"Henry Heimlich, noted for promulgating abdominal thrusts, claimed that back slaps were proven to cause death by lodging foreign objects into the windpipe. The 1982 Yale study by Day, DuBois, and Crelin that persuaded the American Heart Association to stop recommending back blows for dealing with choking was partially funded by Heimlich's own foundation.

According to Roger White MD of the Mayo Clinic and American Heart Association (AHA), "There was never any science here. Heimlich overpowered science all along the way with his slick tactics and intimidation, and everyone, including us at the AHA, caved in."

From the wikipedia link above.