In a May 25, 2004 LOI OSHA states of 1910.151, “The standard, as presently worded, does not explicitly require that an employee or employees be both trained AND required by the employer to render first aid. OSHA has chosen to interpret the standard as imposing a training requirement but not a designation requirement.”
In other words, employers must train employees, but are not required to designate anyone as a formal responder.