Figure 1.
(
a) Example of ECG and SCG beats simultaneously recorded [
2]. (
b) ECG, x, y, and z axis of the SCG during resting and walking from experimental results.
Figure 1.
(
a) Example of ECG and SCG beats simultaneously recorded [
2]. (
b) ECG, x, y, and z axis of the SCG during resting and walking from experimental results.
Figure 2.
(a) Data acquisition system, top-down, clockwise. System block diagram. Photograph of the wireless DAQ (power supply and rechargeable battery are not shown). Screen capture of the DAQ user interface on the computer, (b) Block diagram and photograph of the sensing system.
Figure 2.
(a) Data acquisition system, top-down, clockwise. System block diagram. Photograph of the wireless DAQ (power supply and rechargeable battery are not shown). Screen capture of the DAQ user interface on the computer, (b) Block diagram and photograph of the sensing system.
Figure 3.
Sensor placements. (a) on the same horizontal level. (b) on the same vertical line. (c) on the diagonal line.
Figure 3.
Sensor placements. (a) on the same horizontal level. (b) on the same vertical line. (c) on the diagonal line.
Figure 4.
Spectrum of five subjects with (a) running and (b) walking.
Figure 4.
Spectrum of five subjects with (a) running and (b) walking.
Figure 5.
Block diagram (a) noise removal using one accelerometer for comparison, (b) analog processing steps, and (c) digital processing steps.
Figure 5.
Block diagram (a) noise removal using one accelerometer for comparison, (b) analog processing steps, and (c) digital processing steps.
Figure 6.
SUBTRACTOR on gentle movement. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG (20–50 Hz). Red oval indicates an identified systolic. Blue oval indicates a recognized diastolic. (c) First sensor z-axis. Red circle indicates a small SCG signal. (d) Second sensor z-axis.
Figure 6.
SUBTRACTOR on gentle movement. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG (20–50 Hz). Red oval indicates an identified systolic. Blue oval indicates a recognized diastolic. (c) First sensor z-axis. Red circle indicates a small SCG signal. (d) Second sensor z-axis.
Figure 7.
SUBTRACTOR on walking motion. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG (20–50 Hz). Red oval indicates identified systoles. Blue oval indicates detected diastoles. (c) First sensor z-axis. Red circle indicates a small SCG signal, brown ovals show high-energy portion of walking. (d) Second sensor z-axis. Brown ovals indicate high-energy portion of walking.
Figure 7.
SUBTRACTOR on walking motion. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG (20–50 Hz). Red oval indicates identified systoles. Blue oval indicates detected diastoles. (c) First sensor z-axis. Red circle indicates a small SCG signal, brown ovals show high-energy portion of walking. (d) Second sensor z-axis. Brown ovals indicate high-energy portion of walking.
Figure 8.
ADDER on gentle motion. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG (20–50 Hz). Red oval indicates a recognized systole. Blue oval indicates an identified diastoles. (c) First sensor z-axis. (d) Second sensor z-axis. Red circle indicates a small SCG signal.
Figure 8.
ADDER on gentle motion. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG (20–50 Hz). Red oval indicates a recognized systole. Blue oval indicates an identified diastoles. (c) First sensor z-axis. (d) Second sensor z-axis. Red circle indicates a small SCG signal.
Figure 9.
ADDER on walking motion. (a) Filtered ECG (5–20 Hz). (b) Inverted and filtered SCG (20–50 Hz). Red oval indicates recognized systoles. Blue oval indicates detected diastoles. Orange ovals show results of different reaction (c) First sensor z-axis. Brown ovals show high-energy portion of walking. (d) Second sensor z-axis. Brown ovals indicate a high-energy portion of walking. Red circle indicates a small SCG signal.
Figure 9.
ADDER on walking motion. (a) Filtered ECG (5–20 Hz). (b) Inverted and filtered SCG (20–50 Hz). Red oval indicates recognized systoles. Blue oval indicates detected diastoles. Orange ovals show results of different reaction (c) First sensor z-axis. Brown ovals show high-energy portion of walking. (d) Second sensor z-axis. Brown ovals indicate a high-energy portion of walking. Red circle indicates a small SCG signal.
Figure 10.
Digital processing on gentle movement. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG with SUBTRACTOR (subtraction). (c) Filtered total acceleration. (d) Filtered z-axis acceleration. Red oval indicates a recognized systole. Blue oval indicates a determined diastole. (e) First sensor z-axis. Red circle indicates a small SCG signal. (f) First sensor y-axis. (g) First sensor x-axis. (h) Second sensor z-axis. (i) Second sensor y-axis. (j) Second sensor x-axis.
Figure 10.
Digital processing on gentle movement. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG with SUBTRACTOR (subtraction). (c) Filtered total acceleration. (d) Filtered z-axis acceleration. Red oval indicates a recognized systole. Blue oval indicates a determined diastole. (e) First sensor z-axis. Red circle indicates a small SCG signal. (f) First sensor y-axis. (g) First sensor x-axis. (h) Second sensor z-axis. (i) Second sensor y-axis. (j) Second sensor x-axis.
Figure 11.
Digital processing on walking motion. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG with SUBTRACTOR. (c) Filtered total acceleration. (d) Filtered z-axis acceleration. Red ovals indicate recognized systoles. Blue ovals indicate determined diastoles. Orange ovals show results of different response. Green ovals illustrate better noise suppression. (e) First sensor z-axis. Red circle indicates a small SCG signal. (f) First sensor y-axis. (g) First sensor x-axis. Brown oval indicates high-energy portion of walking. (h) Second sensor z-axis. (i) Second sensor y-axis. (j) Second sensor x-axis. Brown oval indicates high-energy portion of walking.
Figure 11.
Digital processing on walking motion. (a) Filtered ECG (5–20 Hz). (b) Filtered SCG with SUBTRACTOR. (c) Filtered total acceleration. (d) Filtered z-axis acceleration. Red ovals indicate recognized systoles. Blue ovals indicate determined diastoles. Orange ovals show results of different response. Green ovals illustrate better noise suppression. (e) First sensor z-axis. Red circle indicates a small SCG signal. (f) First sensor y-axis. (g) First sensor x-axis. Brown oval indicates high-energy portion of walking. (h) Second sensor z-axis. (i) Second sensor y-axis. (j) Second sensor x-axis. Brown oval indicates high-energy portion of walking.
Figure 12.
Comparison of SNRs on one sensor and two-sensor methods. (a) Gentle movement; (b) Walking.
Figure 12.
Comparison of SNRs on one sensor and two-sensor methods. (a) Gentle movement; (b) Walking.
Table 1.
Signal measurements of using two sensors with SUBTRACTOR on gentle motion.
Table 1.
Signal measurements of using two sensors with SUBTRACTOR on gentle motion.
Sensor Placements | Systolic Vpp (mV) | Diastolic Vpp (mV) | Systolic SNR | Diastolic SNR |
---|
Average | SD | Average | SD | Average | SD | Average | SD |
---|
Two horizontal sensors | 414.7 | 128.0 | 294.1 | 28.1 | 34.4 | 18.8 | 14.3 | 4.1 |
Two vertical sensors | 418.2 | 33.0 | 162.8 | 20.2 | 49.5 | 8.8 | 8 | 1.3 |
Two diagonal sensors | 539 | 112.1 | 281 | 64.6 | 48 | 25.1 | 14.9 | 7.1 |
Table 2.
Signal measurements of using two sensors with SUBTRACTOR on walking motion.
Table 2.
Signal measurements of using two sensors with SUBTRACTOR on walking motion.
Sensor Placements | Detected Systolic Vpp (mV) | Detected Diastolic Vpp (mV) | Distorted Vpp (mV) | Detected Systolic SNR | Detected Diastolic SNR |
---|
Average | SD | Average | SD | Average | SD | Average | SD | Average | SD |
---|
Two horizontal | 524.4 | 21.2 | 272.8 | 49.7 | 427.2 | 110.8 | 4.8 | 5.1 | 0.7 | 0.5 |
Two vertical | 368.6 | 29.5 | N/A | N/A | 699.3 | 55.8 | 4.2 | 3.2 | N/A | N/A |
Two diagonal | 613.4 | 153.4 | 338 | 136.1 | 1478.7 | 495.4 | 0.2 | 0.1 | 0.07 | 0.1 |
Table 3.
Signal measurements of using two sensors with ADDER on gentle motion.
Table 3.
Signal measurements of using two sensors with ADDER on gentle motion.
Sensor Placements | Systolic Vpp (mV) | Diastolic Vpp (mV) | Systolic SNR | Diastolic SNR |
---|
Average | SD | Average | SD | Average | SD | Average | SD |
---|
Two horizontal sensors | 1390.3 | 208.7 | 799.2 | 89.6 | 31.8 | 14.8 | 13.9 | 8.0 |
Two vertical sensors | 1081.3 | 381.6 | 490.2 | 89.6 | 16.9 | 20.7 | 3.1 | 1.6 |
Two diagonal sensors | 1600.9 | 321.4 | 850.1 | 183.6 | 32.2 | 24.4 | 8.6 | 8.1 |
Table 4.
Signal measurements of using two sensors with ADDER on walking motion.
Table 4.
Signal measurements of using two sensors with ADDER on walking motion.
Sensor Placements | Detected Systolic Vpp (mV) | Detected Diastolic Vpp (mV) | Distorted Vpp (mV) | Detected Systolic SNR | Detected Diastolic SNR |
---|
Average | SD | Average | SD | Average | SD | Average | SD | Average | SD |
---|
Two horizontal | 2324.8 | 120.6 | 1244.3 | 156.1 | 2176.4 | 11.0 | 21.1 | 12.8 | 3.0 | 3.0 |
Two vertical | 1018.6 | 379.1 | 564.4 | 89.0 | 2366.6 | 34.1 | 1.3 | 2.1 | 0.3 | 0.4 |
Two diagonal | 1836.1 | 124.6 | 1012.1 | 239.7 | 2385.3 | 76.2 | 0.4 | 0.03 | 0.1 | 0.03 |
Table 5.
Signal measurements of two sensors with digital processing on gentle motion.
Table 5.
Signal measurements of two sensors with digital processing on gentle motion.
Sensor Placements and Methods | Systolic Vpp (mV) | Diastolic Vpp (mV) | Systolic SNR | Diastolic SNR |
---|
Average | SD | Average | SD | Average | SD | Average | SD |
---|
Two horizontal sensors | Subtraction | 414.7 | 128.0 | 294.1 | 28.1 | 34.4 | 18.8 | 14.3 | 4.1 |
Total acceleration | 6.3 | 2.1 | 3.7 | 0.7 | 67.5 | 46.7 | 21.7 | 2.4 |
Z-axis acceleration | 6.2 | 2.3 | 3.6 | 0.8 | 75.3 | 60.1 | 23 | 12.7 |
Two vertical sensors | Subtraction | 418.2 | 33.0 | 162.8 | 20.2 | 49.5 | 8.8 | 8 | 1.3 |
Total acceleration | 13.3 | 1.2 | 5.5 | 1.3 | 69.9 | 36.7 | 11.3 | 9.0 |
Z-axis acceleration | 6.6 | 0.6 | 2.4 | 0.3 | 67.8 | 14.4 | 9.7 | 5.0 |
Two diagonal sensors | Subtraction | 539 | 112.1 | 281 | 64.6 | 48 | 25.1 | 14.9 | 7.1 |
Total acceleration | 11.7 | 4.6 | 4.7 | 1.0 | 84.7 | 81.2 | 17.8 | 1.4 |
Z-axis acceleration | 9.4 | 2.4 | 4.1 | 0.8 | 78.1 | 42.2 | 20.4 | 8.6 |
Table 6.
Signal measurements of two sensors with digital processing on walking motion.
Table 6.
Signal measurements of two sensors with digital processing on walking motion.
Sensor Placements and Methods | Detected Systolic Vpp (mV) | Detected Diastolic Vpp (mV) | Distorted Vpp (mV) | Detected Systolic SNR | Detected Diastolic SNR |
---|
Ave. | SD | Ave. | SD | Ave. | SD | Ave. | SD | Ave. | SD |
---|
Two horizontal | Subtraction | 524.4 | 21.2 | 272.8 | 49.7 | 427.2 | 110.8 | 4.8 | 5.1 | 0.7 | 0.5 |
Total acceleration | 6.4 | 0.7 | 3.2 | 1.4 | 10.66 | 4.3 | 6 | 9.3 | 0.8 | 1.1 |
Z-axis acceleration | 6.9 | 1.0 | 3.5 | 0.6 | 4.1 | 1.1 | 9.3 | 9.1 | 2.2 | 0.7 |
Two vertical | Subtraction | 368.6 | 29.5 | N/A | N/A | 699.3 | 55.8 | 4.2 | 3.2 | N/A | N/A |
Total acceleration | 10.3 | 3.4 | 5.09 | N/A | 12.4 | 8.7 | 3.9 | 4.5 | 0.8 | N/A |
Z-axis acceleration | 5.8 | 0.1 | N/A | N/A | 8.9 | 0.6 | 11.5 | 5.8 | N/A | N/A |
Two diagonal | Subtraction | 613.4 | 153.4 | 338 | 136.1 | 1478.7 | 495.4 | 0.2 | 0.1 | 0.07 | 0.1 |
Total acceleration | 13.7 | 3.2 | 4.9 | 0.2 | 15.9 | 6.1 | 3.9 | 2.3 | 0.09 | 0.1 |
Z-axis acceleration | 10.1 | 2.0 | 4.4 | 0.4 | 20.7 | 7.4 | 1.1 | 0.7 | 0.04 | 0.04 |
Table 7.
The error and missing rates of moving average threshold and interpolation algorithms with total acceleration (Equation (3)) on eight subjects.
Table 7.
The error and missing rates of moving average threshold and interpolation algorithms with total acceleration (Equation (3)) on eight subjects.
Sub-Jects | Manual | Moving Average | Interpolation |
---|
Heart Rate | Sys./Dias. Ratio | Total Sys. | Total Dias. | Systole (%) | Diastole (%) | Systole (%) | Diastole (%) |
---|
Error | Miss | Error | Miss | Error | Miss | Error | Miss |
---|
1 | 78.7 ± 2.7 | 0.50 ± 0.06 | 84 | 84 | 0 | 0 | 1.1 | 1.1 | 1.1 | 1.1 | 2.3 | 2. |
2 | 88.7 ± 3.8 | 0.55 ± 0.09 | 90 | 90 | 2.2 | 3.3 | 2.2 | 3.3 | 1.1 | 3.3 | 1.1 | 3.3 |
3 | 75.2 ± 2.9 | 0.57 ± 0.09 | 76 | 77 | 1.3 | 0 | 1.3 | 1.3 | 2.6 | 1.3 | 2.6 | 2.6 |
4 | 98.9 ± 4.3 | 0.65 ± 0.10 | 100 | 100 | 0 | 0 | 5 | 5 | 0 | 1 | 1 | 2 |
5 | 76.4 ± 4.3 | 0.55 ± 0.04 | 80 | 79 | 0 | 0 | 0 | 0 | 1.2 | 2.5 | 1.2 | 1.2 |
6 | 79.7 ± 2.3 | 0.67 ± 0.10 | 84 | 84 | 0 | 0 | 1.1 | 1.1 | 0 | 2.3 | 1.2 | 3.5 |
7 | 70.6 ± 4.5 | 0.53 ± 0.12 | 72 | 73 | 6.9 | 4.1 | 9.5 | 8.2 | 5.5 | 4.1 | 8.2 | 8.2 |
8 | 102.0 ± 3.2 | 0.72 ± 0.11 | 105 | 106 | 3.8 | 58 | 3.7 | 58.4 | 13.3 | 25.7 | 13.2 | 26.4 |
Average | 83.77 | 0.59 | 76.8 | 77.0 | 1.78 | 8.18 | 2.99 | 9.8 | 3.13.1 | 5.16 | 3.85 | 6.15 |
σ | 11.52 | 0.07 | 11.4 | 11.4 | 2.5 | 20.2 | 3.1 | 19.8 | 4.5 | 8.4 | 4.5 | 8.4 |
Average without subject 8 | 1.2 | 1.1 | 2.4 | 2.7 | 1.2 | 2.3 | 2.2 | 3.5 |
σ without subject 8 | 2.6 | 2.1 | 3.6 | 3.4 | 3.1 | 1.5 | 4.0 | 2.9 |
Table 8.
The error and missing rates of moving average threshold and interpolation algorithms with total Z-axis acceleration (Equation (4)) on eight subjects.
Table 8.
The error and missing rates of moving average threshold and interpolation algorithms with total Z-axis acceleration (Equation (4)) on eight subjects.
Subject | Manual | Moving Average | Interpolation |
---|
Heart Rate | Sys./Dia. Ratio | Total Sys. | Total Dias. | Systole (%) | Diastole (%) | Systole (%) | Diastole (%) |
---|
Error | Miss | Error | Miss | Error | Miss | Error | Miss |
---|
1 | 78.7 ± 2.7 | 0.50 ± 0.06 | 84 | 84 | 0 | 0 | 0 | 0 | 0 | 1.2 | 0 | 1.2 |
2 | 88.7 ± 3.8 | 0.55 ± 0.09 | 90 | 90 | 0 | 2.2 | 0 | 2.2 | 0 | 2.2 | 0 | 2.2 |
3 | 75.2 ± 2.9 | 0.57 ± 0.09 | 76 | 77 | 1.3 | 0 | 1.3 | 1.3 | 0 | 1.3 | 0 | 2.6 |
4 | 98.9 ± 4.3 | 0.65 ± 0.10 | 100 | 100 | 0 | 0 | 5 | 5 | 0 | 1 | 3 | 4 |
5 | 76.4 ± 4.3 | 0.55 ± 0.04 | 80 | 79 | 0 | 0 | 0 | 0 | 0 | 2.5 | 0 | 1.2 |
6 | 79.7 ± 2.3 | 0.67 ± 0.10 | 84 | 84 | 0 | 0 | 1.1 | 1.1 | 0 | 2.3 | 1.2 | 3.5 |
7 | 70.6 ± 4.5 | 0.53 ± 0.12 | 72 | 73 | 6.9 | 5.5 | 9.5 | 9.5 | 8.3 | 5.5 | 10.9 | 9.5 |
8 | 102.0 ± 3.2 | 0.72 ± 0.11 | 105 | 106 | 5.7 | 58 | 5.6 | 58.4 | 16.1 | 29.5 | 16 | 30.1 |
Average | 83.77 | 0.59 | 76.8 | 77.0 | 1.74 | 8.21 | 2.81 | 9.69 | 3.1 | 5.69 | 3.89 | 6.79 |
σ | 11.52 | 0.07 | 11.4 | 11.4 | 2.9 | 20.2 | 3.5 | 19.9 | 6.0 | 9.7 | 6.1 | 9.8 |
Average without subject 8 | 1.5 | 1.1 | 2.9 | 2.9 | 1.6 | 2.2 | 2.5 | 3.3 |
σ without subject 8 | 2.5 | 1.8 | 3.3 | 2.9 | 1.9 | 1.2 | 2.6 | 2.3 |