Adam L. Rieves

Effect of dehydration on phonation threshold flow in excised canine larynges.

Objectives: The minimum airflow necessary to initiate stable vocal fold vibration — Phonation threshold flow (PTF) — May increase as exposure to dry air increases. A critical period of dehydration may exist after which phonation can no longer be initiated. Methods: We collected PTF data for 11 excised canine larynges mounted on a bench apparatus. Trials consisted of cycles of 10 seconds of phonation followed by 3 seconds of rest. During the experimental trials, subglottal flow of comparatively dry air was increased until phonation was initiated, and phonation was sustained for the remainder of the 10-second period. The subglottal flow was then decreased until phonation ceased. No saline solution was applied during the dehydration trials. During the control trials, subglottal airflow was humidified and saline solution was applied frequently to the vocal folds. Results: The PTF increased as exposure to dry air increased during the experimental trials (p = 0.010); this relationship was not statistically significant in control trials. A point existed after which phonation could not be initiated. Conclusions: Knowledge of the effect of exposure to dry air on PTF could be useful in the clinical assessment and prevention of dehydration. Further exploration of this relationship in vivo could be used to evaluate the effectiveness of current hydration therapies and provide theoretical support for the development of new ones.

Cervical Lymph Node Metastasis Model of Pyriform Sinus Carcinoma

Objective: To establish a cervical lymph node metastasis model of pyriform sinus VX2 carcinoma and investigate its metastatic features. Methods: VX2 tumor tissue suspension was transplanted into the pyriform sinus submucosa of 15 rabbits under direct laryngoscopy. Rabbits were randomly placed into 1 of 3 groups, each comprised of 5 rabbits. Health evaluation and histopathological analysis were performed on days 14 (group 1), 21 (group 2), and 28 (group 3) after transplantation. Results: VX2 tumors were transplanted successfully in all rabbits. Dysphagia, weight loss, rhinorrhea, and dyspnea were observed 28 days after transplantation. Deep cervical lymph node metastasis occurred in all rabbits at all time points. The rate of submandibular lymph node metastasis was 60% in group 1, 80% in group 2, and 100% in group 3. The rate of paratracheal lymph node metastasis was 0% in group 1, 80% in group 2, and 100% in group 3. Conclusions: A model of metastatic pyriform sinus carcinoma was established. This model could be used in future studies evaluating diagnostic and treatment methods.

Spatiotemporal analysis of normal and pathological human vocal fold vibrations

PURPOSE For spatiotemporal analysis to become a relevant clinical tool, it must be applied to human vocal fold vibration. Receiver operating characteristic (ROC) analysis will help assess the ability of spatiotemporal parameters to detect pathological vibration. MATERIALS AND METHODS Spatiotemporal parameters of correlation length and entropy were extracted from high-speed videos of 124 subjects, 67 without vocal fold pathology and 57 with either vocal fold polyps or nodules. Mann-Whitney rank sum tests were performed to compare normal vocal fold vibrations to pathological vibrations, and ROC analysis was used to assess the diagnostic value of spatiotemporal analysis. RESULTS A statistically significant difference was found between the normal and pathological groups in both correlation length (P < .001) and entropy (P < .001). The ROC analysis showed an area under the curve of 0.85 for correlation length, 0.87 for entropy, and 0.92 when the 2 parameters were combined. A statistically significant difference was not found between the nodules and polyps groups in either correlation length (P = .227) or entropy (P = .943). The ROC analysis showed an area under the curve of 0.63 for correlation length and 0.51 for entropy. CONCLUSIONS Although they could not effectively distinguish vibration of vocal folds with nodules from those with polyps, the spatiotemporal parameters correlation length and entropy exhibit the ability to differentiate normal and pathological vocal fold vibration and may represent a diagnostic tool for objectively detecting abnormal vibration in the future, especially in neurological voice disorders and vocal folds without a visible lesion.

Localization of the sentinel lymph node in tongue VX2 carcinoma via indirect CT lymphography combined with methylene blue dye injection

Conclusions: Indirect computed tomography lymphography (CT-LG) combined with blue dye injection can locate the sentinel lymph node (SLN) in tongue carcinoma. Objective: To localize the SLN in tongue VX2 carcinoma using indirect CT-LG combined with methylene blue injection. Methods: Eighteen rabbits were placed into three groups: metastasis, hyperplasia, and control. Indirect CT-LG was performed with an iohexol injection into the tongue submucosa. CT images were acquired at 1, 5, and 15 min after injection. Methylene blue was injected into the same area 24 h after indirect CT-LG, followed by SLN identification and histopathological examination. Results: SLNs were visualized with an identification rate of 100%. SLN location identified using CT lymphography was confirmed by methylene blue dye. Control and hyperplastic enhanced SLNs were round or oval without any filling defects. Control rabbits had enhanced SLN attenuation values of 689.2 ± 55.4 HU, 278.4 ± 33.5 HU, and 71.7 ± 9.2 HU at 1, 5, and 15 min after injection, respectively. Hyperplastic rabbits had values of 877.4 ± 69.4 HU, 352.5 ± 43.3 HU, and 80.2 ± 11.5 HU. Filling defects were only observed in the ipsilateral metastatic SLNs of the metastasis group. CT attenuation values of the metastatic SLNs were 687.4 ± 55.6 HU, 535.1 ± 86.6 HU, and 282.3 ± 19.4 HU at 1, 5, and 15 min, respectively, after iohexol injection. Metastatic lymph node attenuation values were significantly greater than those of the control or hyperplastic nodes at 5 (p < 0.001) and 15 min (p < 0.001) after injection.

Multiparameter analysis of titanium vocal fold medializing implant in an excised larynx model.

Objectives: We evaluated the efficacy of the titanium vocal fold medializing implant (TVFMI) for the treatment of unilateral vocal fold paralysis (UVFP) on the basis of acoustic, aerodynamic, and mucosal wave measurements in an excised larynx setup. Methods: Measurements were recorded on 8 excised canine larynges with simulated UVFP before and after medialization with a TVFMI. Results: The phonation threshold flow (p < 0.001) and phonation threshold power (p = 0.008) decreased significantly after medialization. The phonation threshold pressure also decreased, but this difference was not significant (p = 0.081). Jitter (p = 0.005) and shimmer (p = 0.034) decreased significantly after medialization. The signal-to-noise ratio increased significantly (p = 0.05). Differences in mucosal wave characteristics were discernible but not significant. The phase difference between the normal and paralyzed vocal folds (p = 0.15) and the amplitude of the paralyzed vocal fold (p = 0.78) decreased. The glottal gap decreased significantly (p = 0.004). Conclusions: The TVFMI was effective in achieving vocal fold medialization, improving vocal aerodynamic and acoustic characteristics of phonation significantly and mucosal wave characteristics discernibly. This study provides objective, quantitative support for the use of the TVFMI in improving vocal function in patients with UVFP.

Differentiating between adductor and abductor spasmodic dysphonia using airflow interruption.

To measure the laryngeal resistance (RL), subglottal pressure (Ps), and mean flow rate (MFR) of adductor (ADSD) and abductor (ABSD) spasmodic dysphonia patients using the airflow interrupter.

Phonation threshold pressure estimation using electroglottography in an airflow redirection system

The present study proposed to estimate phonation threshold pressure (PTP) noninvasively using airflow redirection into a pneumatic capacitance system.

Evaluation of auditory and visual feedback for airflow interruption.

INTRODUCTION Clinical application of mechanical interruption methods for measuring aerodynamic parameters has been hindered by relatively high intrasubject variability. To improve the intrasubject reliability, we evaluated the effect of auditory and visual feedback on subject performance when measuring aerodynamic parameters with the airflow interrupter. METHODS Eleven subjects performed four sets of 10 trials with the airflow interrupter: no feedback (control); auditory feedback (tone matching subjects F0 played over headphones); visual feedback (real-time feedback of sound pressure level, frequency, and airflow); and combined auditory and visual feedback. Task order was varied across subjects. The effect of each feedback method on mean and coefficient of variation (CV) of subglottal pressure (Ps), mean flow rate (MFR), and laryngeal airway resistance (RL; Ps/MFR) compared with that of the control trials was determined using paired t tests. Feedback methods were compared against each other using one-way repeated measures analysis of variance. RESULTS Each feedback method significantly decreased CV of RL compared with that of the control trials (auditory feedback: P=0.005; visual feedback: P=0.008; and combined feedback: P<0.001). Auditory feedback (P=0.011) and combined feedback (P=0.026) also decreased CV of MFR. Mean MFR was significantly higher during trials with visual feedback compared with that of the auditory feedback. CONCLUSIONS Each feedback method improved the intrasubject consistency when measuring RL. Feedback appeared to have a greater effect on MFR than Ps. Although there is no clear optimal feedback method, each is preferable to not providing any feedback during trials. Evaluating new methods of visual feedback to further improve MFR and thus RL measurement would be valuable.

Phonation Instability Flow in Excised Canine Larynges

OBJECTIVE Disordered voices are often associated with abnormal changes in aerodynamic parameters of subglottal pressure (P(s)) and airflow. Phonation instability pressure (PIP) has been previously proposed to evaluate P(s) at the onset of chaotic phonation. We propose the concept of and measure phonation instability flow (PIF), the airflow at which phonation becomes chaotic. Phonation flow range (PFR), PIF minus phonation threshold flow (PTF), is proposed to assess the range over which normal vocal fold vibration occurs. STUDY DESIGN Repeated measures with each ex vivo larynx serving as its own control. METHODS Pressure and airflow were measured at phonation onset and chaos onset in seven excised canine larynges under three experimental conditions: 0% elongation with no glottal gap; 20% elongation with no glottal gap; 20% elongation with a 3-mm posterior glottal gap. Paired t tests were performed to determine if experimental measurements differed between elongations (0% and 20%) or degrees of abduction (20% elongation with and without a 3-mm glottal gap). RESULTS Both PIF and PFR were dependent on abduction but not elongation. PIP was not significantly dependent on either condition. PIF and PFR showed greater differences for abduction than either phonation threshold pressure (PTP) or PTF. CONCLUSIONS PIF and PFR may be useful parameters in the experimental or clinical settings, particularly when evaluating disorders characterized by a glottal gap, such as vocal fold paralysis and presbylaryngis.

Comparison of labial and mechanical interruption for measurement of aerodynamic parameters

OBJECTIVES/HYPOTHESIS To directly compare the mechanical and labial interruption techniques of measuring subglottal pressure (P(s)), mean flow rate (MFR), and laryngeal resistance (R(L)). METHODS Thirty-four subjects performed 10 trials with both mechanical and labial interruption. P(s) and MFR were recorded, whereas R(L) was calculated by dividing P(s) by MFR. Coefficients of variation were calculated to compare intrasubject precision. A subset of 10 subjects performed the tasks twice with 30 minutes between sessions. Bland-Altman plots were used to determine intrasubject repeatability for each of the methods. RESULTS Mechanical interruption produced coefficients of variation for P(s), MFR, and R(L) of 0.0995, 0.127, and 0.129, respectively. Labial interruption produced coefficients of variation of 0.102, 0.147, and 0.169, respectively. P values were 0.824 for P(s), 0.159 for MFR, and 0.043 for R(L). The Bland-Altman plots revealed comparable repeatability between the two methods. The 95% confidence intervals of the Bland-Altman plots for mechanical interruption were (-0.050, 0.072), (-0.543, 1.832), and (-2.498, 10.528) for MFR, P(s), and R(L). Confidence intervals for labial interruption were (-0.018, 0.031), (0.057, 2.442), and (-3.267, 10.595) for MFR, P(s,) and R(L). CONCLUSIONS Mechanical interruption produced higher precision when measuring R(L) because of more reliable airflow measurements. Mechanical and labial interruption showed comparable repeatability. Further research into using mechanical interruption clinically is warranted.