The latest AAIB bulletin featuring this accident is here
https://assets.publishing.service.go...019_Lo_Res.pdf
The AAIB published Special Bulletin S1/2019 on 25 February 20191 to give preliminary information on the investigation and general information about how aircraft registered in the USA may be operated between the UK and France.
This Special Bulletin contains medical information relevant to the accident to highlight the implications of that information to the General Aviation community.
Results of toxicology tests
Toxicology tests on the blood of the passenger showed a carboxyhaemoglobin (COHb) saturation level of 58%. COHb is the combination product of carbon monoxide (CO) with haemoglobin, the oxygen-carrying protein molecule contained in red blood cells.
CO is a colourless, odourless gas produced from the incomplete combustion of carbon-containing materials. It readily combines with haemoglobin in the blood, decreasing the carriage of oxygen and causing a direct effect on the performance of those parts of the body which rely on oxygen for proper function. A COHb level of 50% or above in an otherwise healthy individual is generally considered to be potentially fatal.
In this type of aircraft, the cockpit is not separated from the cabin2 and it is considered likely that the pilot would also have been affected to some extent by exposure to CO.
Symptoms following exposure to carbon monoxide
Exposure to CO can lead to damage to the brain, heart and nervous system. The symptoms of CO poisoning worsen with an increasing percentage of COHb as detailed in Table 1.
COHb level
Symptoms
Less than 10%
None
20 to 30%
Drowsiness, headache, slight increase in respiratory rate, dizziness
30 to 40%
Impaired judgement, difficulty breathing, blurring of vision, bad headache, increasing drowsiness, stomach pain
40 to 50%
Confusion, blurred vision, shortness of breath, pounding headache, vertigo, loss of coordination, chest pain, memory loss
Over 50%
Seizure, unconsciousness, heart attack
Table 1
Symptoms of increasing levels of COHb
It is clear from the symptoms that exposure to CO can reduce or inhibit a pilot’s ability to fly an aircraft depending on the level of that exposure.
The AAIB is working with the aircraft and engine manufacturers and the National Transportation Safety Board (NTSB) in the USA to identify possible pathways through which CO might enter the cabin of this type of aircraft. Work is also continuing to investigate pertinent operational, technical, organisational and human factors which might have contributed to the accident.