Impedance Audiometry in Serous Otitis Media Daniel J. Orchik, PhD;
\s=b\ The relationship between the results of impedance audiometry and middle ear effusion in serous otitis media was examined in 76 ears immediately prior to myringotomy. Tympanometry and acoustic reflex threshold showed the highest correlation with the operative findings relative to middle ear effusion. The combination of tympanometry and acoustic reflex threshold was superior to the use of either component alone. Results are discussed in terms of clinical implications with specific consideration of hearing screen-
ing programs. (Arch Otolaryngol 104:409-412, 1978)
The
most
of hearing preschool- and levels is serous
common cause
loss in children of
elementary school-age
otitis media.1 In recent years, impe¬ dance audiometry has been advocated as a more efficient means of screen¬ ing for serous otitis media in children when compared with conventional pure-tone methods.-'1 In most applica¬ tions of impedance audiometry to screening, tympanometry has been the major component of the hearing conservation program designed to detect serous otitis media.1"' Assessing the validity of impedance screening has traditionally followed one of two approaches. Either the findings of impedance audiometry are compared with otoscopie findings,1 or the impedance results are compared with postoperative findings at myrin-
Accepted
for publication Feb 29, 1978. From the Department of Audiology and Speech Pathology, Memphis State University (Dr Orchik), and the East Texas Rehabilitation Center, Kilgore (Ms Morff). Dr Dunn is in private practice in Denton, Tex. Reprint requests to Department of Audiology and Speech Pathology, Memphis State University, 807 Jefferson Ave, Memphis, TN 38105 (Dr
Orchik).
Rosemary Morff, MS; James
W.
gotomy.- Recent evidence suggests that agreement between tympanome¬ try and otoscopy is not as strong as
thought.6 When postoperative data have been employed, the results of tympanome¬ try are usually evaluated on the basis of the ability to predict the presence
Dunn, MD months to 14 years, with
absence of effusion in the middle ear.-7-9 Although the presence or absence of effusion is not the only clinically significant finding from the viewpoint of the otolaryngologist, it is a relatively objective finding when compared with routine otoscopie ex¬ amination. The relationship between the re¬ sults of tympanometry and the pres¬ ence of middle ear effusion has been examined by a number of research¬ ers.-81" Although certain tympano¬ metric types, ie, type as described by Jerger et al," have been shown to indicate a high probability of middle sufficient variability ear effusion, exists to suggest that single tympa¬ nometric screening may not be the most efficient means of predicting middle ear effusion common to serous otitis media.1"12 Our investigation was designed to assess whether any combination of components in the impedance audiom¬
etry
static
test
battery (tympanometry,
compliance, acoustic reflex test¬ ing) might prove to be a better indica¬ tor of significant middle ear effusion. If the sensitivity could be so en¬ hanced, the efficiency of impedance screening might be likewise im¬ proved. METHOD
Subjects sample for this investigation includ¬ ears of patients who underwent myringotomy for suspected serous otitis media. Subjects ranged in age from 6 The ed 76
of 4Vè
Experimental Procedure
once
or
a mean
years.
Each subject was brought to the operat¬ ing room area approximately 30 minutes prior to surgery. The patient's transport bed was placed in a position adjacent to a cart that contained
an
electroacoustic
impedance bridge (Madsen 70-72), which was used to gather the impedance data. The following information was obtained for each ear: 1. A tympanogram was plotted from + 200 to -400 mm/ , in 100 mm/H.,0 steps, including the point of maximum compliance. In addition, the points at ±50 mm/ , , in reference to the point of maximum compliance, were plotted. 2. The measurement of static com¬ pliance was obtained for the middle ear. 3. The acoustic reflex threshold was examined at 500 through 4,000 Hz. Tympanograms were classified as either type A, B, or C since the use of these
symbols was thought to represent an easilyrecognized classification system.11 In addi¬
tion, type C tympanograms were further subdivided into three categories on the basis of the magnitude of negative pres¬ sure. A C, classification was applied to
whose point of maximum within the negative pres¬ sure range of -100 to -150 mm/H,0. The point of maximum compliance for a C2 tympanogram fell between -151 and -200 mm/H.,0. Those tympanograms with a point of maxmium compliance greater than -200 mm/rLO were classified as C3 curves. In this manner, tympanograms could be rated on a five-point scale from normal through increasing abnormality. The type A indicated normal function while a type represented the opposite extreme. Types C,, C2, and C, described the intermediate points on the scale. Static compliance was recorded in cubic centimeters by subtracting the volume measure that was obtained with a positive pressure of 200 mm/H.,0 from the volume measure that was obtained at the point of maximum compliance." The acoustic reflex those
curves
compliance fell
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threshold was taken at the lowest level in decibels of the hearing threshold level (HTL) (ANSI-1969), where a consistent deflection of the balance meter could be observed. For the purpose of this analysis, acoustic reflex thresholds were recorded for the probe ear so that they could be
analyzed with the tympanometric and stat¬ ic compliance data for the same ear. The patient was then taken to the oper¬ ating room where the myringotomy was performed. The surgeon (J.W.D.) had no prior knowledge of the impedance data. During the surgery, data relative to the status of effusion in the middle
displays the
ears
then
subjected
No effusion or an insignificant was found in 37 ears. Twentyfour of those ears (65%) showed type A tympanograms, 11 ears (30%) showed type C curves, and two ears (5%) showed type tympanograms. As noted earlier, the 26 type C tympanograms were further differenamount
Table 1— Correlation Coefficients for Tympanometry, Static Compliance, Acoustic Reflex Threshold, and Status of Effusion in Middle Ear at
ear were
Myringotomy Reflex
Threshold, Hz
Middle Ear Effusion .66" -.37* .61* .62* .62* .52*
Static
Variable
Compliance
Tympanogram Static compliance
500 .39s -.11
-.44*
Significant
2,000
1,000 42« 91*
-
4,000 38s
.45* .13 .91s .95*
12
Reflex threshold, 500 Hz Reflex threshold, 1,000 Hz Reflex threshold, 2,000 Hz Reflex threshold, 4,000 Hz Middle ear effusion
10 48:!
51 ' 54 s
at the .01 level.
Table 2—Status of Effusion in Middle Ear
as
Function of
Tympanogram Type
No. (%) of Ears
Tympanogram Type
previous investigation." were
15 ears (38%) were type C tympanograms, and three ears (8%) were type A tympanograms.
to tym¬ amount of
fluid present in the middle ear. With the use of the designations of "moderate" and "impacted" as indica¬ tive of significantly abnormal find¬ ings at myringotomy," 39 ears dis¬ played significant amounts of middle ear effusion. Twenty-one (54%) of those with significant fluid exhibited type tympanograms. Of those
recorded by a second observer, as noted by the operating physician. The presence or absence of effusion was rated by the operating physician on a four-point scale as none, minimal, moder¬ ate, or impaction. A rating of no effusion indicated that the middle ear was dry on examination after myringotomy, whereas a rating of impaction indicated that the middle ear space was completely filled with effusion. The ratings of minimal and moderate were somewhat more subjective but were used to establish a boundary for significant effusion. A rating of minimal was employed to indicate an ear where a very slight amount of fluid was found, while a rating of moderate was used to indicate an ear with a significant amount of effusion but some remaining air space in the middle ear. The operating physician was satisfied with this four-point-rating scale since it provided a means of differen¬ tiating to a somewhat greater degree the status of effusion in the middle ear. The same rating scale had been used in a
The data
remaining,
according
type and the
panogram
Insignificant
Significant
Effusion
Effusion
None
Minimal
14(52) 5(19) 2(9)
10(37) 6(23)
Moderate
Total 27 26 23
Impacted 3(11) 11 (42) 18(78)
4(15) 3(13)
to a
computer analysis that yielded Pearson's
Table 3.—Status of Effusion
multiple correlations (R's) between components of the impedance battery and the status of middle ear effusion at myrin¬ r's and
Function of Magnitude of in Middle Ear
(%)
No.
gotomy.
C3
*C, =
5(56)
Moderate
3(33) 3(23)
negative pressure of 100 to 150 negative pressure of 200 mm H20. =
as
Significant
Minimal
None
C,
mm
Negative Pressure
of Ears
Insignificant Effusion
Tympanogram Type*
RESULTS Tympanometry and Middle Ear Effusion
Of the 76 ears that were examined, 55 were found to have fluid present in the middle ear at myringotomy. Of these, 32 ears were impacted, and seven ears were judged to have moderate amounts of fluid in the middle ear. The remaining 16 ears displayed minimal amounts of middle ear effusion. As shown in Table 1, a significant correlation (r .66, < .01) was found between the tym¬ panogram type and the amount of effusion in the middle ear. Table 2
as
2(15) 2(50)
H„0; C,
negative
Effusion
Impacted 1(11) 8(62) 2(50)
pressure of 151 to 200
mm
Table 4.—Status of Middle Ear Effusion Function of Measured Static Compliance No. of Ears
Insignificant Effusion
=
Static Compliance Normal (> 0.28 cc) Reduced (< 0.28 cc)
None
Minimal
12
10
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Significant Effusion Moderate
Impacted 29
H20;
tiated into three categories according to the amount of negative middle ear air pressure. Table 3 presents a break¬ down of the type C tympanograms as a function of the amount of effusion present in the middle ear at myringo¬
tomy.
Fifteen type C tympanograms dis¬ played significant amounts of effu¬ sion. Of these, one ear (6%) was a C, curve, ten
and four
(67%) were C2 curves, (27%) were C, curves.
ears
ears
Static Compliance and Middle Ear Effusion A small yet significant negative correlation was shown to exist be¬ tween the static compliance measure¬ ment and the amount of middle ear effusion, ie, as the amount of effusion increased, static compliance decreased (r -.37, < .01). Table 4 presents the relationship between the static compliance value and the amount of effusion present in the middle ear. It is apparent that the relationship is not as strong as that found between the results of tympanometry and the amount of middle ear effusion. As shown in Table 4, of the 76 ears that were examined, 19 had static compliance values within the normal range (0.28 to 1.72 cc), as specified by Brooks.14 Of these, 15 (78%) exhibited insignificant effusion at myringoto¬ my. However, significant effusion was discovered in four (21%) of the ears with normal static compliance. Reduced static compliance values (