A miniaturized pressure sensor with inherent biofouling protection designed for in vivo applications.

The design, fabrication, and measurement results for a diaphragm-based single crystal silicon sensor element of size 820 µm × 820 µm × 500 µm are presented. The sensor element is designed for in vivo applications with respect to size and measurement range. Moreover, it is optimized for longtime operation in the human body through a built-in protection preventing biofouling on the piezoresistors. The sensitivity is about 20 mV/V for a change from 500 to 1500 mbar absolute pressure. This result is comparable to conventional sized micromachined pressure sensors. The output signal is not found to be influenced by exposure to 60 °C for three hours, a normal temperature load for a typical sterilization process for medical devices (Ethylene Oxide Sterilization). The hysteresis is low; < 0.25% of full scale output signal. The sensor element withstands an overload pressure of 3000 mbar absolute pressure. Observed decrease in the output signal with temperatures and observed nonlinearity can easily be handled by traditional electronic compensation techniques.

An outbreak of Pseudomonas aeruginosa infection associated with contaminated urodynamic equipment.

Seven patients developed Pseudomonas aeruginosa urinary tract infections following urodynamic studies, over a two-month period. One patient developed septicaemia and meningitis and died following rupture of a berry aneurysm. Two others required hospital admission for intravenous antibiotic treatment. Pseudomonas aeruginosa was isolated from a pressure dome which covered the pressure transducer of the urodynamic system used for assessing bladder pressure. The device packaging carried the symbol designating this as a 'single use' product, but as an economy measure, a local decision had been taken to change the device monthly.