X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Wed, 13 Sep 2006 17:33:12 -0400 Message-ID: X-Original-Return-Path: Received: from web34912.mail.mud.yahoo.com ([209.191.68.191] verified) by logan.com (CommuniGate Pro SMTP 5.1c.4) with SMTP id 1401394 for lml@lancaironline.net; Wed, 13 Sep 2006 13:11:48 -0400 Received-SPF: none receiver=logan.com; client-ip=209.191.68.191; envelope-from=n103md@yahoo.com Received: (qmail 58526 invoked by uid 60001); 13 Sep 2006 17:10:59 -0000 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=Message-ID:Received:Date:From:Subject:To:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=Up218fkatKkc6A4IlvlPs77bC9j6ZNNTp7r0qwjWp9PJjJuuLa9B0pgyjl0/4y/qENko5lVx30ojoNLMfBcYMay/phhvFRXKGhhe5Or/L6Osj4lx1aU6sPnQP4xKHV7CawS0Q3iZBzmqOHMl0g4OyAser7Uzw/bgSsW0GvPMoxE= ; X-Original-Message-ID: <20060913171059.58524.qmail@web34912.mail.mud.yahoo.com> Received: from [69.12.132.145] by web34912.mail.mud.yahoo.com via HTTP; Wed, 13 Sep 2006 10:10:59 PDT X-Original-Date: Wed, 13 Sep 2006 10:10:59 -0700 (PDT) From: bob mackey Subject: RE: High Altitude Oxygen Failure X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="0-1013161409-1158167459=:47009" Content-Transfer-Encoding: 8bit --0-1013161409-1158167459=:47009 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit > 100% oxygen will delay the point at which the dropping > pressure results in hypoxia, but eventually you WILL > reach an altitude where the ambient pressure no longer > forces a gas exchange in the lungs. Not even 100% oxygen > will help at that point. This is true, but the physics behind it has not been explained properly. The oxygen exchange between the blood and the oxygen in the lungs does not require an overpressure as previously stated. Instead, the problem is getting oxygen into the lungs at high altitude. Note that we all have about the same body temperature, 98.6 F or 36 C. At that temperature, the vapor pressure of water is 47 Torr (47 mmHg = 1.85 inHg). http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/watvap.html#c1 http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/watvap.html#c2 At what altitude is the outside air pressure 47 Torr? At that altitude, expanding your lungs will cause water from your lungs to evaporate and completely fill the lung volume. No air enters the trachea as a result of lung expansion. That happens at an altitude of 18500 m or 60,000 feet. At that altitude is is not possible to get *any* oxygen into the lungs by exercising the diaphragm -- while the body is still at 37C, which won't be long. At 35,000', the outside air pressure is sufficient to push pure oxygen into the lung spaces -- just barely. Pressure breathing helps keep some oxygen in the mixture as well as all that water vapor. People can tolerate an overpressure of only about 0.5 psi (1 inHg), so a pressure mask can only help a little bit. At 25,000', breathing 100% O2 at ambient pressure is sufficient for healthy adults to maintain blood saturation in the 90+% range. Smokers may be completely hypoxic. BTW, my vocal cords quit working at about 25,000'. There isn't enough air density for me to drive the vibrations that make voice sounds. At 25-30K, I can croak a bit, but cannot make myself understood over a radio. I didn't notice this in the Miramar pressure chamber, but found out later over the Sierras in a sailplane. -bob --------------------------------- Get your own web address for just $1.99/1st yr. We'll help. Yahoo! Small Business. --0-1013161409-1158167459=:47009 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: 8bit > 100% oxygen will delay the point at which the dropping
> pressure results in hypoxia, but eventually you WILL
> reach an altitude where the ambient pressure no longer
> forces a gas exchange in the lungs. Not even 100% oxygen
> will help at that point.

This is true, but the physics behind it has not been
explained properly. The oxygen exchange between the
blood and the oxygen in the lungs does not require
an overpressure as previously stated. Instead, the
problem is getting oxygen into the lungs at high
altitude.

Note that we all have about the same body temperature,
98.6 F or 36 C. At that temperature, the vapor pressure
of water is 47 Torr (47 mmHg = 1.85 inHg).
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/watvap.html#c1
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/watvap.html#c2

At what altitude is the outside air pressure 47 Torr?
At that altitude, expanding your lungs will cause
water from your lungs to evaporate and completely fill
the lung volume. No air enters the trachea as a result
of lung expansion. That happens at an altitude of 18500 m
or 60,000 feet. At that altitude is is not possible to
get *any* oxygen into the lungs by exercising the
diaphragm -- while the body is still at 37C, which
won't be long.

At 35,000', the outside air pressure is sufficient to
push pure oxygen into the lung spaces -- just barely.
Pressure breathing helps keep some oxygen in the
mixture as well as all that water vapor. People can
tolerate an overpressure of only about 0.5 psi (1 inHg), so a pressure mask can only help a little bit.

At 25,000', breathing 100% O2 at ambient pressure is
sufficient for healthy adults to maintain blood saturation
in the 90+% range. Smokers may be completely hypoxic.

BTW, my vocal cords quit working at about 25,000'.
There isn't enough air density for me to drive the
vibrations that make voice sounds. At 25-30K, I can
croak a bit, but cannot make myself understood over
a radio. I didn't notice this in the Miramar pressure
chamber, but found out later over the Sierras in a
sailplane.

-bob


Get your own web address for just $1.99/1st yr. We'll help. Yahoo! Small Business. --0-1013161409-1158167459=:47009--