Carbon Monoxide poisoning

[sharpenu]

In the current Naui open water book on page 119, one of the symtoms of CO poisoning is listed as cyanosis (blue lips, nail beds, caused by O2 deficiency). I wrote them to say I believed this to be incorrect. The only coloration change I was ever taught was cherry red skin due to the presence of COHb (carboxyhemoglobin), and even that coloration is only present in 2-3% of CO poisoning cases. I received a reply from NAUI stating that cyanosis is common in CO poisoning cases. I disagree, my research and reading has indicated that cyanosis is only present in chronic CO exposure. Any CO exposure to a diver would most likely be Acute. This would result in dizzyness, nausea etc. Am I correct, or not? Is there any change in the effects of CO at higher partial pressures? If a compressor pulls 200 ppm of CO (relatively harmless for short exposure) and I breathe it at say, 4ata, will I experience the same effect as I would 800ppm(a potentially fatal dose) at 1ata? Just wondering...

 

[The Iceni]

I recently attended a diver first-aid course and CO came up on the syllabus.

Like you I was initially surprised to learn that a sufferer is likely to be "slate grey" as opposed to "cherry red", which is what I was taught as a medical student.

After a long discussion we decided that the early "cherry red" sign is seen only at surface pressures and during the initial stages of CO poisoning. After prolonged or high levels of exposure its extreme toxicity causes shock, which is why the victim appears grey. He will also be hypotensive with a fast thready pulse.

This appearance is not the same as cyanosis.

If my memory serves me correctly cyanosis is caused by carbon dioxide combined with haemoglobin to produce blue Carbaminohaemoglobin.

Carbon MONOXIDE irreversibly binds to the haem site preventing both Oxygen and carbon dioxide binding thus producing carbOXYhaemoglobin which is bright red.

(I had it the wrong way round originally. Apologias!)

 

[The Iceni]

Having answered the first part of your question I thought I would leave it to others to fully answer the second part, which I only touched upon.

As I said, in effect, carbon MONOXIDE irreversibly binds to the haem site so its effects are cumulative and even at surface pressures 200 ppm of CO will be toxic in time.

My understanding of Boyles Law confirms that at 4 ata you are, in fact, receiving the equivalent of 800ppm; the partial pressures (i.e. quantity) of all the inspired gasses is simply multiplied by 4.

 

[ScubaJorgen]

Yo Dr

:nono: I am afraid Sharpenu is right on the naming of CO bound to hemoglobin: carboxyhemoglobin COHb. Several sources on the internet say the same.

Probably CO2 bound to hemoglobin is carbaminohaemoglobin.



But it doesn't deteriorate the quality of your answer.....

Bye

 

[Lost Yooper]

One of the most overlooked/ignored dangers of diving is CO2 narcosis. I can't help ya much with the other stuff.

Mike

 

[The Iceni]

ScubaJorgen,

You are quite right. I often get my right and left hands mixed up!

(It must be my age!)

For the record, I TRY to remember it this way.

Carbon monoxide is dangerous because it irreversibly binds to haemaoglobin preventing OXYgen from accessing it.

It forms carbOXYhaemoglobin.

Carbon dioxide changes the colour of haemoglobin from red to blue.

Amines are often found in dyes so I associate CarbAMINOhaemoglobin with the colour blue!

It used to work for me!

(I have edited my erroneous post but humbly acknowledge my mistake.)

 

[DocVikingo]

Dr. Thomas,

LOL. With mnemonics like that, no wonder we're having a tough time sorting out the issue. There are amines all over the place, including in things that are odiferous.

Truth be told, however, I couldn't come up with anything better.

Cheers,

DocVikingo

 

[Stone]

Here's a mnemonic I have found impossible to forget:

"Bad boys rape our young girls, but Violet gives willingly; get some now"

 

[sharpenu]

Push 'trons, do you?

 

[Stone]

I don't push 'trons.

Learned the mnemonic in an electronics course in college. Used it a few times before cell phones and BBSs made 2-meter ham radio old fashioned. N8HZN out.