Dorothy Simpson who called for help from hospital was found dead by her son Dorothy Simpson's son rushed to Bournemouth Hospital but was too late Inquiry said her son Jim 'found her alone having recently passed away' Hospital bosses admit series of failings and apologise to her family Tragedy: Dorothy Simpson, 84, telephoned her family from hospital because she could not breath, and died 20 minutes later A great-grandmother died after she made a desperate phone call to her family to tell them she could not breath because hospital staff failed to care for her. Dorothy Simpson's son rushed to Royal Bournemouth Hospital but when he arrived 20 minutes later she was already dead with an alarm still sounding. Hospital bosses have today admitted a catalogue of errors and apologised following the 84-year-old's tragic death. An investigation revealed failings in care and Chief Executive Tony Spotswood has now written to her family to say sorry. 'It is clear from our investigation that you and your family had a very poor experience whilst your mother was under our care, and for this I am extremely sorry,' he wrote. Mr Spotswood, admitted her son, Jim, 'found her alone, with the observation machine alarming and sadly it appeared that your mother had very recently passed away'. Mrs Simpson, a great-grandmother who lived at Hengistbury Head, Dorset, had telephoned her family to say she could not breathe and was getting no help from hospital staff. When one of her sons arrived at Ward 3 less than 20 minutes later, she had passed away and was alone, with an alarm sounding. The hospital's inquiry admitted Mrs Simpson 'should not have been left on her own at any stage'. It also said there was a 'delay in obtaining antibiotics in liquid form' and a reduced number of nurses on the ward at one point close to when she died. Apology: Bosses at Royal Bournemouth Hospital in Dorset have apologised to the family of distressed Dorothy Simpson because of her poor treatment Failings: Royal Bournemouth Chief Executive Tony Spotswood has apologised to the family, but Mrs Simpson's son Steve, right, says they are 'very angry she was let down by professionals who just let her die, on her own' Mr Spotswood said there has since been a change in leadership on Ward 3 and a 'very experienced' ward sister has since been recruited. He also said staff encouraged her to wear an oxygen mask less than an hour before she died on Saturday, July 27, but she refused to do so. An action plan has been devised to address communication and attitudes of staff, as well as extra training and an electronic system is also being introduced to allow patients' observations to be recorded centrally. Mrs Simpson's son, Steve, said: 'She was an old lady with a terminal lung illness but that day, because of all the failings, she died before her time. I am very angry that she was let down by professionals who just let her die, on her own. Mrs Simpson suffered from end stage lung disease and her family had been told she was unlikely to survive more than a few months.