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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Tue Jan 17, 2006 9:51 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

Roger Kemp wrote:

 	  Quote: 	
		   

 

 Brian,

  Best check again on the nitrogen Narcosis thing at altitude It happens. 

 It is called decompression sickness. 


	


Go read your books again. Nitrogen narcosis is a malady that occurs when

too much N2 is dissolved in the tissues, especially the tissues of the

nervous system. The symptoms are similar to drunkenness but

hallucination is not uncommon. Divers who are "narc'd" have been known

to offer their regulator mouthpiece to passing fish. When N2 is

dissolved in the tissues it isn't coming out in bubbles.



When the body then decompresses again if it is done too quickly, the N2

can come out of the tissue in bubbles. These tend to lodge in the joints

and cause pain which often causes the victim to contort him/herself in

an attempt to relieve the pain, hence the term "the bends". The official

name for this malady is decompression sickness. This is a completely

different malady from nitrogen narcosis. Both involve nitrogen, both

involve pressure change, but the pathology is different as are the symptoms.



 	  Quote: 	
		   The treatment for it is recompression in a dive chamber. 


	


The treatment for decompression sickness is to increase the pressure

again so that the N2 goes back into solution in the blood and tissues.



The prevention of decompression sickness is to reduce the pressure

gradually so that the excess N2 in the tissues can stay in solution and

move into the bloodstream where it can move to the lungs and be exhaled.



 	  Quote: 	
		   I  have had to fly two military aviators to the chamber

 one at Brooks, AFB and the other was at Beale AFB. Both  had to be flown

 with the cabin pressurized to sea level because of the risk of worsening

 the decompression sickness. One of those pilots was my Squadron cc. He had

 a gradual cabin pressure leak due to a slow leaking canopy seal. 


	


Had he been diving? Remember, the pressure change going from sea level

to FL250 is less than the pressure change from the surface to 30 feet

underwater. I suppose it is possible for someone to get decompression

sickness loss of cabin pressure but a slow leak is unlikely to cause the

problem. I am not saying it can't happen but I am skeptical unless there

was some other mechanism acting to raise the level of N2 in the tissue.

Living at sea level is not likely to cause enough N2 to dissolve in the

blood to cause the bends to happen at FL250, especially if the pressure

drops gradually.



 	  Quote: 	
		   There are two ways to get the "Bends."  One is from decompression and the

 other is from compression. 


	


Sorry, no. The Bends occur *only* on decompression. Compression just

causes more N2 to dissolve in the tissues. If the person is suffering

from The Bends recomressing him/her causes the N2 bubbles to go back

into solution. Once that happens you can begin slow decompression thus

allowing the N2 to slowly and safely move from the tissue to the blood

to the lungs and then be exhaled.



 	  Quote: 	
		   In either case, N2 comes out of solution in blood. 


	


No, it doesn't. It *only* does that on decompression, hence the name

decompression sickness.



 	  Quote: 	
		   It  coleses into gas bubbles in the tissue. Most commonly in an

 injured joint. It also can happen in the spinal cord, brain (neurological

 nitrogen narcosis), and the pulmonary tree. (the chokes). That is putting

 it in simple terms.


	


You are describing only decompression sickness. You also called it

nitrogen narcosis which it isn't. Now nitrogen narcosis does happen when

you compress the body in the presence of N2. The greater the pressure,

the greater the symptoms of narcosis.



This is why divers use special breathing gasses that reduce or eliminate

the N2 in the breathing mix (heliox or nitrox) -- so that they are less

likely to experience narcosis while down and less likely to experience

The Bends upon ascending.



 	  Quote: 	
		   In otherwords, every time you take that unpressurised twin above FL 180,

 you are at risk for for developing the "bends".


	


Any time you reduce the pressure on the body there is some chance of

developing decompression sickness. OTOH, the chance is very, very,

*VERY* small for people living at sea level or above who don't dive and

smaller still if the pressure change is gradual, i.e. standard rates of

ascent and not explosive decompression. I think if you go back and

research this you will find that this is an *extremely* rare event.



As a pilot who spent three years operating in the Virgin Islands who

dives and flies, I am *VERY* aware of the dangers from rapid pressure

changes and of going directly from a dive to a flight in an airplane.

For safety we use a rule of thumb of 24 hours between a decompression

dive to a flight because we know that even after a successful and safe

decompression dive, the tissues are still saturated to a higher level of

N2 than someone who has not been diving. The extra 24 hours allows the

body to come back to equilibrium before flying. My rule of thumb is

that, if you have been diving today, we don't fly until tomorrow.



So, yeah, I have some idea how all this works. The threat is vanishingly

small compared to what you are implying unless you have been diving and

then the threat is very real.



And nitrogen narcosis is NOT decompression sickness.



-- 

Brian Lloyd                         2243 Cattle Dr.

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Tue Jan 17, 2006 10:18 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

But don't take my word for it. Here is a really good article on what

nitrogen narcosis is.



http://en.wikipedia.org/wiki/Nitrogen_narcosis



-- 

Brian Lloyd                         2243 Cattle Dr.

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

cjpilot710(at)aol.com
Guest

Posted: Wed Jan 18, 2006 5:27 am Post subject: decompression sickness and narcosis (was: AYS-bound)

Frankly I don't see any  difference except by degree.

  

 You takeoff and go up -  - you decompress.

 You come down to  land  - -  you compress.

  

 You jump in the water  and go down - -  you compress.

 You (hopefully) bob to  the surface - - you decompress.

  

 Now you can never go  deeper (there is a bottom) than you go high (a vacuum mean decompress  right?  Boy, I bet that would hurt ).

  

 But water is thicker  than air, sooooooo it would have more effect per foot than air.   

  

 But how fast you go up  in the air would have the same effect as if you went up to fast in water?   So a guy is sitting in a rocket is going to have the same effect on him as  a guy coming up from the bottom of the ocean?

  

 Hmmmmmmmmmmmmmmm

  

 Gee I'm being to see  what that old fart ment: "If God want man to swim He'd given him fins and he  were suppose to fly He'd given him feathers.  Dearn  foolishness!"

  

 FD44- CAVU, brisk  breeze from the NW, 55 F on the patio.

  

 Jim " Pappy"  Goolsby

viperdoc(at)mindspring.co
Guest

Posted: Wed Jan 18, 2006 7:11 am Post subject: decompression sickness and narcosis (was: AYS-bound)

Well Pappy, in your infinite wisdom you have boiled the issue of altitude verses diving decompression sickness down to its essence. Brilliant! As I was prepared to condense the 1st 8 chapters of Fundamentals of Aerospace Medicine Third Edition, Roy L. DeHart  M.D. MPH, M.S.I.A., pp.1-161, Diving Medicine Second Edition, Alfred A. Bove, M.D. and Jefferson C. Davis, M.D., pp. 5-47, The Society of United States Air Force Flight Surgeons Check List,revised biannually by the USAFSAM residents- 5th edition, pp 83-85 (the down and dirty version) for a discussion of decompression sickness Type I and Type II. But, Pappy since you so eloquently boiled this topic down to its essence, I will refrain from discussions of partial pressures of nitrogen, water, oxygen, carbon dioxide, and inert gasses at 1/2 ATA, 1/4 ATA, 0.10 ATA, 1 ATA, 2 ATA, 3 ATA, and 4 ATA. These all being common altitudes and feet of sea water that man   flying and diving are exposed to. Brian will only claim to know more.

 Dogmatic Viperdoc

 Roger W. Kemp M.D.

 Col. M.C., CFS

 State Air Surgeon

 HQ ALANG

 Senior Aeromedical Examiner -FAA

 Boarded in Anesthesia and Pain Management.

 With a whole lot of alphebet following my name down.

  

  

 



  

 [quote] ---

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Wed Jan 18, 2006 9:32 am Post subject: decompression sickness and narcosis (was: AYS-bound)

Roger Kemp wrote:

 	  Quote: 	
		   Well Pappy, in your infinite wisdom you have boiled the issue of

 altitude verses diving decompression sickness down to its essence.

 Brilliant! As I was prepared to condense the 1st 8 chapters of

 _Fundamentals of Aerospace Medicine Third Edition,_ Roy L. DeHart  M.D.

 MPH, M.S.I.A., pp.1-161, _Diving Medicine_ Second Edition, Alfred A.

 Bove, M.D. and Jefferson C. Davis, M.D., pp. 5-47, _The Society of

 United States Air Force Flight Surgeons Check List_,revised biannually

 by the USAFSAM residents- 5th edition, pp 83-85 (the down and dirty

 version) for a discussion of decompression sickness Type I and Type II.

 But, Pappy since you so eloquently boiled this topic down to its

 essence, I will refrain from discussions of partial pressures of

 nitrogen, water, oxygen, carbon dioxide, and inert gasses at 1/2 ATA,

 1/4 ATA, 0.10 ATA, 1 ATA, 2 ATA, 3 ATA, and 4 ATA. These all being

 common altitudes and feet of sea water that man flying and diving are

 exposed to. Brian will only claim to know more.


	


I don't claim to know more. But I do know when I am right. When I am not

sure I look it up. When it is not a topic I have studied I let someone

else speak in the hope that I will learn something.



That you are an MD with a whole alphabet behind your name does not make

you automatically correct and/or immune from making mistakes. But you

made an error. You then compounded that error when you argue about

correcting your error.



You know what Doc? I don't think I am either smarter or more

knowledgeable than you are. You don't manage to become an MD by being an

idiot. Given that you have been trained far more than I have in this

area I would expect you would have much more knowledge than I. But I

make it a point to know a fair bit about the things that I do. I try to

ensure that the information I have and that I give to my students (in

many areas) is correct. If I discover that I am wrong I go back and make

sure that I correct that information.



This is actually kind of scary. There are probably people who base

life-critical decisions on what you tell them. I now see that, when

faced with evidence that you have made a mistake, rather than saying,

"gee, you're right and I will correct the information," you go off and

try to blow smoke up everyone's ass. You will belittle the source of the

correct information in an attempt to get people to ignore the source

rather than ensure that the others around you have the correct

information. Yup, that is just plain ol' f----- scary.



And Pappy is right about it all being about pressure. It is just that

the devil is in the details. Albert Einstein one put it very succinctly

when he said, "Things should be made as simple as possible -- and no

simpler."



 	  Quote: 	
		   Dogmatic Viperdoc

 Roger W. Kemp M.D.

 Col. M.C., CFS

 State Air Surgeon

 HQ ALANG

 Senior Aeromedical Examiner -FAA

 Boarded in Anesthesia and Pain Management.

 With a whole lot of alphebet following my name down.


	


-- 

Brian Lloyd

Gadfly

Annoying son-of-a-bitch

Asshole

Plain ol' guy with no alphabet after his name

Ordinary pilot

Ordinary CFI



	-- but right

Ernie

Joined: 11 Jan 2006
Posts: 513

Posted: Wed Jan 18, 2006 10:56 am Post subject: decompression sickness and narcosis (was: AYS-bound)

We call it being "Narced" in diving circles. Diving physiology 101.

You go deep, compress, and nitrogen disolves into your tissues, and

you get into a druken like state due to factors beyond my knowledge.

Decompression sickeness also called the bends, is from rapid

de-compression and nitrogen quickly coming out of its soluable state

and back into a gas in your arteries, shake a can of Coke and open,

same thing occurs except its CO2 doing its thing. Those bubbles will

can cause pain or even death due to brain embolisms.



Being narced and the bends are 2 different things and happen at 2 ends

of the spectrum. The only way you would get narced at altitude is if

you were at 90,000 ft and dropped to 20,000 in about 5 seconds, but

getting narced would be the least of your worries.



We have dive computers and tables that we follow which tells us how

many hours we have to wait before acending to any altitude depending

on our dive profile, in order to avoid the bends.



Ernie

viperdoc(at)mindspring.co
Guest

Posted: Wed Jan 18, 2006 12:04 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

Brian,

You are right Narcosis is a malady of descent generally below 150 feet

ocean water. I wrote wrong the term when I was speaking of decompression.

Both are related to Nitrogen going into and out of solution in the blood

and tissue. 

My first statement about pre-breathing 100% O2 prior to ascending to an

unpressurized altitude was in reference (inferred at the time) to

decreasing the risk of altitude decompression sickness. For that you

asserted that you can only get decompression sickness from diving. And

there you are also wrong. I am wrong for saying Nitrogen Narcosis and you

are wrong for asserting that decompression only comes from ascending from a

compression dive. 

The symptoms of Nitrogen Narcosis and Neurological Decompression sickness

can be strikingly similar. One is from descent and the effect of an

increased partial pressure of Nitrogen and other inert gases in

neurological tissue causing mental disorientation. Neurological

Decompression is nitrogen bubbles forming emboli after coming out of

solution as one ascends either from a depth of sea water or from sea level

to altitude. In each case the the common thread is that  the the pressure

decreased after the diver or the aviator was subjected to an increased

atmospheric pressure.

An aviator climbing from 1 ATA at sea level to 1/2 ATA at 18000 ft or 1/4

ATA at 33500ft unpressurized is at an increased risk for nitrogen coming

out of solution and forming "bubbles". The same for the diver that was at 4

ATA ~ 100 feet of sea water (fresh water also) and ascending to the surface

without percautionary decompression stops (not that is always protective

either). Yes, bottom time does influence the risk of developing the

"bends". As does other factors such as dehydration, fatigue, exercise at

depth or exercise prior to diving.

Nitrogen Narcosis is from the increased nitrogen in solution disrupting the

electrical potential transfer across the pre and post synaptic cleft of the

CNS. This most likely being in the Reticular Activating system and the

Cortical mantle. It follows the Meyer-Overton hypothesis that states "all

gaseous or volatile substances induce narcosis if they penetrate the lipids

of the cell wall in a definate molar concentraion that is characaristic for

each type of animal tissue aand approximately the same for all narcotics."

That is measured by the mean alveolar concentration (MAC) of the anesthetic

agent. The measure of an anesthetic concentration of an inert gas is the

concentration of the gas at which only 50% of rats will respond to pinching

their tail with a ring forcep. The so called MAC 50.  So that is the theory

behind why we can give you an inhaled anesthetic at a concentration

inspired greater than sea level concentration and induce amnesia with

sedation for surgery. 

We are comparing Apples and Oranges here.

Sorry Brian for mis-stating Narcosis instead of altitude decompression last

night at 11:20.

Doc 

 	  Quote: 	
		   [Original Message]

 From: Brian Lloyd <brian-yak(at)lloyd.com>

 To: <yak-list(at)matronics.com>

 Date: 1/17/2006 11:51:15 PM

 Subject: decompression sickness and narcosis (was: AYS-bound)

 Roger Kemp wrote:

 > 

 > 

 > Brian,

 >  Best check again on the nitrogen Narcosis thing at altitude It

happens. 

 	  Quote: 	
		   > It is called decompression sickness. 

 Go read your books again. Nitrogen narcosis is a malady that occurs when

 too much N2 is dissolved in the tissues, especially the tissues of the

 nervous system. The symptoms are similar to drunkenness but

 hallucination is not uncommon. Divers who are "narc'd" have been known

 to offer their regulator mouthpiece to passing fish. When N2 is

 dissolved in the tissues it isn't coming out in bubbles.

 When the body then decompresses again if it is done too quickly, the N2

 can come out of the tissue in bubbles. These tend to lodge in the joints

 and cause pain which often causes the victim to contort him/herself in

 an attempt to relieve the pain, hence the term "the bends". The official

 name for this malady is decompression sickness. This is a completely

 different malady from nitrogen narcosis. Both involve nitrogen, both

 involve pressure change, but the pathology is different as are the

symptoms.

 	  Quote: 	

 > The treatment for it is recompression in a dive chamber. 

 The treatment for decompression sickness is to increase the pressure

 again so that the N2 goes back into solution in the blood and tissues.

 The prevention of decompression sickness is to reduce the pressure

 gradually so that the excess N2 in the tissues can stay in solution and

 move into the bloodstream where it can move to the lungs and be exhaled.

 > I  have had to fly two military aviators to the chamber

 > one at Brooks, AFB and the other was at Beale AFB. Both  had to be flown

 > with the cabin pressurized to sea level because of the risk of worsening

 > the decompression sickness. One of those pilots was my Squadron cc. He

had

 	  Quote: 	
		   > a gradual cabin pressure leak due to a slow leaking canopy seal. 

 Had he been diving? Remember, the pressure change going from sea level

 to FL250 is less than the pressure change from the surface to 30 feet

 underwater. I suppose it is possible for someone to get decompression

 sickness loss of cabin pressure but a slow leak is unlikely to cause the

 problem. I am not saying it can't happen but I am skeptical unless there

 was some other mechanism acting to raise the level of N2 in the tissue.

 Living at sea level is not likely to cause enough N2 to dissolve in the

 blood to cause the bends to happen at FL250, especially if the pressure

 drops gradually.

 > There are two ways to get the "Bends."  One is from decompression and

the

 	  Quote: 	
		   > other is from compression. 

 Sorry, no. The Bends occur *only* on decompression. Compression just

 causes more N2 to dissolve in the tissues. If the person is suffering

 from The Bends recomressing him/her causes the N2 bubbles to go back

 into solution. Once that happens you can begin slow decompression thus

 allowing the N2 to slowly and safely move from the tissue to the blood

 to the lungs and then be exhaled.

 > In either case, N2 comes out of solution in blood. 

 No, it doesn't. It *only* does that on decompression, hence the name

 decompression sickness.

 > It  coleses into gas bubbles in the tissue. Most commonly in an

 > injured joint. It also can happen in the spinal cord, brain

(neurological

 	  Quote: 	
		   > nitrogen narcosis), and the pulmonary tree. (the chokes). That is

putting

 	  Quote: 	
		   > it in simple terms.

 You are describing only decompression sickness. You also called it

 nitrogen narcosis which it isn't. Now nitrogen narcosis does happen when

 you compress the body in the presence of N2. The greater the pressure,

 the greater the symptoms of narcosis.

 This is why divers use special breathing gasses that reduce or eliminate

 the N2 in the breathing mix (heliox or nitrox) -- so that they are less

 likely to experience narcosis while down and less likely to experience

 The Bends upon ascending.

 > In otherwords, every time you take that unpressurised twin above FL 180,

 > you are at risk for for developing the "bends".

 Any time you reduce the pressure on the body there is some chance of

 developing decompression sickness. OTOH, the chance is very, very,

 *VERY* small for people living at sea level or above who don't dive and

 smaller still if the pressure change is gradual, i.e. standard rates of

 ascent and not explosive decompression. I think if you go back and

 research this you will find that this is an *extremely* rare event.

 As a pilot who spent three years operating in the Virgin Islands who

 dives and flies, I am *VERY* aware of the dangers from rapid pressure

 changes and of going directly from a dive to a flight in an airplane.

 For safety we use a rule of thumb of 24 hours between a decompression

 dive to a flight because we know that even after a successful and safe

 decompression dive, the tissues are still saturated to a higher level of

 N2 than someone who has not been diving. The extra 24 hours allows the

 body to come back to equilibrium before flying. My rule of thumb is

 that, if you have been diving today, we don't fly until tomorrow.

 So, yeah, I have some idea how all this works. The threat is vanishingly

 small compared to what you are implying unless you have been diving and

 then the threat is very real.

 And nitrogen narcosis is NOT decompression sickness.

 -- 

 Brian Lloyd                         2243 Cattle Dr.

 brian-yak at lloyd dot com          Folsom, CA 95630

 +1.916.367.2131 (voice)             +1.270.912.0788 (fax)

 I fly because it releases my mind from the tyranny of petty things . . .

 - Antoine de Saint-Exupery

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Wed Jan 18, 2006 12:12 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

Ernest Martinez wrote:



 	  Quote: 	
		   Being narced and the bends are 2 different things and happen at 2 ends

 of the spectrum. The only way you would get narced at altitude is if

 you were at 90,000 ft and dropped to 20,000 in about 5 seconds, but

 getting narced would be the least of your worries.


	


And if you were at 90,000' pressure altitude you would already be dead.

Even then it wouldn't happen. It requires a partial pressure of N2 at

about 3 BAR before you start getting enough N2 in your system to

interfere with normal nervous system operation. Nitrogen Narcosis can

only happen when the pressure exceeds that of being 100' deep

underwater. It is not going to happen anywhere on or off Earth when you

are in the atmosphere. Period.



Nitrogen Narcosis comes from the total amount of N2 present in the blood

and tissues. Decompression sickness comes from a too-rapid change in

pressure during ascent/decompression. The one time I would really worry

about decompression sickness in an airplane is during explosive

decompression or right after a dive.



 	  Quote: 	
		   We have dive computers and tables that we follow which tells us how

 many hours we have to wait before acending to any altitude depending

 on our dive profile, in order to avoid the bends.


	


You know, I never paid attention to see if the dive computer continues

to do its thing in an aircraft and give you a decompression stop. I

suppose there is no reason why it couldn't. SMOP (small matter of

programming).



-- 

Brian Lloyd                         2243 Cattle Dr.

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

Ernie

Joined: 11 Jan 2006
Posts: 513

Posted: Wed Jan 18, 2006 12:28 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

I have 2 diver computers that I use, they both have (I think, since I

havent used them in 2 years) a mode which you can call up that says

"OK to fly" when you've spent enough time out of the water. Same

algoritm which tells you when you can dive again.



If I remember correctly from Dive school, the dive tables also had

some basic method for determining how much time must lapse before

flying.



 	  Quote: 	
		  >>Nitrogen Narcosis is from the increased nitrogen in solution disrupting the

electrical potential transfer across the pre and post synaptic cleft of the
	


CNS. This most likely being in the Reticular Activating system and the

Cortical mantle. It follows the Meyer-Overton hypothesis that states "all

gaseous or volatile substances induce narcosis if they penetrate the lipids

of the cell wall in a definate molar concentraion that is characaristic for

each type of animal tissue aand approximately the same for all narcotics."

That is measured by the mean alveolar concentration (MAC) of the anesthetic

agent. The measure of an anesthetic concentration of an inert gas is the

concentration of the gas at which only 50% of rats will respond to pinching

their tail with a ring forcep. The so called MAC 50.

 	  Quote: 	
		  >>


	


Also, the fernaderstand coupling to the finnigan motor spignads, will

de-cobobulate when administered in the presence of sinous friggle

dangle near the copious osmobrosis, causing increased cluster bumpkins

over the entire swaggle noodlefrapses region..



Ernie



On 1/18/06, Brian Lloyd <brian-yak(at)lloyd.com> wrote:

 	  Quote: 	
		   



 Ernest Martinez wrote:



 > Being narced and the bends are 2 different things and happen at 2 ends

 > of the spectrum. The only way you would get narced at altitude is if

 > you were at 90,000 ft and dropped to 20,000 in about 5 seconds, but

 > getting narced would be the least of your worries.

cjpilot710(at)aol.com
Guest

Posted: Wed Jan 18, 2006 12:38 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

Do you know the first  sign of rapid decompression?

  

 You  Fart   like you would not believe.  Just hope its dry.

  

 Pappy

viperdoc(at)mindspring.co
Guest

Posted: Wed Jan 18, 2006 12:42 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

And Now Ernie you are a bonified Meyer - Overton expert!

Doc

 	  Quote: 	
		   [Original Message]

 From: Ernest Martinez <erniel29(at)gmail.com>

 To: <yak-list(at)matronics.com>

 Date: 1/18/2006 2:28:14 PM

 Subject: Re: decompression sickness and narcosis (was:

AYS-bound)
	


 	  Quote: 	
		  

 



 I have 2 diver computers that I use, they both have (I think, since I

 havent used them in 2 years) a mode which you can call up that says

 "OK to fly" when you've spent enough time out of the water. Same

 algoritm which tells you when you can dive again.



 If I remember correctly from Dive school, the dive tables also had

 some basic method for determining how much time must lapse before

 flying.



 >>>Nitrogen Narcosis is from the increased nitrogen in solution

disrupting the
	


 	  Quote: 	
		   electrical potential transfer across the pre and post synaptic cleft of

the
	


 	  Quote: 	
		   CNS. This most likely being in the Reticular Activating system and the

 Cortical mantle. It follows the Meyer-Overton hypothesis that states "all

 gaseous or volatile substances induce narcosis if they penetrate the

lipids
	


 	  Quote: 	
		   of the cell wall in a definate molar concentraion that is characaristic

for
	


 	  Quote: 	
		   each type of animal tissue aand approximately the same for all narcotics."

 That is measured by the mean alveolar concentration (MAC) of the

anesthetic
	


 	  Quote: 	
		   agent. The measure of an anesthetic concentration of an inert gas is the

 concentration of the gas at which only 50% of rats will respond to

pinching
	


 	  Quote: 	
		   their tail with a ring forcep. The so called MAC 50.

 >>>



 Also, the fernaderstand coupling to the finnigan motor spignads, will

 de-cobobulate when administered in the presence of sinous friggle

 dangle near the copious osmobrosis, causing increased cluster bumpkins

 over the entire swaggle noodlefrapses region..



 Ernie



 On 1/18/06, Brian Lloyd <brian-yak(at)lloyd.com> wrote:

 > 

 >

 > Ernest Martinez wrote:

 >

 > > Being narced and the bends are 2 different things and happen at 2 ends

 > > of the spectrum. The only way you would get narced at altitude is if

 > > you were at 90,000 ft and dropped to 20,000 in about 5 seconds, but

 > > getting narced would be the least of your worries.

 >

 >

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Wed Jan 18, 2006 1:27 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

Roger Kemp wrote:

 	  Quote: 	
		   

 

 Brian,

 You are right Narcosis is a malady of descent generally below 150 feet

 ocean water. I wrote wrong the term when I was speaking of decompression.

 Both are related to Nitrogen going into and out of solution in the blood

 and tissue. 

 My first statement about pre-breathing 100% O2 prior to ascending to an

 unpressurized altitude was in reference (inferred at the time) to

 decreasing the risk of altitude decompression sickness. For that you

 asserted that you can only get decompression sickness from diving. And

 there you are also wrong. I am wrong for saying Nitrogen Narcosis and you

 are wrong for asserting that decompression only comes from ascending from a

 compression dive. 


	


Hmm, I just went back and reread what I wrote. I think I made it pretty

clear that any time you have a rapid decrease in pressure, whether

ascending from a dive or ascending into the air, you can experience

decompression sickness. What I was trying to assert is that it is very

unlikely in an aircraft and much more likely from a dive. In fact, here

is what I did say:



"Any time you reduce the pressure on the body there is some chance of

developing decompression sickness. OTOH, the chance is very, very,

*VERY* small for people living at sea level or above who don't dive and

smaller still if the pressure change is gradual, i.e. standard rates of

ascent and not explosive decompression. I think if you go back and

research this you will find that this is an *extremely* rare event."



So, no, I did not assert that decompression sickness only comes from

diving. I did assert it is very difficult to make it happen while flying.



In any of the unpressurized aircraft we fly it is almost impossible to

get a change in pressure that is sufficiently rapid to invoke

decompression sickness. Going up right after a dive so that there is

more N2 in the tissues might cause it tho'.



And a rapid decompression from an 8,000' cabin to a 35,000' cabin might

do it. That is why I made the comment about explosive decompression.



 	  Quote: 	
		   The symptoms of Nitrogen Narcosis and Neurological Decompression sickness

 can be strikingly similar. One is from descent and the effect of an

 increased partial pressure of Nitrogen and other inert gases in

 neurological tissue causing mental disorientation. Neurological

 Decompression is nitrogen bubbles forming emboli after coming out of

 solution as one ascends either from a depth of sea water or from sea level

 to altitude. In each case the the common thread is that  the the pressure

 decreased after the diver or the aviator was subjected to an increased

 atmospheric pressure.


	


Right, that is decompression sickness.



 	  Quote: 	
		   An aviator climbing from 1 ATA at sea level to 1/2 ATA at 18000 ft or 1/4

 ATA at 33500ft unpressurized is at an increased risk for nitrogen coming

 out of solution and forming "bubbles". 


	


The rate of ascent is a key part of that. We change pressure all the

time when we fly. When was the last time you heard of a person in an

unpressurized aircraft experiencing decompression sickness when that

person had not been diving prior to flying? I have never known of a case

but I don't have that much exposure.



As an AME and (I presume) flight surgeon, you probably have a lot more

exposure to that sort of thing. Still, without explosive decomp and

without some prior activity to increase the N2 saturation, how many

cases of decomp sickness have occurred? I hold that it occurs so

infrequently that it is not worth worrying about.



 	  Quote: 	
		   The same for the diver that was at 4

 ATA ~ 100 feet of sea water (fresh water also) and ascending to the surface

 without percautionary decompression stops (not that is always protective

 either). Yes, bottom time does influence the risk of developing the

 "bends". As does other factors such as dehydration, fatigue, exercise at

 depth or exercise prior to diving.


	


Bottom time influences it a lot. It has more effect than all the other

factors you mention. It takes time for the N2 to dissolve in the blood

and then move to the tissues. The longer you are under the greater

partial pressure of N2, the closer you get to equilibrium and the longer

it will take to reach equilibrium again at a lower pressure. That

process can only proceed so fast and any attempt to make it go faster

results in the N2 coming out of solution in gaseous form (bubbles).

Those bubbles hurt.



 	  Quote: 	
		   Nitrogen Narcosis is from the increased nitrogen in solution disrupting the

 electrical potential transfer across the pre and post synaptic cleft of the

 CNS. This most likely being in the Reticular Activating system and the

 Cortical mantle. It follows the Meyer-Overton hypothesis that states "all

 gaseous or volatile substances induce narcosis if they penetrate the lipids

 of the cell wall in a definate molar concentraion that is characaristic for

 each type of animal tissue aand approximately the same for all narcotics."

 That is measured by the mean alveolar concentration (MAC) of the anesthetic

 agent. 


	


I am familiar with that. The problem is finding inert gasses that have

the effect at partial pressures less than 1 atmosphere. Xenon actually

works pretty well but it is too expensive to use for that purpose.



 	  Quote: 	
		   The measure of an anesthetic concentration of an inert gas is the

 concentration of the gas at which only 50% of rats will respond to pinching

 their tail with a ring forcep. The so called MAC 50.  So that is the theory

 behind why we can give you an inhaled anesthetic at a concentration

 inspired greater than sea level concentration and induce amnesia with

 sedation for surgery. 


	


That is all well and good but I wasn't particularly interested in

anesthetizing rats with inert gasses. (Sorry, I couldn't resist.)



BTW, my research experience with blood gasses was working with dogs, not

rats. I worked on a research project to develop a system to

automatically determine blood gas concentrations and then make the data

immediately available as part of a patient monitoring system. Writing

the software and building the dedicated microprocessor hardware for that

project was one of the ways I worked my way through college in the '70s.

We used dogs as research subjects. I am sure that nowadays I would be

drawn and quartered by some PETA enthusiast for even admitting I had

something to do with killing dogs for research purposes.



(We took dogs slated for euthanasia at the pound and performed various

tests on cardiopulmonary function. The dogs were treated kindly and

properly anesthetized prior to operating on them. When we had finished

gathering our data they were then euthenized, which is a nice word for

"killed". I did learn a LOT about cardiopulmonary function from that job

tho'.)



But I digress.



 	  Quote: 	
		   We are comparing Apples and Oranges here.


	


Agreed.



 	  Quote: 	
		   Sorry Brian for mis-stating Narcosis instead of altitude decompression last

 night at 11:20.


	


Right on bro'. It happens. We all make mistakes. The important thing is

to make sure we then get the proper information into people's hands lest

they make erroneous decisions based on improper information. We already

have to make decisions based on insufficient information (as in deciding

what do to in an off-airport landing). Bad information just compounds

the problem.



You get to buy the first round. I will buy the second. 



-- 

Brian Lloyd                         2243 Cattle Dr.

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



Darn, still no alphabet soup after my name and I am not old enough yet

to exchange "curmudgeon" for "asshole".

viperdoc(at)mindspring.co
Guest

Posted: Wed Jan 18, 2006 1:30 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

Pappy,

 That is why you wear a brown fight suit so when you release that wet trapped gas, it does not show up as well!

 Doc

  

 



  

 [quote] ---

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Wed Jan 18, 2006 1:33 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

cjpilot710(at)aol.com wrote:

 	  Quote: 	
		   */Do you know the first sign of rapid decompression?/*

 *//* 

 */You  Fart  like you would not believe.  Just hope its dry./*


	


Yeah, that was the worst thing about taking off your mask in the

hypobaric chamber to experience the effects of hypoxia. Everyone had

farted their asses off and the chamber stunk big time.



BTW, if you haven't taken a 'chamber ride' you should. Seeing what it is

like to experience pressure breathing O2 at 42,000' and hypoxia at

25,000' is good experience.



-- 

Brian Lloyd                         2243 Cattle Dr.

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

talew(at)bellsouth.net
Guest

Posted: Wed Jan 18, 2006 3:36 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

Pappy,

 My older captains taught me to never count on a dry fart after 50 years  old. I believe they were right. Although, you understand, I can' t confirm  that. 

 Terry Lewis 

 [quote]   ---

viperdoc(at)mindspring.co
Guest

Posted: Wed Jan 18, 2006 4:21 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

There are no dry farts over age 55. Just old farts.

 Doc

  

 



  

 [quote] ---

JOffice(at)aol.com
Guest

Posted: Wed Jan 18, 2006 5:06 pm Post subject: decompression sickness and narcosis (was: AYS-bound)

In a message dated 1/18/2006 3:29:43 PM US Eastern Standard Time, erniel29(at)gmail.com writes:

  	  Quote: 	
		  >>>Nitrogen Narcosis is from the increased nitrogen in solution disrupting the

electrical potential transfer across the pre and post synaptic cleft of the

CNS. This most likely being in the Reticular Activating system and the

Cortical mantle. It follows the Meyer-Overton hypothesis that states "all

gaseous or volatile substances induce narcosis if they penetrate the lipids

of the cell wall in a definate molar concentraion that is characaristic for

each type of animal tissue aand approximately the same for all narcotics."

That is measured by the mean alveolar concentration (MAC) of the anesthetic

agent. The measure of an anesthetic concentration of an inert gas is the

concentration of the gas at which only 50% of rats will respond to pinching

their tail with a ring forcep. The so called MAC 50.

 	  Quote: 	
		  >>

Also, the fernaderstand coupling to the finnigan motor spignads, will

de-cobobulate when administered in the presence of sinous friggle

dangle near the copious osmobrosis, causing increased cluster bumpkins

over the entire swaggle noodlefrapses region..

Ernie 	

 Viperdoc-

    Well, I appreciated it anyway...  buy you didn't talk about Argon and Neon as anesthetics at high pp...

    JSL

    (another anesthesiologist-pilot)

L39parts(at)hotmail.com
Guest

Posted: Thu Jan 19, 2006 6:27 am Post subject: decompression sickness and narcosis (was: AYS-bound)

I didn't realize so many CJ pilots were divers.  Here's an interesting  story about SCUBA diving to 900 feet HTTP://outside.away.com/outside/features/200508/dave-shaw-1.html  in the deepest freshwater lake (cave) in the world.

 [quote]   ---

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