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Waveform Capnography


Quantitative Waveform Capnography

The 2010-2015 AHA Guidelines for ACLS now recommend using quantitative waveform capnography in intubated patients during CPR. Waveform capnography allows providers to monitor CPR quality, optimize chest compressions, and detect ROSC (return of spontaneous circulation) during chest compressions.

Also, according to the AHA, continuous waveform capnography along with clinical assessment is the most reliable method of confirming and monitoring correct placement of an ET tube.

What is Waveform Capnography

Quantitative waveform capnography is the continuous, noninvasive measurement and graphical display of end-tidal carbon dioxide/ETCO2 (also called PetCO2). Capnography uses a sample chamber/sensor placed for optimum evaluation of expired CO2. The inhaled and exhaled carbon dioxide is graphically displayed as a waveform on the monitor along with its corresponding numerical measurement.

As an assessment tool during CPR, capnography can help the ACLS provider determine a number of things. It is a direct measurement of ventilation in the lungs, and it also indirectly measures metabolism and circulation. For example, a decrease in perfusion (cardiac output) will lower the delivery of carbon dioxide to the lungs. This will cause a decrease in the ETCO2 (end-tidal CO2), and this will be observable on the waveform as well as with the numerical measurement.

Normal ETCO2 in the adult patient should be 35-45 mmHg.

Two very practical uses of waveform capnography in CPR are: 1.) evaluating the effectiveness of chest compressions; and 2.) identification of ROSC. Evaluating effectiveness of chest compressions is accomplished in the following manner: Measurement of a low ETCO2 value (< 10 mmHg) during CPR in an intubated patient would indicate that the quality of chest compressions needs improvement.

High quality chest compressions are achieved when the ETCO2 value is at least 10-20 mmHg.

When ROSC occurs, There will be a significant increase in the ETCO2. (35-45 mmHg) This increase represents drastic improvement in blood flow (more CO2 being dumped in the lungs by the circulation) which indicates circulation.

For the intubated patient in cardiac arrest, quantitative waveform capnography, is now considered the desired method for monitoring quality of chest compressions and determining when the patient has a ROSC.

This video explains waveform capnography, it benefits, and various applications.

  79 Responses to “Waveform Capnography”

  1. Is there a “normal” EtCO2 reading immediately after ROSC? Would I see an immediate spike to WNL or will it take several minutes?

  2. Jeff,
    Thank you for the course, I passed with 100% written part. See you next time.

  3. Disappointed I could not view video on my IPad!

  4. After reading all these comments , is there anyone who can comment on the accuracy of capnagraphy during CPR being performed with an extraglottic device such as an LMA or King LMA combitube. Since many out of hospital cardiac arrests arrive at our ED with these devises in place, with CPR in progress, it would be interesting to know.

    • I would say any airway device which is placed properly will give an accurate CO2 level. In turn, this would give you a good capnography reading. I think that the LMA or King LMA combitube when placed properly would give ETCO2 results.
      In fact, ETC02 readings may help with better placement of these types of airways. Here is one study:

      Kind regards,

  5. It is intuitive that increased velocity would account for increased EtCO2 and increased EtCO2 correlates with increased number of survivors. But I have some numbers that do not show this – can anyone speculate a reason why increased velocity is not correlated with improved survivor rate

  6. Need to know if these practice questions are similar to what is on the real ACLS test?.

    • All of the questions are developed from the AHA ACLS provider manual. They cover the content that you will see when you take the test. However, they are not the same questions as on the test. All of the practice questions are unique questions developed for this site.

      Kind regards,

  7. Is it possible to use capography with the BMV?

    • The BVM would probably give you inaccurate results if you were using the BVM over a capnography cannula. For best results during cardiac arrest, waveform capnography should be performed with an ET tube in place.

      Kind regards,

  8. How can you use waveform capnography to confirm ET tube placement during CPR. Would it look different than patients without an ET tube. Confused???

    • If an ET tube is not properly placed, you will not see the waveform that should be present as you administer breaths with a bag-vaulve-mask. It is that simple. No waveform=No proper intubation.
      Once the tube is in its proper place, the ETCO2 will be able to be read, but until the ET tube is in place, you will not see the proper waveform that is seen when breaths are administered.

      Kind regards,

  9. Haven’t seen the video but have enjoyed this page. Btw, as an anesthesia doc who’s intubated more than ten, probably less than 20k patients, code intubations can be very challenging at times. Especially in an indulgent population (ours) with skyrocketing BMIs. Prepare for the worst and don’t waste time figuring out that you’re in trouble. Call for help early, it’s a sign of intelligence.

    • i agree! deferring moments are when sometimes you’re thought incompetent if you call for help. Sigh.. better safe than sorry the saying goes.

  10. What website would you recommend that offers a clip viewing waveform capnography?

    • capnography.com is a great start (covers the basics as well as how to troubleshoot some interesting waveforms). If you have access and the ability to pay for it, I just completed the physio-control university’s 5hr course on waveform capnography….very very VERY informative and helpful and provides you with CEs upon completion and passing an evaluation!

  11. What is imCO2, and what is its significance in the waveform.

    • imCO2 means (inspired minimum CO2). The end of inspiration on the capnography waveform is referred to as phase 1 and represents dead space gases. If you notice that the waveform baseline is elevated it can mean a couple of things. The two most common are rebreathing CO2, and contamination of the capnometer. First, ensure that the patients not rebreathing CO2. Second, trouble shoot capnography sensor and replace if contaminated. Here’s a great resource for learning about PetCO2.

  12. Does the Joint Commission now have a standard that addresses the use of end-tidal co2 monitoring in intubated, sedated patients?

  13. I would have loved to see this video but could not hear a single word

    • I checked on the video and the sound seems to be working ok. There are a couple of things you might try. On the actual video screen in the lower right-hand corner there is a volume control This may have been muted. Also your own PC may have muted. You might double check those settings.

      Kind regards,

  14. thanks this explains a lot

  15. When using Capnography in an arrest situation how often should it be documented on the code blue record? Is there a standard?

    • There is no set standard but typically it should be recorded at a minimum at the end of each cycle of CPR (every 2 minutes)

      Kind regards,

    • Since we know that ETCO2 levels consistently below 10 during CPR (“with proper ventilatory rates of 8-10/min”) can be a good indicator of poor viability, it is good practice to print out a waveform if it’s included on your monitors. Therefore, at the 2min mark, when you stop COMPRESSIONS to evaluate the patient’s rhythm, continue ventilations and print a strip (if your equipment allows this)…this strip will demonstrate the patient’s underlying rhythm along with the ETCO2 reading and a capnogram hopefully demonstrating appropriate ventilation. Thus, if/when the code is called due to poor prognosis/outcome, you have proof that you have done everything appropriately and effectively and that despite your best efforts this patient was not going to improve. (information obtained from physio-control’s university course on waveform capnography)

      • If ETCO2 levels are consistently < 10 mmHg it seems there has not been adequate compressions delivered. Totally agree with proper ventilation rates (and volume for that matter) during the event to keep intrathoracic pressures ideal for venous blood return, but it is the ability of the rescuers to deliver excellent compressions to enable the proper gas exchange to achieve appropriate ETCO2 readings. Poor viability related to low end-tidal is related to poor compressions and low CO so I don't think this will prove everything was appropriate – might just be hard to explain why the compressions were not adequate along with the excellent ventilatory effort…

  16. If you palpate the endotracheal cuff upon inflation,
    you have precluded its placement in
    either the esophagus or mainstem bronchus.

    Easy to feel – even on resusci-Annie.

    Try it & do not fret about high tech gadgetry.

  17. Excelent

  18. Are we supposed to intubate when the patient is in the hospital during ACLS or wait until ROSC? I was taught that the new thinking is not stop compressions to intubate but cannot find any rules regarding such in the ACLS book.

    • There is no set answer to this question. The decision to intubate should be based on clinical judgment and experience of the emergency team that is working. I have seen intubation occur more often after ROSC. Recently since implementing rapid response teams, I have seen intubation occurring in the pre-arrest setting so as to thwart an arrest.

      Making the decision to intubate can be difficult because chest compressions must be stopped and the intubation process can be very time consuming. There is no easy answer.
      Kind regards,

      • Why do chest compressions have to stop? Chest compressions don’t really affect visualization of the vocal cords at all! I have intubated my last 4 codes while compressions were being performed by both another medic as well as by an Auto Pulse. Try it! You may be surprised.

      • Thanks for the feedback. I definitely will pass this on to providers who intubate regularly.

      • I agree completely with Rach! All of our pre-hospital paremedics go through extensive training and our protocols clearly state that we will not stop compressions to intubate (we are currently at about a 78% success rate through compressions). If your providers are not experienced or confident enough to intubate through compression they need more practice and simulations.

        Waveform capnography is the gold-standard for monitoring CPR quality and determining patient viability during CPR…however, if providers are unable to intubate without detrimental effects of the patient, you can use capnography with BVM ventilations (just not as reliable/effectve).

      • Totally agree, Jeff. If the code is spontaneous V-fib on a POD 3 bypass patient shock and move on – just like with an ICD they won’t have suffered much hypoxia so restoring the rhythm quickly and deciding what precursed the v-fib (electrolytes, volume, etc.) will be paramount. On the other hand, the patient who has been bradying down and is discovered in PEA with a slow response is most likely hypoxic and will not respond until the airway is secured and oxygen restored.

      • Susan, thanks for the input. Kind regards, Jeff

      • Isn’t it true that the only reason we stop compression to provide breaths in the first place is to avoid bagging emesis, blood, etc. into the lungs? Async CPR is commenced with the advanced airway in place when there is no risk for creating aspiration – it would always be better not to stop due to the loss of coronary and cerebral perfusion during the pause in compressions. Once again, on an asphyxial or hypoxic scenario it would be essential to get the O’s on board; otherwise, especially in witnessed arrests shock and high quality compressions are paramount to ROSC and survival. Thanks for the input

  19. What is the normal/good value of ETCO2 during compressions/advanced aw at 1 breath/6-8sec?

  20. Would have loved to have viewed the video because I would like to understand better. Unfortunately, the volume was barely audible.

    Thomas Greer, RN
    Nashville, TN

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