Tympanometry

T. S. Lian, MD, FACS
Email

Send Email

Recipient(s) will receive an email with a link to 'Tympanometry' and will have access to the topic for 7 days.

Subject: Tympanometry

(Optional message may have a maximum of 1000 characters.)

×


Introduction

Tympanometry is essentially a measure of aural immittance. Immittance [im(pedance) + (ad)mittance] can be described as how energy travels through a system. In terms of the ear, immittance reflects the relative ease of the passage of sound energy through the hearing mechanism, and impedance is the opposition of the passage of sound energy. Tympanometry measures aural immittance with the use of air pressure. In normal situations, the air pressure is equal on both sides of the tympanic membrane, and thus aural immittance is optimal because the tympanic membrane moves most effectively under these pressure conditions. During tympanometry, the pressure in the external auditory canal is varied with application of negative and positive pressure. The movement of the tympanic membrane in terms of compliance is plotted against the variation of pressure, resulting in a graphic representation of immittance called a tympanogram. Because the eustachian tube is involved in pressure equalization of the middle ear space, a relative negative pressure peak seen in a tympanogram would reflect inadequate ventilation by the eustachian tube. This eustachian tube dysfunction can be related to inflammation/infection, masses, and neuromuscular disorders. Tympanometry can also be used to measure the volume of the external auditory canal. A relatively high volume is evidence of a tympanic membrane perforation. Normal volumes in adults range from 0.5 to 2.0 mL and in children range from 0.3 to 1.0 mL. 
A common method for describing tympanograms was popularized by Jerger. This description involves three basic types of tympanograms: types A, B, and C. Type A is a normal tympanogram. Type Ad describes a highly compliant tympanic membrane where there is little impedance. This situation may occur in the face of ossicular discontinuity or scarring of the tympanic membrane in the absence of hearing loss. The type As pattern suggests decreased compliance and can be found in cases of ossicular fixations such as otosclerosis. A type B tympanogram describes a flat tympanogram where there is no peak in compliance and little if any change in compliance with changes of pressure. A Type B tympanogram would be found in cases of middle ear effusions as in serous otitis media; however, a flat tympanogram associated with a relatively high volume would suggest a tympanic membrane perforation. A type C tympanogram has a compliance peak in the negative pressure range beyond an air pressure of -100 mm H2O as occurs when there is inadequate ventilation of the middle ear space, which is reflective of eustachian tube dysfunction. 

Equipment

  • Portable tympanometer

Indications

  • Decreased hearing

  • Hearing loss

  • Possible ear infection or perforation

Contraindications

  • Bleeding

  • Otorrhea

  • External otitis

  • Acute external auditory canal trauma

  • Occlusion of the external auditory canal

The Procedure

Tympanometry is relatively easy to perform and typically lasts only a few seconds. A portable tympanometer is shown. 
Figure 2
Figure 2

Step 1

Prior to performing the procedure, otoscopy should be performed to assess for any relative contraindications for tympanometry as well as the patency of the external auditory structures. An obstructed or impacted cerumen should be removed prior to tympanometry. 

Step 2

With the patient in the sitting position, the helix is gently grasped and pulled in a su- perior posterior direction. 

Step 3

The tympanometry probe is then inserted into the external auditory canal meatus, forming an airtight seal. Pressure readings are then taken, and the tympanogram and associated volume are displayed by the tympanometer. The probe is then removed. 

Complications

  • Abrasion of the external auditory meatus

Pediatric Considerations

In the infant, tympanometry can also be performed in the supine position. 

Postprocedure Instructions

General ear care instructions and any disease-specific instructions should be given. 

Coding Information and Supply Sources

ICD-9 Codes

Suppliers

Tympanometers can be obtained from most medical supply houses. 

Bibliography

Hall JW, Antonelli PJ. Assessment of peripheral and central auditory function. In: Head and Neck Surgery—Otolaryngology . (3rd ed.). Philadephia: Lippincott Williams & Wilkins;  2001:1663–1664.
Jerger JF. Clinical experience with impedance audiometry. Arch Otolaryngol .  1970;92:11–24.
Koike KJ. Everyday Audiology: A Practical Guide for Health Care Professionals . San Diego: Plural Publishing;  2006.
2008 MAG Mutual Healthcare Solutions, Inc.’s Physicians’ Fee and Coding Guide. Duluth, Georgia. MAG Mutual Healthcare Solutions, Inc. 2007.
 
×