ABSTRACT
Objective We aimed to study the performance evaluation indicators of central venous pressure (CVP) measuring system for ICU patients in clinical trials and discuss its impact factors.Methods Ac-cording to the performance evaluation indicators of CVP measuring system based on the Delphi method,a form was created to evaluate the continuous CVP monitoring of 197 ICU patients and then the data were collected.A comparative analysis was performed to verify the factors affecting the performance of CVP measuring system.Results The performance of CVP measuring system was affected by the number of threeway switches,vasoactive drugs and positive end-expiratory pressure,the statistical value was 8.577,-6.773and 3.244.There were no statistically significant differences with respect to performance evaluation indicators of CVP measuring system among the patients with different body positions.Conclusions The performance evaluation indicators of CVP measuring sys-tem proves to be feasible and practical by clinical empirical research.Their influencing factors were dis-cussed and they offer a valuable reference for the determination of the performance of CVP measuring sys-tem in clinical practice.
ABSTRACT
For the existing measurement methods of residual voltage which can't turn the power off at peak voltage exactly and simultaneously display waveforms, a new residual voltage detection method is put forward in this paper. First, the zero point of the power supply is detected with zero cross detection circuit and is inputted to a single-chip microcomputer in the form of pulse signal. Secend, when the zero point delays to the peak voltage, the single-chip microcomputer sends control signal to power off the relay. At last, the waveform of the residual voltage is displayed on a principal computer or oscilloscope. The experimental results show that the device designed in this paper can turn the power off at peak voltage and is able to accurately display the voltage waveform immediately after power off and the standard deviation of the residual voltage is less than 0.2 V at exactly one second and later.