[The syringe pump as actuator--a practical application problem of feedback control systems].

Abstract

Based on a computer simulation programme, the accuracy of the Graseby 3400 syringe pump was tested for its use in a feedback control system of the neuromuscular block. Firstly, a calculation of errors to determine the difference between the target and actual flow rates was carried out. Next, the characteristic curves of the syringe pump were determined under different flow and sampling rates to correct the application software of the feedback controller with a view to obtaining the correct flow rates online. It was discovered that, particularly with short 12 s sampling rates, dose-dependent errors of almost 100% were provable. Therefore, the application of a robust controller and integration of the characteristic curves at the outlet of the controller software are required. For the adoption of syringe pumps in medical feedback control systems, definite determination of the actual infusion quantity using an exact calculation of errors is required. Especially in cases of short sampling rates in combination with low infusion quantities, the syringe pump comes almost to a standstill, which results in extreme differences between target and actual flow rates.