Urodynamics Without Borders

Pressure channel Assessment

Criteria

  • Accuracy: The greater of +/- 3 % of the true value or +/- 1 cmH2O
  • Range: -30 – 250cmH2O
  • Bandwidth: The sampling rate of both channels must be >= 3 Hz
  • Required feature: Equipment must allow reference levels to be reset

Testing

The accuracy of the system can be assessed by connecting the pressure measurement syringe to a line filled with fluid that is open to the atmosphere. The distance between the end of the line can be varied which results in variation in the head of water (hw) applied to the pressure sensor.

hw can be compared to the measured pressure to calculate the accuracy of the system.

The range of the pressure sensor can be found on the corresponding datasheet. The bandwidth can be calculated by running the whole system, calculating the times between the sets of measurements, and then calculating the average sampling frequency. A review of the system software proves that the required feature has been incorporated (the ability to reset reference levels).

Results

The graph below is a Bland-Altman plot comparing the true pressure to the measured pressure. The mean difference between the true and measured pressures is -0.23 cmH2O and the standard deviation of the measured pressure is +/-0.32 cmH2O. This meets the accuracy criteria set out.

The average sampling frequency of the system is X, meaning the system meets the bandwidth requirements. The required feature is fulfilled in the software through a “Zero Channels” function which can be used throughout an investigation