Given the mention of the state of maintenance, was the aircraft even airworthy? Local organisation refused to release an aircraft (100 hourly) when owner pressed not to have certain work done. Owner relented, and paid.

CO poisoning produces permanent damage to red blood cells - it's a signature which remains and can be identified even in a long-deceased body and it gives fairly precise values of the scale. CO poisoning is not just a matter of lack of oxygen (as happens with CO2) - it is actually a poisonous gas. CO "locks" the haemoglobin in the blood such that it can't take oxygen even when it's present. If you suffer CO poisoning beyond a certain level even getting you away from the CO and giving you 100% oxygen via a mask won't save you - you will die unless you are given a rapid and massive transfusion of red blood cells (which is rarely possible).

So the detection of CO poisoning in "a body that had been under seawater for so many days" is not in any way remarkable or strange.

PDR

I wondered about that one...........

I doubt the delay was to the tests, just to the publication of the AAIB Special Bulletin that contained the results.

The most tragic cases of CO poisoniung usually come from campers in the UK. When camping a popular dining solution is to just fire up a disposable barbeque - it's easy, gives a nice charcoaled flavour and involves minimal washing up. But on a typical British camping holiday there is a very high probability that it will be either:

1. Hissing down with rain
2. Blowing a gale
3. Hissing down with horizontal rain

Sadly some decide to use the babeque anyway. To do this they might tip up the sides of their awning/dining-shelter or even just bring the whole thing inside the tent - I've even heard people suggest that this allows the baberque to warm up the tent a bit. The unfortunate fact is that the charcoal burns underneath a layer of ash (the white bit) which resticts the flow of oxygen such that the almost pure carbon produces lots of carbon monoxide (colourless, odourless and deadly). Even in a drafty dining shelter the CO concentration can reach lethal levels very quickly - if the used disposable barbeque is left to burn out inside a tent you will have created a remarkably cost-effective gas chamber for ad hoc executions. So if nothing else, I would ask readers to take away the thought that barbeques are only ever outdoor things - only use in very well ventilated areas no matter hoiw inconvenient that wind may be!

PDR

Any number of things - the two that immediately leap to mind being either a piece of corrosion in a heat-exchanger finally burning through to give a hole, or simply that the late night return flight was through cooler air so the cabin heather was turned up to a higher level (increating the amount of CO being pushed into the cabin). It's equally possible that the CO leak was present from the moment the engine started, but it too half an hour to build up to a fatal concentration.

The whole "it worked yesteday so it is strange that it broke today" argumnent that we hear so often is utterly inappropriate for complex systems - it assumes dice have a memory, which they don't (I checked).

PDR

There is evidence that sedentary smokers are less prone to hypoxia than fit non smokers.

I have no idea if that maps to CO poisoning, but I suppose it's at least hypothetically possible.

G

Icing, alt air selection, dam burst, all with a maybe of course. As is all too well known, it is rarely one single factor, it is when more than one that conspire to combine to form the chain for an accident.

The interesting one in this incident is yet again the one that relates to human factors. By that is meant what was it that placed this particular pilot and his passenger in that aircraft for that fateful flight.

M.O.T
 

Cold you point me to some background on that? My understanding is that, as you say, CO binds very tightly to Hb blocking O2 attachment, but I wasn't aware of any detectable damage to the rbc's themselves. And even if that was the case, I would expect virtually every rbc to be lysed so long post mortem. I had assumed that CO would eventually dissociate from Hb after death because of all the changes that must completely screw-up the Hb molecule. i guess maybe some blood deep in the tissues would be preserved well enough for an analysis?

I was probably a little careless in my choice or words - in this instance by "damaged" I meant that the Hb is permanently put in a state where it cannot transport oxygen - once it has formed CO-Hb i6t is essentially impossible to get it to release the CO and form the O2-Hb which can accept and release oxygen in the "usual" manner, so (in my usage) the Hb is "damaged". There are various ways of determining the propotion of CO-Hb in a blood sample (and indeed in other body fluids) from gas chromatography at the expensive/accurate end to manual spectrometry at the "cheap, time-consuming and reliant on skill" end. But most path labs use an autmated spectrophotometry technique, usually in the form of a specifically designed "CO-oximetry analyser". These machines have proven to be pretty reliable and sufficiently accurate to give a confident post-mortem indication of whether CO-Hb was a cause (or significant contributor) of death.

CO-Hb itself seems to be a remarkably robust and stable molecule which doesn't decay much in normal conditions, and barely decays at all when chilled, so a few days on the sea bed is unlikely to compromise the results significantly. There was a reason why I was aware of all this which I'm afraid I can't go into, but the subject of post-mortem determination of C) poisoning is a well published field because (I understand) CO-poisoning is the most common form of lethal poisoning in the western world. Most of the papers get very technical very quickly, but an easily digestable source would be this one:

https://acutecaretesting.org/en/arti...em-co-oximetry

You may be espcially interested in the section headed "STABILITY OF COHb WHEN MEASURED BY CO-OXIMETRY" (about 2/3ds of the way down) which provides the following:

"A number of studies [23, 27, 28] have addressed the issue of stability of COHb as measured by CO-oximetry in stored blood samples. They have confirmed that COHb is remarkably stable.

No change in CO-oximetrically determined COHb from baseline was noted in postmortem samples collected into heparin and stored for up to 3 years in a refrigerator [28].

Hampson [27] determined that there was no significant change from baseline in COHb for unrefrigerated samples mailed across the US and back again. And Kunsman et al[23] confirmed that stability of CO-oximetrically determined COHb was not dependant on the use of a particular anticoagulant/preservative combination."

HTH,

PDR

Thanks, that's very helpful. And as you say, it goes a long way to explain the lethality of CO, I knew its binding to Hb was tenacious, but had no idea it was locked-in like that. I think I will take a look at the underlying biochemistry out of interest.