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Examples of Threshold Adjustments
Example 1 - Tilt On Threshold is too high
•
(Figure 61). Steps occur on the Tilt graph
during which the peak does not reach the
On Threshold and therefore stimulation does
not occur. Lower the On Threshold to better
match the Tilt data in the graph.
Example 2 - Tilt On Threshold is too high
•
(Figure 62). A stimulation occurs with each
step but the user reports a late stimulation or
the clinician hears (with “Beep on Stim”) and/
or observes a delay in the foot lift. Lower the
On Threshold to initiate the stimulation earlier.
Example 3 - Tilt Off Threshold is too low
•
(Figure 63). Steps occur on the Tilt graph
during which the valley does not reach the
Off Threshold and therefore stimulation is not
retriggered in preparation for the next step.
Raise the Off Threshold to better match the
Tilt data in the graph.
Control Times (Min, Max, and Wait Time)
Min Time -
sets the minimum period of stimulation that is allowed.
Range from 0 to 1.5 seconds
Increments of 0.1 seconds
The Min Time always overrides the Max Time and the Off Threshold. The Min Time ensures
that stimulation continues for a sufficient duration to assure that the toe clears the ground
during swing phase. The Min Time also assures that the swing phase occurs for a specified
amount of time, this prevents poorly timed on and off cycles that may occur with abnormal
tibial motion during swing (usually from ataxia). Adjustment to the Min Time also addresses
periods of faster walking or faster steps when the user spends less time in swing.
Max Time
- sets the maximum period of stimulation that is allowed.
Range from 0.2 to 3 seconds
Increments of 0.1 seconds
The Max Time allows for periods of slower walking or slower steps when the user needs to
spend more time in swing. The Max Time also prevents extended periods of stimulation. For
example, if the user sits down and tilts the leg forwards, the stimulus will be discontinued
after the value set in Max Time has been reached. A correctly adjusted Min Time allows for
faster walking if necessary (for example, speeding up to cross the street) while a sufficiently
long Max Time allows the user the necessary increase in stim time needed to take a slower
step if the situation requires it (for example walking slowly across a rough surface). The
Off threshold overrides the Max Time during walking to ensure that the stimulation is
appropriately terminated at initial contact.
Wait Time
- minimum amount of time after each stimulus that must elapse before a new
stimulus can be initiated.
Range from 0 to 1 second
Increments of 0.1 seconds
Figure 61: Tilt on threshold too high
Figure 62: Tilt on threshold too high
Figure 63: Tilt off threshold too low
Figure 64: Control times adjustment in
Rapid+/Adjustment
Figure 65: Control times adjustment
in Standard
