HSC Section 6 Nov2016 Green Book

Croake et al

after the University of Iowa head and neck protocol for LEMG diagnostics. 21 Laryngeal electromyography was performed on the right thyroarytenoid muscle of 7 partici- pants with normal vocal function on 3 separate occasions with the application of an additional behavioral control for vocal intensity. We hypothesized that time of testing and vocal intensity would significantly alter quantitative mea- sures of thyroarytenoid EMG signals. Materials and Methods Seven participants, ages 18 to 40 years (3 male and 4 female), were recruited and volunteered for this study. Ten participants were initially recruited based on power analysis for the repeated measures design. Two participants did not complete the entire study protocol, and 1 participant had unusable data. All were nonsmokers, English speaking, and free of laryngeal pathology and movement disorders as judged by stroboscopic examination of the larynx. Exclusion criteria were professional voice training, diagnosed bleed- ing disorder, prior head/neck/spinal surgery, and/or intuba- tion within the past 5 years. All procedures were approved by the University of Kentucky Institutional Review Board, and informed consent was obtained from all participants. All assessments were performed at the University of Kentucky Laryngeal & Speech Dynamics Laboratory. Prior to data collection, all participants received a laryngeal exam via videostroboscopy to ensure normal vocal function and structure (Kay Elemetrics Rhino- Laryngeal Stroboscope [Model RLS 9100 B], Kay Elemetrics 70 degree rigid endoscope [Model SN 1541]; PENTAX Medical, Montvale, New Jersey, USA). This examination was performed by a certified/licensed speech- language pathologist and reviewed by a board certified otolaryngologist. After imaging was completed, electromyographic biopo- tentials (μV) were acquired from the right TA muscle via a 25-mm, 30-gauge concentric bipolar needle electrode (XLTEK 101468; Natus Medical, San Carlos, California, USA). The raw EMG signal was routed to a biopotential amplifier (Grass Model 15A54; Natus Neurology, Warwick, Rhode Island, USA) and serially coupled to a 16-bit analog- to-digital converter sampling at 10 kHz (PowerLab 1630; ADInstruments, Inc, Colorado Springs, Colorado, USA). Prior to digitization, analog signals were band-pass filtered (30 Hz–3 kHz @ –3 dB), with an in-line notch filter applied to reduce 60 Hz line contamination. The LEMG analog out- put was paralleled to a stereo amplifier and played over loud speakers to provide the otolaryngologist with auditory feedback of muscle activity during needle insertion. Audio (volts) and sound intensity levels (dB SPL) from the partici- pant’s vocalizations were recorded by a lapel-style micro- phone (Sony ECM44B; Sony Corporation, New York, New York, USA) and a commercially available sound level meter

(REED ST-8850; REED Instruments, Sainte-Anne-De- Bellvue, Quebec, Canada). Both signals were also digitized by the A/D system (audio sampling rate = 2 kHz; sound pressure level = 1 kHz). All signals were recorded in cali- brated units using a proprietary 2-point interpolation method found in our digitization software package (LabChart 7; ADInstruments, Inc). Post-acquisition LEMG signal processing was completed using custom-coded LabChart routines. Laryngeal electromyography testing was performed in a custom-built Faraday booth to reduce electromagnetic field effects. Participants were seated in an examination chair, reclined to approximately 60 degrees, with their heads comfortably supported by a neck pillow. No sedation or anesthetic was used during the needle insertion and record- ing procedure. A ground electrode was placed on the par- ticipant’s neck, below the mastoid process. Thyroarytenoid needle insertion by an otolaryngologist with 10 years of experience performing clinical LEMG procedures was accomplished using a para-medial approach percutane- ously with the electrode directed in a superolateral direc- tion through the cricothyroid ligament with the muscle entered submucosally. Needle electrode placement was confirmed using the following behavioral tasks: normal rest breathing, phonation on sustained /i/, sniff, and sus- tained phonation of falsetto /i/. Upon completion of the study, the needle electrode was removed by the physician and participants were monitored for 15 minutes after the study in case of complications. Digitized raw LEMG signals were full-wave rectified and RMS signal amplitude values were calculated online with the LabChart software package. Root mean square was calculated as the square root of the mean of a series of squared LEMG amplitude values. Root mean square ampli- tudes were used in all analyses to determine if significant variance in the LEMG signal existed as a function of vocal intensity and time of data acquisition. Experimental Protocol Electromyography of the right TA was performed on each participant on 3 different occasions with a minimum of 1 month between adjacent procedures (mean duration = 2.5 months) to allow for tissue healing. Each session took place at approximately the same time of day and lasted no more than 30 minutes (including videostroboscopy). After needle electrode placement was confirmed within the TA, LEMG signals were recorded under 2 task conditions. First, a con- firmation condition was completed by recording baseline LEMG signals while the participant was instructed to relax and breathe normally, sustain the vowel /i/ at a comfortable modal pitch, gently sniff through the nose, and sustain a falsetto /i/. Second, a feedback condition was completed with the participant producing a sustained /i/ at 2 different

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