How do I ensure a thermometer is in contact with the tympanic membrane?

How to Properly Position a Tympanic Thermometer

A tympanic thermometer should not be in direct contact with the tympanic membrane, as this can cause pain and potential injury. Instead, proper positioning involves inserting the thermometer into the ear canal to obtain an accurate reading of the infrared radiation emitted from the tympanic membrane 1.

Proper Technique for Tympanic Temperature Measurement

Preparation

• Choose a speculum that is slightly wider than the ear canal to obtain an air-tight seal 1
• Remove obstructing cerumen (earwax) that prevents adequate visualization of the tympanic membrane 1
• Before inserting the speculum, squeeze the pneumatic bulb halfway (about 50% of the bulb width) 1

Insertion Technique

1. Position the thermometer like a telephone handle, with the grip following the ramus mandibulae 2
2. Insert the speculum deep enough into the ear canal to obtain an air-tight seal, but not deep enough to cause pain 1
3. The thermometer should be positioned in the cartilaginous (outer) portion of the ear canal only 1
4. Take readings immediately after positioning the device in the auditory canal 2

Important Cautions

• Never insert the thermometer deep enough to contact the tympanic membrane - this causes severe pain and potential injury
• Avoid deep insertion that touches the bony ear canal and periosteum, which can be very painful 1
• Allow at least 90 seconds between consecutive measurements for optimal accuracy 2

How to Recognize Improper Positioning

• Patient experiences sudden, sharp pain during insertion
• Resistance is felt during insertion
• Patient pulls away or shows signs of discomfort
• Readings are inconsistent or implausibly low

Clinical Considerations

Tympanic membrane thermometers measure infrared radiation from the tympanic membrane and surrounding tissues, not direct contact temperature. Studies show that infrared tympanic thermometers typically read 0.67°C lower than contact probes placed against the tympanic membrane 2, indicating they are measuring the temperature of the auditory canal rather than the tympanic membrane itself.

While tympanic thermometers show good correlation with core temperature measurements (r=0.976-0.983) 3, 4, their accuracy depends on proper positioning and technique. Poor technique can lead to failure to detect fever in up to one-third of febrile patients 5.

Common Pitfalls to Avoid

• Inserting too deeply or forcefully
• Using a speculum that is too narrow (cannot form proper seal)
• Taking readings too quickly after a previous measurement
• Improper grip position (should be like holding a telephone)
• Presence of excessive cerumen, which should be removed before measurement
• Not accounting for environmental factors that may affect readings

Remember that the goal is to measure the infrared radiation from the tympanic membrane, not to make physical contact with it. Proper positioning in the ear canal allows the thermometer to detect this radiation while maintaining patient safety and comfort.