As mentioned elsewhere in this blog, COHb (carboxyhaemoglobin) is NOT a stable compound. It has a half-life of around four hours when you breathe 'clean air (i.e. 21% O2), which shortens the higher the concentration of oxygen you breathe.
So if someone is tested for COHb levels some hours after exposure, those levels will have FALLEN.
COHb testing is like any other clinical investigation- it must be used judiciously and interpreted in light of other clinical findings. As always, an accurate history is often more inportant than getting a high COHb reading. If someone has symptoms suggestive of exposure, and if those symptoms are worse when they are inside their house, those findings are much more important than getting them to score on a CO-oximeter or a breath meter.
Monday, 11 December 2006
Friday, 17 November 2006
What has hyperbaric treatment to offer?
Treatment with oxygen given under hyperbaric conditions can be life-saving in acute poisoning.
It is generally accepted that if logistically feasible, and if the patient is stable enough to transfer to a unit, those unconscious from CO poisoning should be treated with hyperbaric oxygen (HBOT).
Patients who should be discussed with the nearest hyperbaric chamber facility include those who have been unconscious at any time (irrespective of their current l.o.c.), those with 'hard' neurological findings, pregnant women, and those with pre-existing vascular disease.
HBOT has also been shown to reduce the incidence of DNS and other cognitive sequelae.
It is generally accepted that if logistically feasible, and if the patient is stable enough to transfer to a unit, those unconscious from CO poisoning should be treated with hyperbaric oxygen (HBOT).
Patients who should be discussed with the nearest hyperbaric chamber facility include those who have been unconscious at any time (irrespective of their current l.o.c.), those with 'hard' neurological findings, pregnant women, and those with pre-existing vascular disease.
HBOT has also been shown to reduce the incidence of DNS and other cognitive sequelae.
Optic and other neuritides
CO is especially toxic to the central and peripheral nervous systems.
Optis neuritis is a recognised sequela of exposure, as is peripheral neuritis (sometimes picking out a single peripheral nerve such as femoral, sciatic, ulnar) and various other patterns of mixed neuronal damage.
Optis neuritis is a recognised sequela of exposure, as is peripheral neuritis (sometimes picking out a single peripheral nerve such as femoral, sciatic, ulnar) and various other patterns of mixed neuronal damage.
Cases in the news
This post will be updated periodically with cases currently in the headlines.
As of November 16th 2006, Crookhill Primary School in Gateshead remains closed following a suspected spillage of CO from three boilers situated under a classroom. The school was initially evacuated on November 14th.
As of November 16th 2006, Crookhill Primary School in Gateshead remains closed following a suspected spillage of CO from three boilers situated under a classroom. The school was initially evacuated on November 14th.
Wednesday, 15 November 2006
CO - what is it
Carbon Monoxide is just that - the monoxide of carbon. It is therefore combustible; what it really wants to be is carbon dioxide.
It is produced from the partial combustion of any kind of 'fossil' fuel, and also carbohydrate fuels like wood and paper.
It is colourless and odourless (although the Victorian gas experts say it had an odour of garlic about it.) It is about the same density as air, but since it is usually associated with hot combustion gases, tends to rise in an enclosed environment.
It is produced from the partial combustion of any kind of 'fossil' fuel, and also carbohydrate fuels like wood and paper.
It is colourless and odourless (although the Victorian gas experts say it had an odour of garlic about it.) It is about the same density as air, but since it is usually associated with hot combustion gases, tends to rise in an enclosed environment.
Delayed Neuropsychiatric Syndrome (DNS)
Someone poisoned by CO may seem to make a full recovery, only to relapse perhaps several days later with any of a whole gamut of neurological and psychiatric symptoms. These may even be enough to mimic a full-blown organic psychosis.
This link is to a BMJ editorial mentioning this phenomenon.
Stephen Thom has published extensively over many years about the effects of CO, and this article in the Proceedings of the National Academy of Sciences covers DNS in detail. It has 38 references, many accessible on line.
For more coverage of this phenomenon, try this pdf file (you will need Adobe Acrobat Reader) from the World Health Organisation.
This link is to a BMJ editorial mentioning this phenomenon.
Stephen Thom has published extensively over many years about the effects of CO, and this article in the Proceedings of the National Academy of Sciences covers DNS in detail. It has 38 references, many accessible on line.
For more coverage of this phenomenon, try this pdf file (you will need Adobe Acrobat Reader) from the World Health Organisation.
Monday, 13 November 2006
How do I protect myself, and those around me?
It's basic, and simple. Be AWARE of the possibility. That means having a basic knowledge of how CO is produced, and how it gets into people.
Be ALERT to the presence of the gas - it practice this means splashing out £30-£40 on a domestic CO alarm - or even two.
Do NOT think that if your gas fire is burning with a nice blue flame, and not leaving any soot marks, that everything is OK. While it is certainly true that poorly-vented gas-burning appliances will produce soot and a yellow flame, by the time this is noticeable, there will be a LOT of CO around.
If you think that you or your family are in a contaminated building, get out, and do not return until you are sure it is safe. You should not use any suspect appliances until they have been inspected by a qualified engineer.
Be ALERT to the presence of the gas - it practice this means splashing out £30-£40 on a domestic CO alarm - or even two.
Do NOT think that if your gas fire is burning with a nice blue flame, and not leaving any soot marks, that everything is OK. While it is certainly true that poorly-vented gas-burning appliances will produce soot and a yellow flame, by the time this is noticeable, there will be a LOT of CO around.
If you think that you or your family are in a contaminated building, get out, and do not return until you are sure it is safe. You should not use any suspect appliances until they have been inspected by a qualified engineer.
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