1 / 22

Impedance (Z) vs. Admittance (Y)

Resistance(R) Mass Reactance(Xm) Stiffness Reactance(Xs) Z = ( R 2 + X t 2 ) 1/2. Conductance(G) Mass Susceptance(Bm) Stiffness Susceptance(Bs) Y = (G 2 + B t 2 ) 1/2. Impedance (Z) vs. Admittance (Y). Mass and Stiffness Reactance. Resonant Freq. Mass and Stiffness Susceptance.

gbrinson
Download Presentation

Impedance (Z) vs. Admittance (Y)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Resistance(R) Mass Reactance(Xm) Stiffness Reactance(Xs) Z = (R2 + Xt2)1/2 Conductance(G) Mass Susceptance(Bm) Stiffness Susceptance(Bs) Y = (G2 + Bt2)1/2 Impedance (Z) vs.Admittance (Y)

  2. Mass and Stiffness Reactance Resonant Freq.

  3. Mass and Stiffness Susceptance Resonant Freq.

  4. RESISTANCE AT THE EARDRUM

  5. Reactance at the Eardrum

  6. Tympanogram: • A plot of middle ear admittance as a function of ear canal pressure • Pressure is swept from +200 to -200 or -400 dPa • Should see peak at point where pressures are equal

  7. Static Admittance • Height of tympanogram peak • Adults 3-10 yrs A 0.30 to 1.70 0.25 to 1.05 As < 0.30 < 0.2 Ad >1.70 > 1.05

  8. Gradient = hp/ht

  9. Tympanogram types: • A: peak between +100 and -200 dPa: normal • C: peak beyond -200 dPa: neg pressure • B: no peak flat tymp: effusion • As: peak but shallow: stiff: otosclerosis • Ad: peak off scale: floppy: dysarticulation

  10. Tympanogram Types

  11. Physical Volume Test • Measure of volume of air enclosed under probe Adults 3-10 yrs. Intact TM: 0.9 to 2.0 0.3 to 0.9 TM Perf/Tube: > 2.0 >1.0 Blockage: small volume

  12. The Acoustic Reflex • Stapedius contraction measured as change in compliance • Reflex arc: • peripheral ear, • VIIIth n. • Cochlear nucleus • Superior Olivary Complexes • Medial Nuclei of VII • VIIth nerves to both middle ears

  13. L R MN 7 SOC CN 8th IE ME OE SOC CN 8th IE ME OE MN 7 7th CN 7th CN

  14. Clinical Tests using Acoustic Reflexes: • A.R. Threshold: how intense sound must be to elicit the reflex? • A.R. Decay: Is the degree of a contraction maintained throughout a 10 second stimulus?

  15. AR Threshold: • to pure-tones, 0.5, 1, 2, 4 kHz • = lowest level at which change in admittance can be read • ipsilaterally or contralaterally • should be between 65 and 90 dB SL.

  16. “The Boxes”

  17. Vertical 7th Nerve

  18. Diagonal 8th Nerve

  19. Horizontal Brainstem

  20. Inverted L Conductive/8th Impinging on 7th

  21. Eustachian Tube Function Test: • To see how well the Eustachian tube can resolve the pressure differences introduced with the bridge. • Note tympanogram peak pressure • introduce pressure into canal • Have patient swallow water • recheck tympanogram peak pressure

More Related