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What does it mean when "too much oxygen becomes toxic"?


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#1 Trudy

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Posted 29 November 2007 - 06:38 PM

I have oxygen at night, because according to a sleep study, my oxygen level lowered at night. It has happened that when I'm going through a bad exacerbation, I've been put on it during the day for a limited time. I've been told that if a person gets too much oxygen, it can get "toxic". What does this actually mean? How would a person know if they're getting too much? Is getting too much as bad as getting too little oxygen? I'm sometimes confused by this paradox. Will you please explain this?

Thanks so much for all your informative answers, Dr. Adams! I hope I'm not too late to get this one more in yet. :blink:

#2 Francis V. Adams

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Posted 29 November 2007 - 07:49 PM

Hi Trudy:

This is an important point so I am glad that you brought it up.

It is best to think of oxygen as a drug. You can take too much or too little.

Too much (or high concentrations of) oxygen can produce two important problems.

The first relates to the concentration itself. The air we breathe is 21% oxygen. When you are breathing 2 or 3 liters per minute with your nasal cannula the concentration is between 28 and 35%. If someone is given 60% or greater 02 for more than 24hrs, it can directly damage the lungs. This is called "oxygen toxicity". This happens alot in an ICU where a critically ill person often needs high, even 100% 02 to survive. Fortunately, alot of this is not permanent if the concentration is reduced soon enough.

The second problem related to too much oxygen has to do with how we breathe. One mechanism that stimulates breathing is related to oxygen, the other to carbon dioxide (C02). If an individual's C02 level rises and remains elevated, the primary drive to breathe is the 02 level. Too much oxygen can then reduce this 02 drive, resulting in a further increase in C02 which can then produce a coma. This can be avoided with monitoring of 02 and C02 levels. This is best done with a blood gas (blood must be taken from an artery) although less invasive methods of monitoring C02 (like oximetry for 02) are becoming available.

Best,

Dr. Adams

 Trudy, on Nov 29 2007, 06:38 PM, said:

I have oxygen at night, because according to a sleep study, my oxygen level lowered at night. It has happened that when I'm going through a bad exacerbation, I've been put on it during the day for a limited time. I've been told that if a person gets too much oxygen, it can get "toxic". What does this actually mean? How would a person know if they're getting too much? Is getting too much as bad as getting too little oxygen? I'm sometimes confused by this paradox. Will you please explain this?

Thanks so much for all your informative answers, Dr. Adams! I hope I'm not too late to get this one more in yet. :blink:

Dr. Adams
adamsmd.com





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