Frequency characteristics of pressure transducer kits with inserted pressure-resistant extension tubes.

The accurate monitoring of arterial blood pressure is important for cardiovascular management. However, the frequency characteristics of pressure transducer kits are influenced by the length of the pressure-resistant tube. To date, there have been few studies addressing the frequency characteristics of pressure transducer kits with inserted pressure-resistant extension tubes (pressure-resistant extension tube (ET) circuits). In this study, we examine ET circuits from the viewpoint of the frequency characteristics of pressure transducer kits. DT4812J transducer kits (length 150 cm; Argon Medical Devices, TX, USA) were used. Three original ET circuits were prepared, with the pressure-resistant tube of the DT4812J being extended with a 30-cm length of pressure-resistant tube (180ET circuit), a 60-cm length of pressure-resistant tube (210ET circuit), and a 90-cm length of pressure-resistant tube (240ET circuit). Each of these circuits was evaluated as part of this study. The natural frequency of the original DT4812J circuit was 45.90 Hz while the damping coefficient was 0.160. For the 180 ET circuit, the natural frequency and damping coefficient were 36.4 Hz and 0.162, respectively. For the ET210 circuit, the natural frequency and damping coefficient were 30.3 Hz and 0.175, respectively. For the ET210 circuit, the natural frequency and damping coefficient were 25.3 Hz and 0.180, respectively. As a result of extending the circuit, it was found that the natural frequency decreased drastically, while the damping coefficient increased slightly. When the extension of a pressure transducer kit is required, we should pay careful attention to the major decrease in the natural frequency, which may influence the pressure monitoring.