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Capnography (Nursing)

by Rhonda Lawes

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    00:01 Okay. Now we're gonna look at capnography. This is a beautiful thing. I love this tool.

    00:07 So first of all, you probably like to understand what it is if you haven't been exposed to it before.

    00:13 Okay. So, capnography is noninvasive.

    00:16 You know that's our favorite if we can do that. Capnography can be noninvasive, and it's a way to measure the patient's partial pressure of CO2 at the end of exhalation.

    00:27 I don't have to stick them to get an arterial blood gas to do this.

    00:31 Cool. I can do ongoing capnography so I get consistent ratings.

    00:36 Remember, an arterial stick one time tells me what's going on at that moment.

    00:41 Capnography can help me watch trends in real time.

    00:46 So Capnography waveform is -- represents the amount of carbon dioxide exhaled in air.

    00:52 So look at that drawing, you got zero and then it's up to 40.

    00:56 Well, the top of that waveform represents the amount of carbon dioxide that's breathed out in exhaled air. So the normal is -- sweet. Look at the normal.

    01:09 If you've already done ABG's with us, you know that the normal CO2 on ABG's is 35 to 45.

    01:16 So yey, I love it when all plan comes together and the values are the same.

    01:22 So we're looking at capnography.

    01:24 We know that normal levels on an ABG of CO2 in the blood is 35 to 45.

    01:30 Normal end tidal CO2 is also 35 to 45. Okay.

    01:36 So let's hang out here for just a little bit more because I want you to recognize -- you'll be able to see these waveforms.

    01:44 The top of the waveform is gonna tell us what the level is.

    01:47 And again, what does the top of the waveform measure? Right. End tidal CO2 volume in your exhaled breath. Good. Okay.

    02:05 So capnography gives us the information with each of the patient breaths.

    02:09 It measures the end tidal CO2 in real time. So it assesses ventilation.

    02:15 So we looked at what, ventilation or oxygenation with the pulse ox? Right. That looked at oxygenation. We're looking at ventilation with capnography.

    02:27 So that's the air movement in and out of the lungs. So how do we do this fancy stuff? Well, it's actually pretty simple.

    02:36 We can measure end tidal CO2 with just some special equipment attached to the oxygen delivery method. So we use infrared spectroscopy.

    02:46 It sounds like something from back to the future, doesn't it? But remember, you already know CO2 absorbs infrared radiation.

    02:54 Because we learned about that, right? We're talking about what your blood absorbs.

    02:58 Now we're talking about carbon dioxide, what it absorbs infrared light.

    03:03 Now, a beam of infrared light is passed across the patient's gas sample onto a sensor.

    03:09 Now end tidal CO2 can be measured in an intubated patient because we can add that sensor to their intubation tube.

    03:16 It can also do it with a nasal cannula.

    03:19 So if we're using end tidal CO2 when someone's intubated, yeah, they're invasive procedure to be intubated but the end tidal CO2 is still outside of their body.

    03:29 The nasal cannula, we can also do that. That's awesome.

    03:34 Because intubation is pretty complicated, it needs to be done by someone who's specifically trained on how to do that.

    03:40 But a nasal cannula, we all know how to put on a nasal cannula, it's a lot more straightforward.

    03:46 So this is what it looks like.

    03:48 Now we've -- it's kind of a long picture there but we stretched it out so you can understand all the pieces.

    03:56 So that's actually just a regular nasal cannula with this special feature.

    04:01 So you see you've got the two nasal prongs.

    04:04 Now, we've made the middle piece be extra big just so we could help you understand that there's a barrier there.

    04:11 Now that permanent barrier is what allows us to do the end tidal sampling.

    04:15 You'll see that oxygen comes in and CO2 were measured on the other nare.

    04:21 So you've got a sensor in both one of the nasal prongs. Okay.

    04:26 So this is how an end tidal CO2 nasal cannula is different than just a regular old nasal cannula.

    04:33 There's a permanent barrier in between the two nasal prongs.

    04:36 One has a sensor for the CO2, one has a sensor for the O2.

    04:42 Because, you know, end tidal CO2 represents the amount of carbon dioxide in exhaled air. Good.

    04:50 So the nasal cannula end tidal CO2 sampling simultaneously delivers oxygen and measures carbon dioxide by the sensors in those prongs.

    04:59 So, it's pretty amazing that something this important can be made this small to fit right inside the nasal cannula.

    05:08 So oxygen is delivered in one nare. CO2 is sampled from the other.

    05:13 That's how it works. Remember, you got to sensors.

    05:16 One in each of the prongs and a barrier in between.

    05:21 Okay. Before you go on, I'd really like for you to pause the video and make sure you've read through those thoughts again so it seems very clear to you.

    05:32 Does it make sense to you why it's called divided sampling? How does that help us have undiluted end tidal gas sampling? Those are the kinda concepts I want you to make sure are clear for you.

    05:44 There's a barrier in the middle, having double sensors, one in each prong.

    05:49 One delivers oxygen, one is gonna measure the CO2.

    05:54 So stop and just review that as long as you need to make sure that concept is clear in your mind.

    06:06 Okay. So what do we use these fancy things for? Well, we can monitor the effectiveness of treatments in real time.

    06:12 It's really not that much extra money to have a fancy end tidal CO2 nasal cannula than a regular nasal cannula. And it gives us really helpful information.

    06:24 It'll help us know, are those breathing treatments working? Are the bronchodilators that we're using working? It will help us evaluate treatment.

    06:33 Now, it could also help us make adjustments based on what those levels are.

    06:36 We know if we need to increase or decrease or what we need to do differently to help keep that patient safe.

    06:42 Now, if we have it on an endotracheal tube that can let us know for sure that endotracheal tube is in the right place.

    06:50 Now, the last one is really intense. It can identify return of spontaneous circulation, R-O-S-C.

    06:59 Now this is in the use of a code.

    07:01 The patient is completely arrested and we start CPR and advanced cardiac life support and we can get some readings on an end tidal CO2 that are usually the first signs of return of spontaneous circulation.

    07:13 Because the end tidal CO2 peaks are the earliest signs of ROSC.

    07:18 So even before I can feel a pulse or get a blood pressure, if I can start seeing the end tidal CO2 rising in someone that we're resuscitating, that's a very positive sign. Now, monitoring patients with acute respiratory distress, unconscious, their metabolic acidosis or even having seizures, you can see how this would be really helpful.

    07:41 So, in a full arrest, I'm gonna see peaks in CO2 before I can feel a pulse even at major areas or get a blood pressure. This helps me know we're making some progress when before we may not have been able to tell that.

    07:55 Also, we use it for severe respiratory patients, acute respiratory distress, patients that are unconscious, people who are in metabolic acidosis or having seizures.

    08:07 Okay. So that kinda gives you a feel for some of the applications that we can use it for.


    About the Lecture

    The lecture Capnography (Nursing) by Rhonda Lawes is from the course Respiratory Assessment (Nursing).


    Included Quiz Questions

    1. Capnography
    2. SpaO2
    3. Pulse oximeter
    4. Fraction of inspired oxygen (FiO2)
    1. 35–45 mm Hg
    2. 30–35 mm Hg
    3. 7.35–7.45
    4. 95–100%
    1. Adjust treatment based off EtCO2 levels.
    2. Verify endotracheal tube placement.
    3. Identify return of spontaneous circulation (ROSC).
    4. Verify central line placement.
    1. It measures exhaled air, providing instantaneous feedback on ventilation effectiveness.
    2. It measures peripheral perfusion, providing instantaneous feedback on ventilation effectiveness.
    3. It is not more reliable than a pulse oximeter.
    4. It measures inhaled air, providing instantaneous feedback on ventilation effectiveness.

    Author of lecture Capnography (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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