Contribution of measurement system artifacts to systolic spikes

A clinical study was conducted to determine if the systolic spike often observed in an invasive blood pressure display originates in the measurement system. The clinical system consisted of a catheter, stopcocks, 4 ft of tubing, an amplifier (containing a 12-Hz low-pass filter), and a continuous flush device. A second transducer was connected directly to the patient's catheter, in parallel with the clinical system. Its output was conditioned by an amplifier modified to exclude the low-pass filter. Simultaneous measurements were taken from both transducers, recorded, and later analyzed. A comparison of the traces in the time domain, as well as an analysis of the signals in the frequency domain, suggests that the systolic spike did not originate in the pressure tubing or in the amplifier system.