Surgery – Means for introducing or removing material from body for... – Material introduced into and removed from body through...
Reexamination Certificate
2001-12-10
2004-07-06
Thanh, Loan H. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Material introduced into and removed from body through...
C604S522000, C604S093010, C604S222000
Reexamination Certificate
active
06758828
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of medical devices, particularly to catheter medical devices, and to catheters for the delivery of cells to tissue in patients. More particularly, the present invention relates to catheters or delivery system designs to improve cell survivability during transportation and/or delivery.
2. Background of the Art
Oxygen is a crucial nutrient for human cells. Cell damage may result from oxygen deprivation for even brief periods of time, which may lead to organ dysfunction or failure. For example, heart attack and stroke victims experience blood flow obstructions or diversions that prevent oxygen from being delivered to the cells of vital tissues. Without oxygen, the heart and brain progressively deteriorate. In severe cases death results from complete organ failure. Less severe cases typically involve costly hospitalization, specialized treatments and lengthy rehabilitation.
Blood oxygen levels may be described in terms of the partial pressure of the oxygen dissolved in the blood (O
2
). Typically, for arterial blood, normal blood oxygen levels (i.e., normoxia or normoxemia) range from 90-110 mm Hg. Hypoxemic blood (i.e., hypoxemia) is arterial blood with an O
2
less than 90 mm Hg. Hyperoxic blood (i.e., hyperoxemia or hyperoxia) is arterial blood with an O
2
greater than 400 mm Hg (see Cason et. al (1992), Effects of High Arterial Oxygen Tension on Function, Blood Flow Distribution, and Metabolism in Ischemic Myocardium, Circulation, Vol. 85, No. 2, pp. 828-838), but less than 760 mm Hg (see Shandling et al. (1997), Hyperbaric Oxygen and Thrombolysis in Myocardial Infarction: The “HOT MI” Pilot Study, American Heart Journal, Vol. 134, No. 3, pp. 544-550). Hyperbaric blood is arterial blood with an O
2
greater than 760 mm Hg. Venous blood typically has an O
2
level less than 90 mm Hg. In the average adult, for example, normal venous blood oxygen levels range generally from 40 mm Hg to 70 mm Hg.
In patients who suffer from acute myocardial infarction, if the myocardium is deprived of adequate levels of oxygenated blood for a prolonged period of time, irreversible damage to the heart can result. Where the infarction is manifested in a heart attack, the coronary arteries fail to provide adequate blood flow to the heart muscle. Treatment of acute myocardial infarction or myocardial ischemia often comprises performing angioplasty or stenting of the vessels to compress, ablate or otherwise treat the occlusion(s) within the vessel walls. For example, a successful angioplasty increases the size of the vessel opening to allow increased blood flow.
To reduce the risk of tissue injury typically associated with treatments of acute myocardial infarction and myocardial ischemia, it is usually desirable to deliver oxygenated blood or oxygen-enriched fluids to at-risk tissues. Tissue injury is minimized or prevented by the diffusion of the dissolved oxygen from the blood or fluids to the tissue and/or blood perfusion that removes metabolites and that provides other chemical nutrients.
Conventional methods for the delivery of oxygenated blood or oxygen-enriched fluids to at-risk tissues involve the use of blood oxygenators. Such procedures generally involve withdrawing blood from a patient, circulating it through an oxygenator to increase blood oxygen concentration, and then delivering the blood back to the patient. One example of a commercially available blood oxygenator is the Maxima blood oxygenator manufactured by Medtronic, Inc., Minneapolis, Minn.
There are drawbacks, however, to the use of a conventional oxygenator in an extracorporeal circuit for oxygenating blood. Such systems typically are costly, complex and difficult to operate. Often a qualified perfusionist is required to prepare and monitor the system.
Conventional oxygenator systems also typically have a large priming volume, i.e., the total volume of blood contained within the oxygenator, tubing and other system components, and associated devices. It is not uncommon in a typical adult patient case for the oxygenation system to hold more than one to two liters of blood. Such large priming volumes are undesirable for many reasons. For example, in some cases a blood transfusion may be necessary to compensate for the blood temporarily lost to the oxygenation system because of its large priming volume. Heaters often must be used to maintain the temperature of the blood at an acceptable level as it travels through the extracorporeal circuit. Further, conventional oxygenator systems are relatively difficult to turn on and off. For instance, if the oxygenator is turned off, large stagnant pools of blood in the oxygenator might coagulate.
Perhaps one of the greatest disadvantages to using conventional blood oxygenation systems is that the maximum partial pressure of oxygen (O
2
) that can be imparted to blood with commercially available oxygenators is about 500 mm Hg. Thus, blood O
2
levels near or above 760 mm Hg cannot be achieved with conventional oxygenators.
U.S. Pat. No. 6,180,059 describes a system for the preparation and delivery of a gas-enriched fluid. In applications involving the prevention of ischemia or the treatment of ischemic tissues, the system may be used for the preparation and delivery of an oxygen-enriched fluid including blood to a specific location within a patient's body. The system may include a circuit for oxygenating or enriching blood, e.g., increasing the level of dissolved oxygen in the blood. The system includes an apparatus that combines a gas-supersaturated fluid with blood to form a gas-enriched fluid, advantageously for regional or localized delivery. The gas-supersaturated fluid may include an oxygen-supersaturated physiologic liquid, and the blood to be enriched is blood withdrawn from the patient. The system provided further includes assemblies for supplying controlled flows or supplies of the gas-supersaturated fluid and the blood. The system includes an elongated, generally tubular assembly including a central lumen and at least one end placeable within a patient body proximate a tissue site to be treated, the end including an outlet port for the gas-enriched fluid. The system may include a catheter defining a fluid pathway, including a proximal portion adapted for coupling to supplies of gas-supersaturated fluid and blood, and a distal portion defining a fluid pathway removably insertable within a patient's body, for infusing the gas-enriched fluid to predetermined sites.
U.S. Pat. No. 6,030,358 describes an apparatus for performing site specific microtherapy comprising a pump reservoir and one or more microcatheters dimensioned to be positioned within a tissue site for selectively removing fluids by microdialysis from the tissue'site, the microcatheter(s) being adapted for fluid communication with the pump reservoir to effect the recovery of fluid, the apparatus further comprising a delivery sheath adapted to be positioned into the tissue site, the microcatheter assembly adapted to be positioned within the delivery sheath, the delivery sheath having walls sufficiently permeable to permit a desired flow of fluids between the tissue and the microcatheter assembly in the course of microdialysis. A kit may comprise the apparatus wherein the microcatheter assembly comprises a plurality of microcatheters adapted to be positioned within the delivery sheath. The microcatheter assembly may be adapted to perform microdialysis based on size exclusion in order to remove tissue fluids and solutes based on solute size. The microcatheter assembly may also comprise a plurality of microcatheters, each in the form of a capillary tube having a lumen and semipermeable wall and the apparatus provides a plurality of fluid passageways.
Medical technology has advanced dramatically and swiftly over the past decades. The advances have been particularly significant within the fields of genetic engineering, cell technology, and in their proposed uses in actual therapies. For example, it is an increasingly comm
Conroy Mark J.
Hammer Bruce E.
Mark A. Litman & Associates P.A.
Regents of the University of Minnesota
Thanh Loan H.
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