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Blink Restoring Device for Patients with Unilateral Facial Palsy

BME 227L - Design in Biotechnology
by

Fred Hwang

on 2 May 2010

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Transcript of Blink Restoring Device for Patients with Unilateral Facial Palsy

Blink Restoring Device for Unilateral Facial Paralysis Patients Fred Hwang
Vernon Ollison
Zach Harvanek BME 227L - Design in Biotechnology
Friday, April 23, 2010 Dr. Michael Richard
Dr. Marc Richard
Dr. Nicholas Ramey Overview Introduction Background





Mission Statement - Facial Nerve Paralysis

- Anatomy/Physiology of Blinking

- Current Treatments Design Requirements/Process Primary Requirements




Secondary Requirements


Decision Matrix - Function

- Safety

- Comfort - Aesthetics
- Stimulation Method

- Electrodes Prototype Fabrication/Testing Prototype Fabrication Remaining Issues - Blink Latency

- Safety

- Accuracy

- Testing Results

- Future Tests

Concerns



Improvements



Future work Introduction Background Unilateral Facial Nerve Paralysis http://www.mdconsult.com/das/patient/body/183513348-2/0/10041/36432.html
Bell's Palsy is most common form of facial paralysis


Affliction time varies
- 80% of cases recover in 6 months http://www.horizon-bcbsnj.com/myhealthyhorizon/webmd/Encyclopedia/articles/BellsPalsy/BellsPalsy.jpg Blink Anatomy http://health.howstuffworks.com/human-nature/emotions/other/crying.htm/printable
Blink Purposes: Eliminates foreign particles/bacteria

Moistens eye Bad Things Happen Without Blinks: Dryness Eye
Irritation Eye Pain But seriously... Infection Cornea Damage http://cache3.asset-cache.net/xc/200219992-001.jpg?v=1&c=IWSAsset&k=2&d=6C4008C0FD9EB5A5DB8FEAD22B0BA6904BBC8A168B1E17D712DA00964B7165DBEC7C5022FB410D56 http://img.webmd.com/dtmcms/live/webmd/consumer_assets/site_images/articles/health_tools/pinkeye_slideshow/photolibrary_rm_photo_of_young_man_rubbing_eye.jpg http://www.bausch.com/en_US/images/concern_full_img/dry_eyes_lg.jpg Blink Physiology Contractions Moves Distal to Proximal Whole blink takes 300 ms Pearce, J.M.S., Observations on the Blink Reflex, Eur Neurol 2008;59:221-223
http://www.mda.org/publications/Quest/q76eyecare.html
Current Treatments http://methodistfacialparalysis.com/eyeclosure/
Artificial Tears


Manual Closing


Surgery
- Implantable Weight

- Brings eyelids together

- Invasive procedure for temporary problem - Prevents Use of Eye - Very short-term Solution Primary Requirements Problem Statement Design a temporary device that restores coordinated blinking in patients with unilateral facial paralysis without causing significant patient discomfort.
Function



Safety


Comfort - Detect blinks in non-palsied eye

- Stimulate (complete) blinks in palsied eye - Electrical device must be safe

- Adjustable feature for user's discretion - Minimize Sensation

- Approximately 3 oz. Secondary Requirements - Aesthetics Blink coordination (~ normal blink 300 ms latency)

Minimize device size

Make customizable for any pair of glasses Alternative Solutions Stimulation Method 3 methods How?
Pulse-train stimulation that mimics motor neuron function

How?
Physical device (spring/sling) that mimics upper eyelid motion


Advantages:
No surgery
Adjustable to patient's needs
Prevents muscle atrophy Disadvantages
Lack of stimulation specificity if transcutaneous
Potential discomfort
Muscle fatigue Advantages:
Aesthetics - discrete placement
Disadvantages
Possible reactions/extrusions
Induced ptosis
Unnatural artificial solution
Requires invasive surgery How?
Acetylcholine injections to stimulate nerve activity
Advantages:
Can reduce current magnitude if combined with electrical stimulation
Disadvantages:
Requires surgical insertion
Constant microinjections
Slow absorption Detection Method Functionality:
Measures muscle activity of orbicularis oculi

Advantages:
Well-defined wave-form Disadvantages:
Signal varies between patients
Signal changes with electrode position Functionality:
Measures action potentials of zygomatic branches of facial nerve

Advantages:
Specific measure of blink activity
Disadvantages:
Small signal amplitude
Recording is localized Functionality:
Measures electrical potential across the retina

Advantages:
Electrode placement is not specific
Disadvantages:
Not a direct measure of blink capability
Picks up all movements of the eye - Physical Components

- Functional Capabilities

- Challenges Met

- Overview of Design
Testing Criteria/Results
Prototype Design Signal Detection Signal Analysis/Processing Generated Electrical Response www.biopac.com/ag-agcl-4mm-electrode - Electrodes must be small and light

- Heavy electrodes can:
-cause eye drooping
-obstruct vision
-prevent complete blinks

+ - Gnd (Lateral Canthus) Frequency:


Duration:


Current Magnitude:


Peak Voltage - 100 Hz



- 100 ms



- 2- 12 mA



- 3 - 9 V


Acquired EMG signal Blinks General Eye Movement http://www3.interscience.wiley.com/cgi-bin/fulltext/85513944/PDFSTART
http://www.robotroom.com/Monkey-Mints-Line-Following-Robot2.html
Atmel ATtiny85 Microcontroller Program Determines blink 2nd derivative above cutoff





Duration of signal below cutoff Filters Noise Generates Output Pulse-Train Stimulus Overall Circuit Layout on perf board (prototype)

.25 W resistors

Current limiting diodes protect patients

Potentiometers allow for customizable adjustments Electrodes Circuit + Battery (Attached to Arm) Solution: After some online help (thanks Google!!!!!), much trial-and-error before final program code Challenges: Analog-Digital Convert Funcitionality Difficulty Testing Criteria / Results Blink Latency





Desired standard: "Blink latency should be less than 300 ms"

Accuracy: Fewer than 10% should be greater than 300 ms Specification Rating Results Excellent: 0-99 ms

Good: 100-199 ms

Satisfactory: 200-299 ms Current Drift Detection:

1 hour EKG stimulation is recorded
Range measurements is recorded


Desired standard: "Avoid shocking or causing major sensation in the patient"

("Current magnitude 2 - 12 mA")
Specification Rating Max current = 1.84 mA

Drift of .01 mA in 1 hour

PASS Method Pass/Fail Basis

Peak current must be less than 12 mA Results 3 subjects will blink for 15 min.
About 150 blinks

Blinks will be counted by the individual and compared to the corresponding response by the device

False positives will be counted as frequency per blink
Specification Results Excellent: 95-100%

Good: 90-94%

Satisfactory: 85-89%

False positives will be counted as a separate error category Method Rating Desired standard: "Blinks in the non-palsied eye should be detected with at least 85% accuracy"
Device Safety





Blink Detection Accuracy Future Tests Test Results - Safety testing

- Blink stimulation test

Physical Specifications Battery: 2 type 23A batteries Size: 3.25'' x 2.875'' x 1.5'' Weight: 2.3 oz (67 g.) + + - Method Measure the duration between EMG peak and stimulus initiation




Standard Deviation will be calculated to observe consistency of results Testing Concerns For safety reasons, no human subject was involved in irresponsible tests by three BME seniors.

Hindered ability to test for blink completeness

Did demonstrate working physiological ability on frog
BioPac EL254 AgCl Electrodes If it takes 5 seconds per blink, false positive per 2.5 minutes

UNSATISFACTORY - Make physical container for perf board

- Improve detection accuracy/latency Future Directions EMG measurer for eye?

More testing for optimal design

Patent?

Acknowledgements If not for these people, we would still be making decision matrices... Dr. Gimm
Dr. Marc Richard, Dr. Michael Richard, Dr. Nicholas Ramey
"The Life-Savers": Matt Brown, Marcus Henderson, Dianne Kindel
Google
Average: 203.74 ms (N = 50)

Standard Deviation: 2.26ms

Median: 204 ms

95% confidence interval: 203.74 +/- 0.321 ms

SATISFACTORY Physical Components Duke Medicine Electrode Placement Stimulation of Palsied Eye - Blink Completeness
- Must produce 2 complete blinks
per minute

- Comfort of device
- Must be able to be worn all day - Blink Latency -- Satisfactory (203.74 ms +/- .321)

- Safety -- Pass (max current of 1.84 mA)
- Safe, but not capable of stimulating blinks through human skin
- Need to increase voltage output

- Blink Detection Accuracy -- Unsatisfactory (75.47% blink detection)
- Many misses are due to issue with DC offset
- Possible correction with use of band-pass circuit? - Addition of band pass filter to remove DC offset

- Using transformer/other method to increase voltage Final Prototype
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