How is capillary refill assessed?

Capillary refill is assessed by squeezing blood from an area and observing how quickly it returns to normal color. This is typically performed on a fingertip or toe. The rationale behind this assessment is that it provides an indication of peripheral circulation and the adequacy of blood flow to the tissues. When an area is compressed, blood is pushed out from the capillaries, and upon release, the time taken for color to return reflects the heart's ability to supply blood efficiently to that area. A quick refill time is usually a sign of good perfusion, while a delayed refill may indicate poor circulation or hypovolemia.

Other options included in the question, such as checking pulse regularity, measuring skin temperature, and observing pupil response, assess different physiological functions or conditions and do not directly relate to capillary refill. Therefore, the key aspect that makes option B the correct choice is its direct correlation to the measurement of capillary refill and peripheral blood flow.