Effect of the dynamic response of transducer-tubing system on accuracy of direct blood pressure measurement in patients.

The dynamic responses of 3 transducer-tubing systems (TTS) were documented using square and sine wave generators. The TTS tested were P23 ID with 5 feet tubing (P23-5'), P23 ID with 6 inches tubing (P23-6") and P50A transducer with no tubing (P50). Natural frequencies were 45, 33, and 7 Hz for P50, P23-6", and P23-5', respectively. All were underdamped (damping coefficients 0.1-0.3). Simultaneous measurements of blood pressures by the 3 TTS revealed that systolic pressures recorded by P23-5' were significantly higher (p less than 0.001) than by P23-6" (17%) and P50 (16%). This difference was not influenced by the size of the arterial cannula or by the heart rate. However, the differences were greater with radial, compared to brachial arterial cannulation (p less than 0.02). There were no differences in systolic pressures measured with P23-6" and P50. There were no differences in diastolic or electronic mean pressures recorded by the 3 TTS.