Can Millar Mikro-tip Catheters be used to measure intradiscal pressure?

Yes. The primary application for Millar Mikro Tip Pressure Transducers is the measurement of blood pressure, so all Millar sensors are designed to provide a linear response from -50 mmHg to 300 mmHg. However, intradiscal pressures are commonly in the range of 1000 mmHg to 3000 mmHgMillar sensors have a non-linear overpressure range from -760 mmHg to 4000 mmHg (see attached Millar Sensor Specs) which can accommodate intradiscal pressure measurements. Because there is some variation in the overpressure range of each sensor, it is recommended to perform a non-linear multipoint calibration to provide the most accurate pressure measurements in your range of interest. The Multi-Point Calibration Extension for LabChart software may be used to calibrate over the entire pressure range (0 – 4000 mmHg) using multiple reference points. 

NOTE: You will need a way to provide higher reference pressures than standard blood pressure manometers to perform this calibration (e.g. PTCA syringes).


Millar Pressure Control Units (such as the PCU-2000) have a sensitivity value of 1Volt/100 mmHg and a maximum output of 5 Volts (V). Therefore, when using a Millar Pressure Control Unit, the maximum pressure that can be measured is in the order of 500 mmHg. 


Thus, it is recommended to use an ADInstruments Bridge Amplifier which have a sensitivity of 1mV/100 mmHg. Using a Bridge Amp, the catheters have been tested up to 2600 mmHg (around 54 mV). Even if pressure recordings of up to 4000 mmHg are desired, the values will not be out-of-range of the Bridge Amplifier when using PowerLab and LabChart.


NOTE: Surgically related damage to the catheter is not covered under warranty. Please note that in some instances pressures can exceed 4000 mmHg which will exceed the range of Millar catheters. An alternative 3rd party pressure catheter may be used with ADInstruments Bridge Amplifier for pressures exceeding 4000 mmHg. 


References:
See the attached articles (4) using Millar catheters for the determination of intradiscal 
pressure. 


Intervertebral Disc Measurement.pdf
Nerve root pressure.pdf
Eck intradiscal pressure (Spine 2002).pdf
Intradiscal pressure.pdf