We have transitioned from Walkman's to Pulse Ox meters.. Yay for the 50+ YO group

Interesting but nothing surprising here; it just the same kind of construction every miniature things these days has. For a fairly thorough description of HOW these actually work (there is more to it than Fran's description), the Technology Connections channel has a pretty good video.

Since some of you have asked, here's a simple description of how the oximeter reading is obtained. Hemoglobin molecule in red blood cells changes their light transmission quality proportional to amount of oxygen carried by hemoglobin molecule. If you remember, oxygenated blood is bright red, and low oxygen saturation is dark red. This change in color can be sensed by transmitting both red and infrared light through the finger and sampling what comes out the other side. Signals are chopped so only one color light is on at a time and the resulting signal received shows a waveform of transmission corresponding to the blood flow through the finger. By doing some rudimentary signal analysis and AGC, one can determine the peak to peak values of the corresponding plethysmograph signal. Peak to peak value of the signal is used to determine a ratio between the transmission of the infrared versus the red, and this ratio directly references a lookup table which gives you the corresponding oxygen saturation. I did the design and coding for one of these back in the late 80s and all of the information on operation was within the Nellcor original pulse oximeter patent (which is an actually fascinating read). this patent did not actually cover the determination technique since this is fairly elemental gas chromatography science. Instead it covered a calibration technique which we did in a different way. The bottom line here is that by using this technique of two colors of light transmitted through the finger, one can determine the color of the blood which directly corresponds to the oxygen saturation. Pretty cool eh? I had to determine the look up table values by getting gas cylinders mixed with various concentrations of oxygen to nitrogen which were known to bring saturation numbers down to certain values, take readings of multiple people, and create the look up table values to determine human oxygen saturation numbers. I know another firm that was designing an oximeter would fly people up in an airplane to different altitudes to get their oxygen saturation numbers to become lower and determined the look up table in that way. It was a crazy time. it was also one of the most satisfying engineering projects I've ever been involved in! The unit designed was a hospital grade piece of equipment used in operating room and paramedic situations

I used to have a recording pulse oximeter, so I could wear it while I slept to check on my sleep apnea. The most annoying thing is the cable that looks like a USB cable, but it is not. And once lost, you could no longer download the data from it.

A few years ago, due to congestive heart failure with multiple arrhythmia simultaneously, I became interested in how these and related devices measured pulse. While in a doctor's office I could have the pulse display on a blood pressure machine reading 156, while the pulse oximeter on my finger gave a reading of 38. And my Fitbit would read 78. A stethoscope and second hand on a watch would verify that only the Fitbit was correct. I looked into the algorithm used by the pulse oximeter IC manufacturer and it uses a time window determined by the first few detections to reject anything too early or too late. So my galloping arrhythmia caused half the actual pulses to not be counted. A different algorithm in blood pressure cuffs caused a typically double reading. A few of the old school nurses would instantly reject the modern machine readings and use the tried and true manual method, either fingertips on the wrist or stethoscope on the chest. With the passage of time my arrhythmia is moderately well controlled. One time my cardiologist was looking at the recorded events on my defibrillator and said that anyone else with my amount of PVCs would be sent to the emergency room, but that only 31 events in 90 days was pretty good progress for me.

I think you missed the fact that there are two LEDs, of different colors.They are likely flashed alternately, and the different responses are used to detect blood color.

These super cheap pulse oximeters really started to flood the market during the co vid.

Pretty cute! I've seen similar LED displays with light guide masks. Usually specialized custom stuff where generic ones won't fit.

Very interesting display design. I haven't seen this before.

What a tidy little device. The display is very effective and I like the ability to invert it. I will never tire of seeing inside things.

Short, but very sweet. 😃

Dont get too hung-up on the absolute oxygenation reading, unless you have verified it's accuracy with a hospital-grade machine. What matters is if the device can detect a drop in SpO2; hold your breath for 30 seconds and you should see the reading drop into the low 90's, before returning to normal. Recall that it takes several seconds your blood to circulate all the way down to the tip of your finger. I got a cheap one in early 2020 and it's accurate for the heartbeat (consistent w/ fitbit and blood-pressure cuff). Mine has a graphical display and you can see it's progress as it self-calibrates to get a good pulse reading, like the AGC circuit used in analog TV's. BTW, walking is the most under-rated exercise so dont feel like you need to run a marathon to get into shape.

I bought mine to monitor my blood oxygen levels and pulse rate. As an asthmatic, low oxygen is a sign for the nebulizer, prednisone, or get to the ER. The heart rate shows me how hard my heart is working to get the blood oxygenated and the effort to breathe. A very handy tool.

Fran, you might want to consider getting a fitness tracker. You'll probably have more consistent data than is automatically recorded depending on the device and software.

I wish you put them side-by-side to see if they both provide the same measurements.

I had / have one with an OLED display, bought before COVID out of interest only. Then when the incompetent City of Sydney broke my ankle with dangerously slippery blind pedestrian guidance strips they'd been warned about, the hospital stuck a taped on Covidien braned one with a DE-9 on it. Interestingly, just laying on the bec saw my SpO2 go just bolow the alert level, unless i took the occasional deep breath.

A lot of doctors dislike the availalability of these. I,ve had one for many years now, but I guess people get bent out of the shape when they get a reading in the low 90s, which is fairly normal.

My Mum uses a Fitbit to monitor her heart rate on a more constant basis, and my Dad got a Garmin fitness tracking band, but he wasn't happy with its accuracy, so he switched to a Fitbit too and he's been happy with it since. It really is surprising how much you can do with a flashing LED and a photodiode. I just watched Alec's latest video on Technology Connections about the rain sensors in fancy new cars, and they're basically the same thing. Spoiler alert: it's just shining an LED onto the windscreen at an angle and measuring the reflection.

I have two of those made my Zacurate, purchased from Amazon ($23 each). I brought them with me for a doctor’s visit to compare them to his for accuracy, and they agreed. Also, on mine the display is oriented for self-reading.

Yay! The pin art intro! I’m glad you didn’t give up on it. Looks really cool!

I wish mine had a manual display orientation button. Mine changes orientation automatically and *always* gets it wrong. It's sigh-tek.

I worked on 1980s hospital devices that required a desktop computer size chassis. That is a busy little chip.

I use Apple Watch for years also later on because I (73) had an issue with heart rate and the Apple Watch monitors the heart rate 24/7 , also sends an alarm when the heart rate is high without activity. The Apple Watch also checks the Oxygen saturation.

I always thought the admonishment against mixing batteries was against mixing types (i.e., Alkaline, NiMH, NiCd, etc.) or high voltage differential.

before you sacrificed the cheap one, it would have been cool to put one on each finger to see if they produce the same results..

Fran's got an athlete's heart rate!

😅

Multiple die LEDm to give the two wavelengths for the oxygen level

Would love to know the science behind the Oxygen detection side of this. I can imagine how the pulse meter works but not the Oxygen side. I'd go and research this but I have many many many many many other things I want to know and am already struggling to stay awake long enough to deal with day to day life and this is far down the list of importance but if anyone can deliver this info in a clear way (preferably written in crayon for my own absorbtion) that would be appreciated.

THANK YOU, I asked about this years ago!

I suffer from tachycardia (sinus node) which responds well to meds. However, my blood pressure is a big problem. Managed to get my BP up to 254/80 and my GP wants to see me.

I got one when the covid thing started they said if you got covid and your blood ox went down below 94 you should get help the only problem was my ox would usually be between 92 and 96 and my pulse could go from 49 up to 60 so I thought I must have a faulty machine and I bought a more expensive one only to find I got the same readings it seems that I am one of those people who just have low readings I am still alive and kicking so it must be ok.

Just commenting because I want this video to get more reach

🩺

Neat

gotta say hyio as I start your vid

How have you gone with recovery of your sense of smell following Covid19?

XLNT commentary and knowledge and information about pulse oxygen unit.💕❤️💖❣️ Thanks Fran.😝⚡⚡⚡⚡💥🔥