What Causes Lack Of Breathing In A Person Leading To Death?

Hi, may I answer your health queries right now ? Please type your query here...my mom had three stents put in and while she was in the cath lab she stopped breathing, they did not even have a team on hand and had to call for one, after trying three times to get a tube down her they put her on a ventalator, as a result she was bleeding from the nose and mouth and her pupils where not responsive, she died the next morning, this is so unreal to us, we feel her heart stopped beating to long and she was brain dead, please tell me why they tryed three times before they did a ventalator, we beleive it was too late by than. please help