HSC Section 6 Nov2016 Green Book

Annals of Otology, Rhinology & Laryngology 124(2)

Table 2.  Comparison of Pre-dilation and Post-dilation Pulmonary Function Data.

Median Change, Absolute

Median Change, %

PFT Parameter

Pre-dilation

Post-dilation

P Value

FEV1, L/s

3.23

3.22 2.57 0.77 2.88 6.67 4.21 1.67 0.39 3.97

0.14 0.25

3.9

.177 .720 .155 .156 .001 .906 .001 .001

FVC, L

2.4

10.0

FEV1/FVC

0.74 2.05 3.89 2.36 1.66 0.82 1.83

0.5

5.8

FEF25%-75%

0.41 2.54 1.57 0.13

21.2 56.7 66.8

PEF, L/s PIF, L/s PEF/PIF

< .001

8.4

FEV1/PEF FIF50%, L/s

0.443

56.0 92.0

1.71

Abbreviation: PFT, pulmonary function test.

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. 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

Change in PEF

10

8

6

2 4

L/sec

0

0

10

20

30

40

Months

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).

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

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