Chemical apparatus and process disinfecting – deodorizing – preser – Blood treating device for transfusible blood – Oxygenator
Reexamination Certificate
1998-05-15
2002-05-14
Evanisko, George R. (Department: 3762)
Chemical apparatus and process disinfecting, deodorizing, preser
Blood treating device for transfusible blood
Oxygenator
C422S048000, C604S006090, C604S006110, C604S006140
Reexamination Certificate
active
06387323
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to extracorporeal systems for oxygenating and pumping blood during cardiac surgery. More specifically, the present invention relates to an integrated oxygenator and pump system wherein the oxygenator includes an active element that enhances gas diffusion, the system being sufficiently compact for use in a sterile field.
BACKGROUND OF THE INVENTION
Each year hundreds of thousands of people are afflicted with vascular diseases, such as arteriosclerosis, that result in cardiac ischemia. For more than thirty years, such disease, especially of the coronary arteries, has been treated using open surgical procedures, such as coronary artery bypass grafting. During such bypass grafting procedures, a sternotomy is performed to gain access to the pericardial sac, the patient is put on cardiopulmonary bypass, and the heart is stopped using a cardioplegia solution.
More recently, techniques are being developed, for example, by Heartport, Inc., Redwood City, Calif., that permit cardiac bypass grafting using an endoscopic approach, in which small access openings are created between the ribs and the bypass graft or heart valve repair procedure is performed guided by an image displayed on a video monitor. In the “keyhole” techniques developed by Heartport, the patient's heart is stopped and the patient is placed on cardiopulmonary bypass. Still other techniques being developed, for example, by Cardiac Thoracic Systems, Inc., of Menlo Park, Calif., enable such bypass graft procedures to be performed on a beating heart.
As a consequence of this trend towards minimally invasive cardiac surgical techniques, the need to maintain adequate space within the sterile field surrounding the small access sites has become critical. Whereas in open surgical techniques the sternotomy exposed a relatively large surgical site that the surgeon viewed directly, minimally invasive techniques require the placement of endoscopes, video monitors, and various positioning systems for the instruments that crowd the sterile field and can limit the surgeon's ability to maneuver. In recognition of the increasingly crowded environment in which a surgeon employing minimally invasive techniques must work, a need to miniaturize the equipment employed in “keyhole” cardiac surgical procedures has been recognized.
While improvements have been achieved with respect to many instruments employed in the surgical field, space-saving improvements to previously known cardiopulmonary systems have not kept pace. Such systems generally employ a series of discrete components, including a blood filter, blood reservoir, an oxygenator, a heat exchanger, a blood pump, and one or more control systems for controlling the various components. These components are typically coupled to one another in fluid communication using surgical grade tubing, and generally all of the components are maintained outside the sterile field. Such cardiopulmonary systems are generally coupled to the patient using central cannulation sites, e.g., via the vena cava or right atrium and the aorta, using lengthy tubes that extend through the sterile field and may further restrict the surgeon's ability to maneuver.
A further drawback of previously known cardiopulmonary systems is that in those systems the tubes connecting the patient to the device may constitute a relatively large volume. Consequently, such systems must be primed either with transfused blood products or saline, thus potentially compromising the patient's immune system, diluting the patient's blood, or both. In addition, such previously known systems comprise large non-native surface areas and increase the risk of further jeopardizing the patient's immune system.
In recognition of some of these disadvantages of previously known cardiopulmonary systems, attempts have been made to miniaturize and integrate some of the components of cardiopulmonary systems. U.S. Pat. No. 5,270,005 to Raible describes an extracorporeal blood oxygenation system having an integrated blood reservoir, oxygenator, heat exchanger, pump and pump motor that is controlled by cable connected to a control console. In the embodiments described in that patent, venous blood passes into a reservoir, and then through a filter, a pump, and a static array of hollow fibers for oxygen/carbon dioxide exchange before being returned to the patient. U.S. Pat. No. 5,266,265 to Raible describes a similar system.
While the foregoing patents provide integrated blood oxygenation systems having relatively compact size and reduced priming volume, those systems rely upon relatively short flow paths through the oxygenator to provide adequate oxygenation of the blood. As is well recognized in the prior art, however, oxygenators having short flow paths may provide inadequate gas exchange, due to the development of laminar flow zones adjacent to the exterior of the gas exchange elements.
Whereas laminar flow zones develop in most previously known oxygenators, the large size of the gas permeable fiber bundles used in those devices generally enable adequate mass transfer for oxygen and carbon dioxide. The compact size and static nature of the oxygenators describe in the foregoing Raible patents, however, may lead to the development of laminar flow zones and stagnation zones that impede adequate oxygen and carbon dioxide exchange. One solution to lengthen the flow path for an integrated system is described in U.S. Pat. No. 5,411,706 to Hubbard et al. The system described in that patent recirculates blood through the fiber bundle at a higher flow rate than the rate at which blood is delivered to the patient.
Apart from the recirculation technique employed in the Hubbard et al. patent, other methods are known for interrupting the development of laminar flow zones. U.S. Pat. No. 3,674,440 to Kitrilakis and U.S. Pat. No. 3,841,837 to Kitrilakis et al., which are incorporated herein by reference, describe oxygenators in which an active element stirs the blood within the oxygenator, thereby disrupting the development of laminar flow zones and enhancing mass transfer. Despite favorable test data indicating that such “active” systems do not enhance shearing damage to the blood cells, as reported, for example, in an article entitled “A Rotating Disk Oxygenator,” Artificial Lungs For Acute Respiratory Failure, Academic Press, pp. 211-222 (W. Zapol ed. 1976), that technology has nevertheless been largely abandoned.
In view of the foregoing, it would be desirable to provide a compact extracorporeal blood oxygenation system that provides compact size, low priming volume, low surface area, and the ability to adequately oxygenate blood using an active element that disrupts the formation of laminar flow zones and stagnation zones with the fiber bundles of the oxygenator.
In also would be desirable to provide an integrated extracorporeal blood oxygenator and pumping system having a low priming volume and low internal surface area, thereby reducing blood contact with non-native surfaces, potential damage to blood components, and the risk of infection.
In addition, occasions arise during bypass surgery where it may be desirable to alternate between providing oxygenated blood and blood pumping. For example, in the beating-heart minimally invasive surgical methods developed by Cardio Thoracic Systems, the patient may not be placed immediately on cardiopulmonary bypass. Nevertheless, it may be desirable to use a pump to reduce the load on the heart. At a later stage of the surgery, it may be desirable to rapidly switch from a pump-assisted, beating heart method of surgery to a method involving stopping the patient's heart and placing the patient on full cardiopulmonary bypass.
It would therefore be desirable to provide an integrated extracorporeal blood oxygenator and pumping system wherein the surgeon may select pump operation either with or without inclusion of the blood oxygenator in the fluid circuit.
In addition, it is common practice to maintain a cardiopulmonary unit on standby in an operating
Afzal Thomas A.
Williams Ronald G.
Bianco Patricia
Cardiovention, Inc.
Fish & Neave
Pisano Nicola A.
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