A New Parameter for Dynamic Response Evaluation

Abstract Purpose Obtaining accurate invasive blood pressure readings requires excellent dynamic response of the pressure monitoring circuit. In 2006 and 2020, we reported that Gardner's natural frequency and damping coefficient, which are widely used as evaluation methods, do not reflect the dynamic response of the circuit. Therefore, we propose a new parameter for evaluating the dynamic response of a pressure monitoring circuit. Methods A blood pressure wave calibrator, two pressure monitors with analog output and a personal computer were used to analyze blood pressure monitoring circuits. All data collection and analytical processes were performed using our step response analysis program. Arterial pressure catheters with length of 30, 60, 150, and 210 cm were prepared to investigate "gain at 10 Hz" and systolic blood pressure changes. Results The gain at 10 Hz was close to 1 and the systolic blood pressure difference was small in the short circuits (30 cm, 60 cm), and the gain at 10 Hz was 1.3–1.5 in the 150 cm circuit and over 1.7 in the 210 cm circuit. The difference in systolic blood pressure increased in proportion to the length of the circuit. Conclusions The necessary gain at 10 Hz is determined by how much difference in systolic blood pressure is acceptable. Clinically, a difference of 5 mmHg or less is considered acceptable. Therefore, in order to satisfy this condition, the gain at 10 Hz must be 1.2 or less. The gain at 10 Hz is sufficiently useful as an index for obtaining correct blood pressure.