Measuring body temperature: how do different sites compare?

Abstract

Body temperature has long been recognised as a vital sign in both people and animals. Although fever and chills have been ascribed to pathological processes since Hippocrates, at that time only the hands were used to detect changes in the temperature of the human body. In 1592, a crude temperature measuring apparatus was invented by Galileo Galilei and the documentation of body temperature began. That instrument, however, did not allow quantitative readings to be obtained as it lacked a scale. The introduction of a scale was first seen when Santorio conceived a mouth thermoscope, introduced in his 1612 work entitled Sanctorii Sanctorii Commentaria in Artem medicinalem Galeni (Pearce 2002, Kelly 2010). Several new techniques have been introduced into medical practice since then and technology has been largely incorporated into diagnostic procedures. Nevertheless, in spite of modern blood tests, molecular analyses, CT scans, MRI scans, and many other ancillary methods, physical examination remains the cornerstone of medical practice, allowing assessment of a patient's vital signs and the identification of abnormal characteristics. As part of a physical examination, body temperature measurement may document variations in core temperature that might be associated with many medical conditions. Although fairly simple, measuring body temperature requires a consistent, precise and reproducible method of acquisition in clinical practice. Ideally, temperature would be acquired at the hypothalamus level or at the thermoregulation centre, but, needless to say, those sites are not suitable in a clinical setting. Indeed, the rectal mucosa is still recognised as the 'gold standard' for assessing body

Comparison between rectal and body surface temperature in dogs by the calibrated infrared thermometer

“…Because invasive core body temperature measurements cannot be performed in clinical settings ( Greer et al., 2007 ; Hayes et al., 1996 ), the clinicians opt for measuring rectal temperature (RT) with a digital contact thermometer (DCT). Although RT is in close agreement with the core body temperature, RT is slightly lower and often lags after body temperature changes due to intestinal air, faeces, and masses ( Greer et al., 2007 ; Kreissl and Neiger, 2015 ; Sousa, 2016 ). Importantly, RT measurements are often poorly tolerated, especially by fractious patients and patients with recto-anal and pelvic conditions ( Gomart et al., 2014 ; Hall and Carter, 2017 , Hall et al., 2019 ; Kreissl and Neiger, 2015 ).…”

“…We additionally discovered that due to different temperature ranges and uncalibrated thermometers applied in the previous studies, a direct comparison of results proved challenging ( Sousa, 2016 ). We think that future research on new thermometers or measurement sites should guarantee: (1) a calibrated thermometer, (2) stable conditions (e.g., fixed ambient temperature, the same measuring approach for multiple operators), (3) strict animal acclimatization process, which can take up to one hour.…”

“…Inappropriate IRT positioning probably samples cooler ear canal wall, resulting in anomalous tympanic membrane temperature reading. Similarly, conflicting results were reported when ocular and axillar temperature was studied ( Gomart et al., 2014 ; E. Hall et al., 2019 ; Kreissl and Neiger, 2015 ; Rizzo et al., 2017 ; Sousa, 2016 ; Zanghi, 2016 ).…”

“…Furthermore, the rhythmicity of body temperature is an important physiological process, which depends on body size ( Piccione et al., 2009 ) and location ( Giannetto et al., 2015 ). Ideally, an alternative temperature measurement approach should be accurate but less stressful ( Sousa, 2016 ).…”

Comparing alternatives to canine rectal thermometry at the axillary, auricular and ocular locations

“…Ocular temperature studies could improve by finding the optimal distance and ambient temperature needed to provide accurate readings of surface ocular temperature. References ranges of each location must also be established with each diagnostic tool (Sousa, 2016). Based on the current evidence, rectal thermometry remains the only reliable standard of estimating canine core body temperature in clinical veterinary medicine.…”