EN2.4 | Audiogram and Impedance Interpretation — Summary & Reflection

KEY TAKEAWAYS

PTA axes: x-axis = frequency (250–8000 Hz), y-axis = hearing level in dB HL (0 dB = normal, at TOP; worse = lower on graph). Symbols: O/red = right AC; X/blue = left AC; ]/red = right BC; [/blue = left BC. Air-bone gap (ABG) = AC dB − BC dB; ABG >15 dB = conductive component. Types: conductive = AC elevated + BC normal + ABG; SNHL = AC and BC equally elevated + no ABG; mixed = both elevated + ABG. PTA = average AC at 500, 1000, 2000 Hz; severity: mild 26–40, moderate 41–55, moderately severe 56–70, severe 71–90, profound >90 dB. Configurations: flat = conductive (wax/effusion); high-frequency slope = presbycusis/NIHL (4 kHz notch signature of noise); low-frequency loss = Meniere's (early). Tympanogram Jerger types: A = normal; B flat/normal volume = effusion (OME); B flat/large volume = TM perforation; C = negative pressure = ETD; As = stiff/otosclerosis; Ad = hypermobile/ossicular discontinuity. ABG + Type A tympanogram = ossicular problem (otosclerosis if Type As; discontinuity if Type Ad).

REFLECT

The audiogram is one of those investigations that looks more complex than it is on first encounter — once you know the symbol conventions and the three pattern types, reading a PTA takes about 60 seconds. The harder skill is integration: connecting the audiogram result with the history, the otoscopy findings, and the tuning fork results to reach a coherent clinical picture. Before your next clinical session, look at three actual ENT patient audiograms from the department files (ask the audiologist). For each: read the thresholds, calculate the PTA, identify the type (CHL/SNHL/mixed), note the configuration, and check the tympanogram type. Then verify your interpretation against the audiologist's report. This calibration exercise — seeing where your interpretation matches and where it diverges — is more valuable than any number of textbook questions.