X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 29 Nov 2008 22:08:48 -0500 Message-ID: X-Original-Return-Path: Received: from imo-d20.mx.aol.com ([205.188.139.136] verified) by logan.com (CommuniGate Pro SMTP 5.2.10) with ESMTP id 3323152 for lml@lancaironline.net; Sat, 29 Nov 2008 20:40:35 -0500 Received: from Sky2high@aol.com by imo-d20.mx.aol.com (mail_out_v39.1.) id q.c79.48bd3a01 (65098) for ; Sat, 29 Nov 2008 20:40:33 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Sat, 29 Nov 2008 20:40:33 EST Subject: Re: [LML] Re: 360's at high altitudes X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1228009233" X-Mailer: AOL 9.1 sub 5000 X-Spam-Flag:NO -------------------------------1228009233 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en Well, You and other doctors may believe what you want - I am evidence that =20 #1 below may be a normal response, but it did not happen that way to me. =20 Thus, all of you abnormal pilots out there should consider the value of a p= ulse=20 oximeter. =20 Those of you flying pressurized planes should be concerned with sudden =20 decompression The rest of us have to be concerned about insidious creeping =20= hypoxia=20 (i.e. on a long, mid-altitudes (8000-10000) flight on a hot day). Second o= f=20 all, density altitude should always be considered, not MSL regardless of=20 what the FAA says. And, I will repeat that any individual's response can va= ry=20 because of physical state, fatique, age, weight, etc. =20 See also: =20 _http://www.aeromedix.com/category-exec/parent_id/1/category_id/6/nm/Pulse_O= xi meters_=20 (http://www.aeromedix.com/category-exec/parent_id/1/category_id/6/nm/Pulse_O= ximeters)=20 =20 I have evidence that a person flying commercially at a cabin altitude of =20 8000 feet exhibited the symptoms of hypoxia after falling asleep (shallow =20 breathing) and suffering with the anxiety of repeating her experience again= . =20 You may not want to rely on an oximeter, but it's use and readings are far =20 better than succumbing to even mild hypoxia while piloting. You should be=20 able to recognize hyperventilation and stop it. =20 Your experience may vary. =20 =20 Scott Krueger AKA Grayhawk LNC2 N92EX IO 320 SB 89/96 In a message dated 11/29/2008 6:52:16 P.M. Central Standard Time, =20 rmitch1@hughes.net writes: =20 I guess I showed my obsolescence with the observation about welder=E2=80= =99s oxygen,=20 as one person on the list stated, =E2=80=9Cthey were different twenty years= ago=E2=80=9D, I=20 didn=E2=80=99t realize the spec=E2=80=99s had changed.=20 However, over-reliance on finger pulse oximetry is something that pilot=E2= =80=99s=20 need to understand. The reason is that pulse oximetry measures O2 saturati= on=20 in peripheral blood, which may be different from cerebral oxygen saturation= ,=20 and may lag behind.=20 For more info read the article below which appeared on our international AM= E=20 list. More than a few docs on the list are professors or research docs. =20 They essentially all agree with the concepts.=20 Bob Mitchell=20 L-320=20 Senior AME =20 At the Airlines Medical Directors Association scientific meeting in Orlando= =20 in 2006, Professor John Ernsting presented a joint paper with Group Captain= =20 David Gradwell summarising the theoretical and experimental results of the=20 effect of hyperventilation on arterial oxygen saturation. =20 They concluded that the limitations of pulse oximetry in hypoxia should be=20 widely recognised in aviation. Here are the reasons.=20 Reduction of alveolar PCO2 (partial pressure CO2) to 20 mmHg when breathin= g=20 air at 14k raises arterial SO2 (oxygen Saturation) to 96%, which is produce= d=20 in the absence of hyperventilation by breathing air at 1,500 feet.=20 A degree of hyperventilation is the normal response to acute exposure of=20 breathing air at or above 8,000 feet.=20 Using the relationship between arterial PCO2, arterial SO2 and jugular=20 venous PO2 (partial pressure oxygen), it can be calculated that when air is= =20 breathed at altitudes above 10k, arterial oxygen saturation is a very poor=20 indicator of minimum=20 PO2 in the brain if the individual is hyperventilating. This also applies=20 when oxygen-air gas mixtures are breathed to avoid significant hypoxia at=20 altitude. This is because hyperventilation is known to have a very large ef= fect on=20 arterial SO2 in hypoxia, which is not matched by the cerebral SO2.=20 Professor Ernsing's and David Gradwell's paper confirmed this theoretical=20 calculation by experimental study. The results showed that hyperventilation= =20 which reduced the end-tidal PCO2 produced large increases in arterial SO2 w= hich=20 was not matched by increases in cerebral SO2.=20 The take-home message, which we should share with our high-flying general=20 aviation colleagues, can be summarised thus:=20 1) Hyperventilation is a normal response to any degree of hypoxia.=20 2) This hyperventilation affects the peripheral arterial oxygen saturation= .=20 3) The result is that a pulse oximeter can give misleading information abou= t=20 the saturation of oxygen in the cerbral circulation. Unfortunately, it is=20 not 'fail-safe' because the pulse oximeter may provide reassurance about=20 satisfactory arterial SO2 when in fact the brain is hypoxic.=20 4) Pulse oximetry is a useful tool, but its limitations in aviation must be= =20 recognised. Ideally, an oxygen-enriched gas should be breathed whenever=20 flying above a cabin altitude of 10,000feet.=20 **************Life should be easier. So should your homepage. Try the NEW=20 AOL.com.=20 (http://www.aol.com/?optin=3Dnew-dp&icid=3Daolcom40vanity&ncid=3Demlcntaolco= m00000002) -------------------------------1228009233 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
Well, You and other doctors may believe what you want - I am evidence t= hat=20 #1 below may be a normal response, but it did not happen that way to=20 me.  Thus, all of you abnormal pilots out there should consider the val= ue=20 of a pulse oximeter.
 
Those of you flying pressurized planes should be concerned with sudden=20 decompression The rest of us have to be concerned about insidious creeping=20 hypoxia (i.e. on a long, mid-altitudes (8000-10000) flight on a hot day).&nb= sp;=20 Second of all, density altitude should always be considered, not MSL regardl= ess=20 of what the FAA says. And, I will repeat that any individual's response = ;can=20 vary because of physical state, fatique, age, weight, etc.
 
See also:
 
http://www.aeromedix.com/category-exec/parent_id/1/category= _id/6/nm/Pulse_Oximeters
 
I have evidence that a person flying commercially at a cabin altitude o= f=20 8000 feet exhibited the symptoms of hypoxia after falling asleep (shallow=20 breathing) and suffering with the anxiety of repeating her experience=20 again.
 
You may not want to rely on an oximeter, but it's use and readings are=20= far=20 better than succumbing to even mild hypoxia while piloting.  You=20 should be able to recognize hyperventilation and stop it.
 
Your experience may vary. 
 
Scott Krueger AKA Grayhawk
LNC2 N92EX IO 320 SB 89/96
 
In a message dated 11/29/2008 6:52:16 P.M. Central Standard Time,=20 rmitch1@hughes.net writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>

I guess= I=20 showed my obsolescence with the observation about welder=E2=80=99s oxygen,= as one=20 person on the list stated, =E2=80=9Cthey were different twenty years ago= =E2=80=9D, I didn=E2=80=99t=20 realize the spec=E2=80=99s had changed.

&n= bsp;

However= ,=20 over-reliance on finger pulse oximetry is something that pilot=E2=80=99s n= eed to=20 understand.  The reason is that pulse oximetry measures O2 saturation= in=20 peripheral blood, which may be different from cerebral oxygen saturation,=20= and=20 may lag behind.

&n= bsp;

For mor= e info=20 read the article below which appeared on our international AME list. = =20 More than a few docs on the list are professors or research docs.  Th= ey=20 essentially all agree with the concepts.

&n= bsp;

Bob=20 Mitchell

L-320

Senior=20= AME=20

 

 

At the Airlines Medi= cal=20 Directors Association scientific meeting in Orlando in 2006, Professor John Ernstin= g=20 presented a joint paper with Group Captain David Gradwell summarising the=20 theoretical and experimental results of the effect of hyperventilation on=20 arterial oxygen saturation. 

They concluded that=20= the=20 limitations of pulse oximetry in hypoxia should be widely recognised in=20 aviation. Here are the reasons.

Reduction of alveola= r PCO2=20 (partial pressure CO2)=20 to 20 mmHg when breathing air at 14k raises arterial SO2 (oxygen Saturation) to=20 96%, which is produced in the absence of hyperventilation by breathing air= at=20 1,500=20 feet.

A degree of=20 hyperventilation is the normal response to acute exposure of breathing air= at=20 or above 8,000=20 feet.

Using the relationsh= ip=20 between arterial PCO2, arterial SO2 and jugular venous PO2 (partial pressure oxygen)= ,=20 it can be calculated that when air is breathed at altitudes above 10k,=20 arterial oxygen saturation is a very poor indicator of=20 minimum

PO2 in the brain if=20= the=20 individual is hyperventilating. This also applies when oxygen-air gas mixt= ures=20 are breathed to avoid significant hypoxia at altitude. This is because=20 hyperventilation is known to have a very large effect on arterial SO2 in=20 hypoxia, which is not matched by the cerebral=20 SO2.

Professor Ernsing's=20= and=20 David Gradwell's paper confirmed this theoretical calculation by experimen= tal=20 study. The results showed that hyperventilation which reduced the end-tida= l=20 PCO2 produced large increases in arterial SO2 which was not matched by=20 increases in cerebral SO2.

The take-home messag= e,=20 which we should share with our high-flying general aviation colleagues, ca= n be=20 summarised thus:

 

1) Hyperventilation=20= is a=20 normal response to any degree of hypoxia.

2) This hyperventila= tion=20 affects the peripheral arterial oxygen=20 saturation.

3) The result is tha= t a=20 pulse oximeter can give misleading information about the saturation of oxy= gen=20 in the cerbral circulation. Unfortunately, it is not 'fail-safe' because t= he=20 pulse oximeter may provide reassurance about satisfactory arterial SO2 whe= n in=20 fact the brain is hypoxic.

4) Pulse oximetry is= a=20 useful tool, but its limitations in aviation must be recognised. Ideally,=20= an=20 oxygen-enriched gas should be breathed whenever flying above a cabin altit= ude=20 of 10,000feet= .

 

 



Life should be easier. So should y= our homepage. Try the NEW AOL.com.
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