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PRMRP 2012 Investigator Vignette

Title: Performance of an Innovative, Portable, and Noninvasive Sensor for Trauma Care

Investigator: Babs Soller, PhD; Reflectance Medical, Inc.


The goal of our technology is to provide a non-invasive way to measure muscle PH, muscle oxygen, and blood hematocrit that is small enough, lightweight enough, that it can be used near the battlefield, that can provide an early indication that somebody has internal bleeding and might be at risk for going into shock.

When somebody has an injury and has internal bleeding, the body is really good at maintaining blood pressure and maintaining oxygen delivery because it really wants to keep you alive. And so the way it does that, is that the small blood vessels in the muscle and in the kidney and the liver and the intestines actually constrict, and that sends blood back to the heart and to the brain. So the blood pressure looks fine, your pulse-ox signal looks fine, but you've got reduced blood flow to the muscle. And so therefore' you have to extract more oxygen out of the blood, and so that results in a lower oxygen saturation.

So, our technology is based on near infrared spectroscopy. And near infrared spectroscopy allows us to make non-invasive measurements of blood and tissue chemistry, because near infrared light penetrates through the skin and the fat. The problem is that skin pigment and fat also interferes with our optical signal. So if we want to calculate parameters, we have to eliminate those interferences.

So, this is a cartoon of how we actually do that. We have a single detector, but multiple light sources. So, light that comes from a light source that's close to the detector doesn't penetrate very far. So, we only get some information about the skin pigment. But if we have light from here, it actually passes into the muscle. So, by having a choice of light sources that are close to the detector, and light sources that are far away from the detector, we can get information about the skin pigment, and we can get light that penetrates through a variety of fat thicknesses.

So, the way the sensor works is, when you put it on a patient, it scans all these, and it picks the one that is best for correcting for pigment and best for getting through whatever thickness of fat happens to be over the muscle. And it's totally automated.

This is actually our second generation product, and it's the same sensor. It's in a sleeve. It's a little thicker, and we actually have a computer in here that does all the calculations, and controls all the data collection, and a battery. If you were going to use it, you'd put it in the sleeve; you would then peel the adhesive off, and it would stick to the arm up here.

The whole calculation takes about five seconds. The device can be plugged into any patient monitor that might be near the battlefield, or might be in the ambulance or helicopter, or we even can display it on an Android tablet and eventually on--maybe on a phone pretty soon. So, we now have a very portable device that can go anywhere with the patient. It doesn't have to be plugged into the wall, but displays the three parameters that this care guide sensor calculates, which is muscle oxygen, PH, and hematocrit.