DMK President and former Chief Minister M Karunanidhi who was readmitted to the Kauvery hospital has undergone tracheostomy to optimise breathing a short while ago.<br/><br/>A press release by Dr S Aravindan, Executive Director of the hospital said that the procedure was done to ease the breathing difficulty in throat and lung infection. His condition is said to be stable and he was being treated on antibiotics by a team of doctors.<br/><br/>