Carbon monoxide discussion - split from Fiona Sharp death in Bonaire thread

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Ok, well, even a small amount of carbon monoxide CO can be toxic, having an increasing buildup in the blood at greater depth, then and increasingly toxic effect on ascent as the PPO drops while the PPCO remains bound for a greater time. That is possible, but no information was offered to support that claim.

I have no understanding about rebreathers and can only wonder why this was stated...
View attachment 547396
I wonder if the examining agent had a calibrated CO tester for whatever gases were used, or the physician doing the autopsy had a blood CO tester?

And we know that this is untrue...
View attachment 547397
As it does not include the medical triggers.
So I have always believed without any real knowledge that a small amount of CO inhaled in a rebreather will all eventually get absorbed by hemaglobin because of the recycling effect as opposed breathing in exhause fumes in open air where you will likely expell some of the CO with every breath. Any thoughs on that?
 
So I have always believed without any real knowledge that a small amount of CO inhaled in a rebreather will all eventually get absorbed by hemaglobin because of the recycling effect as opposed breathing in exhause fumes in open air where you will likely expell some of the CO with every breath. Any thoughs on that?
I guess so, but I don't know enough about rebreathers to discuss them. What would be the source of that CO?
 
I guess so, but I don't know enough about rebreathers to discuss them. What would be the source of that CO?
The source doesn't matter. If there is CO in the loop, it will not be scrubbed, and every time it goes around the loop, it will have the opportunity to attach to hemoglobin in the body. I don't remember exactly the time it takes to remove it from the body, but IIRC it's fairly long, like on the order of longer than the dive.

I think what Dave is saying (and I agree) is that if there is some small concentration of CO in the dil cylinder than you'd continue to uptake (instead of send the CO out with the exhaust) until the CO was all taken up and attached to the hemoglobin.
 
I guess so, but I don't know enough about rebreathers to discuss them. What would be the source of that CO?
Part of prepping a rebreather involves pre-breathing it. I alway tell my students to wait until the boat has stopped or is going slow enough upwind to avoid (what you so elequently describe as) the station wagon effect before commencing pre-breathing out of fear that residual CO in divers lungs from exhaust might linger in rebreather loop until it is completely absorbed during the dive, as opposed to OC diver breathing clean air from tank and expelling any residual CO.
 
The source doesn't matter. If there is CO in the loop, it will not be scrubbed, and every time it goes around the loop, it will have the opportunity to attach to hemoglobin in the body. I don't remember exactly the time it takes to remove it from the body, but IIRC it's fairly long, like on the order of longer than the dive.

I think what Dave is saying (and I agree) is that if there is some small concentration of CO in the dil cylinder than you'd continue to uptake (instead of send the CO out with the exhaust) until the CO was all taken up and attached to the hemoglobin.
I would expect CO acts like oxygen that it attaches to hemaglobin more readily than O2 but just like we expel certain amount of O2 I expect not all CO is absorbed on every breath.
 
I would expect CO acts like oxygen that it attaches to hemaglobin more readily than O2 but just like we expel certain amount of O2 I expect not all CO is absorbed on every breath.
Agreed, but if the expelled CO is going roundy roundy the loop, it has a good chance of making it the next breath, and the next, and the next.....
 
Agreed, but if the expelled CO is going roundy roundy the loop, it has a good chance of making it the next breath, and the next, and the next.....
Yes and although I don't know to what degree the roundy roundy action has on the absorbsion of CO logic dictates it has to be considerable. Since the accident was a result of a shore dive then CO would more likely come from the gas source (unless Fiona was a smoker) in which case would an acceptable level of CO in a tank pose a higher risk in a roundy roundy device?
 
Carbon Monoxide will be ambient present in built up areas due to engine exhausts and heating boilers - am shocked the CO tolerance is just
35 ppm. K

( i live and work in London and our respiratory death rate is huge)
 
Carbon Monoxide will be ambient present in built up areas due to engine exhausts and heating boilers - am shocked the CO tolerance is just
35 ppm. K

( i live and work in London and our respiratory death rate is huge)
You need to remember that the NIOSH Recommended Exposure Limit of 35 ppm is based upon the amount of exposure that a person could receive for 8 hours in a day, five days a week over a working lifetime without adverse health effects. But, this is at one atmosphere absolute pressure. All gases are subject to the ideal gas laws and the laws of partial pressures. At 10 meters (33 feet sea water) the partial pressure would be 2x the reading at the surface, and at 30 meters (99 feet sea water) it would be 4x the surface reading. So breathing a scuba tank with 35 ppm at 30 meters (99 feet) would be the equivalent of breathing 140 ppm at the surface. At 7 atmospheres absolute, it would be 6x the surface, or 210 ppm, which is over the Ceiling Limit established by NIOSH (200 ppm). The Ceiling Limit is the limit which cannot be exceeded without immediate problems. IDLH for CO on the surface is 1200 ppm, which is the limit which is "immediately dangerous to life and health."

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