February 2007 Log

February 26, 2007 - CHF/COPD? One, the other, or both?

70 year old man with increasing dsypnea while on diaylsis. History of COPD/CHF. Respiratory rate is in the high 40's. BP 180/100. HR - 112. Sat 90 on 02 by cannula at 2 lpm. No chest pain. ETCO2 38. Upright wave form. Lung sounds -- rales in the bases, with some wheezing. No pedal edema. Man takes 80 mg of Lasix daily. Also on inhalers. Says he has never had trouble breathing quite like this before.

I put the man on a nonrebreather which brought his SAT up to 100%, gave him 3 nitros and one albuterol by neb shoved under the nonrebreather. His ETCO2 went up to 45 but then held steady. RR came down to 38-40.

At the hospital, one doctor thought it was COPD, the other thought there might be some CHF or at least a combination. They gave him nitro paste and a combivent along with some steroids, and ordered a chest x-ray.

The one doctor said the man shouldn't be on the mask because he had COPD. I mentioned his ETCO2 had been holding steady at 45. He looked at me like I was from outerspace. Later he looked the man's records up (the man had been there a month ago for exacerbation of COPD) and announced the man wasn't a retainer. (By saying his ETCO2 was holding steady at 45 I was trying to tell him that.) They did put the man down to a cannula and after a minute, a nurse announced he was satting fine on the cannula at 97. I said, I thought it might drop more.(A minute isn't long enough to desat from 100%). It went down to 94, and then they had the treatment ready for him.

He was doing a little better by the time I left. Was it the nitro? the treatment? or both? I don't know. I wish I could follow up. While one of the doctors thanked me and said good job, I was a little frustrated because I had the capnography, which was providing information, but I felt there was a language barrier between the ED staff and me that prevented me from effectively sharing the information.

I don't want to seem like a wise guy, which is my worry when I try to talk about capnography to someone unfamiliar with it. Who am I to tell a physician or nurse (who I may not know well) something about their patient by bringing up a technology they haven't been trained in or may misunderstand? It is hard to do it. Sometimes they listen, sometimes they are dismissive, most of the time they just say nothing.

1. The capnography seemed to be saying that the problem is perhaps CHF rather than COPD because the wave form is upright. The alveoli are emptying evenly? I just don't know enough yet to be able to say this is true, but it has me thinking.

2. The capnography was saying high-flow 02 is okay because the patient doesn't have a hypoxic drive -- the ETCO2 was constant in the normal range.

I'm not criticizing the hospital or particuarly their care so much as wishing they had capnography, and some education about it so they can make use of (consider) what could be valuable information.

I am also frustrated because I wish more was written about capnography (why I eagerly await the books of Krauss and Page) so I could have some reference to sort some of this out. I am doing my best to understand it, but my expertise is largely self-taught and based on a limited field of research, as well as field observation. I worry sometimes that I am getting it wrong.

One question I want to pursue is capnography and wheezing. When can you have a wheeze and an upright wave form? What type or degree of wheeze will produce an upright waveform? Can it be true, as I am speculating, that "cardiac asthma" wheezes induced by fluid overload will not produce the typical shark fin, but will be more straight up, while obstructive airway wheezes will have the shark fin shape? If this can be proved by a study, it can be a valuable diagnostic tool. I will query some MDs about that. Any thoughts are welcome.

I found the following discussion on a forum at emsvillage.com where one medic says he uses the wave form to distinguish between COPD and CHF.

Cardiac versus Respiratory Wheeze

February 25, 2007 - Cannula Positioning

Today I had an elderly patient with CHF. The initial end tidal was 8, but quickly jumped to 30 when I repositioned the cannula because the patient was a mouth breather. I put a non rebreather on and the number went down to 20. Several times during the call, the numbers moved, and each time when I repositioned the device the numbers came back to near 30.

(The other day I heard a medic patch in with a patient with stable vital signs but an ETCO2 of 9. Positioning of the cannula was probably the issue.)

The point of all this is that positioning the cannula is very important if your reading doesn’t seem right. It can be affected by a patient’s unique anatomy, by the patient’s method and manner of breathing and by their anxiousness during transport, which can shift the cannula position. (The position will affect not only the ETCO2 number but the RR number.) This patient had an initial RR of 48, which gradually came down to 38 due to some NTG SL, which seemed to help the breathing. The ETCO2 rose to 32, and settled there, which I was happy with considering. I stayed alert to make certain the RR wasn’t declining due to the patient growing more tired. Her effort in breathing seemed a bit more relaxed.

This all goes along with what I wrote below about normal values. You can't just always accept the numbers at face value and compare them to traditional norms.

February 20, 2007 - Normal Values

The normal values for ETCO2 are listed at 35-45 mm Hg. I have read that they are really 33-43 due to the possible gradient between arterial Co2 and ETCo2. What is normal anyway? Normal HR is 60-80, Bp 110/70-130/80. It all depends on the person obviously. But as I don't get too concerned with a HR of 88 or a BP of 140/90, I think you have to take the same approach with ETCO2. Most of my patients have ETCO2 in the 28-35 range, it seems. It is an emergency situation and usually they are a little short of breath -- that accounts for it. Sometimes the 02 dilutes it a little. I guess all I'm saying is normal is different for everyone to a point, and that in the emergency setting, it is not uncommon to have many people outside the normal range. I am most concerned with extreme readings that are trending worse.

February 18, 2007 - Cheyene-Stokes

Another medic shared her strips with me. 65 year old with sudden onset altered mental status whose GCS dropped from 10 to 4 early in the call, and who began exhibiting Cheyene-Stokes respirations with periods of apnea.

February 17, 2007 - Hospital Capnography Skill Sessions

Yesterday I taught a skill station on capnography at one of the area hospitals, which was having an education day for nurses. Many of the nurses were from the ED. I was paired with the vendor for Nellcor, which provides the hospital’s Hand Held Capnographs.

I passed out copies of the 10 Things Every Paramedic Should Know About Capnography handout as well as another handout I made called What We’re Talking About-EMS/ED Capnography Interaction, which I hope to soon post here.

The nurses were very interested in this new technology and most of them wondered why they had either never heard of it, or why they only had two machines in the ED. We had a interesting discussion with them. We talked about the costs of capnography and one nurse pointed out how, if capnography can help you decide who needs intubation and who doesn’t, it can save enormous costs both financial and human, not to mention the protection that capnography provides from the costs of an unrecognized misplaced airway.

It was interesting hearing some of the vendor's experiences with other facilities trying to convince them of the benefits of capnography. We decided that if you have capnography, it’s like having Windows while the rest of the world is still using MS- DOS.

It will be interesting to follow up with the nurses in a few weeks and see if they have used the capnography or how their interactions with medics bringing in patients on capnography have changed.

I’m hopeful the hospital will hold more sessions like this one in the future.

February 3, 2007 - Capnography Conversations with Another Medic

I had a long talk with another medic, who uses capnography even more than me. He says he puts it on every ALS patient and some BLS patients simply because it is another source of information to help with the clinical picture. He was telling me about a call for CO posioning. The patient was feeling light-headed and dizzy. The fire department did a sweep of the house and their machine came up with nothing. The ETCO2 was reading 50 even after fifteen minutes of 02 by nonrebreather on an extremely healthy fifty-year old man. The medic asked the fire department to do a more thorough sweep or else their meter had to be off -- something wasn't right. He compared the capnography that is calibrated every day and used all the time in a $25,000 machine versus their machine that sits in a cold truck and isn't used or calibrated much. The fire chief didn't understand what the medic was talking about because he was monitoring for CO and the medic was talking about CO2. Anyway, it turns out the guy had been moving cars in the garage and had left one of them running for awhile and it had sent up a big spray of white smoke while he was running it, and it must have all wafted into the house. I didn't get the whole rest of the story, but I think the point was while the fire department was poo-pooing there being a problem, the capnography was showing that there was something off with the man's ventilation, and in an otherwise healthy man, it was signaling something had happened to change his norm. The C0 was affecting his ETCO2.

I did an internet search to try to find any articles describing a relationship between ETCO2 and CO, and came up dry except for a research grant that listed "Relationship between EtCO2 and carboxyhemoglobin in carbon monoxide" as a topic for study.

Sometimes I think the best use of ETCO2 is to alert us to an as yet unseen problem so we can be vigilant and question what is going on. In this case, instead of poo-pooing the man's symptoms in light of non-CO readings, keeping him on 02 and transporting.

The medic said he found capnography very useful in seizure patients to learn if he needs to ventilate them and for use in patient's having psuedo-seizures. They may be flopping around, but if the capnography shows they are breathing during this episode it can demonstrate they are not having true gran-mal seizures where they would not be breathing.

He also said he has had the same apnea alarm problems I have been having on codes when the ETCO2 is low in the 6 and less zone.


At 4:05 PM, Anonymous Troy Valente - Colorado, USA said...

Hmm . . . that is interesting. I would actually expect ETCO2 to be low on a CO poisoning patient. Thinking through the capnography chain (metabolism to transport to exhalation) if his oxygen transportation abilities were low, less CO2 would be being produced due to lower oxygen delivery equating to lower metabolism. 80% of CO2 is transported dissolved in the plasma. But, if there is inadequate oxygen delivery to tissues, you have less CO2 being created. Therefore, I would anticipate that the problem was not a CO issue, but rather something else. Maybe the interpretation of the patient's situation was incorrect, or something else was being overlooked? Metabolic Acidosis issue? Dehydration? COPD?

At 4:13 PM, Anonymous Troy Valente - colorado usa said...

In regards to Capnography and COPD vs. CHF . . . I address this issue very heavily in capnography presentations I do. I would definitely not be comfortable nebing someone witha normal waveform who is older and/or who has a history of CHF. "Not all that wheezes" is asthma. I just went on a patient last week: 62 yoa female no history of asthma or COPD, but a history of VAD and a prior stroke. Complained of sudden onset of ilipsolateral shaking and SOB/Dypsnea. The other medic started nebing her before I even had a chance to complete my evaluation. Once I got her on capno and saw a normal waveform, but was auscultated wheezing, I quicly removed that neb, which had been going for about 2 minutes and did alleviate the patient's breathing problems. However, you must evaluate the clinical situation. For example, a 22 yoa female with dypsnea and a history of asthma would actually show nomral waveforms with a slightly elevated RR and slightly low ETCO2. This is to be expected in the beginning stages of an asthma attack. However, a 55 yoa male with a history of COPD and CHF who is having a difficulty breathing with a normal waveform . . . personally, I am not going to neb him. I would just monitor him and maintain him on oxygen. If the breathing gets dramatically worse, I will go down the Nitro, Morphine Lasix route. But, that is just me . . .

At 4:18 PM, Anonymous Troy Valente Colorado, USA said...

Correction: the neb did NOT alleviate the patient's breathing problems

At 8:11 PM, Blogger PC said...


Thanks for your excellent comments. I have been puzzling about the CO question, and your explanation seems very logical. Your take on the CHF/COPD is also very thoughful. I'm going to the JEMS conference next week and hope to be taking a capnography class from Bob Page and I'm hopefully get his thoughts on these questions as well.

Please feel free to continue to share you insights. I appreciate any chance to improve my understanding.

Thanks again,


At 9:40 PM, Blogger Anthony said...

Hello all! I'm so excited to be reading posts by other medics who are believers in the multi-factorial benefit of capnography measurement! I feel like out here (in Southern California) I'm working with dark-age medics who don't think twice about checking an SpO2 for ANY patient--and that without understanding how a pulsox works--but who in turn balk and complain or completely ignore the greater and more complete picture Capnography provides! Thanks for letting me know that I'm not alone!

Re. the CO question--I too have found a dearth of information, however, I can guess only this: when the person is poisoned by CO the body is forced into a greater level of anaerobic metabolism leading to lactic acidosis which, in the end, is partially cleared by the bicarb --> to H20 & CO2 method of clearance (hypothetical mechanism: H+ from lactic acid molecule binds with HCO3- to make H2CO3 (carbonic acid) and eventually dissociates to H20 & CO2). How does that sound coming from a wild guess fueled by enthusiasm and two glasses of merlot on an empty stomach?

Look forward to further dialogue! Please email me at chiamami@aol.com for any comments/questions.

Sincerely (And not to brag but to inform)
Tony Ricci
NREMT-P, Flight Medic, Former Corpsman, Current Army Medic, Fire Apparatus Engineer, GEEK


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