Mooney down in Atlantic

[Jeff_S]

Someone above mentioned that the physical sensation you feel when breath holding is actually build-up of CO2 rather than a lack of oxygen. I was reminded of a passage I recently read in the book "The Martian" which I highly recommend by the way (movie comes out Oct. 2).  The lead character is discussing what he would do if he got to the point where his final rescue went Tango Uniform and he knew there were no more chances. He described that he wouldn't just sit there and wait for the inevitable, but rather he would adjust his gas mixture to almost pure nitrogen (as I recall) and just breath his way to sleep peacefully, since the nitrogen breathing would still allow the CO2 to expel and he wouldn't feel a struggle.  Not sure why I just decided to share that somewhat morbid thought, but there it is.

[donkaye, MCFI]

Lots of good information in this thread.  One more very important thing should be mentioned, though.  Hypoxia isn't the only issue with flying high.  Another big issue that affects some people more than others and is a major issue with U2 pilots and can be a deadly as hypoxia is the BENDS.  It is also cumulative.  I've had to deal with that issue for the duration of my Mooney ownership.  Initially, I didn't know what was happening to my number 2.  She complained about joint pain after 3 hours aloft.  It was only after a stop in Rock Springs on the way to Oshkosh one year that I knew I had to find out what was going on.  Her whole chest was covered with blotches.  In hindsight we should have found the nearest hyperbaric chamber, but I was oblivious to what was going on at the time.  Later, calls to Brooks Air Force Hospital in San Antonio and an actual trip to the University of North Dakota brought the issue to the forefront for us.  Over the past 10 years we have mitigated her problems and she has not suffered any incidences of the Bends since.

There are 5 means of mitigation:

1. Pre breath O2 with a sealed mask for ½ hour before flying.  (Not really practical for us).

2. Take an aspirin 1 hour before flight.

3. Hydration--drink plenty of water

4. Slow ascent rate

5. Time aloft.

What I have found works best is the aspirin, water, slow ascent rate, but most important is time aloft.  3 hours is the maximum I'll fly with her.  We have experienced an incident within that time frame only once many years ago.  It was at 17,000 feet and a descent to 13,000 mitigated the issue.

The good news for me (and her) is I don't fly in the flight levels.  18,000 feet is tops for me on extended range.  Usually I'll fly 15,000 to 17,000 feet.  The difference in true airspeed between those altitudes and higher just isn't that much.  I will sometimes climb to 20,000 for 10 minutes when going over the Sierras, but immediately descend when the terrain risk subsides.

If the weather is bad enough to required a climb to the flight levels, we land or don't go at all.  We've ended up having some great experiences is places we never would have gone.

So consider the Bends issue when you are flying high for an extended period of time in addition to the hypoxia issue.  It can occur at a much lower altitude than you might think.

Regarding O2 use for me: above 7,500 feet during the day and from engine start to engine stop at night.

[Jeff_S]

Interesting point. As a scuba dive master I've been well aware of the danger of flying soon after diving, but didn't think about someone getting the bends just from altitude alone. While not an issue for non-pressurized planes, I suppose the bends could be an issue in a sudden decompression scenario as well. Here's an interesting tidbit along those same lines.  The difference between cabin pressure in an airliner at cruise altitudes vs. normal air pressure at or about sea level is the equivalent of being 8 feet underwater. I know this because my brother (the idiot) decided to activate my new dive computer one time while we were enroute to Cozumel, and when we landed it was showing that we were 8 feet under water! After some worry about not being able to reset it (internal battery only) we were relieved when some internal algorithm decided that these idiots couldn't possibly have stayed in the water for 12 hours so it shut itself off.

[ToddDPT]

I wonder if there are other styles of these oximeters rather than the finger end version. Anyone research this? I often wonder if it can be obtained through some other method (like your earlobe with an extension cable). If so, I suspect pilots might be likely to wear it through the flight.

 

 

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Yes, but they are more for medical professionals.  Here is the ear clip only at $172 and you still have to purchase the $325 unit.

http://www.sourcemedicalequipment.com/Nonin-8000Q2-Ear-Clip-Sensor-p/8000q2.htm?gclid=COr10-3Q-ccCFRRlfgodUoMCjg&utm_source=google&utm_medium=cse&utm_term=8000Q2

http://www.sourcemedicalequipment.com/Nonin-8500-Hand-Held-Pulse-Oximeter-p/8500.htm

 

[donkaye, MCFI]

Yes, but they are more for medical professionals.  Here is the ear clip only at $172 and you still have to purchase the $325 unit.

http://www.sourcemedicalequipment.com/Nonin-8000Q2-Ear-Clip-Sensor-p/8000q2.htm?gclid=COr10-3Q-ccCFRRlfgodUoMCjg&utm_source=google&utm_medium=cse&utm_term=8000Q2

http://www.sourcemedicalequipment.com/Nonin-8500-Hand-Held-Pulse-Oximeter-p/8500.htm

 

I just hang mine on the prop control knob and check it every 15 minutes or so.

[Bennett]

Early in this thread I mentioned that I often flew in the flight levels crossing the country, and that some of the times it was at FL270 eastbound. The only reason I went so high was for the tailwinds, and once or twice I caught the lower edge of the jet stream. I hated the way the airplane flew, and the discomfort, but I was generally in a hurry, and being younger and more more foolish, I thought I was immortal. Now that I am older (maybe a bit wiser) I realize the risk factors. So now I fly a J which I have never had above 15,000'. I do use oxygen starting at about 12000', and I can cross the country staying under 12000 by using the southern routes, with good terrain clearances. Slower, and sometimes I am blocked by weather I previously would have flown over, but more comfortable and enjoyable. My J seems to run best between 7000' and 10,000', and I can avoid hypoxia concerns, but if I start feeling fatigued, I will use oxygen, even at 7000'.

[ArtVandelay]

I noticed everybody uses absolute altitudes, does anybody check the density altitudes when deciding to use O2 or what altitude to pick?

[Jeff_S]

Density altitude is not a factor for breathing O2. The reason being, once you have breathed in the air, your lungs instantaneously transform the molecules to body temperature (whether they started out hotter or colder) so the only thing that matters is the pressure altitude.  And so as not to sound like a total know-it-all, I had the same question myself not long ago so I Googled it and found a few reputable sources that gave me that info.

Edited September 15, 2015 by Jeff_S

[kortopates]

I noticed everybody uses absolute altitudes, does anybody check the density altitudes when deciding to use O2 or what altitude to pick?

What would be the relevance of density altitude to us physiologically breathing in the cockpit? Seems that all that really matters is the decreased partial pressure of O2 reducing our ability to assimilate oxygen. Our alveoli are pretty much at constant temperature to begin with which helps to equalize the air temp to our temperature anyway. Just wondering why it would matter? Incidentally, I think you meant pressure altitude.

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[ArtVandelay]

What would be the relevance of density altitude to us physiologically breathing in the cockpit? Seems that all that really matters is the decreased partial pressure of O2 reducing our ability to assimilate oxygen. Our alveoli are pretty much at constant temperature to begin with which helps to equalize the air temp to our temperature anyway. Just wondering why it would matter?

Well from wikipedia"The power output of the engine — power output depends on oxygen intake, so the engine output is reduced as the equivalent dry air density decreases and produces even less power as moisture displaces oxygen in more humid conditions."

If it affects the engine's oxygen intake, it seemed reasonable it might affect ours, hence the question

[ArtVandelay]

Density altitude is not a factor for breathing O2. The reason being, once you have breathed in the air, your lungs instantaneously transform the molecules to body temperature (whether they started out hotter or colder) so the only thing that matters is the pressure altitude.

Points taken, but I'm not sure I buy the "instantaneously", especially when they qualify it with "for practical purposes"  Probably enough to minimize the effects.

[kortopates]

Sorry Teejayevans, after re-reading my post I may have sounded like a jerk - but not my intention. I thought you were thinking along physiological lines. Jeff nailed it - which was what I thought would be the case.

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[bradp]

Density altitude affects the alveolar gas equation (what determines the level or more accurately the partial pressure) of oxygen in the gas exchange parts of your lungs. The more water vapor the higher the density altitude and and lower partial pressure of oxygen. Partial pressure is what drives oxygenation. However this is moot in the very dry environment of breathing oxygen via mask or ambient air in the flight levels.

The reason I asked about pulse oximetry is that spot checks are not the ideal way to monitor ... Continuous oximetry is. Don't get me wrong, spot checks are 1000x better than no oximetry at all, but not as useful as trending and being able to set an alarm at a predefined value (probably 94% as a lower limit in someone with baseline healthy lungs) BEFORE the insidious symptoms of hypoxia set in. For those who have altitude chamber experience, you might be a bit safer with intermittent checks, but symptoms can vary with things like age (alt chamber in your 20s may not be the same as when you're 50), fatigue, hydration status, etc.

The other factor I'd like the group to consider is that the maximal Percent of oxygen that you will get with a nasal cannula setup regardless of whether it has a nerdy looking reservoir thingy is about 30-35% because you are entraining ambient air along with it even if you jack up the flow rate to 4 or 6 liters per minute. With a simple face mask at 6-8 liters per minute you can expect between 40-60% oxygen that you breathe. A non re breathing face mask (the kind with the bag similar to the principle that the fancy airliner masks use) can provide about 85-95% oxygen I ideal conditions using between 10-15 liters per minute of pure oxygen.

What does this mean in real life? Well using the gas equation, and a nasal cannula at FL240 with about 400 mmHg standard atmosphere and assuming no water vapor, you can expect an alveolar oxygen pressure of 70 which equates to an oxygen sat of somewhere near 90-92%. Using a simple face mask you start out with an alveolar pressure of 150 and that equates to an oxygen sat of 99%. A non rebreather mask wouldn't help the saturation much more but they would give you a longer reserve should your oxygen apparatus quit functioning. In that situation you'd start out with an alveolar oxygen pressure of 350.

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[kortopates]

 

 

 

 

For sure, continuous oximetry will be a big improvement. But it seems the technology for a affordable solution in the cockpit is still aways off. As it is, the majority of pilots now are content with a uncalibrated oximeter. By that I simply mean a cheap Chinese one rather than one made by reputable medical company such as Nonin (e.g. Flightstat, Onyx etc) that has spent the time to calibrate their units. There are enough tests out there that show the cheapo's can read falsely high when real O2 sat drops off. Plus the cheapo's often break when dropped. Some suggest taking multiple ones, but why not a reliable and proven reasonably accurate medical quality one

 

 

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Edited September 16, 2015 by kortopates

[donkaye, MCFI]

 

 

For sure, continuous oximetry will be a big improvement. But it seems the technology is for a affordable solution in the cockpit is still always off. As it is, the majority of pilots now are content with a uncalibrated odometer. By that I simply mean a cheap Chinese one rather than one made by reputable medical company such as Nonin (e.g. Flightstat, Onyx etc) that has spent the time to calibrate their units. There are enough tests out there that show the cheapo's can read falsely high when real O2 sat drops off. Plus the cheapo's often break when dropped. Some suggest taking multiple ones, but why not a reliable and proven reasonably accurate medical quality one

 

 

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I've compared my Nonin Flight Stat that constantly has battery problems with my inexpensive Oxi-Go and they read the same.

[Danb]

Why not bring two quality oximeters, as Don pointed out he tested his against the morning flight stat,  no problem just remember to have extra batteries..those darn things run out at the worse times.

this thread has turned into an awesome learning tool, at least we're trying to improve ourselves from someone's tradgety.

 

[kortopates]

I've compared my Nonin Flight Stat that constantly has battery problems with my inexpensive Oxi-Go and they read the same.

In the mid to upper 90s they seem to all be on par, drop in the 80s and I've seen some of the cheapo's report significantly higher. BTW, my flightstat has had no battery problems and still going strong more than a dozen years old.

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[bradp]

In the mid to upper 90s they seem to all be on par, drop in the 80s and I've seen some of the cheapo's report significantly higher. BTW, my flightstat has had no battery problems and still going strong more than a dozen years old.

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All pulse oximetry use the same technology. The variation comes in the quality of the light sensor, light filtration outside the wavelengths of interest and the processing algorithm to tell what's junk and what's real. All pulse oximetry reliability declines with lower saturation. Even the fancy $1000+ oximeters I use at work aren't reliable below about 70%.

One more thing to remember is that carbon monoxide can cause a falsely high pule oximetry reading. That is because carbon monoxide binds to hemoglobin and makes it for all intents and purposes look like red blood to the oximeter. Thus the cherry red skin in Caucasian folks you hear about with carbon monoxide poisoning. An unpressurized aircraft with a minus whatever really cold outside air temperature will invariably be using cabin heat. Please invest in a carbon monoxide detection system (they're cheap). It's just as important as a pulse ox.

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[Marauder]

Yes, but they are more for medical professionals.  Here is the ear clip only at $172 and you still have to purchase the $325 unit.

http://www.sourcemedicalequipment.com/Nonin-8000Q2-Ear-Clip-Sensor-p/8000q2.htm?gclid=COr10-3Q-ccCFRRlfgodUoMCjg&utm_source=google&utm_medium=cse&utm_term=8000Q2

http://www.sourcemedicalequipment.com/Nonin-8500-Hand-Held-Pulse-Oximeter-p/8500.htm

 

I think the answer is something like this. At $500, cheap insurance considering we know of two GA accidents (TBM 900 and the Cirrus 22) and possible this one. Add in a good CO detector like Brad is suggesting, odds in your favor improve. The constant monitoring is the key and that is the reason for my question about these kind of devices. Even if it is inaccurate below 90% I would rather it be accurate at 90% and monitoring me all the time to let me know that I am becoming slightly hypoxic. 5 minutes between readings with a finger tip unit is a lifetime (possibly your lifetime).

A few years ago when I was sitting in a hospital dealing with DVTs and knowing the risk of PEs, I was perfectly fine being wired up like Frankenstein's monster. If it wasn't for that experience, you guys would have missed out on all the fine ladies I brought you.

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[kortopates]

I couldn't agree more. The ear lobe unit look like a great affordable solution (I couldn't follow the link till now to see it); especially in the flight levels. In fact, would be a good SOP to always use on when flying in the flight levesl all alone. I also have been concerned enough to take the Carbon Monoxide threat seriously into install a CO Guardian unit in the panel that replaced my Mooney clock: http://www.guardianavionics.com/aero553-101-001.html . Like everyone, I started with little portable solutions but it wasn't too long before I realized I was kidding myself as it wasn't operational half time for one reason or another. With my panel unit its always there and on for 5 years till it needs a new sensor and there is no way to miss the alarm..

There has been much discussion on the backups too. I wanted to share this very simple and affordable solution that fits in the seat back and will always have O2 when you need it. http://www.mhoxygen.com/index.php/portable-constant-flow/emergency-systems/165-ntg-co-pilo2t-portable-o2 only weighs ounces and you can get replacement cylinders easily enough.

[Piloto]

I wonder if there are other styles of these oximeters rather than the finger end version. Anyone research this? I often wonder if it can be obtained through some other method (like your earlobe with an extension cable). If so, I suspect pilots might be likely to wear it through the flight.

 

 

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It works on your toes. The earlobe sensor will interfere with the headset.

José

[Marauder]

It works on your toes. The earlobe sensor will interfere with the headset.

José

Judging by the look of those toes, it's clear we didn't do a good enough of a job clearing zombies from MooneySpace. Men, and ladies, arm yourselves, we have work to do...

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[Openwheeler3]

During the first week of initial entry rotorcraft training, the Army made all us new 2LTs and the WOCs go through the altitude chamber after a few classes on aeromedical factors, including hypoxia. We were all thinking, "We fly helicopters at tree top level so why do we need to do this?" I am so glad now for the experience. Very enlightening.

My face feels flush and "tingles." They had us remove our mask at 24,000 and stare at a chart of bright colors. It turned to black and white in just a few seconds. Peripheral vision became tunnel vision. Then they took us down to 18,000 to remove the masks again and gave us puzzles or worksheets to do. After 30 - 60 seconds I didn't know what 2 + 2 was, what letter came after C in the alphabet ... or simple stuff like my birthdate or address? I did know somehow to put my mask back on. Some of the "big egos" needed some help to,put their masks back on ... the ones who,were bragging they were super pilots and could leave their masks off longer than us normal pilots.

Funny who and what you remember. Mike Moriarty was probably the sharpest guy in our class of 2LTs. He was sitting next to me  at 18,000 when we were told to take the masks off. I was given clipboard with a work sheet to do. As described above, I didn't know what 2 + 2 was after a minute. Mike was given a plastic PlaySchool Puzzle. Literally, put the round peg in the round hole, square peg in square hole, triangular peg in triangular hole. I specifically remember looking over at Mike. He looked completely dumbfounded at what to do with the square peg! He was staring at it, holding it ... Mike Moriarty, one very sharp guy. I put on my mask then and after a few seconds tapped Mike and pointed at my mask. He put his mask on then too ...

Other lessons that first week included spatial disorientation and meteorology ... They played ATC tapes of pilots last moments after experiencing these (Spatial disorientation - A single pilot army helicopter IFR, no autopilot, given multiple tasks by ATC, came out of the low clouds inverted. Meteorology - A Bonanza flight into a extreme thunderstorm with his family on board. I remember he told the controller that they were still climbing, but the wings were no longer attached to the fuselage ... and he asked the controller what he should do?) Very sobering. Flying can be very unforgiving ... These lessons made such an impression on me that I remember them years later, decades later ... as if it were yesterday. 

I have to second this account.  I did the altitude chamber early this year at FT Rucker and we had several mental tasks to do as well. Additionally, they showed us how our night vision was affected at altitude. A key, as many have mentioned, is knowing how hypoxia feels to oneself.  For me, it's feeling flush and tingly. This knowledge helped me when I first started flying at high altitudes and set the oxygen flow incorrectly a couple of times. 

[Bennett]

I couldn't agree more. The ear lobe unit look like a great affordable solution (I couldn't follow the link till now to see it); especially in the flight levels. In fact, would be a good SOP to always use on when flying in the flight levesl all alone. I also have been concerned enough to take the Carbon Monoxide threat seriously into install a CO Guardian unit in the panel that replaced my Mooney clock: http://www.guardianavionics.com/aero553-101-001.html . Like everyone, I started with little portable solutions but it wasn't too long before I realized I was kidding myself as it wasn't operational half time for one reason or another. With my panel unit its always there and on for 5 years till it needs a new sensor and there is no way to miss the alarm..

There has been much discussion on the backups too. I wanted to share this very simple and affordable solution that fits in the seat back and will always have O2 when you need it. http://www.mhoxygen.com/index.php/portable-constant-flow/emergency-systems/165-ntg-co-pilo2t-portable-o2 only weighs ounces and you can get replacement cylinders easily enough.

Great catch for the portable O2 unit. I will order one in the next few days and keep it in the backseat area where I can easily reach it. I have two "standard" O2 bottles, but I only take them when I plan to go high. This little portable unit will be perfect for those times when I feel a bit fatigued, or when I have to climb for terrain or a set of clouds where I know I will be descending shortly thereafter.

I also have a panel (console) mounted Guardian O2 unit, with a panel mounted annunciator.

[Danb]

Jose

 

they sum nasty looking toes...