lemon
Guest
:shocked2:did i miss something here or has the cardiopulmonary system been redesigned lately?
End tidal CO2 Monitoring
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:shocked2:did i miss something here or has the cardiopulmonary system been redesigned lately?
OP
Hang on a second everyone. Before we all get in line to take our shots at this statement, lets allow a chance to for him/her to qualify this statement. It's so far off what I've learned and practiced, there MUST be something else to it. But I'm with Lemon. The EtCO2 I've read about has everything to do with breathing.
Super, could you have been referring to a V/Q mismatch? One caused by a lack of pulmonary perfusion? In that case, CO2 levels would increase even as minute ventilation increases.
I imagine everyone, prior to your statement, was assuming fairly normal lung function.
Anyone?
Super, could you have been referring to a V/Q mismatch? One caused by a lack of pulmonary perfusion? In that case, CO2 levels would increase even as minute ventilation increases.
I imagine everyone, prior to your statement, was assuming fairly normal lung function.
Anyone?
Garth
Contributor
for every aveoli there is an associated capillary so I can see how he has made that statement. So many things can separate the two... fluid, atelectasis, and full dissassociation seen in ARDs. CO2 is a biproduct of the oxygen transport system. This system is found in the tissue. A defect in bloodflow for any reason would effect this number.
Supermanwoot
Registered
Lets think about it. When do you monitor ETCO2? In an intubated patient, therefore they are not breathing properly by themselves and so a ventilator is breathing for them. You don't measure ETCO2 on a person breathing on their own, nor is it a determinate for when to intubate someone.
ETCO2 is monitored closely when a patients "codes," or goes into cardiac arrest. This is a BLOOD FLOW issue. CO2 is a metabolite of cellular respiration and so it is returned VIA THE BLOOD to the lungs where it is able to be pulled off by the ventilator.
A High ETCO2 during CPR is a good thing. This means the body is getting the oxygen, using it, and returning CO2 via the blood. Its a means of measuring pulmonary perfusion, not the patients ability to breathe because we provide that for them.
If the ETCO2 is LOW, then their body is not getting the oxygen (not being perfused and not returning blood to the lungs).
So now lets apply this to scuba. Is your heart beating? Yes. Are you breathing on your own? Yes.
So why would we need to monitor ETCO2, if anything a high ETCO2 would tell us we are working hard. A low ETCO2 would be the problem, meaning you aren't getting BLOOD FLOW back to your lungs, but in that case just check your own pulse.
What I'm saying is ETCO2 is something completely different than what its being proposed for here.
ETCO2 is monitored closely when a patients "codes," or goes into cardiac arrest. This is a BLOOD FLOW issue. CO2 is a metabolite of cellular respiration and so it is returned VIA THE BLOOD to the lungs where it is able to be pulled off by the ventilator.
A High ETCO2 during CPR is a good thing. This means the body is getting the oxygen, using it, and returning CO2 via the blood. Its a means of measuring pulmonary perfusion, not the patients ability to breathe because we provide that for them.
If the ETCO2 is LOW, then their body is not getting the oxygen (not being perfused and not returning blood to the lungs).
So now lets apply this to scuba. Is your heart beating? Yes. Are you breathing on your own? Yes.
So why would we need to monitor ETCO2, if anything a high ETCO2 would tell us we are working hard. A low ETCO2 would be the problem, meaning you aren't getting BLOOD FLOW back to your lungs, but in that case just check your own pulse.
What I'm saying is ETCO2 is something completely different than what its being proposed for here.
OP
A baseline and studies would have to be established to determine a normal or safe range of end tidal CO2. Whether on a ventilator or breathing on your own, you have CO2 that can be measured.
A sudden increase above established limits for diving can be a sign of CO2 retention.
A sudden increase above established limits for diving can be a sign of CO2 retention.
ETCO2 is a very good proxy for arterial CO2. And we DO measure arterial CO2 as a data point to help us decide when to intubate a patient.
It is true that, in the absence of circulation, CO2 is not returned to the lung, and ETCO2 will be low or absent.
However, in the presence of normal circulation (as would be true of a diver), ETCO2 is a measure of ventilation, and on a rebreather, ETCO2 would reflect the effectiveness of the scrubber at removing CO2 from the loop, AND the effectiveness of the diver, at maintaining adequate ventilation.
CO2 is primarily a reflection of ventilation, and is heavily influenced by anything that reduces the volume of gas that passes through the alveoli. CO2 rises in conditions that impede air flow, like asthma or COPD. CO2 diffuses fairly readily, so a diffusion defect will be reflected in low O2 levels before it impacts CO2.
None of this discussion is really relevant to diving, however, because it all pertains to pulmonary abnormalities. The vast majority of people who dive will have normal lung function, so the determinants of gas transport for them will have to do with things like breathing gas density and work of breathing in the immersed state.
It is true that, in the absence of circulation, CO2 is not returned to the lung, and ETCO2 will be low or absent.
However, in the presence of normal circulation (as would be true of a diver), ETCO2 is a measure of ventilation, and on a rebreather, ETCO2 would reflect the effectiveness of the scrubber at removing CO2 from the loop, AND the effectiveness of the diver, at maintaining adequate ventilation.
CO2 is primarily a reflection of ventilation, and is heavily influenced by anything that reduces the volume of gas that passes through the alveoli. CO2 rises in conditions that impede air flow, like asthma or COPD. CO2 diffuses fairly readily, so a diffusion defect will be reflected in low O2 levels before it impacts CO2.
None of this discussion is really relevant to diving, however, because it all pertains to pulmonary abnormalities. The vast majority of people who dive will have normal lung function, so the determinants of gas transport for them will have to do with things like breathing gas density and work of breathing in the immersed state.
Garth
Contributor
I agree with you superdude but you are wrong about etco2 for breathing patients. Nasal cannulas can be used for etco2, trust me I've used them.
You want to know whether co2 is present after scrubber not after you breath out. Making etco2 not necessarily usable in someone who is presumably healthy diving a rebreather.
You want to know whether co2 is present after scrubber not after you breath out. Making etco2 not necessarily usable in someone who is presumably healthy diving a rebreather.
Supermanwoot
Registered
TSandM, you have the first part correct. Arterial CO2 is a sign of CO2 retention and a means to determine intubation necessity, ETCO2 is not. ETCO2 is Co2 you are EXHALING, and so that is a good thing! The most effective measure would be an arterial CO2 monitor, although that would be very invasive.
Garth
Contributor
I don't think that is what she said. And you are getting further and further from diving relation.
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