The problem is the tricresylphosphate (sp?), known as TCP, which is used as an anti-wear additive in the engine and APU oil. When it gets into the bleed air, the TCP is cooked into organophosphates. I suffered a similar incident years ago, though it was the cabin, not the cockpit that was affected. The crew were sent to hospital for arterial blood sample testing, but they had no idea what to look for, and neither did any of us at the time. I described symptoms similar to CO2 poisoning, but explained that there was no way for CO2 to be responsible. However, rather than looking for something else that would cause these symptoms, the hospital looked only for CO2 levels, wasting our time entirely (and giving us pretty sore arms too). It seems that the NHS are equally as oblivious to the issue and equally unwilling to give any serious investigation into events as the aviation industry itself...