Over the years, I have learned lots of different computing topics. I have never implemented any digital signal processing. The computing tasks, algorithmic complexity, and data analysis components are all the kind of thing I have done before. But I don’t know very much about human physiology.
This week I have learned about pulse oximeters, photoplethysmography, and human physiology related to the pulse and blood flow.
Here is what I can convey: the simple method for measuring the pulse using emitted light produces a signal that is anything but simple. The data is there, but so are artifacts and sources of noise. The sheer number of environmental and physiological variables makes this task daunting, but lots of great work has been done to attempt to divine the meaning of the signal and the reduction of the noise.
One of the most interesting and upsetting things is how little is known about what causes the waveform seen using photoplethysmography (PPG) and why some areas of the body exhibit bizarre effects when using the technique.
You shine a light onto a body part. Then you measure either the light re-emitted (scattered) off the body part or you measure the light transmitted through the body part. Then you analyze the signal and the noise and look for patterns. Or at least display the waveform (hopefully in real-time) so someone can offer therapeutic advice. A pulse oximeter can be used for this task. So far, I have ignored the capability of this device to read blood oxygen levels.
The hardest part has been getting up to speed on the biology material. The next hardest part has been diving into digital signal processing. But I feel like I have mastered these to a large enough degree to effective learn to process signal data and produce a useful GUI.
Once that task is mastered, the problem will be learning to use multiple pulse oximeter devices simultaneously. ^__^