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Annals of Otology, Rhinology & Laryngology 124(2)
prognostic indicators.
23
Patients with isolated subglottic
disease, however, can successfully be managed endoscopi-
cally in approximately 87% of cases.
24
The expectation is
that more than 85% of these patients will have recurrence of
their stenosis within 5 years, requiring a return to the oper-
ating suite.
25
Clinically, the goal is to identify the techniques and
adjuvant therapies that provide the greatest improvement
in airflow and result in the slowest rate of restenosis. Not
surprising, time between surgeries is a commonly reported
metric used to demonstrate the efficacy of an interven-
tion.
26,27
Although clinically relevant, confounding vari-
ables related to the surgical interval raise questions about
its reliability for use in research. Surgeon availability cer-
tainly affects the time between procedures. Physically
active patients are more likely to notice impairment of
airflow than sedentary patients and may seek intervention
sooner. Financial factors may affect a patient’s decision to
seek surgery, as well. It is clear that an objective measure
is needed.
Using PFT data to evaluate airway stenosis is not a new
concept. In the 1970s, a number of studies tried to identify
which values or ratio of values could be used to diagnose
UAO. Empey
18
reported on a series of 10 patients (most
with bilateral vocal cord paralysis), noting that the FEV1/
PEF ratio was greater than 10 in all cases and that the larger
the ratio, the greater the degree of obstruction. In comparing
UAO with chronic obstructive pulmonary disease, Rotman
et al
19
identified 4 measurements that were found to differ-
entiate upper from lower airway disease: (1) FEF50%/
FIF50% > 1, (2) FEV1/PEFR > 10, (3) FIF50% < 100 L/
min, and (4) FEV1/FEV0.5 > 1.5, with the latter 2 measures
being less sensitive.
Pulmonary function tests have been used in a limited
fashion to assess postoperative outcomes following tracheal
resection
28
and endoscopic dilation,
29
but reports have been
generally nonspecific about the degree of improvement and
which measures are of greatest utility in quantifying results.
To examine this issue, Wasserman et al
21
created a model of
fixed obstruction using mouthpieces of decreasing inner
Table 2.
Comparison of Pre-dilation and Post-dilation Pulmonary Function Data.
PFT Parameter
Pre-dilation
Post-dilation
Median Change,
Absolute
Median
Change, %
P
Value
FEV1, L/s
3.23
3.22
0.14
3.9
.177
FVC, L
2.4
2.57
0.25
10.0
.720
FEV1/FVC
0.74
0.77
0.5
5.8
.155
FEF25%-75%
2.05
2.88
0.41
21.2
.156
PEF, L/s
3.89
6.67
2.54
56.7
< .001
PIF, L/s
2.36
4.21
1.57
66.8
.001
PEF/PIF
1.66
1.67
0.13
8.4
.906
FEV1/PEF
0.82
0.39
0.443
56.0
.001
FIF50%, L/s
1.83
3.97
1.71
92.0
.001
Abbreviation: PFT, pulmonary function test.
Table 3.
Influence of Dilation Size on Pulmonary Function Test
(PFT) Parameters.
PFT
Parameter
Dilation Size,
mm
N
Median Change,
Absolute
P
Value
PEF, L/s
15.0
5
4.46
.497
16.5
3
2.4
18.0
9
2.45
PIF, L/s
15.0
5
2.47
.047
16.5
3
1.35
18.0
9
1.51
FEV1/PEF
15.0
5
–0.63
.441
16.5
3
–0.62
18.0
9
–0.36
FIF50%, L/s
15.0
4
2.13
.329
16.5
3
1.38
18.0
9
1.58
0
2
4
6
8
10
Change in PEF
Months
L/sec
0
10
20
30
40
Figure 1.
Change in PEF postoperatively. PEF declines in a
linear fashion after intervention. The slope of the line is unique
to each patient (
P
= .0307).
176