I work for a hospitalist group. Our physician billed a critical care 99291 with 36556 (insertion of non-tunneled centrally inserted central venous catheter) and a 31500 (intubation). I know I need to append a modifier 25 to the 99291, however I can’t seem to figure out what (if any) modifiers to use on the two procedures. Do I need a modifier 51 on the 36556? Help please and thank you!