Welch Allyn TM286 Auto Tymp - User Manual - Manual (Page 56)

52 Test Results Welch Allyn TM286 Auto Tymp
middle-ear system is consistent with a poorly functioning eustachian tube with possible
effusion (serous otitis media) or "glue ear."
A compliance value greater than 1.4 cm
3
(or 1.8 cm
3
) indicates a hyperflaccid tympanic
membrane or a possible disarticulation depending upon how far above the normal range
the value is. Generally speaking, a compliance value of greater than 3.0 cm
3
is indicative
of a disarticulated ossicular chain. Further testing is necessary to confirm this suspicion.
The validity of tympanometry and acoustic reflex testing is dependent upon a healthy
tympanic membrane. A pathological condition at this membrane can mask the true
condition of the middle ear.
Pressure Peak
Normal
Strict rules for middle-ear pressure indicate a normal range of ±50 daPa. However, for
most applications, a normal range of -150 daPa to +100 daPa is used.
Abnormal
Very rarely, an extreme positive pressure condition will be observed. Some researchers
have reported high positive pressures at the onset of acute otitis media.
Pressure values more negative than -150 daPa are indicative of a poorly functioning
Eustachian tube. The severity of this condition is determined by how negative the
pressure is and its impact on the compliance peak.
If no pressure peak is measured over the pressure range of +200 daPa to -400 daPa, then
the letters NP will appear on the screen and the printout. This indicates that no pressure
peak was detected over this pressure range.
Gradient
Normal
When testing a child, the normal range for the gradient is between 60 and 150 daPa.
(Infants may show higher gradient values due to the mobility of their ear canals). The
range of normal is somewhat narrower for adults (i.e., 50 to 110 daPa).
Abnormal
A high gradient value (greater than the high end of the normal range per age group) is
indicative of middle-ear effusion. The reduced compliance values and negative middle-ear
pressure characteristic of developing or resolving otitis media with effusion (OME) will be
manifested in a broad tympanogram with a large gradient value. However, abnormal
Note If the measured compliance value is less than 0.1 cm
3
, the letters NP will be
printed next to the heading cm
3
on the screen and printout. The letters NP
indicate a poorly defined or flat Tympanogram. The Tympanogram may depict a
very shallow peak.
Note If a compliance value is measured to be greater than 1.5 cm
3
, the instrument
automatically changes the range assigned to the graph to 3.0 cm
3
.