IBP Monitoring
15-16
15.6 ICP Transducer ICT/B
15.6.1 Introduction
The ICT/B is one of catheter tip transducers manufactured by Gaeltec. It is designed
for measuring intracranial pressure by the epidural method. It features quite a few
advantages, like ease-to-use and excellent frequency response without artifacts.
The ICT/B has an atmospheric reference pressure channel that connects the back of
the sensing area to the ambient air pressure via the luer fitting on the connector. All
measurements are the difference value compared with ambient air pressure.
Figure 15-13 ICT/B Transducer
A significant feature of the ICT/B is the ability to check the zero drift of the ICT/B
and pressure monitor in-vivo. Not only does this allow accurate measurements, but
also allow the moving of the patient with the ICT/B in the epidural space and easy
reconnection to another monitor.
There is a flat silicone rubber membrane, or balloon, covering the pressure sensing
diaphragm. Two internal tubes connect the two sides of the diaphragm to a female
luer fitting on the connector shell. By introducing approximately 0.2 to 0.3ml of air
from a 1ml syringe the pressure in these tubes will be greater than the ICP being
measured. The exact amount of air is not critical if only it does not exceed the
permitted maximum. When this air is injected, the pressure will cause the balloon to
be lifted from the surface of the sensor and the same pressure will be applied to the
back of the sensor. The strain gauge senses equal pressure above and below which is
equivalent to having zero pressure applied. Thus by injecting a small volume of air,
one can correct the offset of the pressure transducer and check the zero of the
transducer and amplifier.
Signal
out
ut
Transducer
drive
Extension
cable
Temperature compensation and
rid
e balance network
Reference
barometric
pressure
Luer fitting for
zero check by
ballon inflation
Calibration
sleeve
Measured
pressure
Pressure
transduce
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