Simplify the following text for a Grade 11 native English-speaking person.
Original: In response to a polio epidemic ( where many patients required constant ventilation and surveillance ) , BjÃ rn Aage Ibsen established the first intensive care unit in Copenhagen in 1953 .
Simplified: Because of a polio epidemic , BjÃ rn Ibsen established the first intensive care unit in Copenhagen in 1953 .