Evaluating the dynamic performance of a fibre optic pressure microsensor.

The dynamic performance of a new fibre optic sensor intended for measuring physiological fluid pressures is assessed in water. The sensor's sensitivity is evaluated at 23 degrees, 35 degrees and 37 degrees C against a Millar pressure catheter for sinusoidal pressure inputs with frequency ranging from 0.5 to 10 Hz. We found that sensitivity versus frequency is flat to 6 Hz and decreases slightly between 6 and 10 Hz. The sensitivity is slightly lower at 23 degrees C than at 37 degrees C. The reproducibility of measurements is excellent (two separate calibration tests in two consecutive days). The output of the fibre optic system used shows a constant time delay (0.13 s) for all frequencies tested. Experiments suggest that, with current sensor design, its immersion in degassed water prior to use ensures a reliable performance.