The classical Heimlich maneuver with upward abdominal thrusting under the ribcage is no longer recommended by either the American Red Cross or the American Heart Association because of the potential for serious injury, especially to children and the elderly who are most prone to choking. Vigorous back slaps, followed by inward (but not upward) thrusts below the floating ribs should be applied to a choking victim, which works by creating pressure on the diaphram that compresses the lungs and forces air out of the trachea. The maneuver should not be performed on a drowning victim as it is likely to cause vomiting and aspiration; instead, the victim should should be placed on their side if there is evidence of a stable pulse and airway progress, or on the back with CPR chest compressions if no pulse or breathing is detected. Liquid within the lungs will be forced out by normal pulmonary action although all drowning victims should receive immediate evacuation and hospital examination because of the potential for acute respiratory distress syndrome (ARDS) resulting from trauma to the alveoli and inflammation of the pulmonary pleurae. As others have noted, an obstruction in the esophagus, while uncomfortable and may cause reflexive gagging, will not be resolved by abdominal thrusting and generally requires mechanical extraction of the offending morsel if it does not work its way free via peristaltic action.
Henry Heimlich’s case studies used to justify the eponymous maneuver are widely considered to be exaggerated if not outright fraudulent, and he otherwise promoted pseudoscientific treatments such as homeopathy and malariotherapy as a treatment for cancer and AIDS. Heimlich is credited with the invention of the thoracic flutter valve to treat pneumonothorax, although other field surgeons had employed similar jury-rigged devices since the Korean War. Quackwatch.com article on Dr. Henry Heimlich.