X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Wed, 13 Sep 2006 19:12:50 -0400 Message-ID: X-Original-Return-Path: Received: from ms-smtp-04.tampabay.rr.com ([65.32.5.134] verified) by logan.com (CommuniGate Pro SMTP 5.1c.4) with ESMTP id 1401885 for lml@lancaironline.net; Wed, 13 Sep 2006 18:56:54 -0400 Received-SPF: pass receiver=logan.com; client-ip=65.32.5.134; envelope-from=tednoel@cfl.rr.com Received: from tednoel (230.80.118.70.cfl.res.rr.com [70.118.80.230]) by ms-smtp-04.tampabay.rr.com (8.13.6/8.13.6) with SMTP id k8DLuIPC023957 for ; Wed, 13 Sep 2006 17:56:19 -0400 (EDT) X-Original-Message-ID: <048201c6d77f$78249680$0402a8c0@tednoel> From: "Ted Noel" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: High Altitude Oxygen Failure X-Original-Date: Wed, 13 Sep 2006 17:56:29 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_047F_01C6D75D.F0BF7F50" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_047F_01C6D75D.F0BF7F50 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Bob, Are you sure you're not an anesthesiologist? You got the alveolar gas = equation right, even though you left out the effects of exhaled CO2 (it = makes things worse.). I would like to see a source for the overpressure = limitation you cite. Ted Noel MD Diplomate, American Board of Anesthesiology N540TF ----- Original Message -----=20 From: bob mackey=20 To: Lancair Mailing List=20 Sent: Wednesday, September 13, 2006 5:33 PM Subject: [LML] Re: High Altitude Oxygen Failure > 100% oxygen will delay the point at which the dropping > pressure results in hypoxia, but eventually you WILL=20 > reach an altitude where the ambient pressure no longer=20 > forces a gas exchange in the lungs. Not even 100% oxygen > will help at that point.=20 This is true, but the physics behind it has not been=20 explained properly. The oxygen exchange between the=20 blood and the oxygen in the lungs does not require an overpressure as previously stated. Instead, the=20 problem is getting oxygen into the lungs at high=20 altitude.=20 Note that we all have about the same body temperature,=20 98.6 F or 36 C. At that temperature, the vapor pressure of water is 47 Torr (47 mmHg =3D 1.85 inHg).=20 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=20 water from your lungs to evaporate and completely fill=20 the lung volume. No air enters the trachea as a result=20 of lung expansion. That happens at an altitude of 18500 m or 60,000 feet. At that altitude is is not possible to=20 get *any* oxygen into the lungs by exercising the=20 diaphragm -- while the body is still at 37C, which=20 won't be long.=20 At 35,000', the outside air pressure is sufficient to=20 push pure oxygen into the lung spaces -- just barely.=20 Pressure breathing helps keep some oxygen in the=20 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.=20 At 25,000', breathing 100% O2 at ambient pressure is=20 sufficient for healthy adults to maintain blood saturation in the 90+% range. Smokers may be completely hypoxic.=20 BTW, my vocal cords quit working at about 25,000'.=20 There isn't enough air density for me to drive the=20 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=20 sailplane.=20 -bob -------------------------------------------------------------------------= ----- Get your own web address for just $1.99/1st yr. We'll help. Yahoo! = Small Business. ------=_NextPart_000_047F_01C6D75D.F0BF7F50 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Bob,
 
Are you sure you're not an = anesthesiologist? You=20 got the alveolar gas equation right, even though you left out the = effects of=20 exhaled CO2 (it makes things worse.). I would like to see a source for = the=20 overpressure limitation you cite.
 
Ted Noel MD
Diplomate, American Board of=20 Anesthesiology
N540TF
----- Original Message -----
From:=20 bob = mackey
Sent: Wednesday, September 13, = 2006 5:33=20 PM
Subject: [LML] Re: High = Altitude Oxygen=20 Failure

> 100% oxygen will delay the = point at=20 which the dropping
> pressure results in hypoxia, but eventually = you=20 WILL
> reach an altitude where the ambient pressure no longer =
>=20 forces a gas exchange in the lungs. Not even 100% oxygen
> will = help at=20 that point.

This is true, but the physics behind it has not = been=20
explained properly. The oxygen exchange between the
blood and = the=20 oxygen in the lungs does not require
an overpressure as previously = stated.=20 Instead, the
problem is getting oxygen into the lungs at high=20
altitude.

Note that we all have about the same body = temperature,=20
98.6 F or 36 C. At that temperature, the vapor pressure
of = water is 47=20 Torr (47 mmHg =3D 1.85 inHg).=20 =
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/watvap.html#c1
= http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/watvap.html#c2

= At=20 what altitude is the outside air pressure 47 Torr?
At that = altitude,=20 expanding your lungs will cause
water from your lungs to evaporate = and=20 completely fill
the lung volume. No air enters the trachea as a = result=20
of lung expansion. That happens at an altitude of 18500 m
or = 60,000=20 feet. At that altitude is is not possible to
get *any* oxygen into = the=20 lungs by exercising the
diaphragm -- while the body is still at = 37C, which=20
won't be long.

At 35,000', the outside air pressure is = sufficient=20 to
push pure oxygen into the lung spaces -- just barely. =
Pressure=20 breathing helps keep some oxygen in the
mixture as well as all = that water=20 vapor. People can
tolerate an overpressure of only about 0.5 psi (1 = inHg),=20 so a pressure mask can only help a little bit.

At 25,000', = breathing=20 100% O2 at ambient pressure is
sufficient for healthy adults to = maintain=20 blood saturation
in the 90+% range. Smokers may be completely = hypoxic.=20

BTW, my vocal cords quit working at about 25,000'.
There = isn't=20 enough air density for me to drive the
vibrations that make voice = sounds.=20 At 25-30K, I can
croak a bit, but cannot make myself understood = over
a=20 radio. I didn't notice this in the Miramar pressure
chamber, but = found out=20 later over the Sierras in a
sailplane. =

-bob

Get your own web=20 address for just $1.99/1st yr. We'll help. Yahoo!=20 Small Business. ------=_NextPart_000_047F_01C6D75D.F0BF7F50--