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Old 09-25-2012
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Default in ARDS; to reduce PEEP or Fio2

Hey everyone,

Got a question... Assume a pt had ac. pancreatitis and then ARDS to days later:

Cut the chase, He was started on mech ventilation with
PEEP 7m hg
Fio2 80%
Tidal vol 380 ml
Resp rate 14/ min

Now with the ABG back, We see o2 and co2 are towards the upper limits of Normal, right? Whats the best next step?

1 - Decrease fio2
2 - decrease PEEP.

So you choose to decrease Fio2, I assume, NOW THE QUESTION (after all the rambling)
Here's the thing both of the measure would help decrease O2 levels, But how does decreasing the fio2 decrease the chances of O2 toxicity???
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Old 09-25-2012
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For CK you dont need to know how it causes it, but that it causes it because of increased free radicals. Research has shown that FIO2 <60% reduces risk of oxygen toxicity.
In this case its 80%, so you want to reduce it.

For a more detailed explanation, ask an RT in the hospital
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Old 09-26-2012
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Quote:
Originally Posted by rocketprinciple View Post
Here's the thing both of the measure would help decrease O2 levels, But how does decreasing the fio2 decrease the chances of O2 toxicity???
PEEP keeps the alveoli open (mitigates end-expiratory alveolar collapse) for gas exchange to occur.
High concentration of O2 is directly toxic to alveoli causing more inflammation and interstitial edema & collapse.

Quote:
Prolonged or very high oxygen concentrations can cause oxidative damage to cell membranes, the collapse of the alveoli in the lungs, retinal detachment, and seizures. Therefore, current guidelines for patients on mechanical ventilation in intensive care suggests keeping oxygen concentration less than 60%.
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