Capnography

[AnthonyM83]

Just wondering if anyone was interested in writing a littles something on basic capnography as it relates to intubation in the field.

Basically, we had a full arrest yesterday where the medics kept going on and on about the tube and capnography (sacrificing a LOT of CPR time for it) and the CO2 levels and the color on the CO2 censor....and I realized I didn't know that much about it.

Why do we want to keep the CO2 levels at 35-40ish? range, what does it mean when it stays at that level, how does CO2 level tell you you're in or not etc. Kind of the why's and logic behind it all.

Thanks....I know someone wants to take this one!

[EMS49393]

I could roll with your questions, but I doubt I could give any explanation justice. So, my gift to you is a link. I can think of no other document I've seen that explains capnography any better than this document.

Bob Page has done a fantastic job putting out these downloads to further the education of any EMS provider.

Riding the Waves

You can find this and other documents at Edutainment

If you have any questions, feel free to PM me. I'm well versed in this particular program.

[chbare]

Very complex topic to discuss. Why did obtaining capnography (waveform or easy cap) get in the way of CPR? What exactly were they using? It sounds like an easy cap?

Capnography/capnometry is measuring for the presence of carbon dioxide upon exhaling. CO2 being one of the the byproducts of cellular metabolism. Of course, in an arrest state, the body may not be producing CO2 for obvious reasons, so capnography may be difficult to use, especially in a code that has gone on for any length of time.

Capnometry/graphy is an effective objective method of assessing for tube placement because CO2 should be present in exhaled gas. It is a very specific and sensitive test when looking at determining tube placement in the trachea. An easy cap has limited value beyond saying, "yep we have CO2 and a positive color change"

As far as norms: 35-45 is a general guideline used for the "normal" range. This does not account for the acutely or chronically ill patient however.

Waveform capnography can give us additional information about specifics of the respiratory status. For example, a change in the wave form can provide us with information about our patients condition. For example, our asthma patient starts developing complications, we may see the wave change from the normal plateau shape to a "shark fin" shape indicating altered clearance of the alveoli. This can be seen in asthma and COPD patients. Mucus plugs, hiccups, and spontaneous breathing can be identified with wave form assessments as well. We can trend our end tidal values and and even make educated guesses on how the acid/base status will change with changes in ETCO2 values. So long as we have an ABG and relatively unchanged hemodynamic status baseline to work from.

Remember, changing CO2 will change our acid base balance and can ultimately change where electrolytes move. Potassium for example.

Take care,

chbare.

[MSDeltaFlt]

Also, the EtCO2 waveform is one of the two field confirmations of ETT placement. The other one being direct visualization. This is all mute if your monitor cannot print off the waveform. It cannot be confirmed if you cannot prove it with documentation.

Page 17 of the "Riding The Wave" link above shows pretty much what the proper waveform looks like. To me that is more important than just the number itself.

EtCO2 has about a +/- 5 torr margin of error to ABG's PaCO2; usually minus, but not every time. It is also dependent on cardiac output. If they're dead, they're not going to have that much of a cardiac output if any at all. You need to keep that in mind when looking at the waveform.

I'll let Vent work her magic from here.

[VentMedic]

Lots of information to cover if one wants to have thorough knowledge.

Capnography with waveform is preferable over Capnometry (color change) which can be subject to false positive by the presence of CO2 in the esophagus. A good waveform is helpful in determining the tube is in the trachea with each breath. Changes in the waveform can indicate changes in placement, cardiac output or pulmonary status. Different waveforms can help with a field diagnosis as well as trouble shooting problems during ventilation.

Watching the numbers (and waveforms) can prevent over ventilation.

Observing the trend in numbers can be most beneficial to check for sudden changes or change in patient's status. Observing the waveform can give you a clue what the change might be.

The numbers: 35 - 45 mmHg is the norm PaCO2 range for normal lungs to maintain a good pH provided there is not a metabolic acidosis present. PaCO2 is measured by an arterial blood gas.

There is an error of +/-5 as well as a chance the numbers do not correlate to the actual PaCO2 due to deadspace ventilation or V/Q mismatch.

V/Q mismatch can be caused by blood shunting such as what occurs during atelectasis (perfusing unventilated lung area) or by dead space in the lungs (ventilating unperfused lung area) such as what occurs with a pulmonary embolisim or hypovolemia.

If there is an arterial blood gas available we look at the difference (gradient) between the Pet and PaO2.

As far as using ETCO2 during a code, the ETCO2 will increase with effective CPR and ROSC. If you lose circulation or the person doing compressions tires, ETCO2 will fall.

Quick and easy overview:

http://www.capnography.com/outside/911.htm

Another good website which contains alot of other useful info on BiPAP, CPAP, WhisperFlow as well as capnography.

http://elearning.respironics.com/index_f.asp

[Just Plain Ruff]

and don't forget if you get the easy cap the one with the paper in it becomes worthless when it gets wet.

[AZCEP]

and don't forget if you get the easy cap the one with the paper in it becomes worthless when it gets wet.

And don't open it until you are good and ready to use it. I've made the mistake several times of opening the package prior to placing the tube, only to have it fouled by room air before I could use it.

I'd like to add that there are more ways to confirm tube placement than MSDeltaFlight suggested, with all due respect. Capnography is the best of the bunch, but auscultation still has its place, as does esophageal bulb/syringes, BAAM devices. As we are required to have more than two methods of confirmation documented, I tend to use as many as I can think of including some that take quite some time to make changes, ie SpO2 and ECG.

[OVeractiveBrain]

Simple explanation:

The wave measures inspiration expiration. The wave goes up when you expire. At the end of an expiration you get an End-Tidal (tidal volume is the normal volume of gas that goes in and out of your lungs).

It just so happens that there is no CO2 in the air. There is a lot of CO2 in your venous blood. Your body uses sugar and oxygen and makes CO2 and Water. The CO2 has got to be gotten rid of. About "45" (aka 45mmHg) of CO2 is in your venous blood when it gets to the lungs.

45 in the blood, 0 in the lungs, so CO2 leaves the blood into the lungs. When the person exhales, the CO2 comes out into the air, and another 0 CO2 breath is taken in to swap with the new blood.

For reasons of chemistry, the diffusion of CO2 balances out (called "equilibrium") at about "40" (40mmHg, milimeters of mercury). If everythign is working out, bam, 40.

So when you have an arrest, and you put a tube in, you KNOW its in the lungs if you get a wave. Up on exhale, down on inhale. If you were in the esophagus, there would be no change, and certainyl no wave.

Wave = In.

wave from 0 to 40 back down to 0 then up to 40 = greath ventilatory status. Their lungs are doing great. Their heart, blood, brain and kidneys might be toast, but their lungs are doing fine.

Well what does it mean if it only goes up to 20? If you have a 0 to 20 to 0 to 20 waves going on with each breath, you are in the lungs. Your job is about done. Tubes in, tubes right, move em to the ICU.

But what does 20 mean? It either means you hyperventilated a healthy patient (blowing off too much CO2) or their perfusion (heart and blood) is broken. Not your fault.

if the CO2 is above 40 (which is likely post arrest), you are just realzing the effects of not breathing for a while. If you dont breathe, CO2 build up in your blood and your lungs. As you ventilate, and blow off the CO2, the wave should come back down to 40.

What about high flow O2? What about it? Normal air has 0% CO2. 100% oxygen has 0% CO2. You still get an equilibrium near 40 on a healthy patient.

End-Tidal Capnography measures the partial pressure of Carbon Dioxide in mixed expired air. It represents not only the concentration of Carbon dioxide in the blood of the patient being measured, but it also measures the amount of ventilation-perfusion ratio.

Take Away: If you have an up-down-up-down wave, youre in the lungs. If you hit an up-down-up-down wave that goes from 0-40-0-40 and your patient isnt waking up, look to something else other than respiratory. If your wave CHANGES, and isnt flat on the bottom and flat on the top, start looking around the lungs - their airways are changing.

Overactive

[EMS49393]

I find visualizing the cords, ausculation of lung sounds, verifying there are no sounds over the epigastrium, and utilizing waveform capnography to be my preferred methods of confirming my tube placement. My service still carries those little colormetric changing devices, however I refuse to use them. Likewise, there are more medics than not that refuse to use capnography at my service. We don't even carry those esophageal bulbs or baams, as our CQI manager deems they are relatively useless when you have other, more reliable means of confirming your tube placement.

Waveform capnography does one very, very important thing for me that no little colormetric device can do. It shows me ROSC. When I work a code, check for pulses, swear I feel pulses, and look up at my EtCO2 reading to see it is suddenly 80, I know I have achieved ROSC. I then slowly bag down to get and keep a reading of 35-45. It's also nice and easy to point to the monitor and tell the ride along fireman that I get stuck with to "keep that little number between 35 and 45." Those guys get a little excited when they get ahold of that BVM.

Capnography does one thing for my rear end that I appreciate greatly. It proves my tube. In the rare instances I bring in a patient that is intubated, I hit my print button on the monitor before and after my patient is transferred to the hospital bed. I'll be darned if I get called into the CQI office and told that the doctor said my tube was no good. CYA, we have the technology to cover our keisters.

When I had the privilege of RSI and a two hour ride to the hospital, capnography became one of my most important tools with a decompensating respiratory patient. I have put down the overly tired breather and have seen EtCO2 readings in the high 90's with these patients. RSI is not something I ever enjoyed doing, and I took great care to make sure it was in the absolute best interest of my patient before I elected to preform that extremely dangerous intervention. With documentation of waveform capnography, I was very easily able to prove to our physicians exactly how sick my patient was pre-intubation.

It's one thing to tell the receiving facility what you had, it's another thing entirely to prove what you had.

I'm not ashamed to admit capnography is one of my favorite assessment tools. It falls in line right behind my eyes, hands, and ears. I prefer it far and away over the "pulse ox." I'll use them both, but I can tell a great deal more about my patients ventilatory status with waveform capnography. I consider it an invaluable tool, and I hope that more providers take the time to learn and use this resource.

(I do not feel I hijacked this thread, rather I added how valuable capnography is to a paramedic when they are faced with proving their findings to a physician.)

[AnthonyM83]

Thanks everyone.

I got a lot out of this thread. I feel like each post led to the next post in an almost pre-planned lecture series.

Now, I certainly learned more than just the following, but to summarize the main click:

The capnography tracks level of CO2 being exhaled which should go from 0 to 35-45 mmHg, because even during full arrest, the body is still working on the cellular level with good compressions and ventilations. In general, lower numbers mean either ventilations (by patient or by you) are happening too quickly for body to use up O2 and produce CO2 or there's a cardiac, lung, volemic, or cellular problem, since O2 isn't being transported and used up. High numbers occur when circulation returns during a code because the body is suddenly using up a lot more oxygen from each ventilation, thus exhaling a lot more CO2. The target area is 35 to 45 because that keeps optimal pH and CO2/O2 levels in blood.

PS I imagine checking for condensation on tube is because water is the other byproduct in breaking down glucose...