Rescue Breathing?

[systemet]

Interesting discussion.

I'll admit that pulmonary physiology and ventilator management is an area of weakness for me. What you're suggesting with bagging to maintain pre-intubation ETCO2 seems reasonable, at least for patients that have a high minute volume prior to ETI.

But what about the situation where you're patient is in respiratory failure, and their ETCO2 is high? If this is an acute problem, I may be dealing with a simple decompensated respiratory acidosis. Here it would seem like returning ETCO2 to 35-45 would be reasonable.

But what would you recommend as a strategy if the patient has pre-existing COPD? If I don't know their baseline PaCO2, I don't know that their current PETCO2 is correlating with PaCO2, and their pre-intubation PaCO2 is likely to be greatly elevated as a result of respiratory failure. If I bag my patient aggressively to 35-45, I'm going to generate an iatrogenic metabolic alkalosis. If I don't bag my patient aggressively enough they may remain acidemic. What would be a reasonable strategy here?

Edited August 25, 2011 by systemet

[Paramagic]

It depends on the patient. Generally speaking acidosis is better tolerated than alkalosis. If you have an elderly COPD patient who normally has a high baseline PaCO2 (although you would again need an ABG to confirm this) you probably won't want to bag the hell out if them to get their EtCO2 down as you run a number of risks.

For asthmatic patients I basically don't worry too much about the EtCO2. I want to oxygenate them well first of all, then ventilate. I have seen EtCO2 up around 180mmHg in acutely unwell, intubated asthmatics. You will bring that number down, but you need to be careful when doing it. Hypoxia kills, hypercapnia happens. If you try to chase numbers too quickly you will end up breath stacking, causing barotrauma, popping blebs and generally causing all kinds of mischief. Slow and steady is the key here, these aren't the same as the metabolic acidosis patients first described and they will tolerate that acidosis well for some time.

[usalsfyre]

However this gradient is dynamic, so again, without ABG we just have to make an educated guess and get on with it.

More nitpicking but....

If by some miracle I had a gas I'd expect the gradient to remain fairly stable in this patient. Generally you see changes in the ETCO2-PCO2 gradient when there's a change in hemodynamics or alveolar status. Unless I have some reason to suspect there has been a change in one of this two factors, I'd be willing to trust the initial gradient.

[kohlerrf]

Thank you systemet. this topic is generally dealing in uncharted waters of which I feel need to be addressed. With regard to respiratory acidosis as paramagic said this is generally better tolerated than alkalosis partially because we can increase the partial pressure of oxygen which will compensate somewhat for the hemoglobin loss of affinity for oxygen in an acidotic state. However although this occurs we cant lose sight of the fact that the body lives in a very narrow range of pH and the big picture still needs to be corrected.

Regarding your scenario, I would ventilate to what ever was needed to maintain and oxygen saturation of 95%. If his ETCO2 remained at 65mm/mg with a pulsox in the high 90's and not 100% that would be fine with me.

[Just Plain Ruff]

Dang, those on this thread all need to get together and teach an airway class. Ch, where do I sign up to learn about newtonian gradiants and all that. I can't imagine how much I'd learn from you.

[Paramagic]

Dang, those on this thread all need to get together and teach an airway class. Ch, where do I sign up to learn about newtonian gradiants and all that. I can't imagine how much I'd learn from you.

It's threads like this that should be compulsory reading for every skill-monkey who thinks that we are overeducated in the first place. Every day I wake up worrying that I don't know enough to do my job well, and then I confirm that by reading this sort of thread!