Reflective Pulse Oximetry design considerations

Thanks Praveen,

As I want to develope a reflective pulse oximeter with single LED with CC430.I am quite confused with its design and the components to use.I used these for the design a GREEN led , a visible photodetector ,OPA380 as the transimpedance stage with a negative feedback of Rf=1M and Cf=3.3pf.

I was not getting any pulse at the output of TIA (like the output pulse of the AFE440) but when I turn on the lights it is giving some sinusoidal signal of lesser amplitude may be ambient light.

Can you suggest anything about the design.

Thanks.

Traditional pulse oximeter solutions have used two LEDs (Red and IR) for oxygen saturation measurements. Reflective pulse oximeter solution also require two LEDs. Single LED especially Green is ideally suited for wearable Heart rate monitoring applications. For reflective applications, mechanical design of the system, measurement site, test subjects, etc., play a major role in the design.

Unfortunately we are not experts in reflective pulse-ox. However, we have had customers use the AFE4400 directly for reflective pulse-ox in the past.

Amy Ball's post of Sept. 29, 2013, mentions that some customers are using the AFE4400 for reflective pulse oximetry. I assume that means they are using the TIDA-00011 wrist unit, which contains the AFE4400 as front end, mounts the emitter and photo diodes side-by-side on a board in a reflective configuration, and looks like an attractive package for reflective oximetry anywhere on the body.

However, the TIDA-00011  is actually designed as a heart rate monitor, not as an oximeter. In contrast, the very similar TIDA-00010 is designed as a true oximeter, uses a fingertip transmission probe, and substitutes the AFE4490, which has higher performance specs than the AEF4400.

My question is: what steps are needed to convert the TIDA-00011 into an oximeter (a very tempting prospect). Is replacing the AFE4400 with the AFE4490 necessary? What else am I overlooking? Is there some limitation that makes the conversion impractical?

Richard Hochschild

Richard,

What customer is this for? Could we have a little more details on the applicaiton?

Amy,

I'm trying to integrate reflective SpO2 oximetry in a chest strap that will also monitor other physiological functions. The aim is a new product.

I'm trying to clarify whether the TIDA-00011 (using reflectance probe) can be used to monitor SpO2 even though it employs the lower-spec AFE4400 chip intended just for heart rate oximetry?

I understand that the similar TIDA-00010 (using transmission probe) is specifically designed for SpO2 measurement and uses the higher-spec AFE4490 chip.

Your Sept. 29, 2013 post mentions TI customers using the TIDA-00011/AFE4400 for reflectance oximetry. Are they actually measuring SpO2 or just heart rate?

Thanks. 

Richard

Richard,

We don't have much experience with SPO2 on the chest using reflective methods.  It seems possible with the right sensor design and software algorithms.  Nothing in the 4400/4490 prevents use on that part of the body. For a reflective design customers are currently only measuring heart rate.

Thanks for sharing! Do you know this other product from the same brand? http://www.medicalexpo.com/medical-manufacturer/oximeter-412.html