FATIGUE IS LISTED AS ONE OF SEVERAL REASONS THAT A CREW MISSED NON COMPLIANCE WITH A DEFERRED MAINT ITEM UNTIL THE SECOND LEG OF A FLT SEQUENCE THAT WAS ADDED TO A FLT SCHEDULE.

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I OPERATED A FLT FROM CVG TO TRI. UPON ARRIVING AT TRI; LCL CONTRACT MAINT MET THE ACFT TO PERFORM AN INSPECTION OF THE CREW OXYGEN SYS THAT WAS REQUIRED BEFORE EACH FLT DUE TO A DEFERRED MAINT ITEM. UPON CLOSER INSPECTION OF THE MAINT LOG THIS INSPECTION HAD NOT BEEN PERFORMED PRIOR TO LEAVING CVG FOR THE OUTBOUND FLT. THERE WERE SEVERAL FACTORS THAT LED TO MISSING THIS REQUIRED INSPECTION AND ENTRY. THE REQUIRED STICKERS IN THE MAINT LOG AND NEXT TO THE EICAS IN THE COCKPIT WERE NOT THERE OR HAD BEEN PREVIOUSLY REMOVED BY MAINT PERSONNEL. THE PREVIOUS DAY; LOGBOOK HAD AN ENTRY STATING; 'WORK IN PROGRESS ON DMI 199701 OXYGEN LEAK' WITH A RESPONSE ENTRY OF 'ITEM ALREADY COMPLIED WITH ON PAGE 420000 ITEM #2.' REFERRING TO PAGE 420000 INDICATED THAT THE OXYGEN BOTTLE HAD BEEN REPLACED. AFTER CALLING MAINT CTL AND ASKING IF THE BEFORE EACH FLT CHK WAS STILL REQUIRED; THEY INDICATED YES. FINALLY; FATIGUE WAS A MAJOR FACTOR AS I HAD ONLY 2 HRS OF SLEEP THAT DAY SINCE I WAS CALLED DURING THE NIGHT TO FERRY A PLANE TO AN OUTSTATION AND BACK. UPON ARRIVING BACK IN CVG; I HAD THE TRI OUT AND BACK ADDED TO MY SCHEDULE. WHILE LEGAL; THIS ADDITION PUSHED THE CREW AFTER BACK-SIDE OF THE CLOCK FLYING WELL INTO THE EARLY AFTERNOON. THE COMBINATION OF FATIGUE; MISSING DEFERRAL STICKERS; AND CONFUSING/CONTRADICTING MAINT ENTRIES CAUSED ME TO NOT FULLY UNDERSTAND THAT THE BEFORE FLT INSPECTION WAS STILL REQUIRED.