Continuous wave Doppler methods to dialysis access monitoring.

Dialysis access failure is the major cause of morbidity among patients undergoing hemodialysis. Reduced blood flow reveals access malfunction. This work discusses two methods based on directional continuous wave Doppler system to evaluate the access blood flow. By changing the dialysis blood pump flow rate, the variable flow Doppler method measures the access blood flow. Software was developed to make feasible its application during clinical routine. A second method proposes the spectral broadening index (SBI) to characterize the access performance. Preliminary results show that a SBI above 1.9 denotes poor blood flow (less than 600ml/min. Sensibility=80%. Specificity=83%). According to the National Kidney Foundation, patients whose access flow is inferior to 600 ml/min should be referred for fistulogram. The second method is easier to be applied in dialysis sessions.

A low cost Doppler system for vascular dialysis access surveillance.

The National Kidney Foundation guidelines for vascular access recommend access surveillance to avoid morbidity among patients undergoing hemodialysis. Methods to detect access failure based on CW Doppler system are being proposed to implement surveillance programs at lower cost. This work describes a low cost Doppler system implemented in a PC notebook designed to carry out this task. A Doppler board samples the blood flow velocity and delivers demodulated quadrature Doppler signals. These signals are sampled by a notebook sound card. Software for Windows OS (running at the notebook) applies CFFT to consecutive 11.6 ms intervals of Doppler signals. The sonogram is presented on the screen in real time. The software also calculates the maximum and the intensity weighted mean frequency envelopes. Since similar systems employ DSP boards to process the Doppler signals, cost reduction was achieved. The Doppler board electronic circuits and routines to process the Doppler signals are presented.

Equipamento eletrônico para controle automático da temperatura do ar em incubadoras de recém-nascidos / Electronic equipment for automatic control of air temperature in incubators newborns

An electronic equipment to control the temperature and to monitor the relative humidity of the air in incubators of new born was developed in the present work...