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Abstract and Figures

Body temperature is an important component in the diagnoses and treatment of disease in canines. Rectal temperature remains the standard of obtaining temperature within the clinical setting, but there are many drawbacks with this method, including time, access, animal stress and safety concerns. Interest in using infra-red thermometry in canines to obtain body temperature has grown as animal scientists and veterinarians search for non-invasive and non-contact methods and locations of obtaining canine temperatures. Here we review evidence on axillary, auricular, and ocular region canine thermometry and the degree to which measurements in these locations are representative of rectal temperature values. Instrumentation refinement and development, as well as morphologic differences, play an important role in the potential correlation between rectal temperature and these other locations. These caveats have yet to be fully addressed in the literature, limiting the options for those seeking alternatives to rectal thermometry.
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Open Veterinary Journal, (2019), Vol. 9(4): 301–308
ISSN: 2226-4485 (Print) Review Article
ISSN: 2218-6050 (Online) DOI: http://dx.doi.org/10.4314/ovj.v9i4.4
Introduction
Obtaining and recording body temperature is essential
in the proper diagnosis and treatment of canine
patients. Core temperature is considered the gold
standard of body temperature, as it closely reects the
temperature of the internal organs (Allegaert et al.,
2014). The temperature at the hypothalamus is also
a desired location to monitor, as this region is where
body temperature is perceived (Cichocki et al., 2017).
However, clinically, the most conventional method
of taking a canine’s temperature is through the rectal
mucosa, as it continues to be a minimally invasive
method that provides insight to core temperature
(Kreissl and Neiger, 2015). Rectal thermometers have
drawbacks, as they cannot be easily used on aggressive
canids or ones with an infection or rupture of the
anal mucosa (Kreissl and Neiger, 2015). To bypass
the limitations caused by rectal temperatures, studies
have been done using non - contact infrared (IR)
thermometers, and focusing on alternative areas such
as the axilla, auricular canal, and ocular regions of the
canine (Gomart et al., 2014, Zanghi, 2016). Searches
were made through institutional library databases
such as Google Scholar and the National Center for
Biotechnology Information. Searches were made
using the following words: thermometry, temperature,
auricular, ocular, surface, axillary, and canine. As a
result, 50 papers were found. Studies that did not look
at temperature measurements in axillary, auricular,
and ocular locations were eliminated. As a result, 24
scientic studies were involved in this review.
Auricular IR thermometers have been gaining popularity
as an alternative method to rectal thermometers. This
IR device measures the heat produced at the tympanic
membrane of the ear (Kreissl and Neiger, 2015). The
tympanic membrane shares the same blood ow as
the hypothalamus, which further supports temperature
measurement at this location (Kreissl and Neiger,
2015). Auricular thermometers, however, are very
dependent on the correct positioning of the probe
within the ear canal and must reach the tympanic
membrane without damaging the ear (Gomart et al.,
2014). There are also concerns of inaccurate reection
of body temperature in dogs presenting with otitis
externa (González et al., 2002). Despite this concern,
studies have shown that inammation caused by otitis
externa does not necessarily affect the temperature
readings from auricular thermometers (Cichocki et al.,
2017). Auricular thermometers provide more accurate
readings if made specically for veterinary use, as its
curved shape allows the thermometer to have closer
access to the canine’s tympanic membrane (Gomart et
al., 2014). Yet, these models tend to be more expensive
in comparison to human thermometers, making it
difcult for widespread adoption (Gomart et al., 2014).
An alternative location to obtain temperature readings
in canines is the axillary region. The decreased hair
density in this particular region allows for digital
thermometers to measure the surface temperature of
the skin. Temperature readings are taken by placing the
digital thermometer centrally within the axillary region,
as far dorsally as possible (Cichocki et al., 2017). Axilla
temperatures, however, have a poor correlation to rectal
temperature (Cichocki et al., 2017).
Ocular surface temperature (OST) is a third region
that has become an area of interest in obtaining body
*Corresponding Author: Eunice Kahng. California Polytechnic University of Pomona, Pomona, CA 91768, USA.
Email: ekahng@cpp.edu
Submitted: 02/05/2019 Accepted: 15/09/2019 Published: 30/10/2019
Comparing alternatives to canine rectal thermometry at the axillary,
auricular and ocular locations
Eunice Kahng* and Cord Brundage
California Polytechnic University of Pomona, Pomona, CA 91768, USA
Abstract
Body temperature is an important component in the diagnosis and treatment of disease in canines. The rectal
temperature remains the standard of obtaining temperature within the clinical setting, but there are many drawbacks
with this method, including time, access, animal stress, and safety concerns. Interest in using infrared thermometry
in canines to obtain body temperature has grown as animal scientists and veterinarians search for non-invasive and
non-contact methods and locations of obtaining canine temperatures. Here, we review evidence on axillary, auricular,
and ocular region canine thermometry and the degree to which measurements in these locations are representative of
rectal temperature values. Instrumentation renement and development, as well as morphologic differences, play an
important role in the potential correlation between the rectal temperature and these other locations. These caveats have
yet to be fully addressed in the literature, limiting the options for those seeking alternatives to rectal thermometry.
Keywords: Auricular, Axillary, Canine, Ocular, Thermometry.
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E. Kahng and C. Brundage Open Veterinary Journal, (2019), Vol. 9(4): 301–308
302
temperature. Ocular temperature studies originated in
human ophthalmology as a faster method to diagnose
common eye diseases such as keratoconjunctivitis sicca
(Biondi et al., 2013). Ocular temperature is typically
measured with an IR camera, but new studies have been
done using non - contact IR thermometers to evaluate
the temperature in canines (Kreissl and Neiger, 2015).
We will be evaluating canine thermometry data taken
from auricular, axilla, and ocular regions in comparison
to rectal temperature.
Instrumentation
The rst common device used to record body temperature
was glass mercury thermometers. These thermometers
measure temperature by equilibrating with the adjacent
skin or mucosa (Teran et al., 2011). This method takes
at least 3 minutes for the thermometer to fully reect the
temperature of the human or animal (Teran et al., 2011).
Glass thermometers were used for several decades until
the toxic effects of mercury contact were identied
(Teran et al., 2011). Since then, digital thermometers
have been readily used in clinical settings. These
devices are the most common appliance utilized in
veterinary clinics due to their affordability and ease of
use (Kreissl and Neiger, 2015). Digital thermometers
function by two forms of technology, equilibrium
thermometry, and predictive thermometry (Mathis and
Campbell, 2015). Equilibrium thermometry requires
direct contact with the adjacent mucosa to allow the
thermistor within the thermometer to use electrical
resistance to calculate the body temperature, which
can take up to 45 seconds (Kreissl and Neiger, 2015).
Predictive thermometry involves direct contact with
the body as well, but the rate of temperature change is
recorded to algorithmically predict the nal temperature
of the canine, taking less than 15 seconds (Kreissl and
Neiger, 2015). There have been no reported issues
pertaining to these two methods, as they both provide
comparable readings of body temperatures (Kreissl and
Neiger, 2015).
IR technology has been used in the eld of industry
long before it has been used in clinical settings. The
night vision was the rst widespread use of IR in the
military, and eventually IR technology was used to nd
victims hidden in debris from earthquakes and res
(Tan et al., 2009). IR cameras were introduced into the
medical eld in 1956, when scientists discovered that
breast cancer could be detected by measuring elevated
skin temperature (Lahiri et al., 2012). This technology
has improved and expanded over the last 50 years and
has become a popular tool in diagnosing diseases such
as diabetic neuropathy, vascular disorders, dry eye
syndromes, and metastatic liver disease, in addition to
measuring the amount of radiation within the human
body (Tan et al, 2009). In veterinary medicine, IR
cameras have gained popularity within the equine eld,
using thermal imaging to detect injuries in sport horses
(Figueiredo et al., 2013) Equine thermal imaging was
originally used to detect areas of heat caused from
inammation, but has now expanded to discerning
surface temperature responses to anesthetic and drug
treatment in horses.
In addition to aiding in the diagnosis and treatment of
certain diseases, IR thermometry is also being used to
assess body temperature without bodily contact (Lahiri
et al., 2012). There has been positive feedback regarding
the use of non-contact IR thermometers in pediatric
studies, as traditional rectal temperature readings tend
to be stressful and unpleasant for children (Allegaert
et al., 2014). Studies have now looked into using this
same IR thermometry in clinical veterinary medicine,
as an alternative to rectal thermometry. Temperature-
controlled rooms, as well as user expertise play a role
in the accuracy and consistency with IR temperature
readings (Mathis and Campbell, 2015).
Coat length associated with different breeds can
also affect thermoregulation. A study involving 47
racing greyhounds took thermal images of the tendo
calcaneus, musculus gastrocnemius, musculus gracilis,
and musculus biceps femoris portio caudalis before and
after their races (Vainionpaa et al., 2012). The dogs
raced four different distances, 325, 495, 560, and 785 m.
The post-race thermal images were signicantly higher
than the baseline thermal images when looking at the
musculus gastrocnemius region. The other supercial
temperatures were dependent on the measurement point
on the body, but the reference interval for supercial
temperature varied from 0.6°C to 2.1°C depending
on the length of the race (Vainionpaa et al., 2012).
The breed of the canine can also cause more heat loss
due to their lack of fat and thin fur. It is thought that
canines with longer fur tend to have a cooler surface
temperature, due to the insulation of the coat (Kwon
and Brundage, 2019). The thermal cameras showed
that the canines did not suffer from severe hyperthermia
after the races, which indicate that the intrinsic cooling
system is effective (Vainionpaa et al., 2012).
The coat color of the animal may also cause variance in
temperature readings with canines of the same breed.
A study by McNicholl et al. (2016) in Australia found
that greyhounds with darker coat colors such as black,
blue, and brindle had higher post-race temperatures
than of canines with lighter fur colors such as white and
fawn. The mean post-race temperatures of the black,
blue, and fawn greyhounds were 41.1°C ± 0.4°C,
41.1°C ± 0.5°C, and 41.1°C ± 0.4°C, and the mean
post-race temperatures for fawn and white greyhounds
were 40.9°C ± 0.5°C and 40.8°C ± 0.5°C (McNicholl
et al., 2016). McNicholl et al. (2016) also found that
lean canines may dissipate more heat than canines with
less lean body mass. There was a positive correlation
that was seen between body weight and post-race
temperatures (r2 = 0.043). This could be due to the
amount of energy that is used during greyhound races,
since the energy requirements to move a body also
increases with body weight. As a result, metabolic heat
production also arises (McNicholl et al., 2016).
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Axillary temperature
Axillary temperature has become a popular region
for temperature measurement due to its convenience
(Gomart et al., 2014). Experiments done in humans
suggests that axillary temperature is heavily dependent
on body mass, tissue insulation, vasoconstriction,
gender, age, and the environment (Gomart et al.,
2014). Axillary temperatures are generally measured
by placing the tip of the digital thermometer between
the skin of the forearm and thorax within the axilla.
There have been no reported studies looking at IR
axillary temperature measurements in humans. Studies
comparing rectal and axillary temperatures in canines
are summarized in Table 1. In clinical practice, 0.55°C
(1°F) is frequently added to axillary temperatures
in canines to reect core body temperature, but a
recent study using Beagles (n = 26) found this to be
inaccurate (Mathis and Campbell, 2015). The study
found that axillary temperatures taken with a digital
thermometer reect values of 0.7°C–2.1°C lower than
rectal temperature (Mathis and Campbell, 2015). The
dogs were kept in a temperature-controlled room of
21.1°C–22.2°C, with humidity levels at 22%–26%
for 56 days to acclimate the animals. Despite these
controlled conditions, there is little signicance
between rectal and axillary temperatures (r2 = 0.24)
(Mathis and Campbell, 2015).
Another study looked at axillary temperatures from
250 dogs of various breeds (Gomart et al., 2014).
Dogs were brought to the hospital for various health
reasons and were given 30 min to acclimate to the
hospital’s temperature (Gomart et al., 2014). The mean
rectal temperature, taken via digital thermometry, was
38.0°C ± 0.85°C and ranged from 35°C to 40.4°C
(Gomart et al., 2014). The mean axillary temperature was
37.0° ± 1.0° and ranged from 33.4°C to 39.3°C (Gomart
et al., 2014). Although these measurements were taken
from different digital thermometers and uncontrolled
conditions, the mean axillary temperatures had a
stronger correlation (r2 = 0.70) compared to the rst
study (Gomart et al., 2014). The range for axillary
temperatures, however, is much larger in the second
study. This can be due to the dogs exhibiting more
stress or illness from being in a veterinarian hospital.
The calibration of the thermometer used in the second
study was not stated, which could have also contributed
to the range variation (Gomart et al., 2014). Mathis and
Campbell (2015) found that temperature taken from
dogs from an uncontrolled temperature environment
exhibited inconsistent axillary measurement readings.
A third study looked at dogs of assorted breeds
(n = 50) admitted for various surgical procedures, such as
tibial plateau leveling osteotomy, percutaneous laser disk
ablation, and Hemilaminectomy (Cichocki et al., 2017).
The dogs had axillary and rectal temperatures taken three
times, once on the day of admittance into the hospital,
once after the dog had recovered from surgery, and once
more on the day the animal was discharged (Cichocki
et al., 2017). No specic details on room temperature
or the model of the thermometer were given. The mean
for axillary temperatures was 37°C ± 1.18°C, which was
statistically different than mean rectal temperature of
38°C ± 0.88°C (Cichocki et al., 2017). This study had
an (r2 = 0.42), reporting a poor correlation between the
two temperature readings (Cichocki et al., 2017). This is
important to note because axillary temperatures can have
larger temperature uctuations based on the environment
the animal was in prior to recording surface skin
temperature (Mathis and Campbell, 2015). It was also
found that axillary temperatures have a better correlation
with rectal temperatures in hyperthermic canines (Mathis
and Campbell, 2015). This may be because surface
temperatures are elevated in reection to an elevated
core body temperature (Mathis and Campbell, 2015).
Collectively, evidence suggests axillary temperatures
are an unreliable reection of rectal body temperature.
Axillary measurements have the potential to miss signs
of hypothermia and hyperthermia, which can lead to a
misinterpretation of this vital sign parameter. Further
experiments should be carried out to determine the age
and breed variant, which may offer some insight when
this method is appropriate to use.
Table 1. Comparison of axilla temperature to rectal temperature in canines without physical activity. The same digital
thermometer was used within each study to measure axilla and rectal temperatures. There is low correlation between the axilla
and rectal temperature readings among the three studies.
Study:
Axilla Subject Female/Male Rectal °C Axilla °C r2Exercise/
Rest
Device used:
Rectal
Device used:
Axilla
Cichocki et al.,
2017 50 canines 26 female
24 male 38 ± 0.88 37.0 ± 1.0 0.42 Rest Digital
Thermometer
Digital
Thermometer
Mathis et al.,
2015 26 Beagles 17 intact males
9 intact females 38.72 ± 0.37 37.33 ± 0.51 0.24 Rest Digital
Thermometer
Digital
Thermometer
Gomart et al.,
2014
250
hospitalized
canines
Unspecified 38.0 ± 0.85 37 ± 1.18 0.49 Rest Digital
Thermometer
Digital
Thermometer
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Auricular temperatures
Auricular thermometers are commonly used in human
medicine as a relatively fast and validated method of
approximating body temperature (Leduc et al., 2000).
Auricular thermometers are usually IR and utilize
pyroelectric sensors which detect electromagnetic
radiation to calculate the temperature at or near the
tympanic membrane (Sousa et al., 2011). The use of
auricular temperature measurement in dogs has been
fairly recent, and studies suggest that the reliability of
auricular thermometers is dependent on user handling
as well as the model of the thermometer used (González
et al., 2002). Human auricular thermometers do not
perform well in canine ear canals, as the horizontal
and vertical canals curve downward in canines, unlike
in the human ear (Cichocki et al., 2017). Studies have
been carried out in canines to determine the similarity
of auricular temperature to core body temperature.
Studies comparing the rectal and auricular temperature
in canines are summarized in Table 2. An experiment
conducted by Sousa et al. (2011) used various canine
breeds (n = 88) to test the acceptability of dogs
towards auricular thermometers in comparison to
rectal thermometers. It was found that the tolerance of
canines to auricular thermometers was 89.7%, but only
68.2% of dogs were tolerant of rectal measurements
(Sousa et al., 2011). Dogs acclimated within the room
for 30 minutes of 26.2°C, with a humidity of 67.0%
± 17.2% (Sousa et al., 2011). Temperature readings
were taken in the following order; rectal glass mercury
temperature, human IR auricular temperature, rectal
digital temperature, and nally rectal glass mercury
thermometer (Sousa et al., 2011). The mean temperature
documented from rectal readings were 38.8 ± 0.4 (glass-
mercury for 3 minutes), and (38.7 ± 0.4) (digital). The
mean temperature for auricular readings was 39.0°C ±
0.5°C. A weak correlation was shown between auricular
and rectal, as the r2 value ranged from 0.343 to 0.372
(Sousa et al., 2011).
Another study done with 32 dogs, (16 Labradors and
16 Beagles) found that auricular temperatures can also
vary based on the breed, time of day, and activity level
(Zanghi, 2016). Auricular temperatures had a reference
interval of 0.1°C–0.3°C, which was lower than the
rectal temperature in sedentary animals (Zanghi, 2016).
Temperature readings are taken from animals presenting
exercise-induced hyperthermia underestimated rectal
temperature by 0.4°C–0.6°C (Zanghi, 2016). The
correlation between the ear and rectal temperatures was
(r2 = 0.615). This study is important to note because it
suggests auricular temperatures may vary from rectal
temperature based on the breed of the dog, as well
as their activity level (Zanghi, 2016). This study also
suggests that Labradors display consistently higher
body temperatures in comparison to Beagles (Zanghi,
2016). It has been documented that smaller breeds tend
to run higher temperatures than larger breeds. However,
auricular temperatures may be more variant in breeds
of dogs than size alone.
A study carried out by Hall and Carter (2017a; 2017b)
examined the accuracy of auricular thermometers
relative to rectal temperature. Rectal temperature was
taken with a calibrated Vicks digital thermometer and
Vet-Temp VT-150 Instant Ear Thermometer (Hall
and Carter, 2017a). Auricular followed by rectal
temperatures were taken from 24 canines following
20 minutes of unstandardized exercise consisting of a
brisk walk, free run, or playtime with owners. Rectal
temperature readings before exercise ranged from 38.3
± 0.39; auricular temperatures ranged from 37.9 ± 0.53.
Following exercise, rectal temperature reading was
39.0 ± 0.41, and auricular temperature readings ranged
from 38.6 ± 0.50 (Hall and Carter, 2017a). Auricular
temperature underestimated rectal body temperature
82% of the trials, and only 68.4% of temperature
readings fell within the 0.5°C of the differences
between rectal and auricular temperature (Hall and
Carter, 2017a). The great variability in auricular
temperature could be due to the different shape of pinna
presented in various dog breeds. The exercise was also
unstandardized which could have led to some canines
having a higher temperature than others.
Another study conveyed by Hall and Carter (2017a;
2017b) examined the reference range of auricular
temperature in canines. Canines of various breeds
(n = 157) were divided into two groups, pet canines and
sport canines. An additional 30 canines were used to
validate the results of the auricular temperature, which
were separate from the initial experiment. Temperatures
for pet canines (n = 32) were obtained indoors in a familiar
area (at 21.2°C), while canines competing in canicross
(n = 187) had temperatures taken outdoors (in 8.9°C).
The reference range of temperature from canines in
an indoor setting was 37.9°C (range 34.3°C–38.9°C),
while the temperature readings for canines in an outdoor
setting was 37.7°C (range 36.2°C–39.1°C). Carter found
the reference interval of auricular temperature in canines
to be 36.6°C–38.8°C, which is lower than the company
reported (37.7°C–39.4°C) (Hall and Carter, 2017b).
Ocular temperature
Measurement of ocular temperature has been used
widely in ophthalmology in humans to diagnose and
treat diseases such as inammation of the human
lacrimal drainage system, glaucoma, and carotid artery
stenosis (Oztas et al., 2016). The ocular temperature
was rst measured by a bolometer in 1968, which
assessed the IR radiation and temperature of different
regions of the eye globe (Oztas et al., 2016). There
have been increasing studies done on horses relating
to eye thermography, but fewer studies have been done
measuring the eye temperature of canines (Biondi et al.,
2013). A summary of these studies is listed in Table 3.
OST has gained popularity as a potential method to
obtain body temperature in veterinary medicine due
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305
Table 2. Comparison of auricular temperature to rectal temperature in canines with and without physical activity. The same digital thermometer was used within each study to
measure auricular and rectal temperatures. There is low correlation between the axilla and rectal temperature readings among the two studies.
Study:
Auricular Subject Female/
Male Time of day Rectal °C Auricular °C r2Exercise/
Rest Device used: Rectal Device used: Auricular
Zanghi, 2016 16 Labradors
16 Beagles
16 Male
16 Female 9:00 am 38.3 ± 0.5 38.4 ± 0.6 0.615 Rest Digital thermometer Pet-Temp PT-300
11:30 am 38.1 ± 0.5 38.1 ± 0.5 0.615 Rest Digital thermometer Pet-Temp PT-300
12:30 pm 38.0 ± 0.4 37.7 ± 0.6 0.615 Rest Digital thermometer Pet-Temp PT-300
4:30 pm 38.0 ± 0.5 36.9 ± 1.0 0.615 Rest Digital thermometer Pet-Temp PT-300
Pre-exercise
30 minutes 38.3 ± 0.5 37.5 ± 0.8 0.615 Exercise Digital thermometer Pet-Temp PT-300
Post exercise
0 minutes 39.7 ± 0.9 39.2 ± 1.1 0.615 Exercise Digital thermometer Pet-Temp PT-300
Post exercise
15 minutes 38.8 ± 0.7 38.4 ± 0.6 0.615 Exercise Digital thermometer Pet-Temp PT-300
Post exercise
30 minutes 38.3 ± 0.6 37.9 ± 0.7 0.615 Exercise Digital thermometer Pet-Temp PT-300
Sousa, 2016 88 Canines N/A N/A 38.8 ± 0.4 39.0 ± 0.5 0.343–0.372 Rest Digital thermometer Human IR auricular
thermometer
Hall et al., 2019 187
canines
74 females
113 males N/A N/A 36.6°C–38.8°C N/A Rest Unspecified Vet-Temp VT-150
Instant Ear Thermometer
24
canines
15 males
9 females
N/A
pre-exercise:
38.3 ± 0.39
post exercise:
39.0 ± 0.41
pre-exercise:
37.9 ± 0.53
post exercise:
38.6 ± 0.50
N/A Exercise Vicks Comfortflex
Digital Thermometer
Vet-Temp VT-150
Instant Ear Thermometer
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to the advantages of not having to make direct contact
with the animal (Collins et al., 2015). The ocular
temperature has also been used as a method in detecting
dry eye in canines as an alternative to the Schirmer tear
test (Biondi et al., 2013).
Zanghi (2016) examined ocular temperature in
reference to rectal temperature (Zanghi, 2016).
Ocular temperatures were obtained using IR thermal
camera, directed at both eyes in 16 Labradors and 16
Beagles. The reference range of ocular temperature
was determined by creating a rectangular area that
encompassed the whole eyeball, leaving around one cm
outside of the eyelids (Zanghi, 2016). The temperature
of the eyes and rectum were taken at four different times
throughout the day before exercise (9:00 am, 11:30 am,
12:30 pm, and 4:30 pm). The dogs were housed within
an indoor kennel, with the ambient temperature of
78°F–80°F and humidity being at 78%. The reference
interval for ocular temperature was determined from
the four data collection times (9:00 am, 11:30 am, 12:30
pm, and 4:30 pm was 37°C ± 0.1°C in Labradors and
36.9°C ± 0.1°C in Beagles. It was found that Labradors
also had a higher rectal temperature (38.3°C ± 0.1°C) in
comparison to Beagles (37.8°C ± 0.1°C).
The reference range for rectal temperatures was usually
one degree higher than in ocular temperatures. Data
was also obtained from the animals after exercise,
ranging from 30 minutes before exercise to 0, 15, and
30 minutes after exercise. The data collected from
canines after exercise had a closer connection to rectal
and ocular temperature immediately after exercise
(Zanghi, 2016). However, after 15–30 minutes of post-
exercise rest, ocular readings became similar to pre-
exercise readings. Correlation for both pre and post-
exercise was not signicant (r2 = 0.145).
Another study performed with various breeds (n =
300) also tested ocular temperature in relation to rectal
temperature using a non-contact IR ocular thermometer.
Rectal temperature was taken by a digital thermometer
and ocular temperature was taken by placing a non-
contact IR thermometer perpendicular to the left cornea
(Kreissl and Neiger, 2015). The dogs were allowed to
adjust to the indoor room for 30 minutes of unspecied
room temperature. Both thermometers were also
compared to a calibrated thermometer before the
experiment took place. The mean temperature readings
for ocular temperature with an experienced handler
was 37.7°C, with a range of (35.9°C–40.1°C) (Kreissl
and Neiger, 2015). The mean rectal temperature was
38.3°C, with a range of (35.3°C–41.1°C) (Kreissl and
Neiger, 2015). The correlation between IR and rectal
readings was higher than the rst study (r2 = 0.67). This
could be due to the use of instruments that were better
equipped to measurement eye temperature.
Table 3. Comparison of ocular temperature to rectal temperature in canines with and without physical activity. The same digital
thermometer was used within each study to measure ocular and rectal temperatures. There is low correlation between the axilla
and rectal temperature readings among the two studies.
Study:
Ocular Subject Female/
Male Time of day Rectal
°C
Ocular
°C r2Exercise/
Rest
Device
used: Rectal
Device used:
Ocular
Zanghi,
2016
16
Labradors
16
Beagles
16
males
16
females
9:00 am: 38.3 ± 0.5 37.5 ± 0.8 0.145 Rest Digital
thermometer
Thermal IR
camera
11:30 am: 38.1 ± 0.5 37.3 ± 0.9 0.145 Rest Digital
thermometer
Thermal IR
camera
12:30 pm: 38.0 ± 0.4 36.7 ± 0.8 0.145 Rest Digital
thermometer
Thermal IR
camera
4:30 pm: 38.0 ± 0.5 36.9 ± 0.9 0.145 Rest Digital
thermometer
Thermal IR
camera
Pre-exercise
30 minutes 38.3 ± 0.5 37.5 ± 1.1 0.145 Exercise Digital
thermometer
Thermal IR
camera
Post exercise
0 minutes 39.7 ± 0.9 39.9 ± 1.3 0.615 Exercise Digital
thermometer
Thermal IR
camera
Post exercise
15 minutes 38.8 ± 0.7 38.7 ± 0.9 0.615 Exercise Digital
thermometer
Thermal IR
camera
Post exercise
30 minutes 38.3 ± 0.6 38.4 ± 1.0 0.615 Exercise Digital
thermometer
Thermal IR
camera
Kreissl
et al., 2015
300
Canines
Un
specified
Un
specified 38.3 37.7 0.67 Rest Digital
thermometer
Non
contact IR
thermometer
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E. Kahng and C. Brundage Open Veterinary Journal, (2019), Vol. 9(4): 301–308
307
A study carried out by Hall et al. (2019), Fleming, and
Carter examined IR ocular temperature in comparison
to auricular temperature. Studies comparing ocular
and auricular temperatures in canines are summarized
in Table 4. Active canines (n = 30) of various breeds
participating in canicross were used; there was
no specication as to the ambient temperature or
location. Ocular temperatures were taken with two
different devices, Thermofocus Animal non-contact
thermometer and Rycom non-contact IR thermometer
model RC004T. The auricular temperature was taken
rst (Vet-Temp VT-150) followed by immediately
measuring ocular temperature using the Rycom device
by the same handler (Hall et al., 2019). The auricular
temperature readings ranged from 36.3°C to 42.2°C
(median = 38.6°C) and the temperatures read from the
Thermofocus device were 34.0°C–41.6°C (median =
38.1°C) (Hall et al., 2019). The Rycom device read
32.1°C–39.1°C (median = 37.4°C). There was a low
correlation between auricular and ocular temperature
(Hall et al., 2019).
A study carried out in humans by Jen Tan has found
that ocular temperature varies between young and older
patients. Older patients were found to have a lower
corneal temperature, which was speculated to be due
to a slower metabolism (Tan et al., 2011). Further study
should be performed in canines to examine if OST
also varies in older animals, and the accuracy of ocular
temperature as a reection of core body temperature.
Conclusion
Based on the current literature, axillary, auricular,
and ocular do not show a strong correlation to rectal
temperature. Studies regarding temperature obtained
from axillary regions could further be improved by
testing the effects uctuating ambient temperatures
upon surface temperature readings, as well as the effect
of coat color and coat length. The variability of canine
pinna can also affect auricular temperature readings,
and further studies should be performed to determine
if breed variability alone can resolve correlation issues
with rectal temperature. Ocular temperature readings
have been used mainly in horses and people, but few
studies have occurred using canines. Ocular temperature
studies could improve by nding 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.
References
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Table 4. Comparison of ocular temperature to auricular temperature in canines after exercise. Auricular temperature was taken by Vet-Temp VT-150 Instant Ear Thermometer
and used as a reference for body temperature. Two devices were used to obtain ocular temperature, thermofocus animal non-contact thermometer and Rycom IR Thermometer
RC004T. There is low correlation between auricular and ocular temperature within the study.
Study:
Ocular Subject Female/
Male Time of day Auricular °C Ocular °C r2Exercise/
Rest Auricular device Ocular device
Hall
et al., 2019 30 Canines 18 males
12 females Unspecified 36.3°C–42.2°C
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ear thermometer
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non-contact thermometer
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Mean: 35.5°C
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E. Kahng and C. Brundage Open Veterinary Journal, (2019), Vol. 9(4): 301–308
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The ability to monitor body temperature in athletes at risk of hyperthermia is essential in all species. Currently, the only commonly accepted temperature monitoring site in dogs is the rectum. This is impractical in field situations as it takes time, requires additional handlers to restrain the dog and is not tolerated by all animals. Tympanic membrane temperature (TMT) monitoring may provide a rapid measure of body temperature to facilitate identification of heat stress and heat stroke in canine athletes. In human studies, TMT diverges from rectal temperature (RT) as body temperature increases during exercise induced hyperthermia so is not recommended for monitoring human athletes. If the same divergence occurs in dogs, TMT may not be suitable for use when monitoring the temperature of canine athletes. The aim of the study was to determine if TMT diverged from RT following exercise in healthy dogs. 24 healthy dogs were recruited to the study. Body temperature was measured using a veterinary auricular infrared thermometer to record TMT and an electric predictive rectal thermometer. Temperatures were recorded pre- and post-exercise in a non-clinical setting, familiar to the dogs. The mixed model approach showed that exercise had no effect on the difference between RT and TMT (F(1,201)=0.026, P=0.872). The overall mean difference of RT minus TMT was 0.39 °C (n=116). 68.4% of readings fell within the accepted 0.5 °C difference in temperature recording method. In line with previously reported TMT to RT comparison studies in dogs, this study found that TMT measured consistently lower than RT. Using a correction factor of 0.4 °C minimised the difference. The hypothesis that dogs would show greater differences between TMT and RT following exercise was not supported, suggesting that TMT could be used to monitor body temperature in exercising dogs where RT is not possible.
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In our study, we aimed to investigate the correlation of handheld infrared skin thermometer and videothermography device for the measurement of corneal temperature. Forty healthy individuals (80 eyes) were enrolled to the study. Participants underwent a detailed ophthalmologic examination and medical history review for excluding any ocular and systemic diseases. The measurements of the central corneal temperature were performed in a room having constant temperature, humidity, and brightness levels. To avoid any variability, all the temperature measurements were performed in the same examination room by a single examiner. The temperature was measured with a handheld infrared skin thermometer (MEDISANA, FTN) from the corneal surface. The same instrument was also used to measure the subjects' body temperature. Moreover, the subjects underwent the corneal temperature measurement by a noncontact videothermography device (Optris PI 450; Optris GmbH). The male to female ratio was 19:21 among the subjects. The mean age was 25.1±4.7 years. The mean body temperature was 36.93±0.33°C. The mean corneal temperatures measured by the handheld infrared skin thermometer and the ocular videothermography device were 36.94±0.28°C and 35.61±0.61°C, respectively (P<0.01). The mean temperature difference was 1.34±0.57°C, with a 95% confidence interval. There was a moderate correlation between the corneal temperatures measured by the 2 devices in the right, the left eyes, and both eyes, respectively (P=0.450, 0.539, 0.490). Handheld infrared skin thermometers can be used for the evaluation of the corneal temperature. These devices may provide a simple, practical, and cheaper way to detect the corneal temperature, and the widely performed corneal temperature measurements may afford us to understand the temperature variability in numerous ocular conditions in a better way.
Article
OBJECTIVE To compare axillary and rectal temperature measurements obtained with a digital thermometer for Beagles in a temperature- and humidity-controlled environment. ANIMALS 26 healthy Beagles (17 sexually intact males and 9 sexually intact females). PROCEDURES Dogs were maintained in a temperature- and humidity-controlled environment for 56 days before rectal and axillary temperatures were measured. Axillary and rectal temperatures were obtained in triplicate for each dog by use of a single commercially available manufacturer-calibrated digital thermometer. RESULTS Mean rectal and axillary temperatures of Beagles maintained in a temperature- and humidity-controlled environment were significantly different, with a median ± SD difference of 1.4° ± 0.15°C (range, 0.7° to 2.1°C). Mean rectal and axillary temperatures were 38.7°C (range, 37.6° to 39.5°C) and 37.2°C (range, 36.6° to 38.3°C), respectively. CONCLUSIONS AND CLINICAL RELEVANCE Results of this study indicated that the historical reference of a 0.55°C gradient between rectal and axillary temperatures that has been clinically used for veterinary patients was inaccurate for healthy Beagles in a temperature- and humidity-controlled environment. Rectal and axillary temperatures can be measured in veterinary patients. Reliable interpretation of axillary temperatures may accommodate patient comfort and reduce patient anxiety when serial measurement of temperatures is necessary. Further clinical studies will be needed.