What hypoxia sounds like – avweb insider article reflex anoxic seizures

When I blogged about the recent TBM accident on monday, I posed the somewhat rhetorical question of why didn’t the pilot declare an emergency and not just ask for lower, but proceed rapidly lower on his own. The answer may be evident in this tape. The aircraft is a kalitta flying service lear 25 enroute from manassas, virginia to ypsilanti, michigan. When the pilot checks in on the frequency, he’s already deeply hypoxic and slurring his words, but he declares an emergency then, oddly, doesn’t ask for or descend to a lower altitude on his own. This is a stunning example of how tunnel-visioned hypoxia can render you.


Salvation is 20,000 feet lower, but the pilot is focused on getting vectors to his destination.Reflex anoxic seizures although he’s declared an emergency, he declines vectors to a closer airport. Interestingly, there are at least four people involved in some way on the frequency, yet despite the pilot’s obvious incapacitation, the word hypoxia isn’t heard until 3:24. That’s a long time to be oxygen deprived.

The controllers deserved the archie for this incident. Although they did well, they didn’t do as well as they might have had they been trained to quickly recognize a hypoxic pilot, who might not be capable of even formulating intentions, much less saying them. But they figured it out soon enough to make the save and that’s what counts. The tape is now used as a classroom training aid in oklahoma city and I daresay it’s an effective one.Reflex anoxic seizures

In its citation for the award, NATCA said the first officer’s arm was moving violently and contacting the controls, keeping the autopilot offline. Convulsions are the truly dark side of hypoxia and aren’t always listed in the garden variety symptoms. When I did my first chamber ride around 1992, one of the participants convulsed and it was terrifying. As per the training doctrine, at 25,000 feet, half the students remove their masks, the other half keep them on. You’re invited to stay off oxygen as long as you can stand it.

I was in the group with masks on when I noticed another guy in my row going into the funky chicken. I thought he was clowning around but the instructor got a mask on him fast and turned it to emergency flow.Reflex anoxic seizures he came back around in a few seconds and the dance stopped, although he was still twitching for a few minutes afterward. After the fact, he was completely unaware of what had happened. When we finished our training, I asked the instructor how often that happens. Kinda rare, he said, but it does happen.

Which reminds me to mention another kind of hypoxia training that flight safety does. I went through that course a few years ago. Rather than a chamber ride, they have a system that mimics high altitude by having the pilot breath through a mask in which the oxygen partial pressure is reduced. It’s called ROB, for reduced oxygen breathing. The gist of the training is to teach you to recognize your own hypoxic symptoms while you’re still able to make judgments and act.Reflex anoxic seizures it’s all done in the simulator, with actual emergency descents from high altitude. I learned, for instance, that my early onset symptoms are lightheadedness and sweating. Other people may react differently. But better to find that out down here than up there.

Monday A.M. Addition: the FSI course seems to have been dropped, which is too bad. It’s another way to train hypoxia awareness without going to the chamber. This company, however, does offer the equipment for ROB training.

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Comments (10)

Paul, thanks for bringing this issue again.

I think that air traffic controllers are not trained to evaluate the mental clarity or physical fitness of pilots, they don’t read minds nor have eyes in the cockpit.Reflex anoxic seizures therefore, it’s a good thing that pilots be confident about pushing the emergency button expecting immediate remedial action after declaring an emergency. In the case of hypoxia, regardless of the reason, lower is good. But how much lower? In a NTSB report hypoxia was a factor flying at 14,000 ft. (CESSNA T182 N5201F WPR12FA154 fatal(1) even under a low level hypoxic state the pilot may not react correctly or in time to prevent a mishap. So, how much lower? I say, it depends.

In my opinion, the hypoxic effects are an underestimated threat by the majority of pilots and are not ATC procedural issues in day-to-day operations. After the cirrus SR22 and the TBM 900 catastrophes hypoxia will be discussed, evaluated and then tabled to be repeated again.Reflex anoxic seizures

Posted by: rafael sierra | september 15, 2014 11:04 AM report this comment

After several A.F. Pressure chamber rides I’m pretty sure I could recognize the symptoms of hypoxia. On one of the chamber rides, we had all placed our O2 masks back on except one individual in seat #12. The safety monitor outside of the chamber came on the P.A. And asked no. 12 if he was okay. No. 12 nodded affirmatively.

Monitor: no. 12 did you finish your work sheet?

(they gave us a work sheet to fill out with questions like, what is your name, where do you live, what is 10 x 10, etc. To see how far you can get on it.)

Monitor: no.12 are you okay? (affirmative nod again)

Monitor: no 12 can you talk to me? (affirmative nod)

reflex anoxic seizures

Monitor,: no.12 go ahead and place your o2 mask back on. (repeated 3 times)

Monitor: safety observer, go ahead and place no. 12’s mask on him. (he did)

After a few seconds,

Monitor: no. 12 did you hear me talking to you?

No. 12: yes

Monitor: did you hear me asking you if you were okay?

No. 12: yes

Monitor: did you hear me tell you to put your O2 mask on?

No. 12 : yes

Monitor: then why didn’t you answer me or put your O2 mask on?

No. 12: I did answer you and I did put my mask on.

I would highly recommend any training in this area for civilian pilots. Like cognitive learning, recognizing the effects of hypoxia by experiencing them is paramount.

Posted by: RANDALL BOONE | september 15, 2014 11:57 AM report this comment

reflex anoxic seizures

I’ve had two decompressions in jets. The first one was insidious–a leaking door seal inflator grommet in a citation I at FL 390. Since it was a slow leak and the cabin was already at max differential, the cabin only came up at about 200 fpm. When the cabin altitude warning came on, we immediately donned masks and initiated descent. The cabin stabilized at FL 290.

The second one was the failure of a cabin pressure duct on a sabreliner. It happened as we were climbing through FL 290, and it was explosive. We donned the masks and I went to the emergency pressure setting for the cabin pressure. What we HADN’T learned in simulation is how incredibly LOUD it can be in the cabin. I couldn’t talk to the copilot–even shouting.Reflex anoxic seizures I declared an emergency, but couldn’t hear ATC for the noise. We leveled at 10,000 feet and shut off the emergency pressurization. ATC was concerned about loss of required separation with a learjet–but I filed a NASA form, and heard no more about it.

The only fallout from the incident was that the aircraft owner (a private pilot) came up forward to ask what was happening. I told him to go to the back and sit down. Afterward, the owner’s wife was upset–I told her that WE followed procedures–ATC followed procedures–and the airplane did what IT was supposed to do–no problems. That mollified her, but she was angry that I was rude to her husband. I told her that the safety of passengers was part of the training–a flight attendant would have done the same thing–that he was of more use in making sure the aft cabin and passengers were secure than being up front with us.Reflex anoxic seizures that satisfied her–but she made her husband trade up to a new aircraft. (laugh)

Something to think about–we didn’t use headsets in the sabreliner because they interfere with donning the headsets–a lesson learned from the citation incident. Having the headsets would have facilitated the ability to talk to the co-pilot and to ATC–but my actions would have been the same anyway.

Posted by: jim hanson | september 17, 2014 11:19 AM report this comment

I use a pulse oximeter. It stays in the aircraft easily in reach in the glove box. Somehow, mine reads very easily and consistently. If you don’t fly often at altitude and are not used to how your body reacts above 5000DA, start measuring. The percent O2 saturation figure is a great way to replace subjective feelings with a hard, objective number.Reflex anoxic seizures the more you read your numbers the more you get to know how your body reacts to lack of oxygen. Over time you will learn to anticipate the conditions under which you will need to use O2. You will also discover some very simple, mechanical ways of using your own body to compensate. Just try a few things and watch the numbers and you will discover them easily.

Also keep in mind that TIME matters as much as DA. It’s important to monitor your O2 level the entire time you are above 5000DA. The longer you are up, the more your exposure, the greater the chance you will become hypoxic.

Diet and drug use of any kind including smoking can greatly magnify the effects of hypoxia as well as accelerate its onset.Reflex anoxic seizures be especially careful if any of these has been changed between recent flight experience. Also be aware of possible chemical exposures near flight time.

Man was not meant to fly around in a low oxygen environment. We were not designed for high altitude flight and not meant to climb hundreds or thousands of feet per minute. When we are aloft we are in an alien space. Respect this and you’ll be all the more likely to make it to a safe, quiet departure from the world of aviation.

Posted by: FILL CEE | october 3, 2014 12:44 AM report this comment add your comments