22-02-2011, 11:10 AM
[attachment=8932]
The Artificial Heart: A Design Example
The Human Heart
Heart has four chambers
Right chambers pump blood to lungs to receive oxygen
Left chambers pump oxygenated blood from lungs to rest of the body
Right and left atria receive blood
Right and left ventricles pump blood
Valves produce one-way blood flow from atria ® ventricles ® arteries
Energy to pump blood comes from nutrients and oxygen in blood
The blood supply to the heart is provided by coronary arteries
Heart Disease
Heart attack: blockage of coronary artery damages portion of heart muscle
Congestive heart failure: gradual weakening of heart
Millions suffer from heart disease
– Many cases are treatable with lifestyle changes, drugs and/or surgery
– Surviving patients suffering from most severe cases need new hearts!
The Need for a Heart Substitute
100,000 Americans/year suffering from severe heart disease need new hearts
Only 2,000 patients receive heart transplants
Conclusion: many patients die waiting for a new heart!
A suitable alternative to donor hearts could prolong thousands of lives
History of Heart Substitutes
WWII: first open heart surgeries
1953: heart-lung machine successfully used during heart surgery
1958: Drs. Willem Kolff and Tetsuzo Akutsu sustain a dog for 90 minutes with a PVC artificial heart
1967: Dr. Christian Barnard transplants a donor heart into a 59 year old man (he survived 18 days)
1969: Dr. Denton Cooley uses an artificial heart to sustain a patient waiting for a donor (survived 3 days)
1972: Cyclosporine introduced to suppress immune responses of transplant recipients
1982: Dr. William DeVries implants the Jarvik-7 artificial heart into Dr. Barney Clark (he survived 112 days)
Why Heart Substitutes Fail
Immune response “rejects” transplant or side effects due to immune suppression
Infection due to tubes and wires passing through skin
Formation of clots
Damage to red blood cells
Lack of pulsatile blood flow?
Design Process
Identify the problem or need to address
Specify details/criteria of an adequate solution to your problem
Implement various solutions that meet the criteria you specified
Test to determine which solution is most viable
Further testing to refine the solution you chose
Design Refinement
Process is iterative
– You need to repeat various steps after testing
– Make design changes based on test results
Failed designs
– Design didn’t meet criteria
– Could be due to inappropriate criteria