Horses who have been administered pure oxygen in a hyperbaric chamber will not be allowed to start in races in New York for one week afterward, New York regulatory officials said Tuesday.\nJoe Mahoney, a spokesman for the New York State Racing and Wagering Board, said that the board decided to issue the directive to protect the public against possible use of pure oxygen as a performance-enhancing agent. He said the directive was issued under an existing regulation that states that "no other drugs or medications . . . may be administered within one week" of a race. \nMahoney said that an unnamed operator of a hyperbaric chamber had recently asked the New York Racing Association for permission to set up the chamber on the grounds of its Saratoga Racecourse, which was scheduled to open on Wednesday. NYRA denied the request, and the operator moved the chamber to an undisclosed location in Saratoga Springs, he said. As a result, the board issued the directive and said it would require logs of the horses who are administered oxygen in the chamber.\nThough research does not fully validate the claims, some veterinarians contend that pure oxygen delivered in a hyperbaric chamber can enhance performance and aid in healing soft-tissue injuries and in fighting off infection.