Oxygen

[ilovecornfields]

That's interesting and technical information but I'll assume you're not making an argument that in-flight use of a nasal cannula by normally healthy pilots is detrimental.

Certainly extended exposure to high-level oxygen concentrations can be harmful but these aren't the levels of exposure typically experienced by GA pilots.

I just don't want people getting the idea that using O2 in their planes is a bad thing.


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I am absolutely NOT making the argument that using oxygen at altitude is a bad thing. What I'm saying is that you should use oxygen with the goal of maintaining a NORMAL oxygen saturation. We're learning now that both hypoxia and hyperoxia can be harmful and with the availability of inexpensive and reliable pulse oximeters we should be monitoring oxygen saturation and titrating the flow rate in order to maintain a normal SpO2. I like to use 96-98% although some would go lower. I don't think there is anyone here who would have a 96-98% oxygen saturation at 10k feet without using supplemental oxygen.


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[Tom]

1 hour ago, ilovecornfields said:

Actually, increasing oxygen concentration (FiO2) does increase CO2 levels, especially in people with lung disease. The mechanism is somewhat complicated but it has to do with hypoxic pulmonary vasoconstriction and the fact that blood vessels in the lungs normally constrict and direct blood away from areas of the lung with low partial pressures of oxygen. If you increase the FiO2 (fraction of inspired oxygen concentration) then it counteracts this effect and in areas where the lung is poorly ventilated, blood flow will increase to those areas, creating a right to left shunt and allowing blood that has not had the opportunity to exchange CO2 into the systemic circulation. This causes an increase in CO2 levels, proportional to the degree of lung disease and the FiO2. In young healthy lungs, this effect is small but as you deviate away from that the effect is significant. The curves below illustrate this effect starting with healthy lungs at the bottom and severe COPD at the top.

--Off-topic warning--

The only thing that can increase total C02 concentration in the blood is either increased metabolic activity (i.e. increased production of C02) or decreased ventilation (i.e. decreased disposal of C02).  Renal processing notwithstanding/relevant here. 

The point about "not shallow breathing" speaks specifically to the need to increase tidal volume to avoid the consequence of shunting, or, put simply, needing to breath deeply/normally so as to aerate the lower lung to blow off the C02.

I don't see how the graph has anything to do with aviation.  Most pilots don't have severe COPD and fly intubated with an Fi02 of 80%. 

There is really no good to come from providing hazards of 02 use nor good about warnings of "hyperoxia."  Presumably the hyperoxia concern would be related to oxidative concerns, which I'd respond with concerns about normobaric hypoxia.  We've seen brain white-matter changes resulting from normobaric hypoxia as a result of simple chamber flights.  Flying with a little too much 02, if breathing normally, is not a concern whereas flying hypoxic is always going to degrade performance and endurance to some degree..

[jlunseth]

This is more of a question that a statement.  For those of us with the built-in system, I remember reading some posts on this forum years ago to the effect that the built-in system shuts off flow below a certain altitude and I believe it was 8,000.  The system is pressure regulated, says so in my manual, although which way it does not say and you would think it would supply more O2 at lower altitudes than at higher.  At any rate, that's the way diver regulators work.  Is this so, and if it is, what good is it to use the built-in system down low?

[larryb]

This is a CGA 540 valve

[larryb]

This is the mountain high regulator attached to the CGA 540 valve.

[larryb]

And finally this is the transfill station in my hanger to fill the tanks.

[cnoe]

This is a CGA 540 valve

Neat little valve there Larry; I'd never seen one before. Thanks for the photo. Is it threaded for a typical medical cylinder like an E or D? It appears so but I can't see what cylinder you're using in the pics.


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[larryb]

It is a medical E size, 22 cuft I think. I have several. One is the original AEROX and the others from cramerdecker. They are all the same size and look identical.

[cnoe]

Thanks. I'd just never seen a CGA540 in a medical cylinder, but then I've led a pretty sheltered existence.


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[carusoam]

Larry, nice set of photos regarding the O2 systems.

Thanks.

Best regards,

-a-

[ilovecornfields]

--Off-topic warning--

The only thing that can increase total C02 concentration in the blood is either increased metabolic activity (i.e. increased production of C02) or decreased ventilation (i.e. decreased disposal of C02).  Renal processing notwithstanding/relevant here. 

The point about "not shallow breathing" speaks specifically to the need to increase tidal volume to avoid the consequence of shunting, or, put simply, needing to breath deeply/normally so as to aerate the lower lung to blow off the C02.

I don't see how the graph has anything to do with aviation.  Most pilots don't have severe COPD and fly intubated with an Fi02 of 80%. 

There is really no good to come from providing hazards of 02 use nor good about warnings of "hyperoxia."  Presumably the hyperoxia concern would be related to oxidative concerns, which I'd respond with concerns about normobaric hypoxia.  We've seen brain white-matter changes resulting from normobaric hypoxia as a result of simple chamber flights.  Flying with a little too much 02, if breathing normally, is not a concern whereas flying hypoxic is always going to degrade performance and endurance to some degree..

 

Wow, I never imagined it would be so controversial to propose spending less than $50 on a pulse ox and using it to titrate your oxygen to a normal oxygen saturation.

 

With respect to the harms of hyperoxia, I have to disagree with you (and so does a vast amount of medical literature). It's been shown to be a potent coronary vasoconstrictor, is associated with acute lung injury and is associated with worse outcomes for several medical conditions. The heart association removed their recommendation to give oxygen to chest pain patients (unless hypoxic) several years ago for precisely these reasons. Medscape and UpToDate both provide good reviews of this topic if you are interested.

 

How does this apply to aviation? Oxygen is a drug. Use it appropriately and use a pulse ox to make informed decisions. I'm not trying to scare anyone, I'm just advocating appropriate use of oxygen using cheap and readily available tools. The concept of "if a little is good, more is better" rarely applies in medicine and this is no exception.

 

I apologize for taking such a controversial position on the subject and advocating safe evidence-based use of a medical device.

 

 

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[carusoam]

ILC,

we appreciate the technical details, keep them coming.

Best regards,

-a-

[Tom]

7 hours ago, ilovecornfields said:

Wow, I never imagined it would be so controversial to propose spending less than $50 on a pulse ox and using it to titrate your oxygen to a normal oxygen saturation.

With respect to the harms of hyperoxia, I have to disagree with you (and so does a vast amount of medical literature). It's been shown to be a potent coronary vasoconstrictor, is associated with acute lung injury and is associated with worse outcomes for several medical conditions. The heart association removed their recommendation to give oxygen to chest pain patients (unless hypoxic) several years ago for precisely these reasons. Medscape and UpToDate both provide good reviews of this topic if you are interested.

How does this apply to aviation? Oxygen is a drug. Use it appropriately and use a pulse ox to make informed decisions. I'm not trying to scare anyone, I'm just advocating appropriate use of oxygen using cheap and readily available tools. The concept of "if a little is good, more is better" rarely applies in medicine and this is no exception.

I apologize for taking such a controversial position on the subject and advocating safe evidence-based use of a medical device.

Hypothetical concern based on non-contextual application of information is not evidenced-based medicine.  The supplemental oxygen situation for someone having a heart attack is not the same as someone in respiratory failure or another person undergoing anesthesia.  And none of this has anything to do with pilots in GA aircraft.

It is controversial to offer hypothetical concern about an intervention when that concern has already been studied and found to not be clinically relevant when doing so may dissuade the population to benefit from the intervention.  NASA and the aeromedical community has studied this stuff forever, even if Uptodate doesn't have a section on it.  It may be of interest for some to know that astronauts on spacewalks are still using 100% oxygen...

No one advocated against using a pulse-oximeter, but no one should feel afraid of "overdoing it" with oxygen on a GA aircraft flight.  At minimum, the pulse-ox is needed to make sure enough oxygen is being used. 

We should be encouraging more supplemental oxygen use.  It's pointless to caution over-doing it. 

 

 

[JohnB]

An important topic! I ALWAYS use oxygen ANY time I am above 9k feet and much lower on warm days or at night. Here's why

• The average healthy person's oxygen saturation will be at 90% at 9,000 feet, and lower sats at higher altitudes. This is what mine is usually around. And even though you might feel fine, multiple studies have shown your concentration, ability to solve tasks, vision are impaired at 90% saturation level.
• At night, your night vision and color discrimination is enhanced by supplemental oxygen.
• As for warm days, this is just my theory, but I have noticed when I am flying at even 7,000 feet and it is warm at that altitude,  I start noticing my hypoxic symptoms which I was surprised at. I checked my saturation once during a long day flight  at I think 6.5k on a very hot day and it was lower than 90! Put on oxygen, sat went back up and I felt fine. My unproven theory is that warmer air has less concentrated oxygen per mm³ due to air being less dense leading to hypoxia even at lower altitudes. 
• A common symptom of even medium periods of mild hypoxia (i.e. 90% sat) is fatigue, so yes, flying around at this saturation will make you much more fatigued faster.
• Learn your own hypoxia symptoms.When one happens, fix it!

If you haven't already done this, I would highly recommend considering going to a hypoxia chamber to do a hypoxia training course to learn what YOUR own hypoxia symptoms are, what occurs in you first, second and as many other symptoms you can identify so that if you get one of these symptoms in flight, you'll know you probably need to check your sats. Even if you fly with oxygen regularly, a kinked O2 line (I've had that happen) or disconnected hose can occur in flight without you noticing it, and if you know your symptoms, you can pick that up early.

 

John

[donkaye]

9 minutes ago, JohnB said:

An important topic! I ALWAYS use oxygen ANY time I am above 9k feet and much lower on warm days or at night. Here's why

• The average healthy person's oxygen saturation will be at 90% at 9,000 feet, and lower sats at higher altitudes. This is what mine is usually around. And even though you might feel fine, multiple studies have shown your concentration, ability to solve tasks, vision are impaired at 90% saturation level.
• At night, your night vision and color discrimination is enhanced by supplemental oxygen.
• As for warm days, this is just my theory, but I have noticed when I am flying at even 7,000 feet and it is warm at that altitude,  I start noticing my hypoxic symptoms which I was surprised at. I checked my saturation once during a long day flight  at I think 6.5k on a very hot day and it was lower than 90! Put on oxygen, sat went back up and I felt fine. My unproven theory is that warmer air has less concentrated oxygen per mm³ due to air being less dense leading to hypoxia even at lower altitudes. 
• A common symptom of even medium periods of mild hypoxia (i.e. 90% sat) is fatigue, so yes, flying around at this saturation will make you much more fatigued faster.
• Learn your own hypoxia symptoms.When one happens, fix it!

If you haven't already done this, I would highly recommend considering going to a hypoxia chamber to do a hypoxia training course to learn what YOUR own hypoxia symptoms are, what occurs in you first, second and as many other symptoms you can identify so that if you get one of these symptoms in flight, you'll know you probably need to check your sats. Even if you fly with oxygen regularly, a kinked O2 line (I've had that happen) or disconnected hose can occur in flight without you noticing it, and if you know your symptoms, you can pick that up early.

 

John

John is too modest.  He could have put MD next to his name.  He is after all a Cardiologist.  I'd listen to him.

[ilovecornfields]

An important topic! I ALWAYS use oxygen ANY time I am above 9k feet and much lower on warm days or at night. Here's why

• The average healthy person's oxygen saturation will be at 90% at 9,000 feet, and lower sats at higher altitudes. This is what mine is usually around. And even though you might feel fine, multiple studies have shown your concentration, ability to solve tasks, vision are impaired at 90% saturation level.
• At night, your night vision and color discrimination is enhanced by supplemental oxygen.
• As for warm days, this is just my theory, but I have noticed when I am flying at even 7,000 feet and it is warm at that altitude,  I start noticing my hypoxic symptoms which I was surprised at. I checked my saturation once during a long day flight  at I think 6.5k on a very hot day and it was lower than 90! Put on oxygen, sat went back up and I felt fine. My unproven theory is that warmer air has less concentrated oxygen per mm³ due to air being less dense leading to hypoxia even at lower altitudes. 
• A common symptom of even medium periods of mild hypoxia (i.e. 90% sat) is fatigue, so yes, flying around at this saturation will make you much more fatigued faster.
• Learn your own hypoxia symptoms.When one happens, fix it!

If you haven't already done this, I would highly recommend considering going to a hypoxia chamber to do a hypoxia training course to learn what YOUR own hypoxia symptoms are, what occurs in you first, second and as many other symptoms you can identify so that if you get one of these symptoms in flight, you'll know you probably need to check your sats. Even if you fly with oxygen regularly, a kinked O2 line (I've had that happen) or disconnected hose can occur in flight without you noticing it, and if you know your symptoms, you can pick that up early.
 
John

John,

Curious why you would recommend "learning your own hypoxia symptoms" instead of (as opposed to in addition to) "buy a $40 pulse ox, check it against a calibrated one, and use it to spot check your oxygen levels during flight and adjust your flow rate accordingly?"

There's clearly something I'm missing here because I've received a lot of negative feedback regarding my suggestion to use a pulse ox to titrate your oxygen levels and I have to admit I don't really get the pushback (other than the fact that it's the internet and people tend to do things online that the would never do in person). Maybe some people are slow adopters to new technology (if that's the case, I think I still have my KLN-88 "IFR certified" LORAN-C to sell you). Maybe it adds excitement to either use too much or too little oxygen instead of being told the right amount (which is surprising considering how precise people are about FF, ROP or LOP). I can't imagine someone saying "don't waste your time with the EGT, too much fuel never hurt anyone"

I've treated lots of pilots from young Navy pilots to old GA pilots and I have to say that many of you aren't as healthy as you think you are (sorry, but it's true!). While I agree with everything said and I think an altitude chamber is a great experience, depending on "hypoxia symptoms" is less reliable than a pulse ox (just like troponin is much more accurate than myoglobin or CPK. Why would you depend on a less sensitive and specific test when you have access to one that is clearly superior?).

A few months ago I saw an active GA pilot with a 92% oxygen saturation at sea level who told me he didn't use a pulse ox because he "don't need it." I guess he must have read House of God and subscribed to the "if you don't take a temperature, you can't find a fever" philosophy. Unfortunately, aviation tends to be unforgiving with people who take this approach.

Ok, I'm done ranting. I promise this is my last post on the subject. I'm going to use my pulse ox and I'll let everyone make their own choices. Just disappointed to see something so simple turn into something so complicated.


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[cnoe]

Ok, I'm done ranting. I promise this is my last post on the subject. I'm going to use my pulse ox and I'll let everyone make their own choices. Just disappointed to see something so simple turn into something so complicated.

 

Please don't be dismayed. In spite of any dissenting opinions I'm sure that 99% of us understand that using a pulse-ox and supplemental oxygen is nearly always a good thing when flying our winged chariots. Those who don't heed the call are either too lazy or too uninspired (pun intended) to follow the advice. I'll admit that sometimes I fall into the lazy category myself, particularly on shorter or lower flights. Then again I always have O2 and an oximeter at-the-ready for flights approaching 10k, lower flights at night, and of course any time the pulse-ox dictates. Thanks for your input on this!

 

And expect [mention=7104]Carusoam[/mention] to come along shortly with a thorough and informative summary of this (IMO) uncomplicated thread.

[carusoam]

ILC,

1) The rant technique loses the audience faster than a good technical point can be made.

2) An example of this is 201er with the AOAi.

3) Using a single 'non-certified' finger mounted sensor to titrate your dissolved oxygen level without any back-up sounds risky.

4) training to know your personal signs of hypoxia sounds like a great way to recognize when Plan A has gone awry.

5) This topic is like many in aviation, it is a combination of education and experience.

6) Initial experience comes from training. Get as much as you can...

7) Initial education comes from a variety of resources, like discussions around here...

8) when it comes to adjusting O2 levels to a minimum for what ever reason, the human brain runs into logic and recognition challenges when it gets the titration wrong... what's the back-up for this?

9) Announcing you're done discussing the topic is somewhat like taking your bat and ball and heading home... 

10) there are a lot of challenges in having conversations on line.  The more complex the topic, the more effort it takes.

11) stay open minded, you may be misunderstanding something that didn't get typed in properly or got changed by Siri...

12) high O2 is good.

13) low O2 is not so good.

14) Open conversations are improved as everybody gets to know each other.

15) Add enough detail to your avatar so people remember who you are.

16) The signature line has a lot of space as well...

Best regards,

-a-

[Andy95W]

Going to a hypoxia chamber is like getting the instrument rating.

You don't realize how beneficial the experience is until you do it for yourself.

 

[mike_elliott]

3 minutes ago, Andy95W said:

Going to a hypoxia chamber is like getting the instrument rating.

You don't realize how beneficial the experience is until you do it for yourself.

 

CAMI will be bringing their PROTE chamber to the Mooney Summit VI in 2018 for our use and training. It only took about 3 years to get this done, but it will happen!

[JohnB]

7 hours ago, ilovecornfields said:

 

John,

Curious why you would recommend "learning your own hypoxia symptoms" instead of (as opposed to in addition to) "buy a $40 pulse ox, check it against a calibrated one, and use it to spot check your oxygen levels during flight and adjust your flow rate accordingly?"

There's clearly something I'm missing here because I've received a lot of negative feedback regarding my suggestion to use 

 

Oh of course I think EVERY pilot should fly with a pulse oximeter. So I totally agree with that statement. I personally fly with THREE of them. The reason I think you should also know your hypoxia symptoms as if you get a symptom, you'll know you need to check your pulse ox now rather than periodically (which one might forget to do if you're actually hypoxic) 

[Oldguy]

48 minutes ago, mike_elliott said:

CAMI will be bringing their PROTE chamber to the Mooney Summit VI in 2018 for our use and training. It only took about 3 years to get this done, but it will happen!

Looking forward to this for multiple reasons.

I carry a pulse-ox and use it on any flight at or above 5,000 ft. My wife also checks herself with it, so we both know where we are. While it is not one of the panel mounted, calibrated units, from comparison against the one in my doctors office (yes, I took it with me to check it), there is minimal difference in the readings. BUT I do not wear it every minute I am in the plane, and I have experienced a very rapid onset of hypoxia symptoms. On a flight to KISM last year, within 10 minutes my levels went from 94 to 82 at 9,000 ft. without an altitude change. The sequence was:

1. Oxygen level of 94.

2. Mild nausea. (Am I getting airsick in clear air?) Also, thought I caught a whiff of diesel fumes, but at 9,000 ft?

3. Pulse ox check - 82!

4. Multiple shots off of the Oxygen Boost can in copilot seat.

5. Call ATC - descend 7,000 requested/approved.

6. Pulse ox back in the 90's before leveling off.

Items 1-5 happened within about a 10 minute span, so for me, I am very interested in knowing my hypoxia "tells" to help me be aware of my blood oxygen levels as well as the pulse ox monitoring I do. Yeah, I am that kind of belt and suspenders guy who bought an oxygen setup for 2 at SNF this year.

[Oldguy]

2 minutes ago, JohnB said:

Oh of course I think EVERY pilot should fly with a pulse oximeter. So I totally agree with that statement. I personally fly with THREE of them. The reason I think you should also know your hypoxia symptoms as if you get a symptom, you'll know you need to check your pulse ox now rather than periodically (which one might forget to do if you're actually hypoxic) 

I think I was describing this very situation as you were writing your post.

[Bob_Belville]

I use a finger O2 pulse meter regularly. I generally do not go to the O2 tank unless the flight is a couple of hours or more and above about 8000'. (If I flew at night I would start O2 before takeoff.) Even when not using the O2 tank I find that proper breathing can raise O2 from 90-92 to 95+. "Proper" I'd define as intentionally breathing deeper, not faster, using more of the lungs. The key is to then keep breathing right.

[ilovecornfields]

ILC,
1) The rant technique loses the audience faster than a good technical point can be made.
2) An example of this is 201er with the AOAi.
3) Using a single 'non-certified' finger mounted sensor to titrate your dissolved oxygen level without any back-up sounds risky.
4) training to know your personal signs of hypoxia sounds like a great way to recognize when Plan A has gone awry.
5) This topic is like many in aviation, it is a combination of education and experience.
6) Initial experience comes from training. Get as much as you can...
7) Initial education comes from a variety of resources, like discussions around here...
8) when it comes to adjusting O2 levels to a minimum for what ever reason, the human brain runs into logic and recognition challenges when it gets the titration wrong... what's the back-up for this?
9) Announcing you're done discussing the topic is somewhat like taking your bat and ball and heading home... 
10) there are a lot of challenges in having conversations on line.  The more complex the topic, the more effort it takes.
11) stay open minded, you may be misunderstanding something that didn't get typed in properly or got changed by Siri...
12) high O2 is good.
13) low O2 is not so good.
14) Open conversations are improved as everybody gets to know each other.
15) Add enough detail to your avatar so people remember who you are.
16) The signature line has a lot of space as well...
Best regards,
-a-

My apologies. I didn't mean to take my ball and bat home, just got tried of saying the same thing over and over again and having people give bizarre responses that seem to miss the point and just be argumentative. Maybe it's all Siri's fault. I appreciate the PMs and glad I'm not the only one who advocates using well established technology to make flying safer.

When I was in paramedic school we use to joke that all you needed to know was "air goes in and out, blood goes round and round, oxygen is good, blue is bad." Things got a little more complicated in med school and two residencies but I think if you're going to oversimplify things you could probably do a lot worse. As long as you promise not to have lung disease or a heart attack you'll probably do ok with too much oxygen in your airplane for a short time.

Perhaps we can all agree that it is beneficial to know your hypoxia symptoms and to carry a pulse oximeter, although I would caution people that some of the "hypoxia symptoms" are symptoms of a heart attack as well so if your "hypoxia symptoms" don't resolve with oxygen it may be a good idea to get down sooner rather than later.

Thank you to all those who took the time to respond to me.

Raul


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