What is the distance from Oz to O1 if the circumference of the patient's head is 56 cm?

To find the distance from Oz to O1 based on the circumference of the head, we can use a formula that relates the circumference to the distance between electrode placements. In polysomnography, Oz is typically positioned at the back of the head, while O1 is positioned on the left side.

The average distance from Oz to O1 is generally considered to be a percentage of the head circumference. A common calculation used suggests that the distance from Oz to O1 is about 5% of the total head circumference.

In this specific case, with a head circumference of 56 cm, we can calculate the distance:

1. Calculate 5% of 56 cm:

56 cm * 0.05 = 2.8 cm

This calculation shows that the distance from Oz to O1 is approximately 2.8 cm, which aligns with the answer. Thus, option B is correct because it accurately reflects the expected anatomical distances used in polysomnography practices.