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Flying with a pulse - oximeter


Ed Cesnalis

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I never said the plane won't get to 14,000...I said no one would want to or need to be flying at that altitude in the plane.

 

This is where it gets weird.

 

Words have meanings. Put together into a sentence and they can go on to form a complete thought or thoughts.

 

Your exact words were: "And you won't see that unless you get a LOT higher, say around 14k and above which of course is not possible in the CT or any other SLSA." (bolded mine)

 

That is a complete sentence of fairly straightforward construction with an obvious meaning. Really no room for interpretation, nor any context from which it was removed.

 

I knew for a fact that was a false statement, since I knew many Light Sport planes had reported going much higher, so that it was possible.

 

I posted that the statement was in error. That was NOT meant to be an "attack", merely a correction. It's in instructor's DNA to point out errors of fact, and to attempt to address those errors in a dispassionate manner.

 

But there's a deeper concern. I invite anyone to go back and look at the original post to this thread. Then ask themselves how it became about 100Hamburger and his Cirrus.

 

Which was also common on Pilots of America, SportPilotTalk and COPA - for a while, anyway.

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Another interesting point on Pulse Ox........................the hemoglobin in red blood cells (oxygen carrying portion of the blood) has a much higher (like 200 times) affinity for Carbon Monoxide, than for oxygen. Since most O sat monitors measure by photo cell, they will read a falsely high sat with elevated levels of CO (CO is attached to the hemoglobin in the same fashion that O2 does, and the meter does not know the difference). Just food for thought if your level goes up when you might be expecting it to go down while flying.

 

Personally, I like the idea of having a pulse ox meter, but I liken it to the concept of oil analysis in maintenance. As a measurement device, it is subject to errors. We must act accordingly. If my level were to shoot up a bit at altitude, I would at least consider the possibility of an exhaust leak into the cabin.

Every situation is slightly different. Therefore, pulse ox is just one piece of the puzzle.

 

Doug Hereford

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To safely and accurately use an oximeter first get a benchmark by testing levels 5 times in a single day to get your own personal 'norm.'  The Oximeter measures Oxygen saturation which is how much oxygen the blood is carrying compared with its full capacity.

  • An SpO2 of greater than 95% is generally considered to be normal.
  • An SpO2 of 92% or less (at sea level) suggests hypoxemia.

The device works by shining a light thru the skin and measuring translucency.  Both translucency and blood flow at the spot where the measurement is taken can affect the accuracy of a reading. For example, if the area is largely opaque or the blood flow is low or irregular, accurate readings would be difficult.

 

Low atmospheric pressure at high altitude has little to no effect on a pulse oximeter; however extreme low temperature and poor blood circulation will have a pronounced effect.

 

Carbon monoxide molecules, even in a small amount, can attach to hemoglobin replacing oxygen molecules. A pulse oximeter cannot distinguish the differences and the reading will show the total saturation level of oxygen and carbon monoxide. If 15% of hemoglobin has carbon monoxide and 80% has oxygen, the reading would be 95%. So a working and often checked carbon monoxide detector in the cockpit is paramount and required by regulation.

 

A pulse oximeter should not be used on people with smoke inhalation, carbon monoxide poisoning, and heavy cigarette smoking, or having tattoos or finger nail polish on the finger to be used.

 

Low quantity of hemoglobin may affect the result. The normal values for a person is 11 - 18 g/dl.

 

Conditions, such as hypovolemia, hypotension, and hypothermia, may have adequate oxygen saturation, but low oxygen carrying capacity. Due to the reduction in blood flow, the sensor may not be able to pick up adequately the pulsatile waveform resulting in no signal or loss of accuracy.

 

Irregular signals can be caused by irregular heartbeats or by patient's movements.

 

Exposure to strong external light may result in inaccurate readings. Shield the sensors from bright lights.  Strong electro-magnetic fields may also affect readings.

 

Dark skin pigmentation can give over-estimated SpO2 readings when it is below 80%. Find a place where the skin color is lighter.

 

Methemoglobin is a form of hemoglobin that does not carry oxygen  1-2% of haemoglobin is normal. A high level of methaemoglobin would cause a pulse oximeter to have a reading of around 85% regardless of the actual oxygen saturation level.

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Eddie,

I do have a background in pulse ox. Outside of aviation, I am a fire medic in KC. We routinely use Pulse Ox per medical protocol. I DISAGREE that pulse ox should not be used in circumstances that 100Hamburger suggests, rather that is should be used as I suggested.............................one piece of the puzzle. Not end-all be-all. Not diagnostic of anything.  Obviously it has some limitations............like anything in aviation that on its face seems like a revelation............................ It is not. For the cost, it is worth it in my opinion to have one for any kind of flying.

 

 

Doug Hereford

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I'll take back my initial reaction.  I have been testing it learning my range and how often I seem to get the right reading.

 

My range on the ground at 8,000' is 92-95 and at 12,500 I was 88 with no discernible effect.  At 88 I figured I'd limit my time and learn what such a reading means at 12,500'.  At first I expected my readings to be normal for sea level because I am acclimated but I guess that doesn't make any difference.  Acclimated doesn't mean my red blood cells have more O2 saturation at altitude. The advantage is from having more red blood cells.

 

I can see that the saturation decreases with altitude, I need to learn at what levels to become alarmed and what limitations become.

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The CT altitude limits are based on density altitude and weight.  Gliders can get very high also riding thermals and waves, so the engine doesn't matter if you are riding one of those.  If you get above 14k and are not trained to use and have a solid setup for oxygen you will die.  The Cirrus has layers of safety built-in around the oxygen system because high altitude flying will kill you if you don't know what you are doing and are not able to get back down quickly if you run into trouble and/or do not detect there is a problem before it's too late.

 

I must be dead. Maybe that's the smell everyone complains about. :laughter-3293:

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I find that at low O2 sats I lose IQ points and become lazy.

 

Normally, simple mental math like, "How long will it take me to descend from 7,500' to 3,500' at 500 fpm?" or "What is the reciprocal of 330°?" are pretty straightforward. When oxygen deprived, first they become harder to solve, and I may just end up not bothering. Plus little mistakes, like missed checklist items, become an issue.

 

But everyone is different, both to the degree that they are affected and the specific manifestations. I rarely feel fatigue or euphoria, it's just like my brain slowly turns to mush, and I may not care.

 

My experience is that most pilots will lose a little "edge" starting at 8,000' to 10,000'. But some may not. Just try to objectively rate your performance as best you can.

 

Best advice? Like Clint Eastwood said, know your limitations.

 

As an aside, being fit and healthy can only help, but even when I was running marathons and cycling centuries, I had to be aware of my personal limitations. It's NOT a contest where one needs to claim bragging rights to boost ego.

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I agree,

Know your limitations..............and don't base them solely on some meter that measures stuff. Unless it is your "self accountability" meter. That being said,

It is probably good to have some prior experience on your own body's reaction to hypoxia if you plan to fly high. The smartest fliers are the ones who are not very smart........if you know what I mean.

I also wholeheartedly agree with being fit. If you are a pilot...............You have surrendered the privilege being out of shape.

 

 

Doug Hereford

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To safely and accurately use an oximeter first get a benchmark by testing levels 5 times in a single day to get your own personal 'norm.' The Oximeter measures Oxygen saturation which is how much oxygen the blood is carrying compared with its full capacity.

 

  • An SpO2 of greater than 95% is generally considered to be normal.
  • An SpO2 of 92% or less (at sea level) suggests hypoxemia.
The device works by shining a light thru the skin and measuring translucency. Both translucency and blood flow at the spot where the measurement is taken can affect the accuracy of a reading. For example, if the area is largely opaque or the blood flow is low or irregular, accurate readings would be difficult.

 

Low atmospheric pressure at high altitude has little to no effect on a pulse oximeter; however extreme low temperature and poor blood circulation will have a pronounced effect.

 

Carbon monoxide molecules, even in a small amount, can attach to hemoglobin replacing oxygen molecules. A pulse oximeter cannot distinguish the differences and the reading will show the total saturation level of oxygen and carbon monoxide. If 15% of hemoglobin has carbon monoxide and 80% has oxygen, the reading would be 95%. So a working and often checked carbon monoxide detector in the cockpit is paramount and required by regulation.

 

A pulse oximeter should not be used on people with smoke inhalation, carbon monoxide poisoning, and heavy cigarette smoking, or having tattoos or finger nail polish on the finger to be used.

 

Low quantity of hemoglobin may affect the result. The normal values for a person is 11 - 18 g/dl.

 

Conditions, such as hypovolemia, hypotension, and hypothermia, may have adequate oxygen saturation, but low oxygen carrying capacity. Due to the reduction in blood flow, the sensor may not be able to pick up adequately the pulsatile waveform resulting in no signal or loss of accuracy.

 

Irregular signals can be caused by irregular heartbeats or by patient's movements.

 

Exposure to strong external light may result in inaccurate readings. Shield the sensors from bright lights. Strong electro-magnetic fields may also affect readings.

 

Dark skin pigmentation can give over-estimated SpO2 readings when it is below 80%. Find a place where the skin color is lighter.

 

Methemoglobin is a form of hemoglobin that does not carry oxygen 1-2% of haemoglobin is normal. A high level of methaemoglobin would cause a pulse oximeter to have a reading of around 85% regardless of the actual oxygen saturation level.

As a matter of Internet protocol, if and when someone copies and pastes something into a post, it's proper to make that clear and to credit the source. Or to just provide the link. Parts of the above appear to have been lifted verbatim from https://www.amperordirect.com/pc/help-pulse-oximeter/z-pulse-oximeter-limitations.html without accreditation, though other sites may have been used and also not credited.

 

Failure to do so can leave readers unsure of whether the post is the poster's own work, and mislead about his or her level of expertise. Or lack thereof. One can just check Doug's posts on the topic for the right way to handle it.

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I'll take back my initial reaction.  I have been testing it learning my range and how often I seem to get the right reading.

 

My range on the ground at 8,000' is 92-95 and at 12,500 I was 88 with no discernible effect.  At 88 I figured I'd limit my time and learn what such a reading means at 12,500'.  At first I expected my readings to be normal for sea level because I am acclimated but I guess that doesn't make any difference.  Acclimated doesn't mean my red blood cells have more O2 saturation at altitude. The advantage is from having more red blood cells.

 

I can see that the saturation decreases with altitude, I need to learn at what levels to become alarmed and what limitations become.

 

Just FYI, typically a SpO2 of 88 or less is considered by medical personnel to be clinically hypoxic.  if you were in a hospital at 88 they would be putting you on oxygen.

 

Again, the problem with hypoxia is that it is very hard for the hypoxic person to descern the effects.  It's usually noticed by other, non-hypoxic people.

 

When I flew at 11,500ft (the highest I have been as PIC), I checked my SpO2 and it was in the 94 range.  But even so, I could tell I was "not quite as sharp" as I am at lower level.  Almost like I was operating on a slight sleep deficit.

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Those CO dots I keep replacing (because they are required equipment) are basically worthless, as I understand it. They will tell those who find your body why you died.

 

I think that's generally true.  They are there to fulfill a perceived need for CO indication, but don't do much.  

 

Once good thing about the CT, is that I flew last year in Page (unknowingly) with completely broken exhaust pipe, probably for two days and 5-10 hours of flying.  I didn't notice any issues and didn't die.  So the ventilation and resistance to gas getting through the firewall on a CT *seems* pretty good.

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Altitude(feet) Altitude(meters) Air Pressure(mmHg) Oxygen Pressure(mmHg)  % of sea level Oxygen Equivalent O2 partial
pressure at sea level SpO2
Unconditioned SpO2
post-6-0-45858800-1467298827_thumb.jpg

http://fellrnr.com/wiki/SpO2

 

 

Looks lime my numbers at 8,000' and 12,500' are just where they are supposed to be and given the percentage of O2 decrease those numbers are pretty much where they have to be.  I live with 7% less O2 in the atmosphere and I have 93% saturation.

 

90% is the cutoff for the medical workers to get concerned and 80% is the cutoff for organs like heart and brain to start dying.  Does my extra dense blood thickened with more red blood cells make a difference?  I'm sure it does it means I compensate for less satuartion with more O2 carrying cells.  That should mean I'm better at 88 SpO2 than if I had thinner blood at 88.

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You can see Sp02 acclimation difference in the chart above.

 

Take 15,000'

  • Unconditioned = 81.6% almost to the point where vital organs begin to die
  • Conditioned = 89.1% almost low/normal

Guess its a combination of more red blood cells and better Sp02.

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You can see Sp02 acclimation difference in the chart above.

 

Take 15,000'

  • Unconditioned = 81.6% almost to the point where vital organs begin to die
  • Conditioned = 89.1% almost low/normal

Guess its a combination of more red blood cells and better Sp02.

 

But...you said you were at 88 at 12,500ft.  According to your chart that is almost right at the "unconditioned" level of 87 for that altitude.  I don't think a medical worker would be unconcerned if you were at 88 and just say "it's okay, he lives at 8000ft".

 

just IMO, but I think you should be on O2 at a saturation of 88 regardless of conditioning and altitude tolerance.  If you are going to throw away the numbers that a pulse oximeter gives you as invalid, then why bother using one at all? 

 

Here's a paper on high altitude adaptation that is interesting:  http://icb.oxfordjournals.org/content/46/1/25.full.pdf  One line that caught my eye was:  

 

"At one time It was thought that the polycythemia was the most important feature of acclimatization but we now know that its value is much less than that of the hyperventilation."

 

In other words, faster breathing rate is more of a factor in acclimation than is increased red blood cell production according to this paper.

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As a matter of Internet protocol, if and when someone copies and pastes something into a post, it's proper to make that clear and to credit the source. Or to just provide the link. Parts of the above appear to have been lifted verbatim from https://www.amperordirect.com/pc/help-pulse-oximeter/z-pulse-oximeter-limitations.html without accreditation, though other sites may have been used and also not credited.

 

Failure to do so can leave readers unsure of whether the post is the poster's own work, and mislead about his or her level of expertise. Or lack thereof. One can just check Doug's posts on the topic for the right way to handle it.

 

Nonsense.  The information is correct - read it and learn about the subject.  By the way, I have been writing a blog for 7 years which is carried by a dozen social websites and two dozen lists on Twitter...it is read daily by tens of thousands.  So far, no complaints over my style and content.  And only a few death threats from nutcases that take exception to facts written about liberals.

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Nonsense.  The information is correct...

 

 

...and plagiarized.

 

Not the first time, the way.

 

But way to miss the point and change the subject - no one questioned if the info was correct, only that it was posted without attribution, which is generally considered poor form.

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But...you said you were at 88 at 12,500ft.  According to your chart that is almost right at the "unconditioned" level of 87 for that altitude.  I don't think a medical worker would be unconcerned if you were at 88 and just say "it's okay, he lives at 8000ft".

 

The spread between controlled and uncontrolled at 12,500 is still pretty small, the spread increases as you go higher.

 

The point for the medical worker to consider isn't that I live at 8,000' its that my saturation was 88 at 12,500' which is higher than unconditioned.  The medical worker should become concerned if I was lower not higher.  

 

Andy,  I can camp above 14,000' and do strenuous things like climb and hike with no issues.  I'm probably fine at 20,000'.

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The spread between controlled and uncontrolled at 12,500 is still pretty small, the spread increases as you go higher.

 

The point for the medical worker to consider isn't that I live at 8,000' its that my saturation was 88 at 12,500' which is higher than unconditioned.  The medical worker should become concerned if I was lower not higher.  

 

Andy,  I can camp above 14,000' and do strenuous things like climb and hike with no issues.  I'm probably fine at 20,000'.

 

Precisely.  The point being since CT has acclimated to 8,000 he can safely fly much higher without concern.  This does not apply to sea level pilots who probably feel some ill-effect at 8,000 both flying and when skiing.    In Tibet people live at 15,000 feet. imagine being able to climb Mt. Everest without oxygen or getting tired?  They can do it.  Visitors cannot.

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Regarding not being able to tell if you are experiencing hypoxia...  Upon reflection, when I was flying over SLC at about 13.5, I had an incident where I couldn't understand ATC.  I had to have him repeat the instruction several times.  It wasn't that I couldn't hear, but rather I didn't recognize the commands as terminology I understood.  I think we both just gave up as I moved out of the area.  It is possible that I was experiencing hypoxia.  I should have reviewed the recorded ATC communications, but didn't think about it until a couple of years later.

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If you get above 14k and are not trained to use and have a solid setup for oxygen you will die

 

So if I quickly climbed up well above 14k and then descended back down I would die?

That's weird I'm still here...

 

The 100's of plane loads of jumpers (along with the pilots) that used to jump out of my local airport at 17,500 must have all died, no wonder that place is closed down now. It makes sense now thanks for clearing that up.

 

 

 

 

 

I never said the plane won't get to 14,000...I said no one would want to or need to be flying at that altitude in the plane.  That altitude exceeds the POH and a violation of Sport Pilot rules.  Do you break the rules in your plane? 

 

When reading the thread objectively and not looking for ways to attack someone (as happens on the COPA site routinely) the thread has established that flying the CT at it's rated maximum of 12,300 feet density at MTOM can be done without an oximeter and without oxygen safely for most.  The exceptions being sea level guys that have known lung issues like smoking, COPD or age problems.

 

We have lots of mountains above 14k here in Colorado, so technically a sport pilot could need or want to go that high and still remain within 2,000 agl and not break one of the silliest rules ever created.

 

 

I agree that depending on where you live, and what you are acclimated to, and your health and fitness all play into what kind of altitude you can safely fly (not talking about the rules, talking about what's actually real)... but you did state that LSA's can't go above 14k, and that is not accurate. Sorry... you said it.

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