Capacitive Air Bubble Detector Operated at Different Frequencies for Application in Hemodialysis

Authors: Mawahib Gafare Abdalrahman Ahmed, Abdallah Belal Adam, John Ojur Dennis

Abstract:

Air bubbles have been detected in human circulation of end-stage renal disease patients who are treated by hemodialysis. The consequence of air embolism, air bubbles, is under recognized and usually overlooked in daily practice. This paper shows results of a capacitor based detection method that capable of detecting the presence of air bubbles in the blood stream in different frequencies. The method is based on a parallel plates capacitor made of platinum with an area of 1.5 cm2 and a distance between the two plates is 1cm. The dielectric material used in this capacitor is Dextran70 solution which mimics blood rheology. Simulations were carried out using RC circuit at two frequencies 30Hz and 3 kHz and results compared with experiments and theory. It is observed that by injecting air bubbles of different diameters into the device, there were significant changes in the capacitance of the capacitor. Furthermore, it is observed that the output voltage from the circuit increased with increasing air bubble diameter. These results demonstrate the feasibility of this approach in improving air bubble detection in Hemodialysis.

Keywords: Air bubbles, Hemodialysis, Capacitor, Dextran70, Air bubbles diameters.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1056948

References:

[1] Michal Barak, Farid Nakhoul, and Yeshayahu Katz. Pathophysiology and Clinical Implications of Micro Bubbles during Hemodialysis. Seminars in Dialysis. 2008; 21: 232-238.
[2] Bischel MD, Scoles BG, Mohler JG. Evidence for Pulmonary Microembolization during hemodialysis. Chest. 1975; 67: 335-337.
[3] Vivian WA, Malloy KP, Hackett JE, et al. Clinical evaluation of an air embolism detection device. Cardiovasc Dis 1980; 7:425-428.
[4] Nebuya S, Noshiro M, Brown BH, et al. Estimation of the size of air emboli detectable by electrical impedance measurement. Med Biol Eng Comput 2004; 42:142-144.
[5] Markus H. Transcranial Doppler detection of circulating cerebral emboli: a review. Stroke 1993; 24:1246-1250.
[6] Giorgio Rizzoni (2000), Principles and Applications of Electrical Engineering McGraw-Hill Higher Education.
[7] Robert L. Boylestad and Louis Nashelsky(2006),Electronic Devices and Circuit Theory. Ninth Edition.
[8] Christorfer J. Stegmayr, Per Jonsson, Ulf Forsberg and Bernd G. Stegmayr (2007), Development of Air Micro Bubbles in the Venous Outlet Line: an in Vitro Analysis of Various Air Traps Used for Hemodialysis. Journal of Artif Organs, 31, 483-488.