Anger Measurement Technology
Measurement
We will be measuring heart rate, blood pressure (both diastolic and systolic), and muscle tension to determine whether or not the user is experiencing an anger episode at a point in time.
Heartrate
Measuring the heart rate is a key factor in predicting an upcoming anger episode. Cessabit can measure it using Laser Doppler Vibrometry (LDV). LDV uses a low-power laser at a vibrating surface, and the resulting Doppler shift in the reflected signal is measured and used to reconstruct the vibrations of the surface. These vibrations are due to mechanical energy transmitted to the skin from various cardiovascular, respiratory, and other physiological activities. The LDV pulse signal provides a sensitive measure of the coarse aspects of the cardiac signal, including heart rate and heart rate variability, as well as more fine-grained and advanced features reflecting extremely detailed aspects of myocardial function and the arterial system. This approach is better than the frequently used Photoplethysmogram (PPG) because the wrist (dorsal side) is known to be one of the less reliable places for measuring good quality PPG signals, and LDV has been found more effective.
In the happy/excited state, the pulse rate varies from 70 to 100 bpm; in the sad state, it varies from 80 to 100 bpm; in relaxed/normal state, it varies from 60 to 80 bpm; and in the anger state, it varies from 95 to 120 bpm.
Pulse wave signal processing
An averaged pulse wave is extracted as follows:
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The software identifies pulse wave onsets (at the beginning of systole) and an average pulse wave is computed. Figure 4 below shows an example of an averaged pulse wave, APWn=1(t).
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Pulse wave features are extracted from each averaged pulse wave, as follows and as can be seen in Figure.
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Two fiducial points are identified on each wave: the systolic peak (s), and
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the dicrotic notch (dia), using the waveform maximum and its second derivative minimum of the averaged pulse wave, respectively.
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Two pulse wave features are then extracted for each pulse wave: the crest time (CT, i.e. time from pulse onset to systolic peak) and the duration of diastole (tdia, i.e. time from dicrotic notch to pulse end).
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Extracted pulse wave features are analyzed as described in the next section.
Further analysis and stress measurement
The percentage of high-quality pulse waves depends on the state of stress. It was found in recent studies that the main criteria for qualifying pulse waves as high quality was the visual discrimination of the dicrotic notch, aided by visual inspection of the first and second derivatives. The fact that the highest percentage of high-quality signal was found in the relaxation phase indicates that in this phase the pulse wave is less distorted than in the other phases and during the stress phases.[1] Two main parameters change significantly with stress and relaxation:
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tdia (the time from dicrotic notch to end diastole);
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CT (the time from pulse onset to systolic peak).
As shown in Figure 6 above, tdia and CT decrease during stress, which shows that stress increases arterial stiffness and thus impacts reflected wave timing. Therefore, the more these two parameters decrease – the more stress the person is experiencing. These will be used as ancillary parameters to confirm stress events (i.e. anger) by comparing the percentage decrease in tdia and CT from the person’s relaxed state.
Blood pressure
Both, diastolic and systolic blood pressure are key for identifying an incoming anger episode. Our device uses a photonic integrated circuit (PIC) and Laser Doppler vibrometers (LDV) to measure the blood pressure in a non-contact manner from simply wearing the device. LDV is a “vibration-sensing” technique that measures the velocity of a vibrating target, using a laser beam, and can accurately measure one’s blood pressure. The PIC has allowed this technology to be produced in a compact and sleek manner, all wearable on the wrist.
Muscle Tension
Muscle tension is measured via an electrical correlate called electromyography (EMG) and nerve conduction study (NCS), which are typically done at the same time. The signal comes from the nerves controlling the muscles - the more nerves that are firing, the stronger the voltage, and the higher the muscle tension.Electromyography (EMG) is a technique for evaluating and recording the electrical activity produced by skeletal muscles. EMG is performed using an instrument called an electromyograph to produce a record called an electromyogram. An electromyograph detects the electric potential generated by muscle cells when these cells are electrically or neurologically activated.
The signals can be analyzed to detect abnormalities, activation level, or recruitment order, or to analyze the biomechanics of human or animal movement. EMG measures the electrical activity of muscle during rest, slight contraction and forceful contraction. Muscle tissue does not normally produce electrical signals during rest. According to Hopkins Medicine, NCS is a measurement of the amount and speed of conduction of an electrical impulse through a nerve. NCS can determine nerve damage and destruction and is often performed at the same time as EMG. A nerve conduction study (NCS) is a medical diagnostic test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body.
Active wrist sensors are crucial when measuring muscle tension.
These sensors pick up tension in the shoulders, arms and hands.
This is useful because people commonly tighten up in those areas when angry or stressed.
Leg-to-leg SEMG while talking. The patient was unaware that as he became angry, muscle tension in his pelvic floor, legs, and buttocks increased. When he saw the recording, he finally realized that his thoughts and feelings directly affect his body.