From: sbharris@ix.netcom.com (Steven B. Harris )
Subject: Re: Breathing pure oxygen
Date: 20 Sep 1995
Newsgroups: sci.med

In <energoi-1909952138230001@dialup13.fwi.com> energoi@fwi.com (Energo)
writes:

>Is there harmful effects from breathing pure oxygen? When a person gets
>oxygen in a hospital what's the percent oxygen?


Breathing more than 50% oxygen causes slow lung damage, and 100% starts
to cause damage and edema in only 24 hours (at normal atmospheric
pressure-- even faster at higher pressures).  Getting oxygen by prong
tube in your nose is not going to get you more than about 30%.  It's
almost impossible to get above 50%, even with a mask, due to leaks
around the mask when people inhale.  High % O2 must be delivered by
intubation.

                                      Steve Harris, M.D.

From: sbharris@ix.netcom.com (Steven B. Harris )
Subject: Re: Breathing pure oxygen
Date: 22 Sep 1995
Newsgroups: sci.med

In <43qt9n$k5d@ixnews5.ix.netcom.com> john_de@ix.netcom.com (John
DeFiore ) writes:

>In <43o90c$8s4@newsbf02.news.aol.com> pulmon@aol.com (Pulmon) writes:
>>
>>Breathing pure oxygen at sea level (1 atmosphere) will result in fatal
>>lung disease in about 48 hours.
>
>What is the mechanism?



  Some kind of oxidation injury to membranes in lung tissue.  Probably
standard free radical type stuff.  You can measure increases in pentane
and ethane production, and these are mediated by direct oxidation of
membrane unsaturated fatty acids.  It's very much like what happens
when oil-based paint "dries".

                                             Steve Harris, M.D.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.skeptic,sci.physics,alt.folklore.computers,alt.folklore.science
Subject: Re: Wanted: D20-free water supply
Date: 6 Nov 1998 21:41:14 GMT

In <71v5pc$v0m$4@node2.nodak.edu> thweatt@prairie.NoDak.edu (Superdave
the Wonderchemist) writes:

>tim@wfn-shop.princeton.edu wrote:
>
>: In article <363BBC6D.5C939EA@interlog.com>, Dan Evens
>: <danevens@interlog.com> writes:
>:
>: > Would you willingly consume 1% of a lethal dose of any other poison?
>
>: Hmm.  It'd be interesting to see a list of poisons of which people
>: regularly consume 1% of a lethal dose.  Ethanol is certainly on the
>: list, since you're allowed to *drive* after consuming (roughly) a bit
>: less than 10% of a potentially lethal dose.  I suspect most sedatives
>: are as well.
>
>Oxygen.  We live comfortably in an environment where the partial pressure
>of O2 is about .2 ATM.  Without O2 we would die (duh) in a matter of
>minutes.  However at 2ATM partial pressure of O2, we would also die.


At anything much over 0.5 atm O2 partial pressure you'll suffer
increasing lung damage (over days to weeks, depending) and eventually
die.  So normal partial pressure is 30-40% of the damaging and
eventually lethal "dose."