A new type of gown is being used at Cooper University Hospital. A machine blows warm air between layers of paper in the gown to keep patients warm before, during, and after surgery. Doctors say the new gowns, which are made by Minnesota-based Arizant Inc. and cost about $15 each, help patients heal better. In addition, as Medicare expands efforts to tie medical pay to performance, the government is requiring hospitals to report on their efforts to maintain normal body temperatures during surgery beginning January 1. Two percent of pay is connected to reporting on this and other measures known to improve patient results.