Atrotech Atrostim PNS Anwenderhandbuch Seite 4

General Information Atrostim PNS
ATROSTIM PNS PHRENIC NERVE STIMULATOR
PORTABLE BILATERAL MODEL
1 Introduction
The portable phrenic nerve stimulator Atrostim PNS is a diaphragm pacing system for
long-term artificial ventilation in patients who suffer from respiratory muscle paralysis
(RMP) or central alveolar hypoventilation (CAH). Instead of the natural activation of
ever changing firing axons in a randomized fashion, four compartments of the nerve are
stimulated sequentially during each inspiration.
2 Powering of the implant stimulator, stimulation electrode and stimulation
waveform
The stimulator system utilizes the transformer principle (coupled inductive coils) for
percutaneous powering of the implant stimulator. The implants have no batteries; during
powering phase external magnetic energy is picked up by the implants, induced voltage is
rectified and the electricity is stored in capacitors. After the powering phase the link is
suppressed by the controller and an output current pulse of constant width (200 µs) is
generated by the implant stimulator.
Rhythmic contractions of the diaphragm are produced by delivering trains of current
pulses to the phrenic nerves via multipolar electrodes attached on the nerves. One
stimulus sequence consists of four current pulses, each having its own electrode
combination. The Atrostim quadripolar electrode, Fig. 1, is in fact a double bipolar
electrode. During each stimulus sequence, i.e., when stimulus pulse is generated, there is
only one anode/cathode pair active on the nerve. An arrow in each electrode combination
indicates which contacts form the pair and what is the direction of current flow (current
dipole). By (electronically) changing location of the active cathode and controlling the
current injected through it, a desired stimulus can be focused to a desired site of the
nerve.
Fig. 2 shows a complete stimulation waveform consisting of four current combinations. A
smooth and graded diaphragm contraction is achieved by adjusting both current slope
(increase of recruitment) and pulse interval slope (increase of firing rate).
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February 2012