Final answer:
The head of the bed should be raised to 30 degrees for the most accurate jugular vein distention reading.
Step-by-step explanation:
To obtain the most accurate reading of jugular vein distention, the nurse should position the head of the bed raised to 30 degrees. At this angle, it is easier to observe the external jugular vein in relation to the sternal angle, which provides a consistent reference point for measurement. If the bed is too low (supine position) or too high (High-Fowler's), the reading may not be as accurate due to changes in hydrostatic pressure.