Post oximetry PLETH waveform and ABP waveform similarities

Question

As a beginner in medical sciences I found a fact that was seemingly interesting to me.

When I was doing some simulations with patient monitors and advanced cardiac life support cases, I found that the way form between post oximetry PLETH and a BP waveforms looks surprisingly similar.

I understand that post oximetry is a representation of blood flow over peripheral limbs, however its almost exact representation of ABP waveforms got me thinking if dynamic blood pressure can be achieved by monitoring SPO2 only, rather than invasive monitoring which may cause a amount of discomfort.

I tried searching on the Internet, but found no devices articles whatever documenting using SPO2 to measure blood pressure. Are there actually limitations which caused this hypothetical technology to not work, or is it under development in someway where is the evidence of such development, should it exist, was not discovered by me.

I would appreciate any information.

Answer 1

You have observed a relationship in phase/frequency of these two signals, which indicates that you can use both to get the same rate information. In this case, that information is the heart rate.

You cannot infer from this that there is sufficient information in one signal to predict the amplitude of the other. For a given recording, you may be able to use regression to attempt this, but you will likely find the accuracy is not good, and certainly not good enough to extrapolate and predict blood pressure in other patients with only PLETH.

When measuring blood pressure, we are not typically concerned as much with the shape of the waveform as with the mean, maximum, and minimum pressures observed. External blood pressure monitoring is not particularly invasive. When invasive blood pressure monitoring is used it is for the improved accuracy and rapid information; you won't obtain these features with a surrogate.