A319 CONFUSED DSCNT CLRNC WITH HDG ASSIGNMENT IN ZLA AIRSPACE.

Narrative

AT THE TIME OF THE OCCURRENCE; THE FO WAS ABSENT FROM THE COCKPIT (LAVATORY) AND A COMPANY DISPATCHER WAS DOING A REQUIRED OBSERVATION FLT. JUST BEFORE THE FO LEFT; WE WERE GIVEN A DSCNT CLRNC FROM FL350 TO; I THINK; FL240 AND BEGAN OUR DSCNT. I THEN RECEIVED A XMISSION TO 'TURN R TO 280 DEGS' AND READ BACK 'R TO 280' AND BEGAN THE TURN. WHEN THE FO RETURNED; I ADVISED HIM THE ONLY CHANGE WAS HDG 280 DEGS; AND HE RESUMED HANDLING THE RADIOS. A MIN OR 2 LATER; ZLA DIRECTED US TO TURN L TO 180 DEGS AND ASKED WHAT HDG WE WERE ROLLING THROUGH. THE FO ADVISED '280 DEGS ASSIGNED.' ZLA RESPONDED BY ASKING IF WE RECEIVED A NEW CLRNC AND SAID HIS ORIGINAL CALL WAS TO 'EXPEDITE TO 280' MEANING FL280. WE CLARIFIED THE ALT AND HDG AND CONTINUED THE FLT. CONTRIBUTING FACTORS: SINGLE PLT IN COCKPIT WITH NO XCHK OF RADIO XMISSION AVAILABLE. PREVENTIVE STEPS: ALWAYS USE FULL TITLES OF HDG AND ALT ASSIGNMENTS; IE; FL280 OR HDG 280 DEGS. CONFUSION: EXPEDITE TO 280 VERSUS TURN R TO 280. SUGGESTED PHRASEOLOGY: EXPEDITE THROUGH FL280; MAINTAIN FL240.