The most appropriate position for a patient with an arterial bleed to the distal portion of the left arm, with direct pressure applied, would be:
B) Semi-Fowlers with the injured arm held on their abdomen
Elevating the injured arm can help minimize blood flow to the extremity and reduce bleeding. The semi-Fowler's position, where the patient is in a semi-upright sitting position, can further assist in reducing blood flow to the injured arm. Placing the injured arm on their abdomen can aid in controlling bleeding and maintaining elevation.