Arm Position - Organon TOF-Watch SX Manuel D'utilisation

Figure 2. Electrode and transducer placement
3.6 Position of the transducer
The transducer should be placed with its largest flat side against the thumb.
The transducer cable must be fixed in such a way that no traction is applied to the transducer
and that movement of the thumb is not obstructed in any way.
Small sideways movements of the thumb may be noticed during stimulation. If this is the
case, reposition the transducer in such a way that the movement is perpendicular.
The more distal the transducer is placed on the thumb, the stronger the acceleration signal.
This effect can be used to adjust the signal strength.
3.7

Arm position

The arm, used for the acceleration measurement, should be kept immobile during the whole
procedure. Movement of the arm to another position may change the twitch height
considerably. Although the twitch height may still differ from the original value, the train-of-
four ratio will not be affected. At later stages of recovery the patient may perform voluntary
movements of the hand, which in turn may disturb the measurements and recordings.
3.8 Connection to stimulator
Always make sure that the TOF-Watch is switched off or that the display shows the stop symbol
(7) before touching the electrodes.
The proximal electrode is usually connected to the white (Positive) clip on the stimulator cable.
The distal electrode should be connected to the black (Negative) clip.
If both electrodes are near the wrist, the polarity is less critical. The stimulation pulses are
monophasic. Switching the electrode connection (exchanging
increase the stimulation considerably.
3.9 Skin resistance
The skin resistance together with the electrode resistance form the total resistance in the
stimulating circuit. The stimulator in the TOF-Watch is of the constant current type.
This means that the stimulation voltage automatically increases with the resistance.
As long as the voltage remains below the maximum value (= 300 V) the stimulator can deliver
the selected pulse. For a maximal current of 60 mA, the maximal resistance will be 5 kOhm.
If the resistance is above this value, the "skin resistance too high" symbol
displayed, and the stimulation stops. If the current is reduced, the corresponding voltage drops
and stimulation can be resumed.
Insufficient cleaning of the skin may be the cause of a too high skin resistance.
Note that there is not necessarily any relation between high skin resistance and problems
of reaching supramaximal stimulation.
9 | TOF-Watch SX Operator manual 33.512/A
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