A good pulse Oximeter can literally mean the difference between life and death! I have thoroughly tested the Santa Medical Pulse Oximeter while using medical grade oxygen and below I will share my thoughts. Let me start by saying that everyone should have one these...not just people with breathing issues. Have you ever noticed that your pulse and oxygen level are the first things checked at the doctor along with your temperature and blood pressure? That's because knowing your pulse and oxygen level can point the doctor in the right direction, much in the same way that having an Oximeter at home can show you the same important info when you aren't at the doctor. I use my Oximeter to check my oxygen level so I know if I need to raise or lower the oxygen level on my oxygen tanks. Sometimes my oxygen level can change drastically out of nowhere just by walking around or sometime by sitting to long. Sadly, my body usually doesn't give me warning signs that my oxygen level is running low until it is too late and I am close to passing out. That level for me, is usually when the Oximeter goes down to about 88.When I see that number, or even sometimes a number around 90, I know that I need to put my oxygen cannula in my nose and start inhaling oxygen immediately. If I don't start oxygen, then I will most likely pass out. Once I start oxygen with the Oximeter on my index finger, I can watch my oxygen level increase to around 95, and then after a few hours of oxygen it will go up to around 97 on the meter. This Santa Medical Oximeter is very accurate on its oxygen level readings. I have compared it to my old Oximeter from 2009 and they usually show the same reading. Occasionally the number will vary by plus or minus one number but they show the same number a few seconds later. The Santa Medical Oximeter can be used on any finger to obtain a reading but I feel it is MOST accurate when placed on the index finger, and when the index finger is fully inserted and touching the rubber piece that can be felt inside of the meter.. Please note that the rubber piece slightly lifts the fingernail when the finger is inserted. So, you may also be wondering why I purchased a second Oximeter 11 years later, and what the differences were between the two. Well, as I said before, my first pulse Oximeter is from 2011, and it is now 2020. Both puse Oximeters look identical! Boy do I love the new one more though! The new device is 3 times brighter, and that is such a blessing as my eye sight declines. The new device also has the option to press the button (there's only one button) after the device is on and it flips the readout so that the screen isn't upside down if your finger is facing a different direction. Allow me to explain this further with this next two sentences. My old Oximeter required that you lift your hand up and turn your fingers toward your face in order to read the results. The new Oximeter allows you to leave your hand at rest on your lap, and still allows you to read the results without the results being upside down. The last big difference between the two Oximeters is that the new one comes with a velcro case and a lanyard. That may not seem like a big deal now, but these meters are tiny and easy to loose. Having the case not only makes it easier to spot during a "panicky" situation when oxygen levels may be low, but also makes it easier to carry. Prior to having the case, I alway shoved my old meter in my pocket and I was always worried about it getting broken or covered in lint. No more worrying about that with the new case. Lastly I want to just tell you how simple this is to use. Push the one and only button one time and put the meter on your index finger. Within 7 seconds you will have your oxygen saturation and your pulse! Push the button one more time if you want to "flip" the LCD screen. That's it, that's how you use it. I've even used it my with wet fingers and still obtained an accurate reading. PROS: • Accurate readings within 7 seconds. • Comes with case. • Extremely bright! • Obtains readings even when fingers are wet. • Screen orientation can be flipped. • Simple, one button operation. CONS: NONE. To sum up this review, I do not regret my purchase of the Santa Medical Pulse Oximeter one single bit. I probably could have gotten a few more years out of my older 11 year old Oximeter, but with the improvements that have been made to the new meter, I am glad that I purchased a second one. The Santa Medical Pulse Oximeter is a 5 star product and I definitely recommend it! I have also included pictures and a video in my review.