How do you determine which ear to use for an accurate tympanic (ear) temperature reading?

Determining the Correct Ear for Tympanic Temperature Measurement

When using a tympanic thermometer, you should measure temperature in both ears and use the highest reading as the most accurate reflection of core body temperature.

Why Both Ears Should Be Measured

Tympanic temperature measurements can vary significantly between the left and right ears of the same patient, even when taken just minutes apart. This variation can be clinically significant:

• Studies show temperature differences between ears can be as large as 0.6-0.8°C 1
• It's not possible to predict when these differences will occur or which ear will give the higher reading 1
• The ear with the higher temperature reading is more likely to reflect the true core body temperature 2

Proper Technique for Tympanic Temperature Measurement

To ensure accurate readings:

1. Check both ears and record the highest temperature
2. Take multiple readings from each ear when possible to improve reliability
3. Use proper positioning - gently pull the pinna upward and backward (in adults) or downward and backward (in children under 3) to straighten the ear canal
4. Ensure proper probe placement - the probe must completely engage with the tympanic membrane 3
5. Avoid measurement if there is inflammation or blockage of the auditory canal 3
6. Use the same ear throughout a monitoring period if repeated measurements are needed 1

Limitations of Tympanic Thermometry

While convenient, tympanic thermometry has important limitations:

• Tympanic measurements show poor agreement with core temperature measurements from pulmonary artery catheters 3, 4
• Accuracy varies significantly based on user technique and experience 5
• Current guidelines from the Society of Critical Care Medicine and Infectious Diseases Society of America (2023) indicate that tympanic thermometers are poor screening tools for monitoring temperature 3

Hierarchy of Temperature Measurement Methods

For clinical accuracy, temperature measurement methods rank as follows (from most to least accurate):

1. Central thermometers (pulmonary artery, esophageal, bladder) 3
2. Rectal thermometers 3
3. Oral thermometers 3
4. Tympanic membrane thermometers 3
5. Axillary, temporal artery, and chemical dot thermometers (not recommended in critical care) 3

Clinical Implications

The choice of temperature measurement site can significantly impact patient care decisions:

• Inaccurate readings may lead to inappropriate fever workups or missed diagnoses 5
• In one study, using tympanic thermometry could result in inappropriate management in 2-4% of cases when used to detect fever 5
• For critically ill patients, urinary temperature measurements show better agreement with pulmonary artery core temperatures than tympanic measurements 4

When tympanic thermometry is the only available option, measuring both ears and using the highest reading will provide the most reliable estimate of core body temperature.