CO poisoning - Time of useful consciousness

Pi1otguy

Pi1otguy

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Sad to admit I'm a bit ignorant about CO poisoning as it relates to flight safety. Specifically, around 2 topics.

I we wondering if anyone has any insights. The idea that CO poisoning isn't as immediately reversible as other forms of hypoxia is rather unsettling.

You're flying along and the CO monitor alerts for high levels.

1) Is there a general estimate for time of useful consciousness?

2) What's the recovery time to act as PIC?
Seems like the PIC is grounded for at least a day if symptoms of CO poisoning occurred.
 
Uh, lots. Open vents, land without undue delay but don’t compromise safety.

I’ve witnessed a pretty good case, there was lots of dizziness, light headed, not just collapse done.
 
Its going to depend a lot on CO level of both the air, and the pilot. 30 ppm, OSHA says you can be in 8 hours a day. 100 ppm, 20 minutes. Note those are allowances, not an impact to consciousness. Recovery time also varies by exposure. If your BloodCO is less than 5-10%, stay in fresh air and you should recover in minutes/hours. 10-20% you need pure oxygen treatment at the hospital to help purge the CO out of your system. More than that, you may need to be placed in a hyperbaric chamber to force the CO out of your system.

If you believe you are suffering from CO in an aircraft, shut off all heat sources and open all fresh air vents immediately. This will hopefully stop the flow of CO, and help purge the CO out of the aircraft. At the very least it will dilute it. Then land as soon as practical.
 
midwestpa24 said:
If your BloodCO is less than 5-10%, stay in fresh air and you should recover in minutes/hours. 10-20% you need pure oxygen treatment at the hospital to help purge the CO out of your system.
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I guess my confusion is this. Looks like recovery rate is about 0.5% / hr. In theory a few hours suggest that hypoxia would occur much lower.
 
midwestpa24 said:
Its going to depend a lot on CO level of both the air, and the pilot. 30 ppm, OSHA says you can be in 8 hours a day. 100 ppm, 20 minutes. Note those are allowances, not an impact to consciousness. Recovery time also varies by exposure. If your BloodCO is less than 5-10%, stay in fresh air and you should recover in minutes/hours. 10-20% you need pure oxygen treatment at the hospital to help purge the CO out of your system. More than that, you may need to be placed in a hyperbaric chamber to force the CO out of your system.

If you believe you are suffering from CO in an aircraft, shut off all heat sources and open all fresh air vents immediately. This will hopefully stop the flow of CO, and help purge the CO out of the aircraft. At the very least it will dilute it. Then land as soon as practical.
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Because my doors are leaky and my exhaust system is free of cracks, my CO levels in the cabin decrease with cabin heat and increase with all the vents closed. Exhaust leaks in the bottom of the door in certain flight profiles (usually a climb). But it never gets much higher than 9ppm, and goes back to 0ppm most of the time.

Just goes to show that cabin heat is not the only source of CO.
 
Yup…from my memory it takes a while to recover….hours. So you may stop the poisoning…but it will take a while to recover.
Pi1otguy said:
I guess my confusion is this. Looks like recovery rate is about 0.5% / hr. In theory a few hours suggest that hypoxia would occur much lower.
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Also, not everyone starts from the same place. If you're a smoker, inactive, etc, CO could start affecting you more severely at lower concentrations.
 
I was in the studio audience when Dan Bass told his story about crashing his Mooney after being overcome by CO poisoning. I remember a room full of people, listening silently. This story is so unlikely that it is hard to believe, but it happened. I ordered an electronic CO detector that same day and haven't flown without one since. It's a miracle Dan is alive today, and I have no doubt that his portrayal of the events will save lives.

I do not believe the concept of "useful consciousness" applies the same way it does with hypoxic hypoxia. The rate of CO entering the cabin is a big variable, and there's probably no meaningful average case. The key is early detection.

 
1200ppm is considered an atmosphere 'immediately dangerous to life and health' and requires use of supplied air for entry (e.g. an SCBA or a mask on a compressed air tether).

Below is a table from the OSHA site to give you an idea about the recommended short term levels:


Existing short-term exposure guidelines: National Research Council [NRC 1987] Emergency Exposure Guidance Levels (EEGLs):

10-minute EEGL: 1,500 ppm

30-minute EEGL: 800 ppm

60-minute EEGL: 400 ppm

24-hour EEGL: 50 ppm
 
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When i was building my house I used a torpedo heater inside during the winter. Was inside working all day with it running. That night I had a headache and whole body aches like it was the flu. I was 23 and oblivious to how stupid that was. Next day I was mostly fine.
 
Besides the above advice, if you have O2 put it on and turn it up...
 
CO poisoning is poisoning. You are not going to recover much while in the plane flying. The goal is close the heat sources to eliminate the obvious source of the poison, open the vents or use O2 to dilute the additional dose and land before you become too impaired.
 
FORANE said:
Besides the above advice, if you have O2 put it on and turn it up...
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That’s the right thing to do….but pure oxygen will not immediately remove the poison. CO displaces oxygen in your blood so more oxygen won’t fix it until the CO is metabolized or removed from the blood.
 
My barber got CO poisoning on the ground, in his shop. Bad furnace. Ambulance to the ER.

Recovery took several months. Neurological effects. Weeks of not working at all, then more weeks of working part time while not feeling well and not having much endurance. Finally, he recovered fully, and I'm really thankful.

That was completely unlike my experience with hypoxia, in an altitude chamber, when I recovered completely in minutes.
 
NoHeat said:
Recovery took several months. Neurological effects. Weeks of not working at all, then more weeks of working part time while not feeling well and not having much endurance. Finally, he recovered fully, and I'm really thankful.
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There are different levels of damage done by CO poisoning. Physiologically, it produces a condition where the blood is unable to transport the required amounts of oxygen. This will have different effects depending on the type of tissue supplied. At lower COHb levels, the effect is going to be a transient dysfunction of the target tissue. At higher levels, the degree of oxygen deprivation will be enough to cause cell death. In the brain, that cell death follows a somewhat predictable pattern with the initial damage limited to an area centrally in the brain called the 'basal ganglia'. Our brain does have some capability to maintain motor function even if that part of the brain has taken permanent damage, but it often takes many months of neuro-rehab for the victims to get back to somewhat close to full function.
 
Based on the dissociation rates of CO from hemoglobin, the half-life is about 2 hours. Depending on the level of poisoning it would take at least 8-10 hours to recover.

CO is insidious. Not only does it rob oxygenation sites from hemoglobin, it also dramatically decreases the efficiency of oxygen delivery for what oxygen remains. 50% occupancy of one's hemoglobin with CO is fatal, as the remaining 50% oxygen can't be turned loose to tissues.
 
I've told the story of my own bout of CO poisoning several times on POA. Main point here: Three people on the plane, all suffered the effects differently. I passed out after landing, another passenger had a splitting headache, and the pilot was seemingly unaffected.

The lesson is there *is* no "standard" reaction to it....

Ron Wanttaja
 
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