What was found
AT 410 APPROXIMATELY 4 HOURS INTO FLIGHT GOT RT BLEED TRIP OFF. DID QRH AND RESET BLEED. CAME BACK ON, SHUT OFF RT PACK. W/BLEED TRAPPED HAD PRESSURE OF L-35, R-10. W/BLEED SWITCH OFF HAD EVEN DUCT PRESSURE OF 33 PSI. CABIN HELD AT 8.4 PSI AT 8000'. UNABLE TO DESCEND DUE TO ETOPS OPERATIONS PLUS TRAFFIC BELOW AT 400. GROUNDED-YES. PERFORMED INITIAL EVALUATION B737-800 FIM 36-10 TASK 809 PCCV IN OPEN POS AND TURNS FREELY. HSV IN CLOSED POSITION AND TURNS FREELY. PERFORMED ENGINE BLEED AIR SYSTEM HEALTH CHECK, BLEED AIR REGULATOR & HIGH STAGE REGULATOR FAILED & REQUIRE REPLACEMENT. R & R HIGH STAGE REGULATOR, R & R BLEED AIR REGULATOR. LEAK CHECK GOOD, REF B737-800 AMM 36-11-03. R & R BLEED AIR TEMP SENSOR NO LEAK NOTED, REF AMM 36-11-05. ACCOMPLISHED HIGH POWER RUN GROUND VERIFICATION SUCCESSFUL.