Surgery – Instruments – Light application
Patent
1997-01-06
2000-02-22
Dvorak, Linda C. M.
Surgery
Instruments
Light application
128898, A61B 1736
Patent
active
060274980
DESCRIPTION:
BRIEF SUMMARY
FIELD OF INVENTION
The present invention relates to medical life support systems, and, in particular, to the control of cardiopulmonary bypass pumps for open heart surgery and mechanical ventilators to lungs.
BACKGROUND TO THE INVENTION
During cardiopulmonary bypass surgery (CPB), the most common operation conducted in North America, the heart is stopped and the blood which normally returns to the right side of the heart passes through a pump and oxygenating system and is returned to the aorta, thereby bypassing the heart and lungs. The flow of blood is essentially non-pulsatile with a low amplitude waveform having monotonous regularity.
Although a common procedure (in excess of 400,000 open heart procedures per annum are conducted in North America) and although tremendous strides have been made so that open heart surgery is safer for patients, the procedure is not without its dangers. Although the vast majority of patients have marked improvement in their cardiac functional status following their procedure, of concern is the potential for damage to other organ systems which can occur due to the need for CPB.
The following consequences have been identified with conventional non-pulsatile CPB, namely metabolic acidosis, interstitial fluid accumulation, elevated systemic vascular resistance, arteriovenous shunting and impaired brain oxygenation. Of greatest concern is the potential for neurologic damage. Increasingly, well conducted prospective trials have demonstrated an alarming rate of post-operative neuropsychologic disturbances following cardiac surgery. Recent studies have shown that up to 60 percent of patients undergoing open heart surgery have neuropsychologic deficits following their operation, so that as many as 240,000 patients per annum may develop neurologic abnormalities following cardiac surgery. These disturbances are subtle but involve higher cognitive functions of the brain.
Mechanical ventilation of the lungs represents one of the major accomplishments of modern medicine and is one of the cornerstones upon which modern surgery and intensive care is based. Despite many major advances, mechanical ventilation is still associated with a number of alterations in respiratory function which causes morbidity and mortality in patients requiring this type of support. Inability to maintain gas exchange remains one of the major limiting factors with regard to life-support of critically ill patients. Even in healthy patients being ventilated during elective surgery, alterations in gas exchange can be demonstrated. These relate to collapse of small airways and alveoli. Prevention of these alterations would likely represent a major advance in management of all patients requiring ventilatory support. Conventional mechanical ventilation is monotonously regular in delivery of set tidal volume and respiratory rate.
The monotonous regularity of pumping of blood during CPB and of set tidal volume and respiratory rate of a mechanical ventilator is in contrast to the intrinsic spontaneously variable rhythms of heart rate, blood pressure and respiration, associated with a normal functioning heart as well as the considerable range of tidal volume and respiratory rate which a healthy individual demonstrates during breathing.
The article "Predictive Control by Physical Activity Rate of a Total Artificial Heart During Exercise" Maeda et al, ASAIO Transactions, vol. 34, No. 3, pages 480-484, describes a control system for a total artificial heart which will increase cardiac output in response to increased metabolic demands associated with exercise. An accelerometer which senses movement produces signals which increase in proportion to increased activity associated with treadmill exercise. Measured changes in cardiac output in an exercised animal with its own heart are correlated with changes in the output of the accelerometer. Similar changes in accelerometer readings are then used to control the output of an implanted total artificial heart in an animal which is exercised to the same degree. Although the cardiac
REFERENCES:
patent: 4001700 (1977-01-01), Cook et al.
patent: 4448192 (1984-05-01), Stawitcke et al.
patent: 4584996 (1986-04-01), Blum
patent: 5129390 (1992-07-01), Chopin et al.
patent: 5316009 (1994-05-01), Yamada
Suki et al. (Nature, vol. 368, Apr. 1994, pp 615-618).
Croughwell et al. (Ann. Thorac. Surg. 1994, 58:1702-1708).
Maeda, K. et al., Asaio Transactions, "Predictive Control by Physical Activity Rate of a Total Artificial Heart During Exercis", vol. 34, No. 3, Jul. 1988, 480-484.
Michael Heymann et al., "Blood Flow Measurements with Radionuclide-labeled Particles", Progress in Cardiovascular Diseases, vol. XX, No. 1 (Jul./Aug.), 1977, pp 55-79.
Lefevre Gerald Robin
Mutch William Alan C.
Dvorak Linda C. M.
Kearney Rosiland
University of Manitoba
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