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Pulse Oximetry Problems (Nursing)

by Rhonda Lawes

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    00:01 Now, these are the patients that are a little tricky. Alright? If you have very poor perfusion into your fingertips, that's gonna make an inaccurate reading.

    00:10 So, if you for some reason have compromised blood flow into your fingertips, that's not going to give you an accurate pulse ox.

    00:18 You've got more blood perfusion going to the rest of your tissues than you have to your fingers.

    00:24 See, pulse oximeters need a pretty strong pulse to have an accurate reading.

    00:30 People with poor circulation will have a weak reading, so, that's not really gonna help us as much.

    00:36 So, when the peripheral perfusion is poor like someone who has really low blood pressure, severe hypotension, maybe their fingers are ice cold and then, you have that vasoconstriction, so, they're not gonna have good perfusion.

    00:50 Or maybe they've got Raynaud's disease.

    00:52 Sometimes, those arteries aren't -- they're gonna be much less pulsatile.

    00:57 Meaning, you don't have a good pulse.

    01:00 So, that way, it's gonna be difficult to calculate an accurate sat So, what do you do? Well, you're gonna have to look at some type of alternate placement.

    01:09 You might have to put the probe in another area and we have lots of options.

    01:12 You just have to check out what's available on your site.

    01:15 Keep in mind, if I don't have a decent pulse in those extremities, I'm not gonna have a really accurate pulse ox.

    01:23 Also, extreme movement of the hands, that can also be a problem with the pulse oximeter.

    01:28 So, if the patient is super fidgety or moving all around, that's gonna impact the accuracy.

    01:34 So, these are some things you need to have stored in the back of your mind to watch, to also assess, am I getting an accurate pulse ox? Does this patient have good pulse in that extremity? Do they have Reynaud's disease? Is their blood pressure so low, the body is fighting back by clamping down all the peripheral vasoconstrictions, so, I'm not gonna get an accurate pulse ox there.

    01:55 Those are all things that we as nurses do to make sure the data we're recording is actually reflective of the patient.

    02:04 So, talking about pulse oximetry problems, those are the most common ones.

    02:08 There can also be a dye, methylene blue.

    02:12 Now, sometimes, it fits in the patient's circulation, it will really mess up the reading.

    02:17 Now, we use these dyes for some special diagnostic procedures.

    02:21 You'll be aware that that is in the patient and you know a pulse ox is not gonna be that accurate for you.

    02:27 Now, last one is actually fairly common.

    02:29 The patient has finger nail polish or they have artificial fingernails that can also affect the reading.

    02:37 So, we've given you a lot of things, a lot of reasons why there might be a problem with the pulse ox.

    02:42 Pause the video and see if you can come up with at least four things you need to be on the lookout for that could impact the accuracy of a pulse ox reading.

    02:52 So, pause the video, write those down without looking at your notes.

    03:04 Okay, welcome back. Now, look at those four things and think, what would I do as a nurse in those situations? If I had this occur with the patient, do I know what I would do? Good.

    03:18 You're gonna look for an alternate placement of the probe, you're gonna look for an alternate way to monitor the pulse ox, and you might advocate for an ABG if you're really concerned about the patient's oxygenation.

    03:30 So, an abnormal hemoglobin can affect pulse oximeter readings.

    03:34 We all agree about that, right? If you have something weird about the hemoglobin, then, clearly, that's gonna mess up looking at the saturation of the hemoglobin.

    03:43 So, there's a couple cases here. Carboxyhemoglobin and methemoglobin.

    03:49 Okay, if we know that in front of the hemoglobin is what it's connected to, that globin, that's carboxyhemoglobin, we shorten in to that is carbon monoxide.

    04:04 Yeah, that is not beneficial. We'll talk about the methemoglobin in just a minute but let's focus on the carboxyhemoglobin. Carbon monoxide, right? It's not CO2, it's just CO.

    04:18 Carbon Monoxide can strongly combine with hemoglobin and it forms Carboxyhemoglobin.

    04:24 Now, that blocks oxygen from connecting to the hemoglobin and it brings no benefit to your tissues.

    04:31 Now, most pulse oximeters, they can't really tell the difference between a hemoglobin that's bound to carboxy or to oxygen.

    04:41 See, that's the problem. If it's generic, standard pulse ox, all it will register is, "Oh, yup, those hemoglobin are bound to something and it can't tell the difference between helpful oxygen or carbon monoxide.

    04:57 So, a pulse ox on a patient who's been exposed to carbon monoxide is not going to give you their oxygen saturation.

    05:05 So, this is an example where you use your knowledge of how the body works to make sure the patient gets appropriate care.

    05:14 See, carboxyhemoglobin is not carrying oxygen. It's carrying carbon monoxide.

    05:20 That's not only not beneficial to the body, it's harmful.

    05:25 So, you could have a patient who's been exposed to carbon monoxide.

    05:29 Now, their hemoglobins are all loaded up with carboxy. Now, they're carboxyhemoglobin and it -- pulse ox will read that, "Wow, they're like at 98%."That does not reflect oxygenation.

    05:43 That patient is in severe, severe trouble.

    05:46 So, you wanna make sure that you know what's going on with your patient, you know what they've been exposed to, and while you understand that, "Why do I have a pulse ox this high but this patient looks terrible?" Now, how do people get exposed to carbon monoxide poisoning? Well, there's lots of ways.

    06:04 If you have exhaust from a running automobile and you don't have adequate oxygenation or ventilation in the area, sadly, this is one way that people choose for suicide.

    06:14 You might be in a fuel-powered tool or equipment and you don't have good enough ventilation.

    06:20 Or lastly, house fire. You know, a patient could survive a house fire without any burns but what will kill them is what they inhale in their lungs, both carbon monoxide from the burning of the building materials in the home and, also, the damage to internal lung tissue.

    06:39 So, house fires are not necessarily, the deaths are not caused just from burning of the tissue.

    06:45 It can be from what the patients inhale.

    06:48 Okay, so, this part is really kind of a sad point but I just want you to keep in mind, this is an excellent example of how a number can say, "Your patient is doing awesome." But sharp nurses will put together the pieces and realize, "That number doesn't match what I'm seeing in this patient.

    07:07 My assessment, my ability to see them, assess them, listen, auscultate, it's not lining up." And good nurses keep asking why, why, why. So, that's the kind of care you wanna give.

    07:21 This is no different than pulseless electrical activity. That's called PEA.

    07:26 That means if you look up at the monitor, you're gonna have a beautiful P wave, QRS, T wave, everything's gonna look great but there isn't anything going on in that heart.

    07:37 It's not pumping, just the electricity is going through the heart.

    07:41 Monitor says everything's okay but a nurse knows that patient is not perfusing.

    07:47 Same thing with someone who has carbon monoxide poisoning.

    07:50 That monitor, that pulse ox is gonna say, they're awesome.

    07:54 You're gonna know and recognize the difference that they're in trouble.

    07:58 Now, this one, methemoglobin is one that you likely won't see as often as carbon monoxide poisoning but it's a form of hemoglobin that's just it can't carry oxygen and that's why it has that kind of unique name. Now, it might be a genetic component.

    08:14 You might have been born with this, recessive genes have to be inherited from both parents.

    08:18 So, then, you have these red blood cells with hemoglobin that just can't carry oxygen.

    08:25 So, obviously, this is significant and very serious for the patient. You can also acquire this.

    08:32 This means you were born fine, your hemoglobin could carry oxygen but now, you've been exposed to something that's changed your hemoglobin.

    08:40 Usually, it's after some type of poisoning or other compound that changed the hemoglobin.

    08:45 So, pulse oximetry readings will also be inaccurate. They'll be -- look higher than normal.

    08:50 So, remember, these are two examples, carboxyhemoglobin and methemoglobin.

    08:56 The pulse ox readings will not be accurate. Does this happen every day? No, not usually.

    09:03 That's why you have to always have this filed away in your mind to say, "I'm gonna recognize when a machine is giving me inaccurate information about my patient."


    About the Lecture

    The lecture Pulse Oximetry Problems (Nursing) by Rhonda Lawes is from the course Respiratory Assessment (Nursing).


    Included Quiz Questions

    1. Finger nail polish/artificial nails
    2. Cold extremities (Raynaud's disease)
    3. Methylene blue dye
    4. Significant movement of the hands
    5. Fever
    1. Carbon monoxide
    2. Helium
    3. Carbon dioxide
    4. Nitrogen dioxide
    1. House fires
    2. Automobile exhaust
    3. Fuel-powered tools
    4. Electric furnace
    1. Methemoglobin
    2. Carbon monoxide
    3. Carbon dioxide
    4. Alpha hemoglobin

    Author of lecture Pulse Oximetry Problems (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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