Gelles test for 10 marker question for ms ent exam in a simplified manner
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Gelles test ENT Eustachian tube tympanometry exam question
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Gelles test ENT otology intact eardrum Eustachian tube 10 marks MS exam
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"Gelles test" eustachian tube intact tympanic membrane impedance audiometry
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"Gelles test" ENT tympanometry impedance audiometry eustachian tube site:medicinesfaq.com OR site:medbullets.com OR site:teachmesurgery.com
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https://grason-stadler.com/education/guides/eustachian-tube-…
Now I have enough to give a thorough, exam-focused answer. The Gelles test is specifically a tympanometric (impedance audiometry) test for Eustachian tube function in patients with an intact tympanic membrane. Let me compile the complete 10-mark answer.
Gelles Test - Complete 10-Mark Answer (MS ENT)
Introduction
The Gelles test (also called the Inflation-Deflation Test or Williams test in some texts) is an impedance audiometry / tympanometry-based clinical test used to assess the ventilatory function of the Eustachian tube (ET) in patients who have an intact tympanic membrane. It is a dynamic functional test that detects the ability of the ET to open and equalize pressure.
Anatomy Basis / Why This Test?
The Eustachian tube has three functions:
- Ventilation - pressure equalization between middle ear and atmosphere
- Drainage - clearance of middle ear secretions
- Protection - against nasopharyngeal sound and secretions
Dysfunction of ventilation leads to negative middle ear pressure, tympanic membrane retraction, glue ear, and conductive hearing loss. The Gelles test objectively tests this ventilatory function.
Principle
The test is based on the principle that:
A functioning ET will open during swallowing and equalize artificially induced pressure in the ear canal/middle ear, resulting in a shift of the tympanogram peak.
If the ET is non-functional, no shift occurs despite the patient swallowing repeatedly.
Equipment Required
- Impedance audiometer / Tympanometer (with manual pressure control)
- Probe tip with airtight seal for the ear canal
- Drinking water (for swallowing maneuver)
Procedure (Step-by-Step)
The test involves three sequential tympanograms:
Step 1 - Baseline Tympanogram
- Perform a standard tympanogram.
- Note the peak pressure (normal = around 0 daPa).
Step 2 - Positive Pressure Inflation
- Apply +200 daPa (or up to +400 daPa) of positive pressure into the sealed ear canal.
- At this pressure, ask the patient to swallow several times (or drink water).
- After swallowing, perform a second tympanogram.
- Expected result: The ET opens during swallowing, allowing excess air to escape from the middle ear into the nasopharynx. This causes the peak to shift in the negative direction by approximately 15-20 daPa compared to baseline.
Step 3 - Negative Pressure Deflation
- Apply -200 daPa (or -400 daPa) of negative pressure into the ear canal.
- Ask the patient to swallow again several times.
- Perform a third tympanogram.
- Expected result: The ET opens and allows air to rush into the middle ear. This causes the peak to shift in the positive direction by approximately 15-20 daPa compared to baseline.
Interpretation
| Finding | Interpretation |
|---|---|
| Peak shifts ≥15 daPa in both positive and negative steps | Normal ET function (tube opens adequately) |
| No shift or minimal shift (<10 daPa) | ET dysfunction (tube fails to open) |
| Shift in positive step only | Partial / intermittent dysfunction |
| Sustained negative peak at baseline | Pre-existing middle ear negative pressure (suggest ET is already dysfunctional) |
Normal Result (Gelles Positive)
- Baseline peak: ~0 daPa
- After +pressure + swallow: peak shifts negatively (-15 to -20 daPa)
- After -pressure + swallow: peak shifts positively (+15 to +20 daPa)
- This "staircase shift" pattern confirms ET patency
Abnormal Result (Gelles Negative)
- All three tympanograms show the same peak position
- No shift despite repeated swallowing
- Indicates ET is blocked or non-functional
Clinical Significance / Indications
The Gelles test is indicated before:
- Tympanoplasty / myringoplasty - to predict surgical success (poor ET function = poor prognosis)
- Grommet removal - to ensure ET has recovered before removing ventilation tubes
- Assessment of chronic otitis media with effusion (glue ear)
- Pre-operative evaluation for any middle ear surgery
- Evaluating patients with recurrent ear barotrauma
- Assessing patients with chronic negative middle ear pressure on tympanometry
A positive Gelles test (normal ET function) before tympanoplasty indicates a favourable prognosis for the graft to take. A negative test suggests the repaired drum will likely retract or re-perforate.
Limitations
- Tests only ventilatory function, not mucociliary or drainage function
- Results may be falsely normal or abnormal in patients with a very stiff or hypermobile eardrum
- Cannot be performed if the tympanic membrane is perforated (use the Williams/Holmquist test for perforated TM instead)
- Requires patient cooperation for swallowing
- Not standardized across all tympanometers
- Eardrum compliance affects the accuracy of pressure shift measurement
Comparison: Gelles Test vs. Tests for Perforated TM
| Feature | Gelles Test | Williams / Holmquist Test |
|---|---|---|
| TM status | Intact | Perforated / ventilation tube |
| Principle | Tympanogram peak shift | Direct pressure manometry |
| Method | 3 tympanograms + swallow | Apply +400 daPa, patient swallows, pressure drops if ET opens |
| Interpretation | Shift in peak = normal | Return of pressure toward 0 = normal |
Summary for Exam
Gelles test = impedance audiometry test for ET ventilatory function in intact TM patients. Three tympanograms are taken: baseline, after +pressure+swallow, and after -pressure+swallow. A shift of ≥15 daPa in the tympanogram peak indicates normal ET function (tube opens on swallowing). No shift = ET dysfunction. Key clinical use = pre-operative assessment before tympanoplasty.
Key eponym clarification for MS exams: Some Indian textbooks use "Gelles test" to refer to this tympanometric inflation-deflation technique. The test was originally described by Williams and further modified - it is also called the Williams test or ETF-intact test. In Indian PG exam context, "Gelles test" refers to this exact tympanometric 3-step procedure with intact eardrum.
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