Studies of the dynamic response of esophageal manometry systems

Manometry with fluid-filled catheter systems remains an important technique to study esophageal physiology. The influence of mode of infusion, infusion flow rate, and catheter dimensions on the dynamic response and compliance of such systems was studied. To test the dynamic response, a method based on the step response was developed and applied. A pressure impulse--a step function--was produced by burning off a balloon connected to the system. The response to this well-defined impulse recorded by the system--the step response--was analyzed. The highest frequency to which the system responded satisfactorily--the limiting frequency--was calculated and used as a measure of performance. Compliance and inherent postocclusion pressure rise rate were also determined. In low-compliance systems noninfused or infused by hydraulic capillary infusion, limiting frequencies from 8 to 20 Hz were found, and this was much higher than in a high-compliance system infused by a syringe infusion pump. Smaller diameter and increased length of the manometry catheter decreased the limiting frequency. Increased infusion flow rate did not increase the limiting frequency. The step response test seems to be a simple test of dynamic response that can contribute to better understanding of problems involved in pressure recording with fluid-filled catheter systems. Well-performing fluid-filled manometry systems are adequate for esophageal manometry. Inherent postocclusion pressure rise rate is not a measure of dynamic response, and compliance is not the only determinant of performance.