System Manual

26-0002-0005/0 (en) (2022) 60
19 GLOSSARY
19.1 Definitions
Duty Cycle—Percentage of time during which stimulation occurs; stimulation time divided by
the sum of signal on and off times.
Electrode—The mechanical and electrical interface of the Vivistim
®
System to the vagus nerve.
The electrode is part of the Lead.
EMI—Electromagnetic interference
EOL (end of life)—The SAPS software displays an EOL indicator when there is less than 5% of
the battery remaining. EOL indicates that the IPG will cease to function in the very near future
and needs to be replaced for therapy to continue.
ERI (Elective Replacement Indicator)—The SAPS software displays an ERI indicator when
there is less than 15% of the battery remaining. This is a warning to the user that the IPG is
quickly approaching EOL and may stop functioning in the near future.
High Lead Impedance—For the purposes of the Vivistim® System IFUs, any impedance above
10,000 Ω is considered high. Resistance to the flow of output current produced by the IPG,
caused by any of the following: possible fibrosis between the nerve and electrode, dry nerve
(during surgery), Lead fracture, Lead disconnection from the IPG, or high battery impedance
approaching end of life (EOL).
IPG (Implantable Pulse Generator)—The stimulator portion of the Vivistim
®
System, typically
implanted in the chest below the clavicle. The IPG provides stimulation to the vagus nerve
through a connected Lead and Lead electrode.
Lead—An implantable part of the Vivistim
®
System; delivers electrical impulses from the IPG to
the electrodes attached to the vagus nerve; contains flexible conductive wires within a bio-
compatible insulating sheath.
Low Lead Impedance—Lower than expected resistance to the flow of output current produced
by the IPG potentially caused by a short-circuit condition resulting from a break within the Lead
body or connector boot.
MRI—Magnetic resonance imaging
MR Unsafe—An item that poses hazards in all MRI environments.
Output current—Amount of electrical current delivered in a single pulse of a stimulation,
measured in mA.
Paired VNS
™
—VNS delivered by the Vivistim
®
System.
Patient ID—An identifier assigned by the treating physician; generally programmed at time of
implantation.
Pulse width—Duration of a single pulse within a stimulation; measured in μs.
Signal frequency—Repetition rate of pulses in a stimulation; measured in pulses per second
(Hz).