Health Assessment, part 7: Assessing Oxygen Saturation
by Meris Shuwarger May 05, 2023 Updated: August 10, 2023 5 min read
Full transcript and video captions coming soon!
Hi. I'm Meris, and in this video, I'm going to be reviewing how to assess your patient's oxygen saturation. I'll also be talking about the expected findings for oxygen saturation and some nursing considerations. I'm going to be following along using our health assessment flashcards. These are available on our website, LevelUpRN.com if you want to grab a set for yourself. And if you already have your own deck, go ahead and break them out and we can follow along together. All right. Let's get started. All right. So oxygen saturation, which is sometimes abbreviated as SpO2, this is going to be a noninvasive way that we can actually measure what percentage of your patient's hemoglobin is saturated with oxygen, hopefully, and we'll talk about that in a second. So it's looking at the arterial blood and it's going to give us a number, and that number is a percentage. So it means that this percent of your patient's hemoglobin is carrying something, and we hope that is oxygen. So the expected range for an SpO2, the good news is, since it's a percentage, you can just remember it's on the high end. 95 to 100 percent is considered the expected range for a patient's pulse ox. That's another thing you will hear, pulse oximetry or pulse ox. Remember - this is just a pet peeve of mine - it's an oxygen saturation. So if we refer to the patient's O2 sats, we want to call them sats, saturation, not stat. So it's not their oxygen stat, their O2 stat. It's oxygen sat or saturation.
All right. So some nursing considerations. The number one place that we put a probe for pulse oximetry is on the finger. However, there's times that that's not possible, or maybe I'm not getting a good reading on the finger. So depending on what kind of a probe you have available, there's different places we could put it. The fingers are the first one. Earlobe is another good one. The toe is also acceptable. Some facilities, you can do the bridge of the nose, and that all just depends on what kind of actual equipment that you have available to you. Now, things that can, excuse me, interfere with the validity or the reading that you are getting, make it hard to get a good reading, nail polish is one of them because it's important to remember how this pulse oximeter works. It works by passing light from one side of the finger to the other. And on the other end, there's a sensor that is going to see how much light is coming through the other side, and then this is going to give us information about the hemoglobin, how much of it is bound. So if I have something that's obstructing that like nail polish, that could get in the way of my readings. Other things, hypotension and peripheral vascular disease and edema. Anything that is impeding my circulation like hypotension or peripheral arterial or venous disease, that could impair my ability to get a good pulse ox. Edema, again, swelling, it's going to interfere with what that light is looking for. Skin pigmentation, and this is super duper important. We talk a lot about the ways in which racism can be present in medicine even unconsciously, and this is one of the ways.
There are studies that show that pulse oximetry is not as accurate on patients with brown and black skin, and for this reason, they may appear to have higher oxygen saturation levels than a patient with white skin or fair skin. So this is one of those things where it's so important to-- first of all, we need more people in research. We need people who are aware of these racial biases who can find new and innovative ways to measure oxygenation, right? But we also need you as the bedside nurse or whatever your position may be, to understand that I need to treat my patient, not the machine. So if the machine says that they're 95%, but my patient is working really hard to breathe, and I can see that they've got a little bit of cyanosis - they're a little blue around the lips or the fingernails - I don't care what the machine says. I'm treating the patient because that machine is not a perfect object. Some other things that can affect this would be skin temperature. Keep in mind, if I'm very cold, I'm going to get constriction of my-- I'll get vasoconstriction, so again, that's going to impair circulation. Anything impairing circulation can impair these readings.
Now, here's a very important thing to understand. While a decreased oxygen saturation may indicate that your patient has decreased blood oxygen, we can only truly diagnose what is called hypoxemia, which is low oxygen in the blood. Emia is blood and then hypo meaning low and ox meaning oxygen, so low blood oxygen. Hypoxemia can only truly be diagnosed with an arterial blood gas, an ABG. Another super duper important point, so important that we pulled it out as a key point and made it bold in red. If your patient has COPD, chronic obstructive pulmonary disease, it is expected that they may have an oxygen level in the low 90s. That is an expected finding. So if my patient with chronic, longstanding COPD has a pulse ox of 90, 91, 92, we're doing good. We're doing all right. I'm not super worried. And additionally, you can watch videos that Cathy has done on COPD, but there, it's important that we don't try to overcorrect that oxygenation because we will actually knock out their hypoxic drive to breathe, so you need to know that that's an expected finding and not something that requires intervention.
All right. Let's go ahead and test your knowledge of some key facts I provided in this video with my quiz questions. What is the expected oxygen saturation of a patient with COPD? Oxygen saturation in the low 90s is expected for a patient with COPD. How is hypoxemia diagnosed? With an arterial blood gas, ABG. All right. That is it for this video. I hope you found this review helpful. I would love to hear your comments, especially if you have a really funny or unique way to remember things or a good story. I know I want to hear it and so do your other students, your fellow classmates. You're doing a really good job, and I'm super proud of you. Thanks for studying with me.
So earlier in the video, I said that pulse oximetry is looking at how much of your hemoglobin is bound to oxygen, and that is the ideal scenario. However, this is one of those things that I want to tell you about clinical judgment. It's not specific to oxygen. What that pulse oximeter is doing is it's reading how much of your hemoglobin is bound to something. So if your patient has carbon monoxide poisoning, that carbon monoxide actually has a higher affinity to your hemoglobin than oxygen, meaning that it is going to compete with the oxygen and it's going to win out. That carbon monoxide is going to win out and bind to that hemoglobin. And if that hemoglobin is carrying carbon monoxide, it's not carrying oxygen. So you might look at the monitor and they're 100%, but is it 100% oxygen, or is it 100% bound hemoglobin? This is where your clinical judgment comes into play, so super duper important. And also, don't forget that just because you're sitting at the nurse's station and you look at the monitor and it says 98%, you could put that pulse ox on somebody who doesn't have a pulse, and if that pulse ox is able to still pass that light and read the hemoglobin of the blood that's left in that fingertip, they could still have a pulse ox reading. So make sure we are always assessing and treating our patients, not our machines.
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