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Best Practice for Measuring Body Temperatures
Kim Carter, PhD, RN, NEA-BC - Senior Director Nursing Research Purpose of Review The purpose of this review was to examine the literature to identify best practice for non-invasive body temperature measurement for adult hospital inpatients, with a specific focus on axillary temperature. Background Core body temperature (CBT) reflects overall health and endurance. The gold standard location for measuring core body temperature is the pulmonary artery; however, accessing this location is invasive and risky15,21. The esophagus and rectum are also recognized as accurate, but with some risk, inconvenience, and are not practical for many situations21. Therefore, other measurement locations and devices, including contact-type (sublingual mouth, rectum, axillary, and base of urethra) and non-contact-type infrared (IRT) thermometers (tympanic and forehead) are options5. Forehead thermometry includes a thermistor probe, a liquid crystal strip, and an IR thermometer5. There are two types of infrared techniques for surface temperature: point estimation (tympanic IRT or forehead IRT) and IR thermal imaging5. What constitutes “normal” in core and peripheral temperature measurement further complicates the situation. Variations in core body temperatures between rectal (37.04 ͦ C) and urine (36.61 ͦC) are a result of a fundamental problem with how urine core body temperature was measured in the 1970s and 1980s22. Following an analysis of 36 articles reflecting 9227 measurement sites from 7636 subjects in a systematic review of papers published from 1935 to 2017, Geneva and colleagues defined “calculated ranges (mean + standard deviations) were 36.32-37.76 (rectal), 35.76-37.52 (tympanic), 35.61-37.61 (urine) 35.73-37.41 (oral), and 35.01-36.93 (axillary)” (p. 1). Many studies grapple with determining “normal” for each of the methods of measuring body temperature5. The complexity of body temperature measurement is also affected by a variety of influences. Normal oral adult temperature has decreased in Japan24 and in the U.S. at a rate of 0.03 C ͦ per birth decade since 186023. Geneva, et al.’s findings22 are consistent with a normal body temperature lower than the currently accepted normothermia cutpoint of 36.8 ͦC, but not to a level of clinical impact. It is important to consider the patient’s age, blood pressure, pulse rate, time of day, and site of measurement when assessing body temperature 22, 24. Compared to younger adults, healthy older adults have lower body temperatures (an average of 0.23 ͦC) due to slowing metabolism and decline in internal temperature regulation mechanisms, which is clinically important as people aged 60+ may not exhibit a temperature in the traditional fever range22.
The ideal device for measuring core temperature in critical care patients would be continuous, noninvasive, and accurate18. This review followed the evidence-based practice review process outlined by the Ohio State University Fuld Institute to analyze and synthesize the current evidence related to thermometry options. Approach Search Process. The following data bases were searched: 1. HERO: “axillary temperature adult”, published since 2016, English 2. CINAHL: “body temperature” AND “axillary” OR “oral” AND “adult”, 2016, English 3. Google Scholar: “body temperature measurement”, English 4. TRIP: “temperature measurement” 5. Ancestry search yielded Singh, 2000; Jensen 2000 After screening, 21 papers were ultimately included in the analysis. Papers were not included if
