Vanderbilt UniversityDepartment of Biomedical Engineering

Device for Quantification of Re-Innervation of a Laryngeal Muscle

Advisor: Dr. David Zealear

Designers: Thomas Thomasson and Nirav Patel

March 24, 2000

Background•What ?- Development of a design and technique for the quantitative measurement of a re-innervated laryngeal muscle

•Why ?- To increase quality of life for patients suffering from denervated muscular system

•From? -Surgical removal of cancer growth, nerve damage, arytenoidectomy, vocal fold resection.1

•Who ? - Patients that have lost muscle control through paralysis of laryngeal muscles (2estimates of 16,000/yr in U.S., 25% having bilateral paralysis)1. Michaels, Pathology of the Larynx., 1984 2. National Center for Health Statistics, 1996.

Background Cont...

• How ?- Recording EMG readings passes through the developed circuitry while tactile stimulation of the nerves is performed

• Analysis? -Integrated recordings over time show degree of re-innervation and muscle fiber reconstruction counts

• Synkinetic Ratio- Level of Re-innervation over initial nerve signals

Background Cont...• Electrical stimulus must be performed before 7

months after denervation of laryngeal muscle--fibrosis.3

• Stimulus paradigm-- 1 second pulse train with 2msec pulses at 30 Hz with a current of 4-14mA.4

• Neuromuscular block, Botox, suppresses adductor movement allowing greater abductor movement (7mm dynamic opening)5

3,4,5 - Zealear, Billante. Emerging Approaches to Laryngeal Rehabilitation

Objectives• To Measure electromyographical potentials using

electrodes.

• To establish an index of synkinesis that compares pathological nerve re-innervation to normal nerve alignment

• To use index of synkinesis to determine severity of pathology.

• To measure muscle fiber bundles that have been re-innervated (secondary measurement of paralysis severity)

Circuit

•High Pass Filter

•Removes DC noise and low frequency AC noise

•Low Pass Filter

•Cutoff frequency of 100K Hz

•Rectifier

•Returns absolute value of input•Positive Wave Rectifier: Vout = Vin •Diodes Act Linearly in Feedback Loop

Circuit Cont...

• Integrator

– Calculates area under input curve

– Integrates the Rectified Wave Over Time by the equation: Vout = -1/(Rf Cf ) Vin dt

• Peak Detector

– Holds maximum value from the integrator

Circuit Output

Input Signal

Rectified Signal

Integrated Signal/ Peak Value

EMG Signals From Dog Subjects

Signal From Indirect Stimulation of Nerve

Signal From Direct Stimulation of Nerve

Design Implementations• Researched and Designed Circuit for

optimal performance

• Circuit Components selected based on effectiveness and cost efficiency– voltage limitations for powering op amp– minimize DC noise within op amps

• Potentiometer added in Circuit Design for Calibration that will be performed with a 2Vp-p 1kHz sine wave

DesignSafe Analysis

• Circuit Components Shorting – Design Around Hazard While Hard Wiring

• Overloading Circuit – Add Neon Bulb between input Electrodes

• Direct/Indirect Contact With Live Wires– Design Around By Properly Insulating Circuit

and Components

Current Work

• Begin Hard Wiring Circuit onto a Vector Board

• Debug the Vector Board

• Add a digital output meter, which has been ordered, to the circuit to serve as a final output source

Future Work• Use circuit during canine experiments

• Development of index of synkinesis through statistical analysis upon completion of canine experiments

• Begin Poster presentation design