Morbidity and Mortality Meetings are the Answer.

NHS hospitals to start calculating 'needless deaths' | Society | The Guardian
I am a great believer in Morbidity and Mortality meetings - if organised well, they could be a very useful and important tool for quality improvement. I have reformed the way we held them in my department and I have recently written a piece on M&M meetings which was published in HSJ. 
In my opinion, one (reproducible) way of monitoring avoidable deaths in hospitals is a national system whereby every in hospital patient death was discussed at M&M meetings. This would be a local solution to a national problem. Proceeds of the meetings could be recorded in a succinct meaningful way and judgement made on the quality of care given. National Confidential Enquiry on Patient Outcomes and Death have published a useful scale in the past. This is found on the last page of this document.