One of the tests you go through whenever you go for your check-up include oximetry, which measures the amount of oxygen in your blood by measuring the concentration of oxyhemoglobin, which is oxygen carried by a protein (hemoglobin) to your organs. No, you don’t want oxygen in the blood as air: that’s usually one of the Bad Things that gets you sent to the emergency room instead of your physician’s office!
Oximetry tests are often ‘pulse oximetry,’ which measures the amount of oxyhemoglobin in your blood at the same time it takes your pulse. We often remember this as the test where they put a clip on the tip of a finger.
The clip measures your blood oxygen by shining infrared energy – you’re aware of it now, but you’ve never felt it before and you still won’t after this – through your finger. The other side of the clip measures how much light was transmitted through, which is sent to a little computer (everything‘s a little computer these days anyway) that translates that signal into the ‘O2 sat’ reading that you probably overheard the tech say. Here’s a proof-of-concept you can try for yourself – take a red laser pointer and shine it through the tip of your thumb. Notice that some of the light shined through – that is similar to how the pulse oximeter works. Good so far, but there are other places on the body where your O2 sat could be really important, like on an organ, a new skin graft, or literally anywhere else on the body. After all, what might be happening on your hands may not be happening anywhere else on your body, especially if there were injuries involved. And what about outside of a hospital setting – blood oxygen is also important to professional athletes, as it affects their performance in endurance events (in addition to, you know, not dying). Is there any other way to do this?
Wouldn’t be much of a post if there weren’t, so here we go: the authors of this week’s OPEN ACCESS Featured Article propose that one could use a ‘skin’ made of organic LEDs (OLEDs). The authors propose using this as an actual skin graft-
-but they didn’t actually do that in the study. Instead, they tried it out on a volunteer that DID NOT REMOVE ANY SKIN but instead taped an array of OLEDs to various places in the body and (among other tests) compared it to the readings given out by a typical pulse oximeter on the finger. The OLED array worked by reflecting light (red and infrared OLEDs) back to the same side of the skin rather than transmitting it through the skin as with pulse oximeters. The authors then tested it against atmospheric conditions that simulated being in a higher altitude, but not that high. Can you imagine what the ethics board would have to say about potentially killing a volunteer by simulating the atmosphere on top of Mount Everest!?
(they also simulated ischemia by inflating a blood pressure cuff on a volunteer’s arm – I don’t think that would’ve killed the volunteer either, especially because that’s something we played around with when we were bored)
Of course it worked (wouldn’t be published otherwise), but was it comparable to traditional pulse oximetry? Results show that indeed it did in the altitude simulation test – as the amount of oxygen went down, similar to what happens in upper elevations, both pulse and OLED oximeters had similar O2 sat readings at different places in the body. Bear in mind that this is what should happen because you wouldn’t want any part of the body getting less oxygen than all else, and you couldn’t tell because one probe on one part of the body says you’re OK. The ischemia simulation showed similar sensitivity with the OLED oximeter, which means that it would’ve tracked blockages just as well.
So pulse oximetry is a tried-and-true method of measuring O2 sats, and why do we need this kind of R&D? Remember what I mentioned earlier – pulse oximetry requires light to be transmitted through skin, tissue, probably some bone, then through to the other side. This means that you’re limited to toes, fingers, maybe even earlobes. On the other hand, these OLED arrays rely on reflection, and many of the target blood vessels in oximetry are close to the surface anyway, so there’s no need for red light or infrared signals to penetrate through a thicker part of the human body, like a leg or a forehead (two places where this was applied in the study), which minimizes the issue of the reading not working because the reading got really weak as it traveled through the body. Remember the laser test you probably tried a few paragraphs ago? Notice that none of the beam shows up if you shined it through, say, your abdomen (another sample site in the study)?
For all you know, someone will integrate something like this into runner gear, like safety lights or reflectors (the authors have a patent for this, apparently – read the Featured Article). And why not? Monitor your health and performance while not looking out of place in, say, a glow run…?
Thoughts? Comments? Weird tingling in your extremities? Let me know in the space below (after a chat with your physician, thanks), leave a like if you like, share it on your social media, and you don’t need to be a WordPress member to do it! If you’re not doing so already, please follow and thanks again for stopping by. And to my loyal followers, I am very well aware that this is my first blog post in several weeks, but what can I say, assistant professor life and all that, so in short-
Featured Article: Khan Y, Han D, Pierre A, Ting J, Wang X, Lochner CM, Bovo G, Yaacobi-Gross N, Newsome C, Wilson R, Arias AC. (2018). A flexible organic reflectance oximeter array. Proceedings of the National Academy of Sciences 115(47) E11015-E11024. DOI: 10.1073/
Featured Image: Public Domain (Author: Jill Wellington, 2000)