Published studies for EtCO2 through King Airway?

[FiremedicMike]

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Sorry if this is the wrong section, and I did try calling King Systems but have yet to receive a reply.

I'm putting together an ACLS update for my department. As you all well know, EtCO2 is being hammered home in the new AHA update, with the goal of maintaining peri-arrest EtCO2 of 10mmHg or greater. I will also be stressing the use of EtCO2 during our arrests, and while I have used EtCO2 with a king airway before and assume I was getting accurate readings, I would much prefer the ability to reference that assertion during my presentation.

Is anyone aware of any published studies that EtCO2 monitoring through a king airway is accurate?

 

[la gringa]

no i don't, but when i asked for EtCO2 during a code, no one could find the right cord. uhhhh.... didn't end up mattering 🙁

 

[Hamhock]

Sorry if this is the wrong section, and I did try calling King Systems but have yet to receive a reply.

I'm putting together an ACLS update for my department. As you all well know, EtCO2 is being hammered home in the new AHA update, with the goal of maintaining peri-arrest EtCO2 of 10mmHg or greater. I will also be stressing the use of EtCO2 during our arrests, and while I have used EtCO2 with a king airway before and assume I was getting accurate readings, I would much prefer the ability to reference that assertion during my presentation.

Is anyone aware of any published studies that EtCO2 monitoring through a king airway is accurate?

What do you mean by "accurate"?

Expired gas is expired gas. What does the tube it is coming from have to do with it?

Remember, the EtCO2 is not an "accurate" measurement of PaCO2.

HH

 

[FiremedicMike]

What do you mean by "accurate"?

Expired gas is expired gas. What does the tube it is coming from have to do with it?

Remember, the EtCO2 is not an "accurate" measurement of PaCO2.

HH

Fair enough, but is there any potential that stomach gasses may alter an EtCO2 reading at all? This would be the only difference between hooking it up to an ETT, where all gas passing through is coming from the lungs, whereas there is (more?) potential for stomach gasses coming up through a King.

I'm asking that question honestly, my knowledge of this subject is well below yours.

 

[southerndoc]

King will not give you an answer because the King Airway is not FDA approved for pre-hospital use. They were cited by the FDA for marketing it for off-label use in 2009. It's only approved for use in patients undergoing anesthesia who have been fasting (unless they've recently gained approval).

 

[FiremedicMike]

King will not give you an answer because the King Airway is not FDA approved for pre-hospital use. They were cited by the FDA for marketing it for off-label use in 2009. It's only approved for use in patients undergoing anesthesia who have been fasting (unless they've recently gained approval).

That's very interesting, it seems to be pretty widely used in pre-hospital airway, even taking mention in classes and (if memory is serving me correctly) referenced in pre-hospital textbooks.

 

[southerndoc]

That's very interesting, it seems to be pretty widely used in pre-hospital airway, even taking mention in classes and (if memory is serving me correctly) referenced in pre-hospital textbooks.

It's considered an off-label use to use it in an emergency. Others can discuss it, but King cannot because they can only discuss what it's approved for.

 

[psychbender]

Fair enough, but is there any potential that stomach gasses may alter an EtCO2 reading at all? This would be the only difference between hooking it up to an ETT, where all gas passing through is coming from the lungs, whereas there is (more?) potential for stomach gasses coming up through a King.

I'm asking that question honestly, my knowledge of this subject is well below yours.

What "stomach gases" do you think might alter the reading? The reading you will get from the King will not be significantly different from the reading you will get from an LMA or an ETT, though I don't believe you will see this in a published study, as I doubt one has been done.

 

[proman]

Remember, the EtCO2 is not an "accurate" measurement of PaCO2.

HH

Care to explain this statement?

 

[Hamhock]

Care to explain this statement?

Sure.

(although, I think it depends on what the OP means by 'accurate')

EtCO2 is certainly related to PaCO2, but it is not an accurate - or precise - measurement. That is, very often - especially in unstable cardiopulmonary cases (when EMS would be sticking in King tubes) - the EtCO2 is dramatically lower than the PaCO2. And the relationship between the two varies within one patient as cardiac output varies in the unstable patient.

...but I know, proman, that you know this...so, I am not sure what you are getting at. 😕

HH

(OP -- I think you will really get more out of answers here if you are more explicit regarding quantitative EtCO2 vs. continuous waveform-quantitative EtCO2 vs. other and what exactly you mean by 'accurate')

 

[proman]

Sure.

(although, I think it depends on what the OP means by 'accurate')

EtCO2 is certainly related to PaCO2, but it is not an accurate - or precise - measurement. That is, very often - especially in unstable cardiopulmonary cases (when EMS would be sticking in King tubes) - the EtCO2 is dramatically lower than the PaCO2. And the relationship between the two varies within one patient as cardiac output varies in the unstable patient.

...but I know, proman, that you know this...so, I am not sure what you are getting at. 😕

HH

(OP -- I think you will really get more out of answers here if you are more explicit regarding quantitative EtCO2 vs. continuous waveform-quantitative EtCO2 vs. other and what exactly you mean by 'accurate')

What am I getting at? I think you're throwing the baby out with the bath water.

Every monitor has limitations, and end tidal gas monitoring is no exception. The OP asked about accuracy of EtCO2 when used with a supraglottic airway. The correct answer is that it depends. EtCO2 is most reliable when used in a closed ventilation system, like that of an intubated patient because leaks in the system reduce the measured CO2. Supraglottic airways do not necessarily have tight enough seals, but frequently do. In that case, the EtCO2 does correlate with the alveolar CO2.

I take issue with your assessment of the reliability of EtCO2 monitoring because it's a vital component of my practice, one that I use on every patient I take care of. Obviously the EtCO2 won't be identical to PACO2 or PaCO2. Alveolar and/or physical deadspace is the primary cause of this difference. Conditions that produce dead space ventilation (such as PE) produce characteristic EtCO2 patterns. Why is EtCO2 lower that PaCO2 in "unstable cardiopulmonary cases"? Because of the low cardiac output state and V/Q mismatch, an intrinsic patient pathology. I disagree that it's "dramatically". For instance, during codes with effective CPR, you will see a reasonably normal EtCO2. I'd argue that the presence of EtCO2 is more important than the PaCO2 value. I'm a cardiac anesthesiologist. I've taken care of many patients with low cardiac outputs. EtCO2 does not necessarily differ that much even with low CO. One demonstrates cardiac output and effective gas exchange, the other simply reflects production of carbon dioxide. Which would you rather know?

In the OP's scenario, the EtCO2 is a reliable method of assessing quality of resuscitation, with either endotracheal or supraglottic airways. The OP should go to PubMed and search for end tidal carbon dioxide monitoring and supraglottic airways for more.

 

[FiremedicMike]

What am I getting at? I think you're throwing the baby out with the bath water.

Every monitor has limitations, and end tidal gas monitoring is no exception. The OP asked about accuracy of EtCO2 when used with a supraglottic airway. The correct answer is that it depends. EtCO2 is most reliable when used in a closed ventilation system, like that of an intubated patient because leaks in the system reduce the measured CO2. Supraglottic airways do not necessarily have tight enough seals, but frequently do. In that case, the EtCO2 does correlate with the alveolar CO2.

I take issue with your assessment of the reliability of EtCO2 monitoring because it's a vital component of my practice, one that I use on every patient I take care of. Obviously the EtCO2 won't be identical to PACO2 or PaCO2. Alveolar and/or physical deadspace is the primary cause of this difference. Conditions that produce dead space ventilation (such as PE) produce characteristic EtCO2 patterns. Why is EtCO2 lower that PaCO2 in "unstable cardiopulmonary cases"? Because of the low cardiac output state and V/Q mismatch, an intrinsic patient pathology. I disagree that it's "dramatically". For instance, during codes with effective CPR, you will see a reasonably normal EtCO2. I'd argue that the presence of EtCO2 is more important than the PaCO2 value. I'm a cardiac anesthesiologist. I've taken care of many patients with low cardiac outputs. EtCO2 does not necessarily differ that much even with low CO. One demonstrates cardiac output and effective gas exchange, the other simply reflects production of carbon dioxide. Which would you rather know?

In the OP's scenario, the EtCO2 is a reliable method of assessing quality of resuscitation, with either endotracheal or supraglottic airways. The OP should go to PubMed and search for end tidal carbon dioxide monitoring and supraglottic airways for more.

Thank you for taking the time to post this, it's exactly what I was looking for. I will check out pubmed..

 

[FiremedicMike]

Also, for those asking, "accurate" as it ralates to my question means that the readout with the king airway could be used to measure CPR quality in the arrest scenario as per the latest ACLS guidelines.