This photograph, taken in the 1950's, depicts Dr. C. Park, Anesthesia Resident, Baltimore City Hospital; Capt. Martin McMahon, Chief, Baltimore Fire Department Ambulance Service and Dr. Peter Safar, Chief, Department of Anesthesia, Baltimore City Hospital, performing one of the earliest resusucitation studies using CPR. Dr. Safar's research in the 1950's and 1960's was supported by the US Army.