CPAP and CO Poisoning

[CPAPMedicCO]

At about 0900 this morning I received a call from one of our area clinics here in Crested Butte, Colorado advising me that we had a case of CO Poisoning. BTW I am Critical Care Paramedic that volunteers for our Fire Protection District here as well as a clinical person for Emergent Respiratory Products. The patient was a 48yo male snow plow driver who apparently backed his plow into a snow bank and bent the exhaust system. The exhaust was then blowing into the cab of the plow. The patient advises he became real SOB, nauseous, and weak, “like I was going to pass out.” A co-worker took him to the Clinic for treatment. He initially presented with cherry red skin, unsteady gait, muscle tetany, weakness, headache, and N/V. Initially they got a SPO2 reading of 82% on room air. They placed him on a NRB mask at 15LPM and called me. They have purchased an Emergent CPAPos Porto2Vent and had it set up. I arrived to help initiate CPAP treatment while the patient was on the NRB mask with saturations about 92% on 100% oxygen at 15 LPM. Placing the soft seal mask on the patient and advising him to take a really deep breath and exhale hard, I titrated the unit up to 10cm H2O and the patient was breathing on the system. The initial D-Cylinder lasted 25 minutes and we quickly switched tanks. Monitoring vitals, the patient remained normo-tensive throughout the treatment and his saturations continually climbed to 97-99%. The second D-Cylinder again lasted 25 minutes. The patient was able to communicate with the staff, advising that his headache, muscle tetany, weakness, and N/V had subsided. The patient wanted to discontinue treatment. CPAP was discontinued by the physician at the clinic. After being off the CPAP unit for about 10 minutes, his vitals remained normal, SPO2 remained 99-100% at an elevation of 9375ft above sea level, and the patient had no complaints. His skin color returned to normal, his saturations remained 99-100%, and subsequently the patient was discharged three hours after presenting to the clinic. The only unfortunate thing about this case, if you want to call it unfortunate, is that our RAD57 CO Monitors have not arrived yet and I was unable to get a CO reading on the patient. I do know that blood was drawn before and after the CPAP treatment and sent into town to the lab. We are approximately 288 ground miles from Denver where the closest HBO chamber is. Due to weather conditions, about another 1-2 feet of snow expected today, we were unable to get a flight for life team here. This patient, if transported, would have had to gone by ground ambulance to Gunnison Valley Hospital by Crested Butte Fire Protection District EMS and then by ground to Denver by Gunnison Valley Hospital EMS. (All of which currently have the Emergent CPAPos Porto2Vent System) I know that there is a lot of discussion about the use of CPAP for CO Poisoning but no real hard data supporting it. I thought I would share one of my personal clinical experiences.

[BushyFromOz]

very interesting. Total n00b observation here, but is a low SPO2 reading "normal" in C0 poisoning? I thought it would give a false reading?

Thanks for writing this up, and welcome to the city 8)

[VentMedic]

very interesting. Total n00b observation here, but is a low SPO2 reading "normal" in C0 poisoning? I thought it would give a false reading?

Thanks for writing this up, and welcome to the city 8)

The patient may also have had a bronchospastic or hypoventilatory component. The Hb not attached by CO may have desaturated.

CPAP is good if it helps with their work of breathing. However, it they must "work at breathing" with the CPAP on, then it is defeating the effort. I would also not advise placing CPAP on someone who is vomiting.

Also, for CO poisioning, with the different CPAP machines on the market, use care to keep the FiO2 at 1.0. Adding more PEEP or cmH2O may not make a difference if there is not an existing lung pathology that warrants it. It can also add to the work of breathing. Not all CPAP systems are created equal. However, the Porto2Vent is definitely better than some.

Even with the RAD 57, your prehospital treatment probably would not have varied since you suspected CO and was using as close to an FiO2 of 1.0 as possible. If it affected your choice of facilities to take the patient, then yes, the RAD 57 would have made a difference.

[BushyFromOz]

The patient may also have had a bronchospastic or hypoventilatory component. The Hb not attached by CO may have desaturated.

Yeah i gave that a thought and came back to alter my post but you beat me

[DwayneEMTP]

Just out of my head (meaning without looking it up to help prevent myself from looking like a bonehead)

I also thought the SPO2 didn't differentiate between CO and H2O, that it would read high.

Though it sounds as if he was able to watch it trend to that point, which may have given him confidence, wouldn't 99%-100% sat on room air at 9400 ft. cause you to be suspicious of the reading secondary to CO poisoning?

Just wondering...

Dwayne

[medic001918]

The presence of CO does make the pulse oximetry inaccurate. The CO binds to the hemoglobin the same way oxygen does. The oximeter can't differentiate between the two, and sees the hemoglobin molecule as "fully saturated." Really, the pulse oximeter is only measuring a saturation of how full the molecule is.

End tidal capnography tends to be a far better diagnostic tool for respiratory cases as changes are witnessed in real time. Pulse oximetry is about 3-5 minutes behind the patient in most cases.

Shane

NREMT-P

[VentMedic]

End tidal capnography tends to be a far better diagnostic tool for respiratory cases as changes are witnessed in real time. Pulse oximetry is about 3-5 minutes behind the patient in most cases.

Shane

NREMT-P

But, you are measuring two totally different aspects of Respiration: Ventilation and Oxygenation with each device.

[CPAPMedicCO]

Because in my career I only worked at sea level in the inner city prior to moving to Colorado, would the altitude have something to do with the low readings?

I would have suspected higher false readings as well, but they seemed normal. This was done in a clinic and there was no RAD57 or ETCO2 and EMS was never called. I was called by one of the medics who worked there asking me if CPAP was appropriate. Thank you for your posts. I was accused of this being a sales pitch when it was honestly a fact finding mission.

[VentMedic]

The altitude would affect the SpO2 but it would also depend on the patient's acclimation and Hb available. His respiratory symptoms would be dependent on his total carrying capacity. Even small amounts of CO can produce the other symptoms. The other thing to consider would be a touch of altitude sickness if he was from sea level and not a native to the area.

Since CPAP and Hyperbaric are two very different therapies, the CPAP would be beneficial for CO poisioning only if it visibly reduced his work of breathing and 100% O2 could be delivered. Of course if there are other lung processes involved such as the pt having COPD or Fibrosis, then yes, it would probably be beneficial. If the guy was 48 y/o with a pack of cigarettes in his pocket, he probably has 30 - 60 pack years of damage already to his lungs. CPAP might help him out provided he was not vomiting.

The half-life of carboxyhemoglobin is approximately 5 hours. For example: If the patient has a level of 30% COHb, it will take five hours for the level of carboxyhemoglobin in the blood to reduce to 15% COHb, once the exposure is terminated.

Did the hospital or clinic mention what his COHb measured at on the CO-Oximeter? or if they have a CO-Oximeter with their ABG lab?

[AZCEP]

CPAP may help some, but all in all the best thing to do is to use high concentrations of oxygen and support vital functions until the hemoglobin is willing to release the CO into the exhaled air. Using 100% oxygen will effectively quarter the half-life of the CO. Using VentMedic's numbers, five hours is cut down to roughly 90 minutes.

CO monitoring would have been nice, but the patient presentation indicated a significant exposure, so it wasn't going to change what you were going to do in the setting you were in.