The nurse chooses a sphygmomanometer that has a circular gauge and a needle that registers the millimeter calibrations.This type of device is known as a(n) _____ manometer.

A) mercury
B) electronic
C) aneroid
D) direct (invasive)

The aneroid manometer has a glass-enclosed circular gauge containing a needle that registers millimeter calibrations.Metal parts in the aneroid manometer are subject to temperature expansion and contraction and must be recalibrated at least every 6 months to verify their accuracy.Before using the aneroid manometer,make sure the needle is pointing to zero.With mercury manometers,pressure created by inflation of the compression cuff moves the column of mercury up the tube against the force of gravity.Millimeter calibrations mark the height of the mercury column.Electronic or automatic blood pressure machines consist of an electronic sensor positioned inside a blood pressure cuff attached to an electronic processor.You measure arterial blood pressure either directly (invasively)or indirectly (noninvasively).The direct method requires electronic monitoring equipment and the insertion of a thin catheter into an artery.The risks associated with invasive blood pressure monitoring require use in an intensive care setting.