Pathway Technical Reference Manual
Proprietary 36 of 190
The test subject controls the temperature changes during the time defined for this sequence,
after which the temperature returns to the Baseline Temperature.
See section7.7.3, page 76, for full description of program details and parameters.
2.8.4 Limits Method
This reaction time inclusive method consists of a string of stimuli of continuously changing
intensity. With each stimulus, when the subject perceives a predefined sensation, he/she
manually stops the stimulus.
The Limits method is the most widely used method for threshold determination, because it
requires the shortest test procedure of all methods, and it can measure not only pain
thresholds, but also non-painful thermal thresholds.
See section 7.7.4, page 77 for full description of program details and parameters.
2.8.5 Levels Method
In the Levels method, stimuli are increased by a predetermined initial step until the first YES
response. Stimuli are then decreased by one half the initial step until a NO is given.
Subsequently, the direction changes according to the response: increase for NO and decrease
for YES. The step size is halved at every direction change. The test is terminated when the
step reaches a small enough size, as pre-determined by the user. The threshold is determined
by taking the mean of the last YES and the last NO.
A modified version of the Levels method allows you to hold the temperature for a predefined
period at the destination value. See section7.7.5, page 78 for full description of program
details and parameters.
2.8.6 Thermal Sensory Limen (TSL)
Another reaction time dependent method is the detection of the Thermal Sensory Limen
(TSL).
In this algorithm, once started, the stimulus temperature does not stop at Baseline but
continues directly from the warm threshold to the cold threshold and vice versa. After several
oscillations between warm and cold sensory thresholds, the ‘Limen’ of no thermal sensation is
calculated as the difference between means of cold-sensation and warm-sensation. Using the
TSL method, allows for the Limen or ‘no thermal sensation’ area to be calculated.
See section7.7.6, page 81 for full description of program details and parameters.
2.8.7 VAS Search Method
In VAS Search method, first Ramp & Hold stimulus with predefined intensity and duration is
given and the subject is asked to estimate the perceived magnitude of pain. The intensity of
the next stimulus is set according to the response – increases if the reported pain rating is
lower than the desired, decreases if the reported pain rating is higher than the desired. The
step size by which the intensity of the next stimulus is changed can be predetermined during
program creation or set by the operator during the test. The VAS Search method can be used
to individually define what temperature is associated with patient's pain rating.
The temperature associated with the subject individualized rating of pain can be determined in
one of two modes – automatic and manual.
In Manual mode only the first stimulus is predefined, the intensity of the next stimulus is set
by the operator during the program run using the following window that pops up after each
trial:
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