EDITORIAL COMMENT Clinical
Applications of Ear Thermometry Patricia S. Beach, MD*, David P. McCormick, MD* Guest Editors
In January of this year a symposium was held in San Diego, California, to discuss the current state of knowledge about infrared thermometry. This supplement to Clinical Pediatrics is composed of manuscripts prepared based upon those presentations. All manuscripts have been peer-reviewed prior to publication. This supplement
presented in an effort to inform practitioners about this technology which has potential for facilitating the care of children. Each practitioner must determine the utility of this method in his or her own setting. Infrared thermometry measures the infrared flux (flow of heat) from the surfaces of the tympanic membrane and is
new
the
canal. Within a fraction of a second, it &dquo;takes a snapshot&dquo; of the heat emanating from these surfaces. The method may be attractive to clinicians because of the ease and speed of measurement, acceptability to parents and children, and cost savings in personnel time required in taking a child’s temperature. The introductory comments by Barton Schmitt, M.D. remind us of &dquo;fever phobia,&dquo; an entity well known to pediatricians.’ He reminds us that fever is only one of many clinical parameters, is not necessarily bad, and a child does not need to be &dquo;treated&dquo; without consideration of other issues. Furthermore, body temperature may fluctuate rapidly and temperature varies depending on the body site and the method of measurement. This supplement discusses factors which affect temperatures taken from any site as well as regional differear
*Associate Professor, University of Texas Medical Branch at Galveston, Department of Pediatrics, Galveston, Texas Correspondence to Dr. Beach, Associate Professor, Department of Pediatrics, C-19, University of Texas Medical Branch at Galveston,
Galveston, TX 77550.
ences in body temperature. Many features of ear thermometry are discussed, including cost, relationship to reference oral and rectal temperatures, technical aspects and use in children of different ages.’ Practitioners who begin to use
should be familiar with these details in order to make accurate clinical interpretations of ear
tympanic thermometry temperatures.
Milewski et al.3 have reported the correlations between pulmonary artery, rectal and tympanic membrane temperatures and the limitations of each method and site of temperature. Oral temperatures are influenced by tachypnea, crying, eating or drinking, the location of the thermometer in the mouth, the length of time the thermometer is left in place, and the ability of the child to cooperate. Rectal temperatures may change before or after oral temperatures. Measurement of pulmonary artery or aortic artery blood temperature obviously are inappropriate outside an intensive care setting. Confusion may develop as to the best site for measurement of core temperature. Some authors state that the blood supply of the tympanic membrane is &dquo;the same&dquo; as that of the hypothalamus. In fact, both areas are supplied by the common carotid artery.’ The hypothalamus receives blood from the anterior cerebral artery, which is a branch of the internal carotid; the ear canal and tympanic membrane are supplied from the external carotid artery via the maxillary artery and middle meningeal artery. An argument can be made that change in tympanic membrane temperature may reflect changes in hypothalamic temperature better than temperature measured at a more distant site, say the rectum. Temperatures measured in the ear may be affected by a variety of factors. A high ambient temperature tends to elevate the tympanic membrane temperature.5 Cerumen in the ear canal does not appear to affect the otic temperature, 3
Downloaded from cpj.sagepub.com at NORTHERN KENTUCKY UNIV on June 16, 2015
but orientation of the measuring probe may have a slight effect on the measurement. Measurement of tympanic membrane temperatures may also be technically difficult in small infants for a variety of reasons. Otitis media may slightly elevate the otic temperature, but by a clinically insignificant amount.’7 It is not currently possible to make recommendations regarding use of infrared tympanometry in children with significant ear pathology, such as those with indwelling pressure equalizing tubes or draining ears, since sufficient numbers of such patients have not been studied. More patients with high temperatures also need to be studied, since otic temperature devices may give slightly lower readings at high body temperatures when compared with rectal temperature measurements, and relatively few patients with high temperatures were studied in the papers presented here. Infrared thermometry probes are provided with &dquo;offsets.&dquo; An offset is a numeric constant which is added to the otic temperature in order to generate values which are equivalent to the oral or rectal temperature. The device can be set to add offsets determined by the manufacturer automatically. Since the most appropriate offset may be influenced by different patient populations and environmental factors,8 clinicians should familiarize themselves with these differences. Several of the articles in the supplement refer to sensitivity and specificity. In most cases, the ear temperature is adjusted by an offset when sensitivities and specificities are calculated. These terms are defined as follows:
Sensitivity ~~~~~~~~~Y
&dquo;
Specificity
_ &dquo;
Pred!ct)ve PositivePredictive Positive Predictive Value Value Value == =
.,
..
,-...
true
true positives positives + false negatives
true
true negatives negatives + a se positives
®
~
~
References 1. Schmitt B. Behavioral aspects of temperature-taking. Clin Pediatr 1991; suppl: 8-10. 2. Weiss M. Tympanic infrared thermometry for full-term and preterm neonates. Clin Pediatr 1991; suppl: 42-45. 3. Milewski A, Ferguson KL, Temdrup TE. Comparison of pulmonary artery, rectal, and tympanic membrane temperatures in adult intensive care unit patients. Clin Pediatr 1991; suppl: 13-16. 4. Sabotta J, Figge FHJ. Meninges, cerebral blood vessels, hypophysis, nerves and vessels of the head. In: Atlas of human anatomy, vol. 3, 1974: (ed. Hild WJ), New York: Hafner Press 61 & 213. 5. Zehner WJ, Temdrup TE. Impact of moderate ambient temperature variance on the relationship between oral, rectal and tympanic membrane temperatures. Clin Pediatr 1991; suppl: 61-64. 6. Chamberlain JM, Grandner J, Rubinoff JL, et al. Comparison of a tympanic thermometer to rectal and oral thermometers in a pediatric emergency department. Clin Pediatr 1991; suppl: 24-29. 7. Kelly B, Alexander D. Effect of otitis media on infrared tympanic thermometry. Clin Pediatr 1991; suppl: 46-48. 8. Fraden J, Lackey RP. Estimation of body sites temperatures from tympanic measurements. Clin Pediatr 1991; suppl: 65-70.
positives truepositives po~il#~l##positives positives true
true
.
Negative Predictive Value =
We hope that the papers included in this supplement will provide information which is useful to the clinician who must decide whether this new technology will meet individual needs. If the reader is currently using or plans to use tympanic thermometry, actual interpretation and application of available technology should be clarified by information presented here.
true
+
false
true negative negatives + false negatives
negative
Note that these calculated values give some idea of the accuracy of the device at a given temperature, but little insight into how close an individual ear temperature is to the reference oral or rectal temperature. Each reading is either at or above the reference temperature (true positive) or below it (false negative). A &dquo;correlation coefficient&dquo; represents the agreement between the various measurement techniques. Correlation coefficients are reported by many authors in this supplement. 4
Downloaded from cpj.sagepub.com at NORTHERN KENTUCKY UNIV on June 16, 2015
Applications of Ear Thermometry Patricia S. Beach, MD*, David P. McCormick, MD* Guest Editors
In January of this year a symposium was held in San Diego, California, to discuss the current state of knowledge about infrared thermometry. This supplement to Clinical Pediatrics is composed of manuscripts prepared based upon those presentations. All manuscripts have been peer-reviewed prior to publication. This supplement
presented in an effort to inform practitioners about this technology which has potential for facilitating the care of children. Each practitioner must determine the utility of this method in his or her own setting. Infrared thermometry measures the infrared flux (flow of heat) from the surfaces of the tympanic membrane and is
new
the
canal. Within a fraction of a second, it &dquo;takes a snapshot&dquo; of the heat emanating from these surfaces. The method may be attractive to clinicians because of the ease and speed of measurement, acceptability to parents and children, and cost savings in personnel time required in taking a child’s temperature. The introductory comments by Barton Schmitt, M.D. remind us of &dquo;fever phobia,&dquo; an entity well known to pediatricians.’ He reminds us that fever is only one of many clinical parameters, is not necessarily bad, and a child does not need to be &dquo;treated&dquo; without consideration of other issues. Furthermore, body temperature may fluctuate rapidly and temperature varies depending on the body site and the method of measurement. This supplement discusses factors which affect temperatures taken from any site as well as regional differear
*Associate Professor, University of Texas Medical Branch at Galveston, Department of Pediatrics, Galveston, Texas Correspondence to Dr. Beach, Associate Professor, Department of Pediatrics, C-19, University of Texas Medical Branch at Galveston,
Galveston, TX 77550.
ences in body temperature. Many features of ear thermometry are discussed, including cost, relationship to reference oral and rectal temperatures, technical aspects and use in children of different ages.’ Practitioners who begin to use
should be familiar with these details in order to make accurate clinical interpretations of ear
tympanic thermometry temperatures.
Milewski et al.3 have reported the correlations between pulmonary artery, rectal and tympanic membrane temperatures and the limitations of each method and site of temperature. Oral temperatures are influenced by tachypnea, crying, eating or drinking, the location of the thermometer in the mouth, the length of time the thermometer is left in place, and the ability of the child to cooperate. Rectal temperatures may change before or after oral temperatures. Measurement of pulmonary artery or aortic artery blood temperature obviously are inappropriate outside an intensive care setting. Confusion may develop as to the best site for measurement of core temperature. Some authors state that the blood supply of the tympanic membrane is &dquo;the same&dquo; as that of the hypothalamus. In fact, both areas are supplied by the common carotid artery.’ The hypothalamus receives blood from the anterior cerebral artery, which is a branch of the internal carotid; the ear canal and tympanic membrane are supplied from the external carotid artery via the maxillary artery and middle meningeal artery. An argument can be made that change in tympanic membrane temperature may reflect changes in hypothalamic temperature better than temperature measured at a more distant site, say the rectum. Temperatures measured in the ear may be affected by a variety of factors. A high ambient temperature tends to elevate the tympanic membrane temperature.5 Cerumen in the ear canal does not appear to affect the otic temperature, 3
Downloaded from cpj.sagepub.com at NORTHERN KENTUCKY UNIV on June 16, 2015
but orientation of the measuring probe may have a slight effect on the measurement. Measurement of tympanic membrane temperatures may also be technically difficult in small infants for a variety of reasons. Otitis media may slightly elevate the otic temperature, but by a clinically insignificant amount.’7 It is not currently possible to make recommendations regarding use of infrared tympanometry in children with significant ear pathology, such as those with indwelling pressure equalizing tubes or draining ears, since sufficient numbers of such patients have not been studied. More patients with high temperatures also need to be studied, since otic temperature devices may give slightly lower readings at high body temperatures when compared with rectal temperature measurements, and relatively few patients with high temperatures were studied in the papers presented here. Infrared thermometry probes are provided with &dquo;offsets.&dquo; An offset is a numeric constant which is added to the otic temperature in order to generate values which are equivalent to the oral or rectal temperature. The device can be set to add offsets determined by the manufacturer automatically. Since the most appropriate offset may be influenced by different patient populations and environmental factors,8 clinicians should familiarize themselves with these differences. Several of the articles in the supplement refer to sensitivity and specificity. In most cases, the ear temperature is adjusted by an offset when sensitivities and specificities are calculated. These terms are defined as follows:
Sensitivity ~~~~~~~~~Y
&dquo;
Specificity
_ &dquo;
Pred!ct)ve PositivePredictive Positive Predictive Value Value Value == =
.,
..
,-...
true
true positives positives + false negatives
true
true negatives negatives + a se positives
®
~
~
References 1. Schmitt B. Behavioral aspects of temperature-taking. Clin Pediatr 1991; suppl: 8-10. 2. Weiss M. Tympanic infrared thermometry for full-term and preterm neonates. Clin Pediatr 1991; suppl: 42-45. 3. Milewski A, Ferguson KL, Temdrup TE. Comparison of pulmonary artery, rectal, and tympanic membrane temperatures in adult intensive care unit patients. Clin Pediatr 1991; suppl: 13-16. 4. Sabotta J, Figge FHJ. Meninges, cerebral blood vessels, hypophysis, nerves and vessels of the head. In: Atlas of human anatomy, vol. 3, 1974: (ed. Hild WJ), New York: Hafner Press 61 & 213. 5. Zehner WJ, Temdrup TE. Impact of moderate ambient temperature variance on the relationship between oral, rectal and tympanic membrane temperatures. Clin Pediatr 1991; suppl: 61-64. 6. Chamberlain JM, Grandner J, Rubinoff JL, et al. Comparison of a tympanic thermometer to rectal and oral thermometers in a pediatric emergency department. Clin Pediatr 1991; suppl: 24-29. 7. Kelly B, Alexander D. Effect of otitis media on infrared tympanic thermometry. Clin Pediatr 1991; suppl: 46-48. 8. Fraden J, Lackey RP. Estimation of body sites temperatures from tympanic measurements. Clin Pediatr 1991; suppl: 65-70.
positives truepositives po~il#~l##positives positives true
true
.
Negative Predictive Value =
We hope that the papers included in this supplement will provide information which is useful to the clinician who must decide whether this new technology will meet individual needs. If the reader is currently using or plans to use tympanic thermometry, actual interpretation and application of available technology should be clarified by information presented here.
true
+
false
true negative negatives + false negatives
negative
Note that these calculated values give some idea of the accuracy of the device at a given temperature, but little insight into how close an individual ear temperature is to the reference oral or rectal temperature. Each reading is either at or above the reference temperature (true positive) or below it (false negative). A &dquo;correlation coefficient&dquo; represents the agreement between the various measurement techniques. Correlation coefficients are reported by many authors in this supplement. 4
Downloaded from cpj.sagepub.com at NORTHERN KENTUCKY UNIV on June 16, 2015
