Look for causes of electrical interference. The MPVS Ultra uses AC current and measures very small voltages.
Possible sources of electrical interference include electrocautery devices, pumps, ungrounded operating tables, ventilators/respirators, fluorescent lamps, transformers, fans, and warming plates. Isolate any sources of electrical interference by moving them away from the catheter. Often, the source and type of interference can be diagnosed by observing the frequency of the noise. A noise frequency of 100Hz (Europe) or 120Hz (USA) may be emanating from overhead lights or a DC power supply. Power lines generate a 50Hz (Europe) or 60Hz (USA) noise signal. If possible, use DC current for lab equipment. Otherwise, shut off the interfering appliance briefly while recording data, or disconnect it from the wall outlet. Another option is to add a low-pass digital filter of 50 Hz in your recording software to eliminate some of this noise.
If none of the above steps help eliminate the noise you are observing, fluid may have got inside the catheter, or the catheter may have a broken pressure sensor. If you suspect fluid has got inside the catheter or the pressure sensor is broken, contact ADInstruments Support for information on how to return the catheter for evaluation and possible repair.