Video-based method of quantifying performance and instrument motion during simulated phonosurgery.

OBJECTIVES/HYPOTHESIS: To investigate the use of the Video-Based Phonomicrosurgery Instrument Tracking System to collect instrument position data during simulated phonomicrosurgery and calculate motion metrics using these data. We used this system to determine if novice subject motion metrics improved over 1 week of training. STUDY DESIGN: Prospective cohort study. METHODS: Ten subjects performed simulated surgical tasks once per day for 5 days. Instrument position data were collected and used to compute motion metrics (path length, depth perception, and motion smoothness). Data were analyzed to determine if motion metrics improved with practice time. Task outcome was also determined each day, and relationships between task outcome and motion metrics were used to evaluate the validity of motion metrics as indicators of surgical performance. RESULTS: Significant decreases over time were observed for path length (P < .001), depth perception (P < .001), and task outcome (P < .001). No significant change was observed for motion smoothness. Significant relationships were observed between task outcome and path length (P < .001), depth perception (P < .001), and motion smoothness (P < .001). CONCLUSIONS: Our system can estimate instrument trajectory and provide quantitative descriptions of surgical performance. It may be useful for evaluating phonomicrosurgery performance. Path length and depth perception may be particularly useful indicators.

Quantitative evaluation of phonomicrosurgical manipulations using a magnetic motion tracking system.

OBJECTIVES/HYPOTHESIS: To present and evaluate the magnetic-based phonomicrosurgery instrument tracking system, a novel and objective method of acquiring instrument position data during simulated phonomicrosurgery. The position data can be used to compute quantitative motion metrics. This system was used to objectively evaluate the motion performance of novice and expert surgeons during phonomicrosurgical simulations and determine the differences between these groups. STUDY DESIGN: Prospective cohort study. METHODS: A magnetic-based phonomicrosurgery instrument tracking system was developed, including a workbench, independent task, motion metrics, and computer program. Based on this system, three experts' and six novices' motion data were collected and analyzed. RESULTS: Experts demonstrated significantly better motion smoothness along the y-axis for the dominant hand. For the nondominant hand, experts demonstrated better motion smoothness along all three axes, shorter path length, and better depth perception (P < .05). Experts also demonstrated higher quality of operation (P < .001). No significant difference in time was noted (P = .671). CONCLUSIONS: Parameters derived from magnetic-based motion tracking were able to differentiate between expert and novice surgeons. These parameters have the potential to be used in phonomicrosurgical training as feedback to enhance the training process.

Differentiating arytenoid dislocation and recurrent laryngeal nerve paralysis by arytenoid movement in laryngoscopic video.

OBJECTIVE: To present a new method of quantifying arytenoid movement during inspiration and determine if it can be used to distinguish arytenoid dislocation from vocal fold paralysis. STUDY DESIGN: Case series with chart review. SETTING: Retrospective study conducted in a university laboratory based on university hospital data. SUBJECTS AND METHODS: Endoscopic videos from 8 patients with dislocation and 5 patients with vocal fold paralysis diagnosed by electromyography were included. Vector analysis measured cuneiform movement, an indirect measurement of arytenoid movement, during 1 inspiration. Measurements normalized and not normalized to vocal fold length were evaluated. Interrater reliability (2 raters) and intrarater reliability (1 rater performing the analysis twice) were evaluated using intraclass correlation coefficient (ICC) analysis. Raters were blinded to subject group during analysis. RESULTS: Pixel-valued cuneiform movement was 81.16 ± 25.62 for dislocation and 30.22 ± 23.60 for paralysis (P = .019). Unitless cuneiform movement was 0.58 ± 0.17 for dislocation and 0.24 ± 0.18 for paralysis (P = .030). Interrater ICC was 0.942 for pixel-valued measurements and 0.962 for unitless measurements. Intrarater ICC was 0.909 for pixel-valued measurements and 0.881 for unitless measurements. CONCLUSIONS: Both pixel-valued and unitless measures of arytenoid movement were significantly greater in arytenoid dislocation than vocal fold paralysis. Pixel-valued measurements were included to demonstrate the ability to make quantitative comparisons across subjects without precise knowledge of camera precision, provided position is approximately stable, as each measurement is inherently normalized by vocal tract length. Future studies will apply this new method of evaluating vocal fold immobility disorders on a larger scale and incorporate a more diverse group of etiologies.

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 subject's 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.

Classification of glottic insufficiency and tension asymmetry using a multilayer perceptron.

OBJECTIVE: Laryngeal function can be evaluated from multiple perspectives, including aerodynamic input, acoustic output, and mucosal wave vibratory characteristics. To determine the classifying power of each of these, we used a multilayer perceptron artificial neural network (ANN) to classify data as normal, glottic insufficiency, or tension asymmetry. STUDY DESIGN: Case series analyzing data obtained from excised larynges simulating different conditions. METHODS: Aerodynamic, acoustic, and videokymographic data were collected from excised canine larynges simulating normal, glottic insufficiency, and tension asymmetry. Classification of samples was performed using a multilayer perceptron ANN. RESULTS: A classification accuracy of 84% was achieved when including all parameters. Classification accuracy dropped below 75% when using only aerodynamic or acoustic parameters and below 65% when using only videokymographic parameters. CONCLUSIONS: Samples were classified with the greatest accuracy when using a wide range of parameters. Decreased classification accuracies for individual groups of parameters demonstrate the importance of a comprehensive voice assessment when evaluating dysphonia.

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.

Optimal arytenoid adduction based on quantitative real-time voice analysis.

HYPOTHESIS: The optimal degree of arytenoid rotation for arytenoid adduction (AA) can be determined using quantitative real-time voice analysis. STUDY DESIGN: Repeated measures with each larynx serving as its own control. METHODS: Unilateral vocal fold paralysis (VFP) was modeled in five excised canine larynges. Medialization laryngoplasty (ML) was performed, followed by AA. The optimal degree of arytenoid rotation was determined using real-time measurements of vocal efficiency (V(E) ), percent jitter, and percent shimmer. After the optimal degree of rotation was determined, the arytenoid was hypo- and hyperrotated 10% ± 2% of the optimal angle to mimic hypoadducted and hyperadducted states. Aerodynamic, acoustic, and mucosal wave measurements were recorded. RESULTS: Mean optimal angle of arytenoid adduction was 151.4 ± 2.5°. V(E) differed significantly across experimental conditions (P = .003). Optimal AA produced the highest V(E) of any treatment, but this value did not reach that produced in the normal condition. Percent jitter (P < .001) and percent shimmer (P < .001) differed across groups and were lowest for optimal AA. Mucosal wave amplitude of the normal (P = .001) and paralyzed fold (P = .043) differed across treatments. Amplitude of both folds was highest for optimal AA. CONCLUSIONS: V(E) and perturbation parameters were sensitive to the degree of arytenoid rotation. Using real-time voice analysis may aid surgeons in determining the optimal degree of arytenoid rotation when performing AA. Testing this method in patients and determining if optimal vocal outcomes are associated with optimal respiratory and swallowing outcomes will be essential to establishing clinical viability.