Development of the BION Microstimulator for Treatment in ... - IFESS

Development of the BION ® Microstimulator for Treatment in Obstructive Sleep Apnea.
Ross Davis*, Gregoire Cosendai, Isabel Arcos, Douglas Kushner, Delta Mishler, Christopher Decker,
Anne-Marie Ripley, Dennis Maceri, Donna Sanderson, Yitzhak Zilberman, Joseph Schulman.
Alfred Mann Foundation, 28460 Av. Stanford, Valencia, California, 91355.
The BION ® system is a wireless network of up to 255 single-channel implantable microstimulators controlled
and powered by an RF link from the BION ® Control Unit (BCU). Each stimulator is encased by a ceramic
cylinder capped with an iridium cathode and an anode of platinum-iridium. The BION ® device is 16.7 mm long
and 2.4 mm in diameter. Each stimulator produces asymmetric biphasic capacitively-coupled constant-current
pulses. Pulse width (0 to 500 µsec), pulse amplitude (0 to 40 mA) and pulse frequency (0 to 600pps per BION ® ,
with 3,472 pps shared among all active BION ® microstimulators) are controlled digitally and powered by the
controller via a 2 MHz AC magnetic link.
Microstimulator
The BION ® external system (BES) system was designed to provide a fitting interface running on a PC and a
battery-operated control unit (BCU) that can independently operate
up to 8 BION devices via a transmitting antenna. The BCU operates
in two modes, connected to a PC for fitting purposes and Stand-
Alone to allow the user to be independent. In Stand-Alone mode
three sets of stimulation can be selected. The flexibility of the BES
allows the user to generate various forms of bursts. The usual form of
burst is composed of ramp-up, burst-on and burst-off, repeated
as needed.
BCU
Obstructive Sleep Apnea (OSA) affects 2-4% of the U.S.
population, causing up to 60 apneic episodes/hour. The main cause
is the compromised pharyngeal airway by the tongue during sleep,
especially R.E.M. sleep. Our aim is to introduce 1-2 BION ®
on each side adjacent to the hypoglossal nerve (HGN), to cause
contraction of the genioglossal muscle, to open this
compromised airway during sleep.
Sheep Study:
devices
To test the feasibility of this procedure, implantation of 28 functional BION ® microstimulators was completed
into 7 adult sheep using a minimally invasive surgical technique. Through a 5 mm neck incision, a stimulating
electrode probe was used to find the HGN in the lower jaw. A tailored plastic introducer (dilator + sheath) was
then used to insert and test the position of the BION ® device before depositing it adjacent to the nerve. The
BION ® device could be retrieved up to the next 7-10 days by reopening the small wound and withdrawing a
subcutaneously placed suture attached to the superficial end of the device, which could then be reinserted. Two
sheep (8 BION ® devices) died prematurely due to pneumonia unrelated to the implantation. The remaining 5
sheep with 20 BION ® devices were evaluated for stimulation thresholds over the long-term. Nine of 10
anteriorly inserted devices and 4 of 10 posteriorly placed were found to be consistently below
30µCoul./sq.cm./phase and stable over the 93-163 days studied. The other 7 (1 anterior, 6 posterior) were of

higher thresholds and generally had lower stability. Electrode-to-nerve distances in 2 sheep (8 implants) showed
a direct correlation to threshold values. The anterior neck approach to the HGN provided a closer and thus lower
and more stable stimulation threshold level. Separately, histological evaluation of tissues subjected to higher
stimulation showed no chronic tissue damage. Initial histological results revealed an average tissue capsule of
0.163mm (s.d.= 0.115mm).
mA
mA
10
8
6
4
2
12.0
10.0
8.0
6.0
4.0
2.0
0.0
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Thresholds
Sheep # 5, 200 µsec, 20 pps
All BIONs
0 25 50 75 100 125 150 175
Days
BION Distance to Nerve & Threshold
0
0 5 10 15 20 25 30
Distance (mm)
Cadaver Study and Implant Procedure:
Probe insertion Introducer+Probe BION /Hypoglossal Nr.
AR
AL
PR
PL
AR
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PL

To further evaluate this surgical technique, in August 2002, a fresh cadaver with a 49 cm (19½ inch) neck
circumference had the left hypoglossal nerve exposed through a 5 cm incision, at a depth of 3 cm approximately.
Moving to a different location, the above described insertion technique was used through an anterior midline
approach at 1 cm above the hyoid, angled left at 15 degrees to a depth of 4 cm. Upon reopening the initial
incision on the left side, the cathode of the BION ® device was found to be lying adjacent to the HGN.
In order to test the functionality and reliability of the BES to control BION ® devices implanted in the lower jaw,
one BION ® device with attached wires was placed adjacent to the hypoglossal nerve and its stimulation output
was monitored. The antenna was placed under the chin using a garment specifically designed for the sleep apnea
application that holds the antenna in the optimal anatomical position for driving BION ® devices.
System Testing:
The results on the cadaver test showed that the BION ® External System was capable of delivering enough power
to BION ® devices inserted adjacent to the hypoglossal nerve. The BION ® device was capable of reaching
stimulation parameters as high as 10 mA, 200 us, 20 pps, which was reliable, even under antenna displacements
of up to 4 cm contra-laterally to the anterior BION ® implantation site.
Based on the above in-vivo and cadaver studies and based on additional in-vitro qualification studies, we are
submitting an FDA IDE for the treatment of obstructive sleep apnea by using the BION ® system; this is in
conjunction with one of the primary U.S. sleep disorders research centers.
[BION ® is a registered trademark of Advanced Bionics Corporation, Valencia, CA.]
Acknowledgements to P. Mobley, K. Fey, D. Canfield, C. Byers, C. Tanacs, M. Vogel, M. Chamberlain, D.
Richards, N. Embrey and J. Adomian for their considerable contributions.