Learning-Based Screening of Endothelial Dysfunction From Photoplethysmographic Signals
Abstract
:1. Introduction
2. Methods
2.1. Endothelial-Dysfunction Screening Methodology
2.1.1. PPG Endothelial-Dysfunction-Dataset Collection
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- Fasting for at least 8 h
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- No drug consumption in the previous 6 h
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- No smoking in the previous 6 h
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- No intense physical activity in the hours immediately preceding the exam
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- No nail polish
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- VenoScreen® (medis). VenoScreen was connected via a USB interface to a computer equipped with the CardioVascular Lab software package (MEDIS company, Ilmenau). The software verified, evaluated and displayed the measured PPG signals.
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- Prakticus II aneroid sphygmomanometer® (Friedrich Bosch GmbH & Co. KG). The sphygmomanometer, applied above the elbow on the subject’s left arm, was used to induce blood-flow blockage while measuring the blood pressure.
- Noise: Inevitably, the PPG signal contained high-frequency noise, which resulted from ambient light, thermal noise and other unclassified noise. The power line represented another noise source characterized by 50 Hz sinusoidal interference, probably accompanied by a number of harmonics [18]. To remove this noise, a simple filtering approach was applied, i.e., low-pass filter with 20 dB attenuation at 8 Hz [19].
- Baseline wander: Baseline wander filtering was required in order to minimize changes in beat morphology, which did not have cardiac origin [18]. The technique used for baseline wander filtering consisted in down-sampling the PPG signal to 2 Hz, followed by forward/backwards filtering using a second-order low-pass Butterworth filter with a cut-off frequency of 0.5 Hz [20]. After that, the signal was unsampled and subtracted from the original PPG signal.
- Outliers: To remove outliers, the “isoutlier” function (The MathWorks, Inc., Natick, MA, USA), was applied to the PPG signal. A point was considered outlier when its value was more than three scaled median absolute deviations (MAD) away from the PPG signal median. The outliers were detected every 10 s and they were replaced by the mean value calculated in the same interval.
2.1.2. Feature Extraction
- Systolic Amplitude ():
- Inflection Point Area ratio ():
- Pulse Interval ():
- Hearth Rate ():
- , which is the time between the systolic and diastolic peaks:
- Stiffness Index ():
- Augmentation Index ():
- Recovery Time (). indicates how many seconds, from the maximum value of the PPG during the post-occlusion phase, are required to return to PPG pre-occlusion condition (Figure 3a).
2.1.3. Classification
2.2. Experimental Protocol
3. Results
4. Discussion and Conclusions
Author Contributions
Funding
Acknowledgments
Conflicts of Interest
References
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Features | Mean ± SD |
---|---|
SA | |
IPA | |
PI | |
HR | |
SI | |
AI | |
RT |
Features | Mean ± SD |
---|---|
Age (years) | |
BMI (Kg/m) | |
PP (mmHg) |
Classifier | |||
---|---|---|---|
KNN | 0.64 | 0.59 | 0.62 |
RF | 0.66 | 0.63 | 0.63 |
SVM | 0.71 | 0.59 | 0.73 |
Classifier | |||
---|---|---|---|
KNN | 0.64 | 0.52 | 0.64 |
RF | 0.49 | 0.44 | 0.44 |
SVM | 0.71 | 0.67 | 0.69 |
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Calamanti, C.; Moccia, S.; Migliorelli, L.; Paolanti, M.; Frontoni, E. Learning-Based Screening of Endothelial Dysfunction From Photoplethysmographic Signals. Electronics 2019, 8, 271. https://doi.org/10.3390/electronics8030271
Calamanti C, Moccia S, Migliorelli L, Paolanti M, Frontoni E. Learning-Based Screening of Endothelial Dysfunction From Photoplethysmographic Signals. Electronics. 2019; 8(3):271. https://doi.org/10.3390/electronics8030271
Chicago/Turabian StyleCalamanti, Chiara, Sara Moccia, Lucia Migliorelli, Marina Paolanti, and Emanuele Frontoni. 2019. "Learning-Based Screening of Endothelial Dysfunction From Photoplethysmographic Signals" Electronics 8, no. 3: 271. https://doi.org/10.3390/electronics8030271
APA StyleCalamanti, C., Moccia, S., Migliorelli, L., Paolanti, M., & Frontoni, E. (2019). Learning-Based Screening of Endothelial Dysfunction From Photoplethysmographic Signals. Electronics, 8(3), 271. https://doi.org/10.3390/electronics8030271