Biosensor crunch time

RE: Biosensor crunch time

aswinvenu — Fri, 07 Aug 2020 21:24:39 GMT

Hi Drew,

ECG and PPG (Photoplethysmograph) signals are very highly correlated. Consider your heart like an electric pump. ECG talks about the armature current and PPG talks about the pumping action. PPG is also correlated to the pressure at which the blood has been pushed through the blood vessels. Algorithms used to calculate the BP using cuffless monitors use this correlation.

Ventricular Depolarization happens -> ventricles contracts -> when the pressure increases more than 120mmhg -> aortic valve opens -> bloods gets squeezed out from the chamber -> it travels through the vessels and reaches you finger tip where you are measuring the PPG.

calculate - pulse transit time (PTT). This will be proportional to the pressure (or pulse wave velocity). But we are all different and we do have slightly different anatomy. Our blood vessel thickness and elasticity is different. This is a variable parameter in the BP calculation. So we have to perform calibrations with different readings and finally make a regressive model to calculate the BP. (Blood vessels looses its elastic property over time so calibrations is required periodically)

Regards,

Aswin

RE: Biosensor crunch time

e14 Contributor — Tue, 27 Mar 2012 18:54:34 GMT

ron5329, you mention your BP drops and your heart rate is rocketing? Please look into Postural Orthostatic Tachycardia Syndrome, this may be what you are suffering from. I have been diagnosed with this and it is the reason I am interested in building this project. If you have a heart monitor you can test yourself, lie down for 10-20 minutes, completely flat, no moving or talking and relax. Work out your resting heart rate. Then immediately stand and stand as still as possible, no moving or talking or fidgeting. Monitor your heart rate for the next 30 minutes. If your heart rate increase more than 20 bpm (ie, goes from 60 lying down to 80+ standing) this is considered abnormal. If within 10 minutes of standing your heart rate increase more than 30 bpm, or at any point goes over 120bpm, then you meet the diagnostic criteria for POTS. I hope this is helpful, your heart should not be increasing that much without significant exercise. Please see a Doctor, preferably a cardiologist and mention POTS.

RE: Biosensor crunch time

e14 Contributor — Thu, 23 Jun 2011 22:43:10 GMT

Very interesting, I want to build something like this to monitor BP,PR,temp, and oxygen level with the addition of a way to record all of these things when they are off normal. With A-fib sometimes my BP drops, and my PR goes skyhi and bounces all over the place from 98 to 170. Sometimes for only a couple minutes sometimes for hours. I can tell when it's out of whack but it would be nice to be able to monitor it. Thanks for your comments. ron5329