What is the role of a tympanogram (tympanometry) in assessing middle ear function for a family physician?

Tympanometry for Family Physicians

Tympanometry is an essential objective tool that family physicians should use to confirm or rule out middle ear effusion when the diagnosis is uncertain after pneumatic otoscopy, with a flat (type B) tympanogram having high predictive value for middle ear fluid. 1

Primary Role and Clinical Utility

Tympanometry objectively measures tympanic membrane mobility and middle ear function by recording how the tympanic membrane responds to varying air pressure in the external auditory canal. 1 This provides quantifiable, recordable data that complements the more subjective findings from pneumatic otoscopy. 2

Key Clinical Applications

• Confirming suspected middle ear effusion when pneumatic otoscopy findings are equivocal or difficult to interpret 1
• Distinguishing between middle ear effusion and normal middle ear status, with sensitivity of 90-94% for detecting effusion 1
• Detecting tympanic membrane perforation or ventilation tube patency through equivalent ear canal volume measurements 1
• Providing prognostic information: A flat (type B) tympanogram predicts poor spontaneous resolution, with only 20% resolution at 3 months and 28% at 6 months 1

Interpretation of Tympanogram Types

Type A (Normal)

• High-peaked tympanogram significantly decreases the probability of middle ear effusion 1
• Associated with healthy middle ear in 78% of symptomatic visits and 87% of asymptomatic visits 3

Type B (Flat)

• Highest probability of middle ear effusion or tympanic membrane perforation, both causing conductive hearing loss 1
• Positive predictive value for middle ear effusion ranges from 49-99% 4
• Cannot distinguish between otitis media with effusion (44%) and acute otitis media (56%) at symptomatic visits 3
• Indicates middle ear effusion in 87% of asymptomatic examinations 3

Type C (Negative Pressure)

• Peak shifted toward negative pressure, suggesting eustachian tube dysfunction 5
• Low probability of middle ear fluid and associated hearing loss 1
• By itself, type C is an imprecise estimate and does not have high sensitivity or specificity for middle ear disorders 4

Technical Considerations

Equipment and Probe Tone Selection

• Standard 226 Hz probe tone for children ≥6 months and adults 1
• 1,000 Hz probe tone required for infants <6 months, as the standard 226 Hz tone is insensitive to middle ear effusion in this age group due to highly compliant ear canals 1
• Available as handheld portable units or desktop machines 1

Equivalent Ear Canal Volume

• Normal range: 0.3-0.9 ml in children 1
• Low volume (<0.3 ml): Suggests cerumen obstruction or probe against canal wall 1
• High volume (1-5.5 ml): Indicates tympanic membrane perforation or ventilation tube, requiring further examination if unexpected 1

Integration with Clinical Examination

Pneumatic otoscopy remains the primary diagnostic method, as it is easier to perform and has comparable sensitivity with higher specificity (80%) compared to tympanometry (50-75% specificity). 1 However, tympanometry is easier to perform and more useful in managing children with otitis media than pneumatic otoscopy in primary care settings. 1

Recommended Diagnostic Approach

1. Perform pneumatic otoscopy first to assess tympanic membrane appearance and mobility 1
2. Obtain tympanometry when diagnosis is uncertain after attempting pneumatic otoscopy 1
3. Use tympanometry to document middle ear status objectively, especially for follow-up and monitoring 1

Common Pitfalls and Limitations

Diagnostic Limitations

• Cannot distinguish between acute otitis media and otitis media with effusion—both produce flat (type B) tympanograms 3
• Not reliable in infants <7 months when using standard 226 Hz probe tone due to compliant ear canals 4
• Requires clinical correlation: Type B and C tympanograms need integration with history and otoscopic findings 1

Practical Barriers

• Equipment cost and maintenance requirements 1
• Limited training: Many family physicians lack adequate training in tympanometry technique and interpretation 1, 6
• Underutilization: 40.6% of Danish general practice clinics did not perform any tympanometry over a one-year period 6
• Minor procedural discomfort may occur, and some children find it bothersome or frightening 1

Solutions to Common Problems

• A 6-hour practical and theoretical course significantly improves GP knowledge and skills 6
• After training, 70% of GPs reported tympanometry often provided important information, and 48% reported it changed their management several times over 2 weeks 6
• Ensure proper technique: Create air-tight seal, use age-appropriate probe tone, and calibrate equipment regularly 1, 6

Quality Improvement Opportunity

Tympanometry represents a readily available but underutilized means of assessing middle ear status that can improve diagnostic accuracy and reduce false-positive and false-negative diagnoses. 1 The objective data obtained serves as a valuable adjunct in diagnosis and follow-up of middle ear disease, particularly when integrated with pneumatic otoscopy findings. 5