I was a St. John Ambulance officer for many years, before children etc. got in the way. I have also taught loads of people first aid.
When I look at a patient now, I make a decision about their background and whether they are a safe bet for risking mouth to mouth and other unprotected treatments. This is based on visual evidence available and undoubtedly introduces a certain amount of unjustified prejudice. Sorry, but the first rule of first aid is to ensure your own safety.
Would I take a decision not to resuscitate an individual in a major city who looked like they might fit steriotypes of being a tramp, drug user or other medical risk to me. You bet. My life is more valuable to me and my family than theirs, whatever the 'have-a-go heroes' might say.
Would a defibrillator have made a difference to this lady? Maybe, as has been said, it depends on her condition. However, given that Network Rail are now providing automatic external defibs on most major railway stations and many larger offices have them, it would hardly be unreasonable in this multi-million pound business to expect to find one on an airliner. In a straight myocardial infarction, the individual's survival chance decreases by 10 - 15% per minute after the initial 3 minutes, unless they receive defibrillation. Basic cardiac drugs, if you have qualified medical staff on board, add to the increased chance of survival significantly.
Would a mask have made a difference, in this case no, since the nurse carried out resuscitation anyway. However, in the event there is a reluctance to resuscitate, based on a risk assessment (however valid) carried out by a trained first aider at the scene (and risk assessments should hardly be alien to professional pilots) it might influence a decision where someone is worried about what they might catch.
I once read an article in the British Medical Journal by a biker, with multiple body piercings and tatooes, who had nearly died following a road accident. Whilst semi-conscious in A&E, he overheard someone say something like 'Oh, don't bother with him, he's probably got AIDS or something'. Fortunately someone did bother - turned out he was an A&E registrar from another hospital. Lesson 1 is don't make judgements based on prejudice. Lesson 2 is, you probably will anyway. The protective equipment might, in a similar situation, save the life of someone who is actually a valuable member of society.
I completely understand the reluctance to take the risk without it. The equipment (masks at least) costs hardly anything, so the message to Ryanair and any other operators who don't take their responsibilities towards safety of passengers as seriously as Network Rail - get on with it.
HH