There are several sites for measuring core and surface body temperature. Intensive care units use the core temperatures of the pulmonary artery, esophagus, and urinary bladder. These measurements require the use of continuous invasive devices placed in body cavities or organs and continually display readings on an electronic monitor.(Potter , Patricia A. . Fundamentals of Nursing
Obtain intermittent temperature measurements from the routinely used sites of the mouth, rectum, tympanic membrane, temporal artery, and axilla. You can also apply noninvasive chemically prepared thermometer patches to the skin. Oral, rectal, axillary, and skin temperature sites rely on effective blood circulation at the measurement site.