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Hypoxia Incident Today

helodriver

helodriver

Member
I am currently flying King-Air 200's at work. We had a post maintenance flight today that really got my attention.

After doing our ground checks we took off and started a climb to 10,000. All of our tests were per the check-list and returned normal outcomes. We then started a climb to 16,500 to do some engine checks and complete the final checks on the pressurization system. Everything was normal. The final check includes "Dumping" the cabin to check the warning lights and ensure the O2 mask fall when the cabin altitude goes above 12,500. So everything worked as advertised and we leveled at 16,500 and started the engine checks. After a few minutes I started feeling euphoric. (I mean other than the usual euphoria that comes along with getting to fly for a living.) It took about 5 seconds for me to realize that I was hypoxic. I checked the cabin altitude and sure enough it was at 16,500. The warning light was still on. I announced the problem and that I was descending. My Co-Pilot called center and we returned home.

I am thankful that I have had Altitude Chamber training and knew instantly what was wrong with me. I just wanted to share this story.
 
One more thing.

I forgot to add the reason why the cabin stayed at 16,500. For whatever reason, the dump valve stayed open after we tested it. After landing the mechanics tested it and it worked fine.
 
I whole-heartedly agree on the importance of chamber rides for those routinely flying above O2 altitudes! I've been doing them every 3 years throughout my career, and it's really important to be able to recognize your symptoms.

Paul
 
helodriver said:
I am currently flying King-Air 200's at work. We had a post maintenance flight today that really got my attention.

After doing our ground checks we took off and started a climb to 10,000. All of our tests were per the check-list and returned normal outcomes. We then started a climb to 16,500 to do some engine checks and complete the final checks on the pressurization system. Everything was normal. The final check includes "Dumping" the cabin to check the warning lights and ensure the O2 mask fall when the cabin altitude goes above 12,500. So everything worked as advertised and we leveled at 16,500 and started the engine checks. After a few minutes I started feeling euphoric. (I mean other than the usual euphoria that comes along with getting to fly for a living.) It took about 5 seconds for me to realize that I was hypoxic. I checked the cabin altitude and sure enough it was at 16,500. The warning light was still on. I announced the problem and that I was descending. My Co-Pilot called center and we returned home.

I am thankful that I have had Altitude Chamber training and knew instantly what was wrong with me. I just wanted to share this story.
Click to expand...

I can assure you from first hand experience that your controlled chamber 'feeling' and your next real world 'feeling' when hypoxia hits don't have to be the same. Flight Surgeon told me later that it's not impossible for symptons to change for whatever reason.
 
Another symptom is blue finger nails.

Flat landers flying at 10,500' - 12,500 always feel a little weird and checking for blue nails is what I do to make sure it isn't hypoxia.

How did you get that 200 to 16,500 not knowing it was unpressurized? I flew those things a long time ago and it seems to me it has a few bells and whistles including one for no cabin pressure above 12,500. Maybe that system was not working?

That's serious stuff an any high altitude machine. Payne Stewart, the golfer, is long gone since the Citation he was a passenger on climbed very high and everyone went to sleep.
 
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I live at ~50' msl and spent 1.5 hrs at 10,000 feet.. I didn't feel the effects in flight, but after tying down and going to lunch I had a POUNDING headache... Something that's really usual for me.

After a few hours, it went away. But now I know that 10K is o2 land for me... Since I moved closer to sea level, my lung capacity isn't quite what it used to be.
 
David-aviator said:
Another symptom is blue finger nails.

Flat landers flying at 10,500' - 12,500 always feel a little weird and checking for blue nails is what I do to make sure it isn't hypoxia.

How did you get that 200 to 16,500 not knowing it was unpressurized? I flew those things a long time ago and it seems to me it has a few bells and whistles including one for no cabin pressure above 12,500. Maybe that system was not working?

That's serious stuff an any high altitude machine. Payne Stewart, the golfer, is long gone since the Citation he was a passenger on climbed very high and everyone went to sleep.
Click to expand...

We had dumped the cabin at 10,000 to make sure the dump switch worked. You then have to climb and check the cabin climb rates at various settings to make sure the pressure controller works throughout its settings. Yes the 12,500 light came on. It was supposed to. Yes the masks came down, they were supposed to. The cabin seatbelt sign came on like it was supposed to. The the dump valve didn't close when the switch was released.

There is no doubt that it was our fault for not checking to see that the cabin was descending properly after we were finished with that part of the check.
 
Boy, this sounds an awful lot like what might have happened to golfer Paine Stewart in his Learjet accident where all on board perished due to the effects of hypoxia. Perhaps a dump valve stuck open? As you may know, this airplane launched off into a zero pressure cabin and they apparently got all the bells and whistles and still became incapacitated.

Anyone considering the use of oxygen in an RV ought to try to look into one of the FAA-sponsored altitude chamber rides. One should know their own symptoms of hypoxia and even though they may change over time, euphoria is euphoria, and the sense of well being that you experience is an eye opener. It's kind of fun too!
 
lucky said:
I can assure you from first hand experience that your controlled chamber 'feeling' and your next real world 'feeling' when hypoxia hits don't have to be the same. Flight Surgeon told me later that it's not impossible for symptons to change for whatever reason.
Click to expand...

I've had numerous chamber rides through the years and how your body responds to a hypoxia event can change over time. That's one of the reasons it's a firm scheduled event every three years. However, the ride is not only to show what your symptoms may be but also help you recognize other possible symptoms in the people you are sharing the cockpit and/or cabin with. Even a single seat "fighter pilot type" should be able to recognize symptoms when his wingman may be in trouble.

I'd suggest if anyone has an opportunity to take the academic course and "do a ride" that they make time in their schedule. The variations in both the symptoms and effects are real eye openers.

And, if you want some more excitement, try practicing RD?s!
 
Terry...

We had dumped the cabin at 10,000 to make sure the dump switch worked. You then have to climb and check the cabin climb rates at various settings to make sure the pressure controller works throughout its settings. Yes the 12,500 light came on. It was supposed to. Yes the masks came down, they were supposed to. The cabin seatbelt sign came on like it was supposed to. The the dump valve didn't close when the switch was released
Click to expand...
What I cannot understand from your post(s), is surely you were wearing Oxy masks when you "dumped" the cabin? Or not... :confused:

I am also of the view, that after numerous hypoxia chamber runs, the lesson for me was not that "I know my symptoms". What I do know is that they are not very apparent, even when "looking" for them, and under stress / activity, almost certainly would not notice them :(

Andy
 
Reply to Andy,

We dumped the cabin at 10,000 and released the switch at 12.5. No we weren't wearing O2 masks. Our rules don't require it until 14k. Normally this would have been a non issue. I learned a big lesson. This was my first maintenance test flight in the 200. In helicopters we very rarely went to 10k.

You can bet from now on, level off will be at 12.6 . Until everything is working and the cabin altitude is down and stabilized I will not continue the climb.

This was my first maintenance test flight, and it was with a very senior pilot. I don't care how experienced someone is, if it doesn't seem right then you shouldn't be doing it. Just because it has always been that way doesn't mean it is right. One of our crew resource points is to never rely on the experience of the person your flying with. Just because a pilot is more experienced or senior to you doesn't mean that everything that he does is right.

I am not a new aviator, just new to airplanes. I knew better.
 
We dumped the cabin at 10,000 and released the switch at 12.5. No we weren't wearing O2 masks. Our rules don't require it until 14k
Click to expand...
OK - I see now. Over here, both Civil and Mil it is on O2 at/above 10K' cabin, and max cabin 25K'. And positive Oxy flow checks at time intervals and passing Alt levels.

As you say, lesson learned, and well worth passing on as you have done... I now fly ex-Mil jets as an instructor, and avoid anything above 10K' cabin - without the support, equipment and regular Mil training, I find the prospect of risking hypoxia as a step too far ;) It worries me how some of the owners are keen to go up high, without that support :mad:

Andy
 
One of those small oxymeters that are available to pilots would be very useful if you fly above about 10k feet. Simply slip a finger into it and it'll report the blood oxygen level in percentage.

I've found that I like to maintain at least 92%, and that I can adjust the oxygen flow to achieve that. There's a direct, rapid relationship.

It's a great safety device, in my opinion. Highly recommended.

David Paule
(And except for owning and using one, I have no connection to them.)
 
David Paule said:
One of those small oxymeters that are available to pilots would be very useful if you fly above about 10k feet. Simply slip a finger into it and it'll report the blood oxygen level in percentage.

I've found that I like to maintain at least 92%, and that I can adjust the oxygen flow to achieve that. There's a direct, rapid relationship.

It's a great safety device, in my opinion. Highly recommended.
Click to expand...

I'm seriously thinking about one of these. Recently spent 8 days in the hospital and had one of these clipped to a finger or toe, while on supplemental oxygen the whole time. A few times, it drop below 90, set off the alarm, and I'd have to adjust my breathing, even if it took one of those nose strips or mental thoughts of breathing to keep everything in order. I'm already convinced to get one, since I often fly 10,500 to 12,500 without oxygen most of the time, and always with above that. I'm not a "flat lander", so I'm use to higher altitudes to start with. But now I'd like to know for sure!

L.Adamson -- RV6A
 
Shockwave said:
What is the purpose of being able to dump a plane's pressurization?
Click to expand...

A dump valve, also known as a safety valve, is to prevent over pressurization and thus possible structural damage. The outflow valve normally controls pressurization, but the safety valve opens if the outflow valve malfunctions, thus limiting cabin pressure.
 
Shockwave said:
What is the purpose of being able to dump a plane's pressurization?
Click to expand...

Another purpose is smoke and fume elimination. Cabin fire suppression is another. One more is when landing at an airport with a pressure altitude higher than 12,500 feet. One more is on the ground when you can't get the doors open.
 
hypoxia

Hypoxia is just one effect of a fairly rapid ascent from sea level to 16.5.
"Mountain sickness" can also occur at levels above 10K. Usual result is a "pounding headache", although lethargy, fatigue, nausea and vomiting and difficulty with mental functions can also occur. Night vision is also affected.

High altitude pulmonary edema is the worst form of mountain sickness and usually occurs at much higher levels and with longer exposure but some individuals are highly susceptible at lower levels. One of the members I used to "non-technical" climb with got sick at 10K, almost had to be carried out, and thereafter was unable to climb or hike at that level, even with oxygen as a backup. You may not have any problems but keep that in mind if your passenger starts to get ill.

High altitude chambers are very useful for demonstrating and familiarizing individuals with their own reactions to hypoxia, but also can have their own set of problems. Rapid decompression, like those done in a military protocol, can induce one of the various forms of the "bends" and is an emergency. Individuals past 40 and smokers have a higher incidence of problems. So, a class III medical may be a false sense of security and for older individuals, you might want to get some basic checks first.

Most of the forum members probably already know this but a pulse ox may also be misleading if a lesser amount of hypoxia is combined with elevated CO levels. A number of years ago, before portable CO monitors were available, one of my mentors augured his twin into the ground one night killing himself and his wife and the final suspected cause was carbon monoxide. The higher you go, the more precautions you should take.
Dave A.
RV-6A still not done
 
koda2 said:
High altitude chambers are very useful for demonstrating and familiarizing individuals with their own reactions to hypoxia, but also can have their own set of problems. Rapid decompression, like those done in a military protocol, can induce one of the various forms of the "bends" and is an emergency. Individuals past 40 and smokers have a higher incidence of problems. So, a class III medical may be a false sense of security and for older individuals, you might want to get some basic checks first.
Click to expand...
The number of possibly "bent" people from chambers has prompted RAAF to go to Hypoxia simulation/Reduced O2 Breathing Device using a mask/O2 at ground level that just delivers low O2 air. Perfectly good for purpose but much less fun.
One advantage the set up could come to you rather than you go to chamber.
John
 
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I'm an active AirForce flyer and get to go to the chamber every 5 years. I just went to the Beale AFB chamber not long ago. My symptons had changed quite a bit from the last time I was there. They do several vision acuity demos and then you get to do some basic math on paper as you become hypoxic. By the end all I had was a line across my paper. It's pretty funny to watch other peoples reactions. Blue lips and nails are very obvious when a person is full on Hypoxic.

I hope there's no one on here that thinks they can handle it or won't be affected by it. It will kick your butt even at lower altitudes. We did our Demos at 18,000 ft. One guy was completely incapicitated in 3 minutes. I put my mask on at 4 minutes after everything was black and white and my whole body was tingling. One guy made it 8. TOC (Time of useful consciousness) goes down dramatically above 18.
 
Hypoxia

Hypoxia is real! My trip to Sun-n-Fun in 2006 was almost 3 fatal!

I have been saving this story inside for a while but maybe just one person will be saved from reading it!

I finally talked my wife(a nervous flyer) in to flying our new -6 to Sun-n-fun in April 2006. The plane was ready to go. The extended range tanks were full 55gal on board total! The new hard points were installed in the baggage floor for my infant daughters car seat. That morning was an overcast in Indianapolis at about 2000ft so I just filed IFR to get on top. The weather was good most of the way cruising at 11000ft. No problem. I had flown the same trip 2 years before with a friend. We stayed at 11000ft for over 3.5 hours until we got to northern Florida and we made a turn now direct to LAL. I did not have anything for breakfast so I wouldn't have to go to the bathroom. I was getting hungry so we got out some snacks. I wasn't sure if I was hungry OR thirsty or tired or sleepy or all of the above. The next thing that I remember is my wife beating me with a rolled up magazine. For me it was like being in a dream. As luck would have it our trusty Trio EZ Autopilot was holding us straight. I new something was wrong with me I just didn't know what. I mumbled to center that I needed lower and it was all I could do to push the stick over. I started waking up at about 5-6 thousand feet. I'm sure I was all over the place! I told center that we had a problem and had to land at Ocala FL. We entered the pattern at Ocala and made a crappy landing but we were safe!
At the time, even days after that I was not sure what had happened. I thought maybe we had and exhaust leak but everything was fine. It was me! When at Sun-n-Fun I bought an O2 system and a pulse oximeter that I still use today.
Here are the things I learned from this near death experience.

1. Flying at 11,000ft is ok but always figure in the density altitude inside the cabin! Here is an example!
Density Altitude Calculator


Altitude feet 11000
Air Temperature inside cabin degrees 75F your heater is on!
Altimeter Setting inches Hg 29.92
Dew Point degrees F 50


Density Altitude 14619feet
Absolute Pressure inches Hg 19.794
Relative Density % 63.73

You can see from this chart that the density altitude in our cabin that day was almost 15000ft!!! Would you put on O2 at 15K? Density altitude effects the performance of your lungs just like it effects the performance of your wings!
2. Our Trio EZ pilot saved our lives that day!
3. Ask any nurse or doctor. If you are brought to the hospital and your blood O2 level is lower than 90% they will administer O2 to you. use a pulse oximeter at altitude and monitor you O2 level put on your O2 system or descend to a lower altitude if you blood O2 level drops below 95% plus you will feel better and have more energy at the end of a flight!
4. The military always uses O2 above 5000ft and always at night for a reason!
5. This high performance RV will fly higher and longer than you!
 
Aviation Physiologist

Well as a USAF Aviation physiologist theirs nothing that warms my heart more than a good thread on hypoxia.

In 1999 I patented the Reduced Oxygen Breathing Device (ROBD) that was mentioned previously and it is currently in use by the USAF and USN for refresher hypoxia training. My vision for it was to conduct simulator based emergency procedure training of a loss of cabin Pressurization while distracted flying a tactical event. You fly the sim with the normal O2 mask and while "flying the sim" we deliver hypoxic air through the regulator. While great for that purpose it will never replace "the chamber" for a couple reasons.

1)I want you to see the symptoms of hypoxia in yourself and others. Cyanosis in the chamber isnt blue its pale and worth you observing in the student across from you in the chamber

2) In the chamber we will demonstrate "low grade" hypoxia to you which will demonstrate the visual deficits of hypoxia at an equivalent pO2 of 8,000ft for 2hr.

3) You haven't really lived until you've experienced Boyle's law first hand along with 15 other taco eating pilots demonstrating gas expansion in public.

We take decompression sickness very seriously, I have had it twice, neither in the altitude chamber. Prior to starting the chamber flight you will prebreath 100% O2 in a USAF aviation mask for 30 min to denitrogenate your system. The max altitude will not exceed FL250 to minimize the effects of evolved gas disorders. How many turbo Mooney drivers brebreath O2 prior to a cross country at Fl250?

The Rapid decompression is optional for you and separate from the main chamber flight. The rate of accent 6,000ft per sec for the FAA profile, the USAF profile is 12,000ft/sec. A slower assent significantly reduces the chance of an evolved gas disorder.

In my 19.5 yrs in the Air Force, I have never had an FAA student get the "bends", but that doesn't mean it isnt a risk. I have had plenty of USAF students get DCS.

During the FAA course, In addition to the hypoxia training we spend alot of time talking about spatial disorientation, visual illusions, fatigue and other human factors that contribute to aviation mishaps.

Come spend a day at your nearest altitude chamber.
 
Lungs vs Wings

n700jl said:
Flying at 11,000ft is ok but always figure in the density altitude inside the cabin! ..... density altitude in our cabin that day was almost 15000ft!!! Would you put on O2 at 15K? Density altitude effects the performance of your lungs just like it effects the performance of your wings!
Click to expand...

Hi, the temperature and humidity of the air in the lungs by the time it is absorbed into the blood stream is essentially constant. At the interface it is always hot and humid... So, density altitude does not impact lungs like it does wings. For lungs, you only need to look at pressure altitude.
 
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Hypoxia

Eric,
Please base your response on facts. Please follow the following link!http://www.cawg.cap.gov/html/operations/other/mtfury1d.ppt#461,9,Note:

Factors influencing hypoxia (8)
The appearance of the signs and the severity of the symptoms of acute hypoxic hypoxia depend on the following variables:-

a. Altitude level.
b. Rate of ascent.
c. Duration at altitude.
d. Ambient temperature.
e. Physical activity.
f. Individual factors:- Inherent tolerance. Physical fitness. Emotional state. Acclimatization.

This is from a reference article The Internet Journal of Pulmonary Medicine™ ISSN: 1531-2984
see this link for the entire articalhttp://www.ispub.com/journal/the_internet_journal_of_pulmonary_medicine/volume_3_number_2_43/article/aerospace_medicine_part_1.html

Fly safe and do not let hypoxia happen to you!
 
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n700jl said:
Eric,
Please base your response on facts. Please follow the following link!http://www.cawg.cap.gov/html/operations/other/mtfury1d.ppt#461,9,Note:

Factors influencing hypoxia (8)
The appearance of the signs and the severity of the symptoms of acute hypoxic hypoxia depend on the following variables:-

a. Altitude level.
b. Rate of ascent.
c. Duration at altitude.
d. Ambient temperature.
e. Physical activity.
f. Individual factors:- Inherent tolerance. Physical fitness. Emotional state. Acclimatization.

This is from a reference article The Internet Journal of Pulmonary Medicine? ISSN: 1531-2984
see this link for the entire articalhttp://www.ispub.com/journal/the_internet_journal_of_pulmonary_medicine/volume_3_number_2_43/article/aerospace_medicine_part_1.html

Fly safe and do not let hypoxia happen to you!
Click to expand...

Jon, your kidding right??? In the same article you had quoted:
"Moderate altitude is defined as 5,000-10,000 ft above SL. As the altitude increases, the barometric pressure (PB) decreases. This fall in the PB affects the available PO2. The O2% remains stable at about 21%. At sea level, the partial pressure of O2 available in the environment is equal to 0.21 times the PB (760 mm Hg), or 159 mm Hg. After saturation with water and expired CO2, the partial pressure of alveolar O2 (PAO2) is 103 mm Hg, as calculated by the following equation: PAO2 = FiO2 (PB - PH2O) - PaCO2 [FiO2 + (1 - FiO2/R)]
(PB is the ambient barometric pressure, PH2O is the pressure exerted by water vapor at body temperature, FiO2 is the fraction of inspired oxygen, PaCO2 is the alveolar carbon dioxide pressure, and R is the respiratory exchange quotient.)

Although the O2% in inspired air is constant at different altitudes, the fall in atmospheric pressure at higher altitude decreases the partial pressure of inspired oxygen and hence the driving pressure for gas exchange in the lungs. "

I bolded and highlighted the critical sections above. I believe the ambient temp comment from the other section is referring to the fact that the body needs to work harder to warm unusually cool air, or cool unusually hot air. Typically interior temps of planes are within a comfort band.
Regardless, the facts support that the body responds to pressure altitude and the wings/engine/prop to density alititude.
 
Ultimately, I think the gist of this thread is that every person will experience symptoms at a different point, and everyone should be aware of their limitations. I too have only experienced symptoms in the same manner as the original poster...during a maintenace test flight of a corporate airplane. The crew WAS on oxygen while I verified the operation of the outflow and safety valves, and mask drop function at high cabin altitudes. I could only stand it for a few minutes before feeling sick to my stomach. That short flight definitely opened my eyes to the detrimental effects of oxygen deprivation.
 
Hypoxia and D.A.

Eric,
Please follow this link! I think it will be an eye opener for you on this very important subject.http://www.fly-low.com/issue/flhigh.pdf Maybe you will believe Jefferson Koonce who is Professor at the U.S. Air Force Academy.

"As the density altitude increases from
9.000? to 14,500? the reduction in the
amount of oxygen molecules in the air and
the reduced pressure of the atmosphere
decreases the ability
to transfer oxygen into
the blood at the higher
altitude. At the high
altitudes, the proportion
of oxygen in the air is
still 20%, but the air is
much less dense and
therefore less oxygen
molecules available to
exchange in the lungs for the carbon
dioxide generated through metabolic
action."

These are fantastic little airplanes that we are building and flying. After over 330hrs of flying my RV-6 I have learned to respect what the capabilities of the airplane are and now I know what my capabilities are. I always figure in the density altitude. I responded to this thread so this would not happen to someone else.
Fly safe fly right and build it light!:p
 
Thanks!

That was not only very informative, it really makes sense.
Thanks for sharing that
 
Purse Lip Breathing

Folks, don't forget that you can use purse lip breathing on exhalation to increase oxygen sats. It's not much but any help without additional oxygen might buy you some extra help till you can decend.

It's taught to patients with breathing problems to improve their saturation.
 
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