HSC Section 6 Nov2016 Green Book

Journal of Voice, Vol. - , No. - , 2015

TABLE 6. Correlation Coefficients (r) Among High-Speed Digital Image Parameters Parameters N L - Minimal GA SI GAW O q MLK O q SLK N L

-O-LPD MLK

-Amplitude Mean N G

GA difference index

0.90 *

0.46 * 0.33 y

0.65 * 0.69 * 0.47 *

0.54 * 0.47 * 0.56 * 0.42 *

0.34 y 0.24

0.15 0.05

N L

-minimal GA

1

SI GAW

— — — — — —

1

0.04 0.10 0.03 0.13

0.39 *

GAW

O q N G O q

— 0.69 * — 0.14

0.10

-O-LPD LTG

0.19

0.50 *

MLK

— 1

0.65 *

0.19 0.28 0.03

N GL

-integral glottal width -MW magnitude mean

— — 0.51 * — — —

0.51 * 0.59 *

N L

Abbreviations: GA, glottal area; N L

-, normalized by vocal fold length; SI, speed index; GAW, in glottal area waveform; O q

, open quotient; N G

-, normalized by

glottal cycle; O-LPD, opening longitudinal phase difference; LTG, in laryngotopography; MLK, in multi-line kymography; N GL

-, normalized by glottal cycle and

vocal fold length; MW, mucosal wave; SLK, in single-line kymography. * P < 0.001. y P < 0.01.

videostroboscopy, which is considered to be meaningful espe- cially because a large part of vibratory characteristics of VFA were reflected in the time parameters (eg, open quotient). Second, with the use of HSDI, the rate of successful image evaluation increased by 1.5 folds at a rough estimate because videostroboscopic study was successful only in 67.3% because of desynchronization in the present study. The relatively high rate of desynchronization in VFA may be explained by their poor acoustic profile. Patel et al 8 reported that HSDI could be used to augment videostroboscopy for assessment of moderate-to-severe dysphonia, especially in patients with jitter exceeding 0.87%, shimmer exceeding 4.4%, and a signal-to- noise ratio of less than 15.4 dB. In the present study, 21.7% of the VFA group fitted these criteria. Third, with the application of multiple analysis methods, the present study documented the characteristics of vocal fold vi- brations of VFA more extensively and multidirectionally than previous reports, in which vocal fold vibrations were either qualitatively evaluated or quantitatively evaluated with only limited parameters. 5,6 Although HSDI has disadvantages in comparison with video- stroboscopy such as a relatively long time required for analysis (approximately 30 minutes per HSDI at present), a high cost, and the lack of instantaneity (with videostroboscopy, the result of modulation in F 0 , sound pressure level, or register can be observed directly and instantaneously), 7,8,16 HSDI is considered to be a good supplementary tool in the assessment of VFA. Amplitude and integral glottal width The amplitude mean of VFA was comparable with that of vocally healthy subjects, in this study, which was a consistent result with the previous study. 5 Although not statistically signif- icant, the amplitude of VFA was larger in males and smaller in females than vocally healthy subjects. Various factors can affect amplitude such as amplitude increases as intensity or subglottal pressure increase, or as pitch or stiffness decrease. 6,9,16,17 In female VFA, poor pulmonary function is reported to be frequently associated, 2 which may lead to decreased subglottal

pressure and decreased amplitude. In male VFA, a greater glottal flow and lower tension of the thyroarytenoid muscle owing to the muscular atrophy can increase the amplitude. 6,18,19 On the other hand, N GL -integral glottal width demonstrated a significant difference between the control and VFA groups. The N GL -integral glottal width may be a sensitive parameter than the amplitude per se because it has the characteristics of both amplitude and open quotient ( Table 6 ). 13

Open quotient and speed index Significant intergroup differences were observed in O q

SLK and GAW was

MLK but not in O q

GAW . This is probably because O q

O q

not a parameter to reflect the size of glottal gap (O q GAW be- comes one whether a glottal gap is small or large). Interestingly, the results of O q SLK were comparable with those of O q MLK , although O q MLK that assesses the overall glottal area should reflect the pathophysiology of the disease better than O q SLK . Perhaps, the midglottal level may represent the vibratory dy- namics of overall glottis well enough in VFA, and the informa- tion of the glottal ends included in O q MLK may have been less important. Correlation analysis revealed that high O q SLK and O q MLK were associated with poor aerodynamic and acoustic conditions ( Table 4 ). These results seem to stand to reason because weak glottal closure reflected in high open quotient should lead to high glottal flow with high air turbulence. Speed index of VFAwas smaller than that of vocally healthy subjects. Small speed index in the VFA group may originate from the decreased restorative force of the laterally displaced vocal fold toward the medial direction resulting from the disar- rangement of collagen fibers or decreased elastin fibers in the lamina propria, the decreased mass or tension of the vocal fold owing to the muscular atrophy. 1,18,19 Contrary to open quotient, SI GAW was more sensitive than SI SLK or SI MLK , probably because SI GAW reflects the general vibratory dynamics than SI SLK or SI MLK ( Table 2 ). Speed index had similar relationships with acoustic and aerodynamic parameters to open quotient ( Table 4 ). These results accord with the find- ings in the literature, reporting that smaller speed index leads to poorer aerodynamic or acoustic results. 20,21

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