THE DETAILS OF the car crash that killed Diana, Princess of Wales, have been so rehearsed that it is doubtful if there are any surprises to come from fresh examination of the facts. For a doctor, the main interest of last Sunday’s TV programme on the Princess’s death were the pathology results from the analysis of the driver’s blood. These were particularly surprising when assessed in conjunction with the film of the driver taken not long before the Princess set off on her last journey. He was seen tying his shoelaces, doing what was known by prep school gym masters as a knees full bend.

People who are poorly co-ordinated become unsteady when they do a straightforward knees full bend. The driver not only had to squat on his haunches without losing his balance but also had to shift his weight from one side to the other. Furthermore, when he was looking at the laces he wouldn’t have been able to use his eyesight to help to maintain his balance. The inability to maintain a steady posture, and not to sway around once the eyes are shut and no information to the brain about the position of the limbs is being transmitted by sight, is called Romberg’s sign.

In the standard Romberg test the patient is asked to stand upright with their eyes open. They then have to close their eyes. If their sense of balance is affected by alcohol, or some other cause, they begin to sway or stagger.

The test results presented to the inquiry into the accident also showed that the carbon monoxide level in the driver’s blood was 27 per cent; it was suggested that this could have been the result of the stuffy atmosphere in the tunnel. This level is not hugely high, but it is excessive. By chance a recent edition of the Journal of the Royal Society of Medicine includes an account of an elderly woman who was twice admitted to hospital with acute cardiac failure. The first time she was breathless, had a rapid pulse rate, her lower lung fields were waterlogged, her heart was fibrillating, and a diagnosis of heart failure secondary to long-standing high blood pressure was made. After three days in hospital she was fit enough to go home. However, she was back in hospital before nightfall. One of the paramedics who collected her the second time had noted a smell of gas. As a result, carboxyhaemoglobin levels in her blood were checked. Her reading was 20 per cent carboxyhaemoglobin, appreciably lower than that allegedly found in the Mercedes driver’s blood but enough in her case to precipitate cardiac failure.

The severity of symptoms of carbon monoxide poisoning are dependent on the general health of the patient, their age and how long they have been exposed to the gas. A level of 27 per cent, although excessive, wouldn’t always be expected to cause disabling symptoms. A very fit man might only suffer severe headaches and breathlessness with a carboxyhaemoglobin level of up to 30 per cent.

Every year in Britain 50 people die accidentally from carbon monoxide poisoning. Many more suffer lasting neurological damage. The most common causes are poorly maintained appliances and poor ventilation.

Symptoms of small doses of carbon monoxide are often missed and misdiagnosed as being the result of a viral infection or overwork. Any blood levels above 10 per cent are likely to cause symptoms. Ninety per cent of people will have chronic headaches, 50 per cent will feel nauseous and 30 per cent will feel drowsy.

THE MAIN CAUSES OF POISONING

Carbon monoxide (CO) can be given off by any home appliance that burns a fossil fuel — gas, coal, wood, or oil — if the appliance isn’t working properly or if the room isn’t well ventilated.
Gas boilers and fires: if a gas fixture is not given enough ventilation, or if the flue or chimney is blocked, the appliance will emit CO.
Barbecues: burning charcoal can cause a build up of CO if the barbecue is indoors.
Coal fires; coal fire stoves: if the fire isn’t well ventilated there will be a CO build-up.
Cars: a car left idling in a garage for a long time will create CO unless the garage is well ventilated.