CUSA
®
Clarity Ultrasonic Surgical Aspirator System Operator’s Manual
2-9
Tissue Select Feature
electrical power (which is directly related to the acoustic power present at
the tip, which results in fragmentation) to the handpiece. Consider the
power delivered to the handpiece in three terms:
• Initial power: the quantity of power necessary to drive the tip vibration
in air; that is, no contact with tissue
• Adaptive power: the power necessary to maintain tip vibration under
load (in contact with tissue). When the tip encounters load, a feedback
loop in the system senses the additional load and provides additional
power to maintain tip vibration.
• Maximum power: the greatest power output the console can provide.
Maximum power is the sum of initial and adaptive power.
A Common Misunderstanding of the Amplitude Setting
It has been common practice to decrease the amplitude setting when
encountering critical structures. The reasoning behind this practice is that
the lower amplitude setting results in slower fragmentation rate and
greater selectivity, thus greater control to help avoid damage when
dissecting near the critical structures. Consider this reasoning more
carefully:
• True: Decreasing the amplitude setting also decreases the
fragmentation rate.
• True: Because the fragmentation rate is slower, the surgeon has a
little more time to move the tip away from a critical structure before
damaging it; therefore, the surgeon seems to have greater selectivity
and control.
• False
: The surgeon gains greater selectivity, thus greater control and
precision, when dissecting near critical structures.
Why does the decrease in amplitude not give greater selectivity and
control? Decreasing the amplitude does not greatly affect the adaptive
power.
Decreasing the amplitude leaves plenty of adaptive power.
When the tip contacts critical structures, it still has more than enough
power to fragment them if the surgeon applies pressure or prolongs the
tip-tissue contact. Therefore, decreasing the amplitude setting gives the
following results:
• Reduced fragmentation ability
• Reduced fragmentation rate
• Little increase in selectivity
• Little reduction in adaptive power
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