Optimum control of the Hemopump as a left-ventricular assist device.
A general framework for designing an optimum control strategy for the Hemopump is described. An objective function was defined that includes four membership functions, each constructed based on the desired values of one of the four members: stroke volume, mean left atrial pressure, aortic diastolic pressure and mean pump rotation speed. The Hemopump was allowed to operate either at a constant speed or at two different speeds during a cardiac cycle. The goal was to maximise the objective function by varying the magnitude and timing of the pump speed. Using a canine circulatory model, it was demonstrated that, in general, different cardiac conditions or different clinical objectives require different operation parameters. For example, when a left ventricle with minor ischaemia was simulated, and the main objective was to increase stoke volume, the objective function was maximised, from a value of 0.877 when the pump was off, to 0.946 when the pump was operated at speed 2 (18 500 revolutions min(-1)). On the other hand, for a severely ischaemic heart, the optimum pump speed became speed 3 (20 000 revolutions min(-1)), which maximized the objective function to 0.943 (from 0.707 when the pump was off). The results also suggest that it is more beneficial to operate the Hemopump at two different speeds during a cardiac cycle (a higher speed during systole and early diastole, and a lower speed during late diastole) than to maintain a constant speed throughout the cardiac cycle.
He
P
P
Department of Biomedical, Industrial & Human Factors Engineering, Wright State University, Dayton, Ohio, USA. phe@cs.wright.edu
Bai
J
J
Xia
D D
DD
D000818:Animals; D003198:Computer Simulation; D004285:Dogs; D006353:Heart-Assist Devices; D006439:Hemodynamics; D008955:Models, Cardiovascular; D017202:Myocardial Ischemia / Q000503:physiopathology / Q000628:therapy*
Eur J Cardiothorac Surg. 2002 Aug;22(2):228-32
12142190
Artif Organs. 1996 Jun;20(6):650-61
8817972
Artif Organs. 1996 Jun;20(6):641-9
8817971
Artif Organs. 2003 Oct;27(10):926-30
14616537
Med Biol Eng Comput. 2002 May;40(3):344-53
12195983
Int J Cardiol. 1997 Dec 1;62 Suppl 1:S23-7
9464579
ASAIO J. 2003 Jul-Aug;49(4):355-64
12918574
Ann Thorac Surg. 1995 Feb;59(2 Suppl):S46-51
7840699
Ann Thorac Surg. 2004 Jan;77(1):143-9; discussion 149-50
14726050
Artif Organs. 1998 May;22(5):405-10
9609349
ASAIO J. 2001 May-Jun;47(3):272-4
11374772
Ann Thorac Surg. 1999 Aug;68(2):761-3
10475484