In-vitro evaluation of sensors and amplifiers to measure left ventricular pressure in mice

Mice are becoming more common as research models, and several companies now manufacture sensors and instrumentation to measure left ventricular (LV) pressure and volume in mice. It is often assumed that pressure is easier to measure than volume, and that all sensors perform similarly, but there are differences. We measured in-vitro the frequency and step responses, immersion response, stability, accuracy, linearity, and sensitivity to lateral or bending force of several solid-state sensors and amplifiers commonly used in mice. We tested 4 microsensors each from Millar, Scisense, and RADI, and also fluidfilled catheters. All solid-state sensors were stable with drifts of <1 mmHg/hr, had flat frequency response to >1 kHz, and were accurate and linear to within +/-2 mmHg from 0-300 mmHg. The frequency response of the fluid-filled catheter was down by 50% at 30 Hz. The amplifiers from Millar, Scisense, and RADI, had time delays of 0.2, 3.2 and 10.6 ms respectively. The Millar and RADI sensors were unresponsive to lateral forces, but the Scisense catheters had sensitivities as high as 5.3 mmHg/g. There are significant differences in solid state pressure sensors and amplifiers which could generate offsets, time delays, and distortions which could go unrecognized in-vivo.