Atrotech Atrostim PNS Anwenderhandbuch Seite 43

Surgical procedure for pediatric patients Atrostim PNS
Possible variation
An alternative technique has been developed where suturing of the strips is avoided. One
incision is made parallel to the nerve in a distance sufficient to place the electrode bridge
between the incision and the nerve. Now one pocket is created from the incision to the nerve.
On one side of the bridge, a pocket continues behind the nerve to the other side of the nerve
to contain the electrode strip behind the nerve. On the opposite edge of the bridge, a pocket
is created subpleurally over the nerve of sufficient size to contain the electrode strip in front
of the nerve. For the next step, sutures are placed at the tip of each strip. These sutures are
pushed to the bottom of each pocket using small Crile forceps. The sutures are pushed
through wholes in the pleura and then are used to pull the electrode strips into their pockets,
while at the same time gently pushing the electrode matrix into place. Now electrode testing
is performed, see page 19. Once proper function of each electrode has been proved the
incision is closed with two to three sutures. The pulling sutures may be cut or may be sutured
to the pleura. The electrode wire is anchored to the pleura by aid of the lugs.
5 PRECLOSURE TESTING / CHECKING OF THRESHOLD CURRENTS
After placement of the electrode, threshold currents are checked. Do not proceed
further before acceptable threshold currents are achieved. For the test set-up, see
Appendix 1, page 19. The threshold current is increased gradually (in 0.3 mA steps)
until a first diaphragmatic twitches are observed (by visual checking, fluoroscopy,
ultrasound or acceleration meter (Glenn, Sairenji 1985)). Because during threshold
testing only one combination is active the pulse interval is four times as long as
indicated on the programming module. This causes vibration, which helps to
differentiate threshold movements from other unintended muscle twitches. At
suprathreshold current a vibrating strong diaphragm contraction should occur. Now
the current is decreased in smaller steps (0.1 mA) until the threshold level is reached
again. The threshold current value is recorded (see Form 1 - Patient Forms).
Repeat the procedure with the other three combinations. The unipolar threshold
currents should be in the range of 0.5 to 2.0 mA. The difference between the lowest
and the highest threshold current should not exceed 1 mA. If the difference is larger,
slight repositioning of the according strip will change the difference to an appropriate
level. Once the above mentioned values are achieved the electrode has been placed
correctly and symmetrically.
If a programming module switch fails, it may cause wrong programming of the
stimulus controller. Therefore, the operator of the programming module must
observe closely the effect of any change he/she makes in the module parameters, and
watch for any discontinuity or nonlinear functionality.
12
April 2008