Week 3 - Investigation of HRV Codebase

 Week 3 - Investigation of HRV Codebase

HRV with Pacer.
HRV Peak and Low pulses.



At the beginning of the Week 3 Iteration the group took a look at the HRV code base which includes the following features:

- Manual peak detection on button A press.
- Pacer graph alongside HRV measurement.
- Delta_t : Time between pulses.
- Local display using Micro: Bit LED Matrix.



From using the lab testing that was done the following conclusions were made:

- For Bio-Feedback the idea of attaching LED's to Balloons was proposed.

- Pulse sensor is hard to get a good reading from but when it does it looks very good
        This is because the sensor works ideally when the user is static because it is a Photoelectric type sensor. 

Because of this issue i decided to take a closer look at the type of sensor the team is using along with the pros and cons.
            


Ref[1]

Ref[1]


From the research done on the Reflection type sensor it shows that the sensor works better based on 
the change in blood vessel volume. This varies for different people because of different rates of blood flow throughout the body.

From doing further research i have found that ECG readings are proven to be more accurate than Reflection type sensors with the drawbacks of having to be placed on specific area of the users arms. 

Excerpt from article:

Readings obtained through the ECG method have proven to be more accurate and comprehensive than those obtained through PPG. This is mainly because ECG reads the electrical signals produced by the heart activity directly, while PPG provides a more indirect measurement, using light reflection to detect the pulsating activity of the heart. When it comes to ease and accuracy of measuring, PPG can be measured at several positions on the body and offers a wide range of measurement possibilities, while ECG requires more specific anatomical placement of electrodes on the body.
Ref[2]


This would mean a new sensor would have to be obtained which might not be the best idea this far into the project but could provide the team with a more accurate measurement for HRV. 
The drawback of measuring ECG would be that the sensor probes would have to be connected to the users wrists rather than their thumb or index finger.

A sensor with some potential could be the Sparkfun AD8232 which has the capabilities to take an ECG reading or DFRobots ECG heart rate sensor.

Ref[3]

Ref[4]


For these sensors we could make them less intrusive by adding an everyday item such as a a wrist strap over the sensor, this would help cover the sensor while also securing it in place:


 

Once an accurate measurement is obtained the values can then be mapped to a sound, this procedure is called Sonification and will help bring the project to life.

Sonification using Bandlab / Midi

Ref[5]


By using Sonification some potential use cases could be having a heartbeat sound playing in sync with the users heart.

Other uses could be a resonator value that increases based on how good the measurement coming from the pulse sensor is.

For example if there is a weak connection the sound could be low and off beat opposed to a strong connection that could be louder and on beat with the users heart beat.

Midi could also be used to play relaxing music to help the user relax and control their breathing.




Along with sonification there are some other variables that could potentially be calculated once a clean HRV measurement is obtained:
Ref[1]







References:

Ref [1]: https://www.rohm.com/electronics-basics/sensor/pulse-sensor#:~:text=is%20explained%20below.-,Reflection%2DType%20Pulse%20Sensor%20(Optical%20Sensor%20for%20Heart%20Rate%20Monitor,using%20a%20photodiode%20or%20phototransistor.

Ref [2]: https://www.kenkou.io/ecg-and-ppg-technologies-for-heart-rate-variability-hrv-tracking/#:~:text=ECG%20can%20produce%20accurate%20data,does%20not%20require%20settling%20time.

Ref [3]: https://littlebirdelectronics.com.au/guides/173/heart-rate-sensor-with-arduino

Ref [4]: https://www.dfrobot.com/product-1540.html

Ref [5]: https://www.bandlab.com/studio



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