selection algorithm. A list of the employed features including a short description and corresponding abbreviations is given in Table 1.

Table 1

List and description of the interacting feature set.

Feature nameAbb.Description
Relative rise timeRRTTime between the onset an the systolic peak. Normalized by pulse duration.
Relative slope timeRSTTime between the systolic peak and the end of the pulse. Normalized by pulse duration.
Dicrotic-diastolic ratioDDRAmplitude relation between the dicrotic notch and the diastolic peak. Set to 1.1 if no diastolic peak could be detected.
Relative downslope sumRDSCumulative sum of the downslope. Normalized with pulse duration.
Relative euclidean lengthRELEuclidean length of the downslope. Normalized by pulse duration.
Downslope derivative meanDDMMean value of the pulse derivative during the downslope.
Downslope derivative varianceDDVVariance of the pulse derivative during the downslope.
Downslope positive derivativeDPDNumber of downslope samples exceeding a fixed threshold. Normalized with downslope duration.
Relative horizontal streakRHSLongest streak of samples with slope values within a fixed interval. Normalized with the downslope length.

The features are either calculated from the time domain signal (see Figure 3) or its first derivative (see Figure 4). For better generalization, all features are calculated on pulses with normalized peak-to-peak amplitude.

In the classifier training stage, modern machine learning algorithms are trained to generate a model that is able to automatically group unknown pulses into one of the four classes. In this work, we utilized and evaluated an artificial neural network (ANN), a support vector machine (SVM) and a bagged tree classifier (BTC). The SVM algorithm is only applicable to binary separation problems, therefore we decomposed the four-class pulse classification into a sequence of two binary classification steps. In order to avoid overfitting during classifier training and to get an unbiased estimation of classification performance, we divided all available data into training and test sets. Consequently, the algorithms learned only from the training sets and performance metrics were solely calculated from the test sets.

Figure 3 Features derived from the time domain signal.
Figure 3

Features derived from the time domain signal.

Figure 4 Features derived from the first derivative of the time domain signal.
Figure 4

Features derived from the first derivative of the time domain signal.

3 Results

In this section we present the results of the performance evaluation of the proposed approach. We carried out simulations on two major datasets. A summary of the class distribution within the two datasets can be found in Table 2.

Table 2

Class distribution in the training and test data.

ClassIIIIIIIVSum
Arm lift (train.)11533964403892378
Arm lift (test)10054314581562047
MIMIC II (train.)8005002007002200
MIMIC II (test)994298944941880
Total39521625119217398505

The first dataset comprises a measurement study with ten healthy subjects, eight males and two females, aged between 21 and 28 years, that was conducted at our laboratory. During each measurement, a custom-made, wireless PPG sensor node that is part of our body sensor network rBSN [7] was attached to the right index finger. The sample rate of the sensor was 500 Hertz. All measurements were conducted in standing position. At the beginning of the measurement, the subject’s right arm was pointing towards the floor. After 1 min elapsed, the right arm was lifted by 45°. This was repeated until the subject’s arm pointed towards the ceiling. This measurement protocol was developed and chosen, because incrementally lifting the arm reliably generates the digital volume pulses that gradually shift from class I to IV.

The second dataset was extracted from the MIMIC II waveform database [8], which is available online from the PhysioNet archive. Because accurately timed annotations of cardiovascular events that dynamically change the digital pulse waveform are missing, we used the patients age to identify recordings with different pulse classes. For obtaining class I pulses, we chose recordings from patients aged 35 years and less. Class II and class III pulses could be extracted from recordings of patients aged between 40 and 65. Class IV pulses were obtained from subjects older than 80 years. The PPG recordings in the MIMIC II database were sampled at 125 Hz. Reference labelling was obtained by consensus of multiple experts after independent visual inspection. We estimated the performance in form of the F1-score as it is a measure of a classifiers accuracy that considers both precision and recall. F1 = 1 means perfect classification and F1 = 0 means that all classifier decisions are wrong.

The classification results on the test datasets are given in Table 3. As one can see, in the arm lift dateset, all classifiers produce comparable results. In the PhysioNet dataset, the ANN and the BTC get slightly higher F1-scores for class II than the SVM. In return, the SVM gets a better F1-score in class III. Overall, the detection accuracy for class I pulses is much better than for the others. This effect can be explained by taking a look at class distribution shown in Table 2. As there are much more class I pulses in the training datasets, their shape is learned better. Furthermore, the separation of class II from class III and class III from class IV pulses during the annotation process was not trivial, so labelling errors might also cause a degradation of the classification performance. To evaluate if a combination of the classifiers could be used to improve classification, we fused the classifiers by calculating the mean of their individual class votes and then rounding the result. The result of this fusion can be found in the last row in Table 3. For both datesets, this fusion did not lead to a significant improvement, hence suggesting that the classifiers have a strong agreement also when they are misclassifying.

Table 3

Summary of the classification results on the test datasets.

Classification algorithmArm liftMIMIC II
Class IClass IIClass IIIClass IVOverallClass IClass IIClass IIIClass IVOverall
ANN0.9490.7240.75950.6760.8420.9700.8750.6470.9360.928
SVM0.9490.7320.7910.7290.8520.9350.7930.8910.9910.921
BTC0.9530.7530.7950.7050.8570.9670.8570.6750.9330.920
FUSION0.9550.7530.7990.7120.860.9680.8630.7650.9620.937

4 Conclusion

Due to its unobtrusiveness and its cheap and easy obtainability, automated interpretation of the digital volume pulse waveform measured by photoplethysmography will play a significant role in the development of novel hemodynamic monitoring devices. In this work we have successfully demonstrated a novel approach for pulse waveform classification based on modern machine learning techniques that automatically groups digital volume pulses into the waveform classes defined by Dawber et al. This information could for example prove valuable in the assessment of the cardiovascular system during surgical operations or monitoring on intensive care units. In future works, we aim at improving the classification performance by exploring more features.

Author’s Statement

Research funding: The author state no funding involved. Conflict of interest: Authors state no conflict of interest. Material and Methods: Informed consent: Informed consent has been obtained from all individuals included in this study. Ethical approval: The research related to human use complies with all the relevant national regulations, institutional policies and was performed in accordance with the tenets of the Helsinki Declaration, and has been approved by the authors’ institutional review board or equivalent committee.

References

[1] Awad AA, Haddadin AS, Tantawy H, Badr TM, Stout RG, Silverman DG, et al. The relationship between the photoplethysmographic waveform and systemic vascular resistance. J Clin Monit Comput. 2007;21:365–72.10.1007/s10877-007-9097-5Search in Google Scholar PubMed

[2] Convertino VA, Grudic G, Mulligan J, Moulton S. Estimation of individual-specific progression to impending cardiovascular instability using arterial waveforms. J Appl Physiol. 2013;115:1196–202.10.1152/japplphysiol.00668.2013Search in Google Scholar PubMed

[3] Dawber T, Thomas H, McNamara P. Characteristics of the dicrotic notch of the arterial pulse wave in coronary heart disease. Angiology. 1973;24:244–55.10.1177/000331977302400407Search in Google Scholar PubMed

[4] Millasseau SC, Ritter JM, Takazawa K, Chowienczyk PJ. Contour analysis of the photoplethysmographic pulse measured at the finger. J Hypertens. 2006;24:1449–56.10.1097/01.hjh.0000239277.05068.87Search in Google Scholar PubMed

[5] Zong W, Heldt T, Moody G, Mark R. An open-source algorithm to detect onset of arterial blood pressure pulses. In: Computers in Cardiology; 2003. p. 259–62.10.1109/CIC.2003.1291140Search in Google Scholar

[6] Zhao Z, Liu H. Searching for interacting features. In: International Joint Conference on Artificial Intelligence; 2007.Search in Google Scholar

[7] Pflugradt M, Mann S, Tigges T, Görnig M, Orglmeister R. Multi-modal signal acquisition using a synchronized wireless body sensor network in geriatric patients. Biomed Eng. 2015;61:57–86.10.1515/bmt-2014-0178Search in Google Scholar PubMed

[8] Saeed M, Villarroel M, Reisner AT, Clifford G, Lehman LW, Moody G, et al. Multiparameter intelligent monitoring in intensive care II (MIMIC-II): a public-access intensive care unit database. Crit Care Med. 2011;39:952–60.10.1097/CCM.0b013e31820a92c6Search in Google Scholar PubMed PubMed Central

Published Online: 2016-9-30
Published in Print: 2016-9-1

©2016 Timo Tigges et al., licensee De Gruyter.

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Articles in the same Issue

  1. Synthesis and characterization of PIL/pNIPAAm hybrid hydrogels
  2. Novel blood protein based scaffolds for cardiovascular tissue engineering
  3. Cell adhesion and viability of human endothelial cells on electrospun polymer scaffolds
  4. Effects of heat treatment and welding process on superelastic behaviour and microstructure of micro electron beam welded NiTi
  5. Long-term stable modifications of silicone elastomer for improved hemocompatibility
  6. The effect of thermal treatment on the mechanical properties of PLLA tubular specimens
  7. Biocompatible wear-resistant thick ceramic coating
  8. Protection of active implant electronics with organosilicon open air plasma coating for plastic overmolding
  9. Examination of dielectric strength of thin Parylene C films under various conditions
  10. Open air plasma deposited antimicrobial SiOx/TiOx composite films for biomedical applications
  11. Systemic analysis about residual chloroform in PLLA films
  12. A macrophage model of osseointegration
  13. Towards in silico prognosis using big data
  14. Technical concept and evaluation of a novel shoulder simulator with adaptive muscle force generation and free motion
  15. Usability evaluation of a locomotor therapy device considering different strategies
  16. Hypoxia-on-a-chip
  17. Integration of a semi-automatic in-vitro RFA procedure into an experimental setup
  18. Fabrication of MEMS-based 3D-μECoG-MEAs
  19. High speed digital interfacing for a neural data acquisition system
  20. Bionic forceps for the handling of sensitive tissue
  21. Experimental studies on 3D printing of barium titanate ceramics for medical applications
  22. Patient specific root-analogue dental implants – additive manufacturing and finite element analysis
  23. 3D printing – a key technology for tailored biomedical cell culture lab ware
  24. 3D printing of hydrogels in a temperature controlled environment with high spatial resolution
  25. Biocompatibility of photopolymers for additive manufacturing
  26. Biochemical piezoresistive sensors based on pH- and glucose-sensitive hydrogels for medical applications
  27. Novel wireless measurement system of pressure dedicated to in vivo studies
  28. Portable auricular device for real-time swallow and chew detection
  29. Detection of miRNA using a surface plasmon resonance biosensor and antibody amplification
  30. Simulation and evaluation of stimulation scenarios for targeted vestibular nerve excitation
  31. Deep brain stimulation: increasing efficiency by alternative waveforms
  32. Prediction of immediately occurring microsleep events from brain electric signals
  33. Determining cardiac vagal threshold from short term heart rate complexity
  34. Classification of cardiac excitation patterns during atrial fibrillation
  35. An algorithm to automatically determine the cycle length coverage to identify rotational activity during atrial fibrillation – a simulation study
  36. Deriving respiration from high resolution 12-channel-ECG during cycling exercise
  37. Reducing of gradient induced artifacts on the ECG signal during MRI examinations using Wilcoxon filter
  38. Automatic detection and mapping of double potentials in intracardiac electrograms
  39. Modeling the pelvic region for non-invasive pelvic intraoperative neuromonitoring
  40. Postprocessing algorithm for automated analysis of pelvic intraoperative neuromonitoring signals
  41. Best practice: surgeon driven application in pelvic operations
  42. Vasomotor assessment by camera-based photoplethysmography
  43. Classification of morphologic changes in photoplethysmographic waveforms
  44. Novel computation of pulse transit time from multi-channel PPG signals by wavelet transform
  45. Efficient design of FIR filter based low-pass differentiators for biomedical signal processing
  46. Nonlinear causal influences assessed by mutual compression entropy
  47. Comparative study of methods for solving the correspondence problem in EMD applications
  48. fNIRS for future use in auditory diagnostics
  49. Semi-automated detection of fractional shortening in zebrafish embryo heart videos
  50. Blood pressure measurement on the cheek
  51. Derivation of the respiratory rate from directly and indirectly measured respiratory signals using autocorrelation
  52. Left cardiac atrioventricular delay and inter-ventricular delay in cardiac resynchronization therapy responder and non-responder
  53. An automatic systolic peak detector of blood pressure waveforms using 4th order cumulants
  54. Real-time QRS detection using integrated variance for ECG gated cardiac MRI
  55. Preprocessing of unipolar signals acquired by a novel intracardiac mapping system
  56. In-vitro experiments to characterize ventricular electromechanics
  57. Continuous non-invasive monitoring of blood pressure in the operating room: a cuffless optical technology at the fingertip
  58. Application of microwave sensor technology in cardiovascular disease for plaque detection
  59. Artificial blood circulatory and special Ultrasound Doppler probes for detecting and sizing gaseous embolism
  60. Detection of microsleep events in a car driving simulation study using electrocardiographic features
  61. A method to determine the kink resistance of stents and stent delivery systems according to international standards
  62. Comparison of stented bifurcation and straight vessel 3D-simulation with a prior simulated velocity profile inlet
  63. Transient Euler-Lagrange/DEM simulation of stent thrombosis
  64. Automated control of the laser welding process of heart valve scaffolds
  65. Automation of a test bench for accessing the bendability of electrospun vascular grafts
  66. Influence of storage conditions on the release of growth factors in platelet-rich blood derivatives
  67. Cryopreservation of cells using defined serum-free cryoprotective agents
  68. New bioreactor vessel for tissue engineering of human nasal septal chondrocytes
  69. Determination of the membrane hydraulic permeability of MSCs
  70. Climate retainment in carbon dioxide incubators
  71. Multiple factors influencing OR ventilation system effectiveness
  72. Evaluation of an app-based stress protocol
  73. Medication process in Styrian hospitals
  74. Control tower to surgical theater
  75. Development of a skull phantom for the assessment of implant X-ray visibility
  76. Surgical navigation with QR codes
  77. Investigation of the pressure gradient of embolic protection devices
  78. Computer assistance in femoral derotation osteotomy: a bottom-up approach
  79. Automatic depth scanning system for 3D infrared thermography
  80. A service for monitoring the quality of intraoperative cone beam CT images
  81. Resectoscope with an easy to use twist mechanism for improved handling
  82. In vitro simulation of distribution processes following intramuscular injection
  83. Adjusting inkjet printhead parameters to deposit drugs into micro-sized reservoirs
  84. A flexible standalone system with integrated sensor feedback for multi-pad electrode FES of the hand
  85. Smart control for functional electrical stimulation with optimal pulse intensity
  86. Tactile display on the remaining hand for unilateral hand amputees
  87. Effects of sustained electrical stimulation on spasticity assessed by the pendulum test
  88. An improved tracking framework for ultrasound probe localization in image-guided radiosurgery
  89. Improvement of a subviral particle tracker by the use of a LAP-Kalman-algorithm
  90. Learning discriminative classification models for grading anal intraepithelial neoplasia
  91. Regularization of EIT reconstruction based on multi-scales wavelet transforms
  92. Assessing MRI susceptibility artefact through an indicator of image distortion
  93. EyeGuidance – a computer controlled system to guide eye movements
  94. A framework for feedback-based segmentation of 3D image stacks
  95. Doppler optical coherence tomography as a promising tool for detecting fluid in the human middle ear
  96. 3D Local in vivo Environment (LivE) imaging for single cell protein analysis of bone tissue
  97. Inside-Out access strategy using new trans-vascular catheter approach
  98. US/MRI fusion with new optical tracking and marker approach for interventional procedures inside the MRI suite
  99. Impact of different registration methods in MEG source analysis
  100. 3D segmentation of thyroid ultrasound images using active contours
  101. Designing a compact MRI motion phantom
  102. Cerebral cortex classification by conditional random fields applied to intraoperative thermal imaging
  103. Classification of indirect immunofluorescence images using thresholded local binary count features
  104. Analysis of muscle fatigue conditions using time-frequency images and GLCM features
  105. Numerical evaluation of image parameters of ETR-1
  106. Fabrication of a compliant phantom of the human aortic arch for use in Particle Image Velocimetry (PIV) experimentation
  107. Effect of the number of electrodes on the reconstructed lung shape in electrical impedance tomography
  108. Hardware dependencies of GPU-accelerated beamformer performances for microwave breast cancer detection
  109. Computer assisted assessment of progressing osteoradionecrosis of the jaw for clinical diagnosis and treatment
  110. Evaluation of reconstruction parameters of electrical impedance tomography on aorta detection during saline bolus injection
  111. Evaluation of open-source software for the lung segmentation
  112. Automatic determination of lung features of CF patients in CT scans
  113. Image analysis of self-organized multicellular patterns
  114. Effect of key parameters on synthesis of superparamagnetic nanoparticles (SPIONs)
  115. Radiopacity assessment of neurovascular implants
  116. Development of a desiccant based dielectric for monitoring humidity conditions in miniaturized hermetic implantable packages
  117. Development of an artifact-free aneurysm clip
  118. Enhancing the regeneration of bone defects by alkalizing the peri-implant zone – an in vitro approach
  119. Rapid prototyping of replica knee implants for in vitro testing
  120. Protecting ultra- and hyperhydrophilic implant surfaces in dry state from loss of wettability
  121. Advanced wettability analysis of implant surfaces
  122. Patient-specific hip prostheses designed by surgeons
  123. Plasma treatment on novel carbon fiber reinforced PEEK cages to enhance bioactivity
  124. Wear of a total intervertebral disc prosthesis
  125. Digital health and digital biomarkers – enabling value chains on health data
  126. Usability in the lifecycle of medical software development
  127. Influence of different test gases in a non-destructive 100% quality control system for medical devices
  128. Device development guided by user satisfaction survey on auricular vagus nerve stimulation
  129. Empirical assessment of the time course of innovation in biomedical engineering: first results of a comparative approach
  130. Effect of left atrial hypertrophy on P-wave morphology in a computational model
  131. Simulation of intracardiac electrograms around acute ablation lesions
  132. Parametrization of activation based cardiac electrophysiology models using bidomain model simulations
  133. Assessment of nasal resistance using computational fluid dynamics
  134. Resistance in a non-linear autoregressive model of pulmonary mechanics
  135. Inspiratory and expiratory elastance in a non-linear autoregressive model of pulmonary mechanics
  136. Determination of regional lung function in cystic fibrosis using electrical impedance tomography
  137. Development of parietal bone surrogates for parietal graft lift training
  138. Numerical simulation of mechanically stimulated bone remodelling
  139. Conversion of engineering stresses to Cauchy stresses in tensile and compression tests of thermoplastic polymers
  140. Numerical examinations of simplified spondylodesis models concerning energy absorption in magnetic resonance imaging
  141. Principle study on the signal connection at transabdominal fetal pulse oximetry
  142. Influence of Siluron® insertion on model drug distribution in the simulated vitreous body
  143. Evaluating different approaches to identify a three parameter gas exchange model
  144. Effects of fibrosis on the extracellular potential based on 3D reconstructions from histological sections of heart tissue
  145. From imaging to hemodynamics – how reconstruction kernels influence the blood flow predictions in intracranial aneurysms
  146. Flow optimised design of a novel point-of-care diagnostic device for the detection of disease specific biomarkers
  147. Improved FPGA controlled artificial vascular system for plethysmographic measurements
  148. Minimally spaced electrode positions for multi-functional chest sensors: ECG and respiratory signal estimation
  149. Automated detection of alveolar arches for nasoalveolar molding in cleft lip and palate treatment
  150. Control scheme selection in human-machine- interfaces by analysis of activity signals
  151. Event-based sampling for reducing communication load in realtime human motion analysis by wireless inertial sensor networks
  152. Automatic pairing of inertial sensors to lower limb segments – a plug-and-play approach
  153. Contactless respiratory monitoring system for magnetic resonance imaging applications using a laser range sensor
  154. Interactive monitoring system for visual respiratory biofeedback
  155. Development of a low-cost senor based aid for visually impaired people
  156. Patient assistive system for the shoulder joint
  157. A passive beating heart setup for interventional cardiology training
https://doi.org/10.1515/cdbme-2016-0046
Keywords for this article
cardiovascular monitoring; machine learning; photoplethysmography; pulse waveform analysis
Creative Commons
BY-NC-ND 4.0

Articles in the same Issue

  1. Synthesis and characterization of PIL/pNIPAAm hybrid hydrogels
  2. Novel blood protein based scaffolds for cardiovascular tissue engineering
  3. Cell adhesion and viability of human endothelial cells on electrospun polymer scaffolds
  4. Effects of heat treatment and welding process on superelastic behaviour and microstructure of micro electron beam welded NiTi
  5. Long-term stable modifications of silicone elastomer for improved hemocompatibility
  6. The effect of thermal treatment on the mechanical properties of PLLA tubular specimens
  7. Biocompatible wear-resistant thick ceramic coating
  8. Protection of active implant electronics with organosilicon open air plasma coating for plastic overmolding
  9. Examination of dielectric strength of thin Parylene C films under various conditions
  10. Open air plasma deposited antimicrobial SiOx/TiOx composite films for biomedical applications
  11. Systemic analysis about residual chloroform in PLLA films
  12. A macrophage model of osseointegration
  13. Towards in silico prognosis using big data
  14. Technical concept and evaluation of a novel shoulder simulator with adaptive muscle force generation and free motion
  15. Usability evaluation of a locomotor therapy device considering different strategies
  16. Hypoxia-on-a-chip
  17. Integration of a semi-automatic in-vitro RFA procedure into an experimental setup
  18. Fabrication of MEMS-based 3D-μECoG-MEAs
  19. High speed digital interfacing for a neural data acquisition system
  20. Bionic forceps for the handling of sensitive tissue
  21. Experimental studies on 3D printing of barium titanate ceramics for medical applications
  22. Patient specific root-analogue dental implants – additive manufacturing and finite element analysis
  23. 3D printing – a key technology for tailored biomedical cell culture lab ware
  24. 3D printing of hydrogels in a temperature controlled environment with high spatial resolution
  25. Biocompatibility of photopolymers for additive manufacturing
  26. Biochemical piezoresistive sensors based on pH- and glucose-sensitive hydrogels for medical applications
  27. Novel wireless measurement system of pressure dedicated to in vivo studies
  28. Portable auricular device for real-time swallow and chew detection
  29. Detection of miRNA using a surface plasmon resonance biosensor and antibody amplification
  30. Simulation and evaluation of stimulation scenarios for targeted vestibular nerve excitation
  31. Deep brain stimulation: increasing efficiency by alternative waveforms
  32. Prediction of immediately occurring microsleep events from brain electric signals
  33. Determining cardiac vagal threshold from short term heart rate complexity
  34. Classification of cardiac excitation patterns during atrial fibrillation
  35. An algorithm to automatically determine the cycle length coverage to identify rotational activity during atrial fibrillation – a simulation study
  36. Deriving respiration from high resolution 12-channel-ECG during cycling exercise
  37. Reducing of gradient induced artifacts on the ECG signal during MRI examinations using Wilcoxon filter
  38. Automatic detection and mapping of double potentials in intracardiac electrograms
  39. Modeling the pelvic region for non-invasive pelvic intraoperative neuromonitoring
  40. Postprocessing algorithm for automated analysis of pelvic intraoperative neuromonitoring signals
  41. Best practice: surgeon driven application in pelvic operations
  42. Vasomotor assessment by camera-based photoplethysmography
  43. Classification of morphologic changes in photoplethysmographic waveforms
  44. Novel computation of pulse transit time from multi-channel PPG signals by wavelet transform
  45. Efficient design of FIR filter based low-pass differentiators for biomedical signal processing
  46. Nonlinear causal influences assessed by mutual compression entropy
  47. Comparative study of methods for solving the correspondence problem in EMD applications
  48. fNIRS for future use in auditory diagnostics
  49. Semi-automated detection of fractional shortening in zebrafish embryo heart videos
  50. Blood pressure measurement on the cheek
  51. Derivation of the respiratory rate from directly and indirectly measured respiratory signals using autocorrelation
  52. Left cardiac atrioventricular delay and inter-ventricular delay in cardiac resynchronization therapy responder and non-responder
  53. An automatic systolic peak detector of blood pressure waveforms using 4th order cumulants
  54. Real-time QRS detection using integrated variance for ECG gated cardiac MRI
  55. Preprocessing of unipolar signals acquired by a novel intracardiac mapping system
  56. In-vitro experiments to characterize ventricular electromechanics
  57. Continuous non-invasive monitoring of blood pressure in the operating room: a cuffless optical technology at the fingertip
  58. Application of microwave sensor technology in cardiovascular disease for plaque detection
  59. Artificial blood circulatory and special Ultrasound Doppler probes for detecting and sizing gaseous embolism
  60. Detection of microsleep events in a car driving simulation study using electrocardiographic features
  61. A method to determine the kink resistance of stents and stent delivery systems according to international standards
  62. Comparison of stented bifurcation and straight vessel 3D-simulation with a prior simulated velocity profile inlet
  63. Transient Euler-Lagrange/DEM simulation of stent thrombosis
  64. Automated control of the laser welding process of heart valve scaffolds
  65. Automation of a test bench for accessing the bendability of electrospun vascular grafts
  66. Influence of storage conditions on the release of growth factors in platelet-rich blood derivatives
  67. Cryopreservation of cells using defined serum-free cryoprotective agents
  68. New bioreactor vessel for tissue engineering of human nasal septal chondrocytes
  69. Determination of the membrane hydraulic permeability of MSCs
  70. Climate retainment in carbon dioxide incubators
  71. Multiple factors influencing OR ventilation system effectiveness
  72. Evaluation of an app-based stress protocol
  73. Medication process in Styrian hospitals
  74. Control tower to surgical theater
  75. Development of a skull phantom for the assessment of implant X-ray visibility
  76. Surgical navigation with QR codes
  77. Investigation of the pressure gradient of embolic protection devices
  78. Computer assistance in femoral derotation osteotomy: a bottom-up approach
  79. Automatic depth scanning system for 3D infrared thermography
  80. A service for monitoring the quality of intraoperative cone beam CT images
  81. Resectoscope with an easy to use twist mechanism for improved handling
  82. In vitro simulation of distribution processes following intramuscular injection
  83. Adjusting inkjet printhead parameters to deposit drugs into micro-sized reservoirs
  84. A flexible standalone system with integrated sensor feedback for multi-pad electrode FES of the hand
  85. Smart control for functional electrical stimulation with optimal pulse intensity
  86. Tactile display on the remaining hand for unilateral hand amputees
  87. Effects of sustained electrical stimulation on spasticity assessed by the pendulum test
  88. An improved tracking framework for ultrasound probe localization in image-guided radiosurgery
  89. Improvement of a subviral particle tracker by the use of a LAP-Kalman-algorithm
  90. Learning discriminative classification models for grading anal intraepithelial neoplasia
  91. Regularization of EIT reconstruction based on multi-scales wavelet transforms
  92. Assessing MRI susceptibility artefact through an indicator of image distortion
  93. EyeGuidance – a computer controlled system to guide eye movements
  94. A framework for feedback-based segmentation of 3D image stacks
  95. Doppler optical coherence tomography as a promising tool for detecting fluid in the human middle ear
  96. 3D Local in vivo Environment (LivE) imaging for single cell protein analysis of bone tissue
  97. Inside-Out access strategy using new trans-vascular catheter approach
  98. US/MRI fusion with new optical tracking and marker approach for interventional procedures inside the MRI suite
  99. Impact of different registration methods in MEG source analysis
  100. 3D segmentation of thyroid ultrasound images using active contours
  101. Designing a compact MRI motion phantom
  102. Cerebral cortex classification by conditional random fields applied to intraoperative thermal imaging
  103. Classification of indirect immunofluorescence images using thresholded local binary count features
  104. Analysis of muscle fatigue conditions using time-frequency images and GLCM features
  105. Numerical evaluation of image parameters of ETR-1
  106. Fabrication of a compliant phantom of the human aortic arch for use in Particle Image Velocimetry (PIV) experimentation
  107. Effect of the number of electrodes on the reconstructed lung shape in electrical impedance tomography
  108. Hardware dependencies of GPU-accelerated beamformer performances for microwave breast cancer detection
  109. Computer assisted assessment of progressing osteoradionecrosis of the jaw for clinical diagnosis and treatment
  110. Evaluation of reconstruction parameters of electrical impedance tomography on aorta detection during saline bolus injection
  111. Evaluation of open-source software for the lung segmentation
  112. Automatic determination of lung features of CF patients in CT scans
  113. Image analysis of self-organized multicellular patterns
  114. Effect of key parameters on synthesis of superparamagnetic nanoparticles (SPIONs)
  115. Radiopacity assessment of neurovascular implants
  116. Development of a desiccant based dielectric for monitoring humidity conditions in miniaturized hermetic implantable packages
  117. Development of an artifact-free aneurysm clip
  118. Enhancing the regeneration of bone defects by alkalizing the peri-implant zone – an in vitro approach
  119. Rapid prototyping of replica knee implants for in vitro testing
  120. Protecting ultra- and hyperhydrophilic implant surfaces in dry state from loss of wettability
  121. Advanced wettability analysis of implant surfaces
  122. Patient-specific hip prostheses designed by surgeons
  123. Plasma treatment on novel carbon fiber reinforced PEEK cages to enhance bioactivity
  124. Wear of a total intervertebral disc prosthesis
  125. Digital health and digital biomarkers – enabling value chains on health data
  126. Usability in the lifecycle of medical software development
  127. Influence of different test gases in a non-destructive 100% quality control system for medical devices
  128. Device development guided by user satisfaction survey on auricular vagus nerve stimulation
  129. Empirical assessment of the time course of innovation in biomedical engineering: first results of a comparative approach
  130. Effect of left atrial hypertrophy on P-wave morphology in a computational model
  131. Simulation of intracardiac electrograms around acute ablation lesions
  132. Parametrization of activation based cardiac electrophysiology models using bidomain model simulations
  133. Assessment of nasal resistance using computational fluid dynamics
  134. Resistance in a non-linear autoregressive model of pulmonary mechanics
  135. Inspiratory and expiratory elastance in a non-linear autoregressive model of pulmonary mechanics
  136. Determination of regional lung function in cystic fibrosis using electrical impedance tomography
  137. Development of parietal bone surrogates for parietal graft lift training
  138. Numerical simulation of mechanically stimulated bone remodelling
  139. Conversion of engineering stresses to Cauchy stresses in tensile and compression tests of thermoplastic polymers
  140. Numerical examinations of simplified spondylodesis models concerning energy absorption in magnetic resonance imaging
  141. Principle study on the signal connection at transabdominal fetal pulse oximetry
  142. Influence of Siluron® insertion on model drug distribution in the simulated vitreous body
  143. Evaluating different approaches to identify a three parameter gas exchange model
  144. Effects of fibrosis on the extracellular potential based on 3D reconstructions from histological sections of heart tissue
  145. From imaging to hemodynamics – how reconstruction kernels influence the blood flow predictions in intracranial aneurysms
  146. Flow optimised design of a novel point-of-care diagnostic device for the detection of disease specific biomarkers
  147. Improved FPGA controlled artificial vascular system for plethysmographic measurements
  148. Minimally spaced electrode positions for multi-functional chest sensors: ECG and respiratory signal estimation
  149. Automated detection of alveolar arches for nasoalveolar molding in cleft lip and palate treatment
  150. Control scheme selection in human-machine- interfaces by analysis of activity signals
  151. Event-based sampling for reducing communication load in realtime human motion analysis by wireless inertial sensor networks
  152. Automatic pairing of inertial sensors to lower limb segments – a plug-and-play approach
  153. Contactless respiratory monitoring system for magnetic resonance imaging applications using a laser range sensor
  154. Interactive monitoring system for visual respiratory biofeedback
  155. Development of a low-cost senor based aid for visually impaired people
  156. Patient assistive system for the shoulder joint
  157. A passive beating heart setup for interventional cardiology training
Sign up now to receive a 20% welcome discount
Institutional Access
How does access work?
Have an idea on how to improve our website?
Please write us.
© 2026 De Gruyter Brill
Downloaded on 1.3.2026 from https://www.degruyterbrill.com/document/doi/10.1515/cdbme-2016-0046/html
Scroll to top button