Selected Diagrams/images and Descriptions of various Oxygenating Methods and Systems

This is a newly added page for selected images, diagrams and descriptions of some of the various methods of oxygenating parts of the body. These examples are to show some of the  various and diverse methods of approaching oxygenating the body that bypass the lungs.  Some of these are directly referenced in the posts and pages of this site; others are not mentioned here but are reproduced for your convenience (and with hopes that you will avail yourself of allied information here.)

New to this page is a method that has only come to attention here in 2016, though the technique was announced in 2012. Its relatively low-tech description is now listed first, ahead of the more involved mechanical methods that have been on this page for some years now.

-Injectable Oxygen

injectable oxygen search 3

“A team led by researchers at Boston Children’s Hospital has designed tiny, gas-filled microparticles that can be injected directly into the bloodstream to quickly oxygenate the blood. The microparticles consist of a single layer of lipids (fatty molecules) that surround a tiny pocket of oxygen gas, and are delivered in a liquid solution. The microparticles would likely only be administered for a short time, between 15 and 30 minutes, because they are carried in fluid that would overload the blood if used for longer periods.”

injectable oxygen search

Will this, perhaps, be the technology that gets us over the hump of bypassing the lungs for consciousness exploration?  Further details here in link.  Listen to the doctor-inventor of this technique discuss the development in an interview:  https://wordpress.com/page/mergenthalerlinotype.wordpress.com/554

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-Intra-peritoneal perfusion of oxygenated fluorocarbon

U.S. Patent 4,963,130

“This invention relates generally to artificial respiratory devices and methods, and more particularly to chemical methods for providing whole body oxygenation of a mammal whose respiratory system is partially or completely inoperative. More particularly, the present invention relates to methods and devices for treating mammals suffering from anoxia.”

BACKGROUND OF THE INVENTION
“There are many post-traumatic and post-operative patients who develop major pulmonary complications which interfere with or preclude adequate oxygenation. The ‘shock lung’ best characterizes this syndrome complex. Severe pneumonias, smoke inhalation, acute respiratory obstructions, pre-mature birth, and birth-related pulmonary injury also can lead to the same general problems with oxygenation. Patients with massive pulmonary embolism and hemothorax also suffer from severe hypoxemia. Combining patients in these categories, there is a substantial population of patients at high risk, but whose conditions are potentially reversible, given adequate oxygenation.  The present invention utilizes an oxygenated fluorocarbon liquid for general body oxygenation, which is applied as a circulation through the peritoneal cavity. The aforementioned incorporated patents and patent applications reference in detail various prior art publications relating to fluorocarbons and their medical uses.”

SUMMARY OF THE INVENTION
“The present invention provides a novel method of whole body oxygenation of the tissue of a living mammal comprising the steps of: providing an oxygenated fluorocarbon-containing liquid; injecting said oxygenated fluorocarbon liquid into the peritoneal cavity of said mammal; and withdrawing said fluorocarbon liquid from said cavity, said injecting and withdrawing being conducted at a rate sufficient to oxygenate at least a portion of the tissue of said mammal. …Accordingly, the method of the present invention provides a novel ‘artificial lung’ which may be used to provided sufficient oxygen to the blood to maintain life even in the presence of complete or near complete respiratory failure.”

“…Accordingly, the method of the present invention has been demonstrated as being useful in treating systemic anoxia under conditions where the subject mammal’s respiratory system is not capable of providing normal arterial pO.sub.2 tensions.”

-Oxygenated flourocarbon nutrient solution

U.S. Patent 5,085,630

“The invention provides novel improved oxygenated fluorocarbon nutrient solutions for treatment of hypoxic-ischemic neurologic tissue in mammals. The invention also provides methods of making such nutrient solution and methods of administering them. ”

BACKGROUND OF THE INVENTION
” ‘Stroke’ or focal cerebral ischemia presents an extremely complex patho-physiological problem. Stated most simply, cerebral ischemia is the reduction or loss of blood flow to all or part of the brain with a subsequent reduction or loss of oxygen and substrate delivery to the tissue. As a cause of death, stroke ranks third after heart disease and cancer. When not lethal, it is associated with a type of morbidity which can ruin lives, leaving patients unable to cope with daily existence and imposing a heavy burden on the family and society. The disease’s economic impact is staggering: for the year 1976, direct and indirect (lost wages) costs have been estimated to be 7.4 billion dollars. Accordingly there is an enormous need for providing a effective treatments for this disease.”

SUMMARY OF THE INVENTION
“The present invention provides novel improved fluorocarbon nutrient solution for circulation through cerebrospinal fluid pathways, and methods for using the novel nutrient formulation to treat central nervous tissue hypoxic-ischemic conditions.

Applicants have recognized that there is a therapeutic time window through which neuron can be reached and resuscitated. The method of the present invention is designed to bypass obstructed vascular circulation and deliver cerebral metabolic needs through an alternate cerebral spinal fluid (CSF) circulation portal. Since particle size exerts a major influence in brain penetration from CSF, the method of the present invention is hypothesized to permit diffusion of oxygen, glucose, electrolytes and essential amino acids into ischemic neural tissue when presented in abundance in the cerebral spinal pathway. Thus, a rapidly exchanging cerebral spinal fluid perfusion system is provided to amply supply these materials and, at the same time, remove metabolic waste. The cerebrospinal fluid (CSF) pathway system, which intimately bathes and permeates brain and spinal cord tissues, constitutes a unique anatomical relationship within the body. Although it has some similarities to systemic lymphatics its anatomical arrangement differs considerably from that of lymph. Indeed, this system has been named the ‘third circulation’.  Due to the extensive area of CSF-tissue contact over the cerebral and cord surfaces, in the miniature Virchow-Robins spaces, and cerebral ventricles, the cerebrospinal fluid system constitutes a vast, complex and intimate therapeutic avenue for access to central nervous tissue. Excepting certain infections and neoplasms where the cerebrospinal fluid is now utilized as a treatment conduit, the cerebrospinal fluid system has not been otherwise widely exploited as an easily accessible therapeutic route and has never been used as a continuous therapeutic diagnostic circulation system in man. The present invention is predicated on the recognition that, when regional cerebral blood flow is interrupted, such as after major stroke, or is otherwise seriously impeded by profound vaso-spastic states, the cerebrospinal fluid pathway actually represents the only practical and viable anatomical route by which these tissues may be readily treated. This results from the fact that the usual vascular delivery system is either occluded or non-functional, and thus tissues within affected territories cannot be properly served.

In accordance with the present invention, essential cellular substrates are delivered to beleaguered ischemic brain regions by utilizing the ‘back door’ cerebrospinal fluid delivery route. Accordingly the present invention provides a novel nutrient emulsion for penetration into regions suffering vascular deprivation.

It has been found that the cerebrospinal fluid to brain relationship is not characterized by the rigid and highly selective barrier mechanism which are present at the blood-brain interface. Thus, the penetration rate of materials from cerebrospinal fluid regions to the brain relate largely to small molecular size, that is, small substances penetrate deeply while large molecules move slowly into brain substance. Although entry rates are generally inversely proportional to molecular weight, penetration is also influenced by lipid solubility and the molecular configuration of the penetrating substance. Accordingly, the present invention provides a nutrient emulsion containing essential brain nutrients including selected electrolytes, having a relatively low molecular size which, in accordance with the methods of the present invention, are caused to relatively freely diffuse from either the ventricular or subarachnoid fluid regions into the brain matter to be treated. Accordingly, the present invention provides novel nutrient emulsion which has been purified, balanced and perfected to fall within narrow phyliologic limits while nonetheless providing the desired nutritional characteristics referred to above.

The present invention also provides novel methods for treating hypoxic-ischemic neurologic tissue by circulating the oxygenated nutrient emulsion through cerebrospinal fluid pathways, particularly those pathways which contact brain and spinal cord tissue. According to these methods, treated tissues exhibit a substantially improved ability to resist and/or repair damage which would otherwise result from vascular occlusion. In accordance with the preferred method of the present invention, the novel oxygenated nutrient emulsion is circulated through this cerebrospinal fluid route by injecting it into brain vesicles and withdrawing it from the cisterna magna or the spinal subarachnoid space to nourish and to treat central nervous tissues. In other instances the fluid may be injected into the subarachnoid space and withdrawn from another subarachnoid position. The preferred embodiment oxygenate nutrient emulsion should be circulated to tissues to be treated in amounts sufficient to provide adequate gas exchange.

The formulation of the nutrient solution of the present invention has several unexpected advantages over other formulation heretofore known. It was discovered by the inventors that there is a relationship between the relative viscosity of the nutrient solution and its ability to perfuse the cat brain. It was found that there is a substantial reduction in the pressure needed to perfuse these solutions through a fixed resistance with increasing dilution, even at flow rates as low as one milliliter per minute. This discovery, coupled with the greater oxygen carrying capacity of bis-perfluorobutyl ethylene, has made it possible to use a lower concentration of perfluorocarbon in the nutrient solution of the invention…. The formulation of the invention is thus more viscous and relatively easier to perfuse. It has also been found that providing an electrolyte profile and osmotic pressure mimicking the cerebrospinal fluid of the mammal also improves the efficacy of the nutrient solution. Further, the exclusion of four amino acids, glutathione, cysteine, ornithine and glutamine, from the group of amino acids included in the nutrient solution, and the inclusion of sodium bicarbonate in amounts sufficient to increase the buffering capacity of the nutrient solution to more closely resemble cerebrospinal fluid of the mammal were also discovered to contribute to the improved efficacy of the nutrient solution of the present invention.”

from DETAILED DESCRIPTION OF THE INVENTION

“The nutrient solution of the invention is preferably administered according to the method set forth in U.S. Pat. No. 4,445,500 which is specifically incorporated as if fully set forth herein. The nutrient solution of the invention is perfused tissue areas by injection of the nutrient solution at a first point in the cerebrospinal pathway and substantially continuously withdrawing fluid from the cerebrospinal pathway at a second point which is selected to create a circulation of the nutrient solution in the vicinity of hypoxic-ischemic tissue to metabolically sustain the tissue during treatment.”

SIGNIFICANCE

“…The possible mechanism by which this technique preserves the tissue after a permanent vessel occlusion are numerous but three that are likely are: 1) that the perfusion supports the tissue for enough time to allow collateral circulation to improve to the point of providing functional supply, 2) the residual emulsion in the extravascular fluid spaces is assisting in the transfer of oxygen and nutrients from adjacent normally perfused areas, and 3) that the perfusion interrupts the normal pathophysiological cascade, removing toxic metabolites, and normalizing the ionic microenvironment, thus preventing secondary brain damage, (13). Each of these mechanisms could be operating to some degree. These findings, in combination with the results indicating efficacy, suggest that this nutrient solution of the invention (in Example 1) could have clinical utility in the treatment of acute focal cerebral ischemia, a disease for which there is no currently accepted efficacious treatment. ”

Peritoneal Artificial Lung (PAL)

U.S. Patent 4,661,092

“A process for the treatment of hypoxia is provided. The process involves the infusion of highly oxygenated perfluoro-chemicals into the peritoneal cavity of a patient, for oxygen transport into the body and carbon dioxide transport out of the body. The oxygenated perfluorocarbons are subsequently removed from the peritoneal cavity. The infusion and removal can be on a continuous or intermittent basis.”

BACKGROUND OF THE INVENTION
“Many situations in the practice of clinical medicine produce temporary and reversible lung failure. In this situation, hypoxia, or inadequate oxygenation of the blood may be life threatening or fatal. An incomplete list of the clinical settings in which this might arise includes (abbreviated list; full list on patent itself) :

(B) Heart and lung surgery patients

(C) Fulminent pneumonia

(F) Severe emphysema

(G) Lung transplants

The current treatment techniques available for acute life threatening hypoxia include positive pressure ventilation which requires the passage of a per nasal or per oral endotracheal tube, and attachment to a pressure controlled or volume controlled machine ventilator. The problems associated with this procedure include difficulty in initiation, trauma to the nasal or pharyngeal tissue and structures, errors of intubation of the esophagus thus further compromising ventilations; inadvertant intubation of the right main stem bronchus with hyperexpansion of the right lung and collapse or atelectasis of the left lung, damage to the pharynix and vocal cords, on rare occasions erosion through the inominate artery and exanguanation, and not the least, rather extreme discomfort to the patient.

A second form of support in the hypoxic circumstance is with a membrane oxygenator. This is primarily used during a surgical procedure which requires temporary cardiac arrest, such as open heart surgery (i.e. coronary bipass surgery, cardiac valve surgery, and repair of congenital cardiac abnormalities). This procedure requires a highly skilled, well organized team, and can be used for an extremely short period of time, usually for a matter of two to six hours. This procedure produces increasingly severe changes in the blood components, secondary to membrane trauma, hemolysis of red cells, platelet lysis, release of clotting factors, and large volume anticoagulant therapy. All of these may lead to severe tissue toxicity, massive hemorrhage, and cellular destruction if the procedure is not terminated within the time limits stated.

Clearly, an alternative form of tissue and blood oxygenation would be extremely beneficial and, in many of the aforementioned cases, life saving.”

SUMMARY OF THE INVENTION
“The process of the present invention generally involves the infusion of highly oxygenated perfluorochemicals into the peritoneal cavity with concomitant oxygen transport into the body and carbon dioxide transport out of the body.

In accordance with one embodiment of the process, a source of oxygenated perfluorocarbons is provided in a continuous flow therefrom through the peritoneal cavity of a patient which is established, for oxygen transport into the patients body. To accomodate continuous flow through the peritoneal cavity, there is further provided fluid inflow access to and fluid outflow discharge from the peritoneal cavity of the patient.

Further, fluid inflow access to and fluid outflow discharge from the peritoneal cavity of the patient is established by first and second indwelling catheters adapted to be surgically implanted in the peritoneal cavity of the patient. Also, the source of oxygenated perfluorochemicals may comprise a cylinder of oxygen providing O.sub.2 to a perfluorochemical oxygenator reservoir. Continuous flow of oxygenated perfluorochemicals from the reservoir may be by a pump.

In other embodiments of the process, oxygenated perfluorochemicals can be intermittently added to the peritoneal cavity with subsequent drainage following the transport of a portion of the available oxygen.

Accordingly, by the present invention, a process for the treatment of hypoxia is provided which involves infusing oxygenated perfluorochemicals into the peritoneal cavity of a patient, for oxygen transported to the body; and subsequently removing the oxygenated perfluorocarbons from the peritoneal cavity.”

DETAILED DESCRIPTION
“A. Basic Process and Apparatus

The process of the present invention involves the infusion of highly oxygenated perfluorochemicals into the peritoneal cavity of a subject with concomitant oxygen transport into the body and carbon dioxide transport out of the body. The oxygen and carbon dioxide transport occurs through the capillaries of the peritoneal membrane and associated organ systems. The peritoneum is a two square meter, highly vascularized, highly permeable membrane in a closed space in the abdominal region.”

Peritoneal Artificial Lung diagram

Peritoneal Artificial Lung

Apparatus and method for extrapulmonary blood gas exchange (IVOX: Intravenous method of Oxygenation)

U.S. Patent 4,850,958

“An in vivo extrapulmonary blood gas exchange device having a bundle comprised of a plurality of elongated gas permeable tubes being bound at each end and enclosed within a respective air tight proximal and distal chamber. A dual lumen tube having an outer lumen and an inner lumen is situated relative to the gas permeable tubes such that the outer lumen terminates within the proximal chamber and such that the inner lumen terminates within the distal chamber. The apparatus includes means for selectively adjusting the overall, outside diameter of the bundle of gas permeable tubes to provide either a furled, small insertion diameter when inserting the apparatus into the venae cavae of a patient or an unfurled, expanded oxygenation diameter after the apparatus is in place within the venae cavae and the bundle of gas permeable tubes is deployed therein. The apparatus is inserted into the patient through a single incision at one of the right external iliac, common femoral or internal jugular veins. A plurality of crimps along the length of the gas permeable tubes maintain the tubes in a spaced relation one from another such that blood surface contact with the gas permeable tubes is maximized, disturbed flow of blood over the tubes is achieved and laminar blood flow between and around the gas permeable tubes is inhibited.”

BACKGROUND

2. The Prior Art

“Thousands of patients in hospitals suffer from inadequate blood gas exchange, which includes both inadequate blood oxygenation and inadequate removal of carbon dioxide (CO.sub.2). These conditions are commonly caused by varying degrees of respiratory inadequacy usually associated with acute lung illnesses such as pneuminitis, atelectasis, fluid in the lung, or obstuuction of pulmonary ventilation. Various heart and circulatory aliments such as heart disease and shock can adversely affect the flow of blood and thereby also reduce the rate of blood gas exchange.

Currently the most widely used methods of treating these types of blood gas exchange inadequacies involve increasing the flow of oxygen through the lungs by either increasing the oxygen concentration of the inspired gases or by mechanically ventilating the lungs. Both methods result in placing further strain on the lungs, which may be diseased and unable to function at full capacity. In order to allow diseased or injured organs to heal it is generally best to allow these organs a period of rest followed by a gradual increase in activity. The current methods of treating inadequate blood gas exchange, however, force the diseased or damaged lungs to work even harder rather than allowing them a period of rest and recovery.

Various devices have been developed which are capable, at least for a limited period of time, of taking over the gas exchange function of the lungs. Many extracorporeal blood oxygenators are in common use and are employed most frequently during heart surgery. These devices are capaable of providing blood oxygenation sufficient to carry the patient through the surgical procedure. These oxygenators include devices which bubble oxygen into the blood as the blood flows through the device. This is usually followed by a section of the device which defoams the blood to make it acceptable for reinjection into the patient.

Another group of extracorporeal oxygenators employ gas permeable membranes. These devices take many different shapes and configurations; however, the basic concept of operation is the same in all of these devices. Blood flows on one side of the gas permeable membranes while an oxygen rich gas flows on the other side of the membrane. As the blood flows through the device, the oxygen travels across the gas permeable membrane and enters the blood. This allows oxygenation of the blood without actually introducing oxygen bubbles into the blood and without the corresponding need for an extensive defoaming apparatus.

Gas permeable membranes used in such extracorporeal oxygenators are of two types. One type uses a microporous membrane which allows blood gas interface through micropores in the membrane. The other type is a continuous membrane which does not have micropores but which allows blood gas exchange through the membrane without the blood gas interface.

The microporous and bubble oxygenators discussed above are not suited for use outside the setting of a cardiopulmonary bypass procedure, and are thus typically designed for short term extracorporeal use. As a result, these devices are of limited use in the long term intensive care of respiratory patients.

In vivo extrapulmonary blood gas exchange has been attempted in the art. One known device consists of a plurality of small diameter gas permeable tubes connected to headers at each end. The headers are connected on one end to a source of oxygen rich gas and on the other end to an exhaust means.

The apparatus is positioned within the venae cavae by means of a two-step process. First, an incision is made in the patient’s femoral or iliac vein or internal jugular vein and in the patient’s jugular vein. A radiopaque guide catheter is inserted into the jugular vein and is guided through the superior and inferior venae cavae using a fluoroscope, so as to exit through the incision in the fermoral or iliac vein or internal jugular vein. Second, the device is attached to the guide catheter and is pulled into the vanae cavae by withdrawing the guide catheter from the jugular vein.

While the method of inserting this extrapulmonary blood gas exchange device within a patient’s venae canae has been successfully demonstrated, still there are some drawbacks. First, the need for two incisions in the patient’s venous system not only increases the complexity of the procedure but also subjects the patient to significant trauma and safety risk. In addition, the need to insert a guide catheter from the patient’s jugular vein to the femoral or iliac vein or internal jugular vein exposes the patient to a serious risk of damaging the sensitive intimal tissues of the patient’s venous system.

Furthermore, the blood gas exchange device itself must have a small overall diameter to be able to pass through relatively narrow veins such as the jugular vein. As a result, when the device is within the venae cavae, which have a much larger diameter than the jugular vein, the blood flow bypasses the gas permeable tubes. Thus, blood contact with the surface of the gas permeable tubes is reduced.

In an attempt to avoid this problem, a sprial or undulating arrangement of the gas permeable tubes has been used. This increases the blood contact with the gas permeable tube surfaces. Also, the undulating or sprial arrangement of the gas permeable tubes reduces laminar blood flow through the vanae cavae. Laminar blood flow is undesirable because such flow possesses a boundary layer between the bulk flow of the blood and the surface of the gas permeable tubes. This boundary layer of blood significantly reduces gas transfer. The undulating or spiral arrangement of the gas permeable tubes offers limited improvement in performance of the device.”

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

“The present invention seeks to resolve a number of the problems which have been experienced in the art, as identified above. More specifically, the apparatus and method of this invention constitute an important advance in the art of extrapulmonary blood gas exchange, as evidenced by the following objects and advantages realized by the inventon over the prior art.

One object of the present invention is an apparatus and method for in vivo extrapulmonary blood gas exchange in which oxygen is added to and carbon dioxide is removed from circulating blood without molesting, forcing, or irritating ailing or diseased lungs and which requires only a single venous incision for inserting the device within the patient.

Additionally, it is an object of the present invention to provide an apparatus for in vivo blood oxygenation which may be adjusted to have a narrow diameter for insertion within the patient and which can be expanded to fill the venae cavae during blood oxygenation.

Still an additional object of the present invention is an in vivo extrapulmonary blood gas exchange apparatus and method which more effectively inhibits laminar blood flow through the venae cavae, and around the gas permeable tubes, thus improving gas transfer efficiency by achieving disturbed flow of blood over the gas permeable tubes.

Another object of the present invention is an apparatus for in vivo blood oxygenation which maximizes blood surface contact with the gas permeable tubes, and which is relatively nonthrombogenic and provides efficient blood gas exchange.

Still a further object of the present invention is an apparatus and method for in vivo blood oxygenation which eliminates the risk of introducing an air embolism into the blood stream of the patient.

Additional objects and advantages of the invention will be apparent from the description which follows, or may be learned by the practice of the invention.

Briefly summarized, the foregoing objects and advantages are realized by the apparatus and method of the present invention, which are designed for use on a routine basis and can be used with a more simple surgical procedure. Particularly, the apparatus and method of the present invention can be used instead of the routine lung ventilation or the more invasive extracorporeal membrane oxygenation systems now used to treat patients with inadequate blood gas exchange.

In one embodiment of the present invention, the apparatus comprises a dual lumen tube containing two coaxial lumens. The first lumen opens into a first chamber to which a plurality of gas permeable tubes are attached. The second lumen of the dual lumen tube extends past the first lumen and passes among the gas permeable tubes. Both the second lumen and the gas permeable tubes open into a second chamber. The gas permeable tubes are crimped to form the tubes into a wavy pattern in order to maintain the tubes in a spaced relation one from another so that the blood may flow freely between and around the tubes thereby enhancing blood surface contact with the gas permeable tubes. In addition, the wavy pattern of the gas permeable tubes tend to inhibit laminar blood flow between and around the tubes so as to cause disturbed flow of blood over the tubes.

The apparatus is inserted into a patient through an incision made in either the common femoral vein, external iliac vein or internal jugular vein or internal jugular vein. Before insertion, the second chamber is preferably twisted relative to the first chamber. In this way, the gas permeable tubes are stretched and held tightly together so that the overall diameter of the device is smaller than its untwisted diameter. After insertion into the venae cavae, the second chamber is allowed to unwind so that the gas permeable tubes fill the venae cavae.

The second chamber is twisted relative to the first chamber by means of a stylet which passes through the second lumen and engages the end of the second lumen. Because the second lumen is nonrotatably secured to the second chamber, twisting the stylet simultaneously twists the second chamber. Thus, by twisting the stylet relative to the first chamber, the second chamber is twisted. The stylet is locked so that it cannot unwind during insertion within the patient. After insertion, the stylet is unwound and removed so that the gas permeable tubes fill the venae cavae.

One of either the first or second lumens is connected to a source of oxygen rich gas. The other lumen is connected to an exhaust tube or other means for allowing the gas to flow out of the device. The oxygen rich gas flows into the gas permeable tubes. As venous blood flows around the gas permeable tubes, oxygen passes from the tubes into the blood causing blood oxygenation, and carbon dioxide passes from the blood into the tubes and out of the body. Gas flow through the tubes is augmented and risk of air embolism is eliminated by applying suction to the exhaust tube. The tubes are constructed of a material which allows effecient gas transfer yet is impervious to blood and is also relatively nonthrombogenic.”

FROM  DESCRIPTIONS OF THE DRAWINGS (EDITED):

“Because gas transfer is a primary function of the apparatus, the gas transfer surface area in contact with the blood is preferably maximized. To increase the gas transfer surface area without unduly increasing the size of the apparatus, a large number of very small diameter gas permeable tubes are used. In addition, the gas permeable tubes are preferably thin-walled in order to enhance gas permeability.

The total number of tubes and the cross-sectional diameter of each tube are both considered in determining a preferred operating embodiment of the in vivo apparatus. The apparatus must be small enough to be inserted into the venae cavae through a smaller peripheral vein, yet have a large enough gas transfer surface to achieve the desired blood gas exchange. Thus, as the cross-sectional diameter of the gas permeable tubes increases, the total number of tubes which can be used decreases.

Each gas permeable tube 12 preferably has an outside diameter in the range from about 200 microns to about 350 microns. Depending upon the size of the patient (i.e., whether infant or adult) and the amount of oxygenation therefore required, the number of gas permeable tubes 12 will vary. For example, in applications for the apparatuses to be used with infants, typically the apparatus would contain approximately 90 tubes. For applications of the apparatus which are intended for use with adults, up to 1500 tubes may be used.

The gas permeable tubes are preferably maintained in a spaced relation one from another such that the blood surface contact with the gas permeable tubes is maximized and such that laminar blood flow between and around the tubes is inhibited and disturbed blood flow over the tubes is achieved. To achieve this in one preferred embodiment of the present invention, the gas permeable tubes include a plurality of crimps which form the tubes 12 into a wavy pattern. The crimps of the gas permeable tubes 12 also aid in permitting the tubes to be slightly stretched as they are twisted so as to elongate the bundle of tubes 12 when it is desired to narrow the overall outside diameter of the bundle of 12’s for purposes of forming the insertion diameter as described above.

Since the gas permeable tubes will be in contact with flowing blood, it is critical to minimize thrombosis formation. As a result, the gas permeable tubes are preferably constructed of a thrombo-resistant material. In one embodiment of the present invention, the gas permeable tubes include a support material constructed of polypropylene coated with a thin siloxane polymer. The siloxane is relatively nonthrombogenic. However, in a preferred embodiment the siloxane surface is coated with thrombo-resistant materials to further minimize thrombosis formation.”

“Once the apparatus 10 is in place, inner lumen 26 preferably will be connected to a source of oxygen-enriched gas and outer lumen 24 preferably will be connected to a vacuum or some other exhaust means. As a result, oxygen-enriched gas will travel through the inner lumen 26 into distal chamber 30 and there into the distal ends 16 of the gas permeable tubes 12.

During the time the oxygen-enriched gas is within the gas permeable tubes it will be able to oxygenate the blood traveling through the venae cavae. In addition, carbon dioxide will be able to pass from the blood into the gas permeable tubes and thereby be removed from the blood stream. As discussed above, oxygen and carbon dioxide can readily travel through the walls of gas permeable tubes 12, but blood cannot enter the tubes. Thus, oxygenation can occur without the blood being directly exposed to gas bubbles.”

“Operation of the device at such low pressures will enhance carbon dioxide removal, yet also provide adequate blood oxygenation. The driving force behind blood gas transfer in the present invention is the difference between the partial pressures of the oxygen and carbon dioxide in the blood stream and the partial pressures of the oxygen and carbon dioxide in the gas permeable tubes. Lowering the pressure within the gas permeable tubes necessarily promotes transfer of carbon dioxide from blood into the gas permeable tubes. On the other hand, lowering the pressure within the gas permeable tubes reduces the partial pressure of oxygen in the gas permeable tubes. But because nearly pure oxygen is used, the partial pressure of oxygen is still sufficiently high to achieve adequate blood oxygenation.

Traditionally, blood oxygenation has been the primary goal in patients suffering from acute respiratory failure. However, it has been found that removal of carbon dioxide from blood is also important. Thus, operation of the device at subatmospheric pressures enhances the overall effectiveness of the device.”

“Similarly, the principles disclosed in connection with the present invention may readily be utilized in an extracorporeal blood gas exchange device. For example, blood removed from a patient could be simply passed through a large tube containing the present invention. As the blood flows past the gas permeable tubes, the blood is oxygenated and the blood releases carbon dioxide. The blood is then returned to the patient. Such extracorporeal use represents a substantial simplification of over existing extracorporeal methods.

In summary, the method and apparatus disclosed herein is a significant departure from the traditional extrapulmonary blood gas exchange systems of the prior art. In the present invention, only a single venous incision is required for inserting an extrapulmonary blood gas exchange device within the patient. In this way, oxygen is added to and carbon dioxide is removed from circulating blood without molesting, forcing, or irritating ailing or diseased lungs. In addition, the overall outside diameter of the apparatus may be adjusted to have a narrow diameter for insertion within the patient or adjusted to have an expanded diameter during blood oxygenation. As a result, blood surface contact with the gas permeable tubes is maximized, laminar blood flow through the venae cavae is inhibited and disturbed flow of blood over the tubes is achieved, thereby providing efficient blood gas exchange.”

IVOX: Intravenous method of Oxygenation diagram

IVOX: Intravenous method of Oxygenation

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Integrated blood oxygenator and pump system… having means for reducing fiber breakage

U.S. Patent 6,224,829

“Improvements to integrated blood pump/oxygenator having a rotating hollow fiber bundle assembly that both oxygenates and pumps blood are provided. A plurality of vanes arranged along a central shaft of the device increase pressure near the center of the fiber bundle to prevent microbubble generation and blood trauma. Shearing loads imposed on the fiber elements of the fiber bundle are reduced by the addition of a reinforcement structure, while the gas flow path is configured to minimize flooding and loss of oxygenation efficiency due to occasional rupture of fiber elements. Blood trauma may be further reduced by contouring the vanes and other components of the device.”

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.

Recently, the development of minimally invasive techniques for cardiac bypass grafting, for example, by Heartport, Inc., Redwood City, Calif., and CardioThoracic Systems, Inc., Menlo Park, Calif., have placed a premium on reducing the size of equipment employed in the sterile field. Whereas open surgical techniques typically provide a relatively large surgical site that the surgeon views directly, minimally invasive techniques require the placement of endoscopes, video monitors, and various positioning systems for the instruments. These devices crowd the sterile field and can limit the surgeon’s ability to maneuver.

At the same time, however, the need to reduce priming volume of the oxygenator and pump, and the desire to reduce blood contact with non-native surfaces has increased interest in locating the oxygenator and pump as near as possible to the patient.”

FROM THE SUMMARY OF THE INVENTION

“In a preferred embodiment, the integrated blood pump/oxygenator includes a plurality of vanes arranged along a central shaft that increase pressure on the blood side relative to the gas side near the center of the fiber bundle, and, hence, prevent the formation of gas microbubbles in the blood. The vanes also gradually accelerate blood prior to entering the fiber bundle, thereby reducing blood trauma. Shearing loads imposed on the fiber elements of the fiber bundle during high speed rotation are addressed by the addition of a reinforcement structure that extends around or within the fiber bundle. These reinforcement structures also assist in reducing shear stress imparted to the blood, hence reduce blood trauma. In addition, the gas manifolds of the pump/oxygenator are configured to reduce flooding and loss of efficiency due to occasional rupture of fiber elements.”

DETAILED DESCRIPTION OF THE INVENTION (EDITED)
“The present invention provides an integrated blood pump/oxygenator that overcomes the drawbacks of previously known devices. In accordance with the principles of the present invention, the integrated system may be placed in or near the sterile field and has a low priming volume, e.g., 200 cc or less. A pump/oxygenator constructed in accordance with the principles of the present invention is expected to: (a) have little or no gas leakage into the blood and consequent bubble formation; (b) experience little or no cavitation, even at high speeds; (c) be less prone to rupture of fiber elements; (d) induce little or no blood trauma; and (c) provide adequate oxygenation capability even when occasional rupture of fiber elements occurs.”

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Extra-Corporeal Membrane Oxygenation System (ECMO), officially known as Extracorporeal Circulation Apparatus 

U.S. Patent 4,828,543

“A method and apparatus for extracorporeal circulation and treatment of blood. The apparatus comprises means for circulating and for treating blood, with a control system for controlling the circulating means. The circulating means includes tubing that directs blood to and from a microporous membrane. An arterial pump controls the flow rate of blood entering the filter; a venous pump controls the flow rate of blood exiting the filter. The filter includes a sealed, ported chamber surrounding the membrane. The rate of filtration of components removed from the blood through the membrane is directly proportional to a transmembrane pressure. Display and input devices transmit information between the central processor and an operator who operates the apparatus. The display and input devices include a keypad and an alphanumeric display. Sensors measure pressures within the tubing, at the inlet and outlet of the filter. Fluid flow rate can be calculated from the speeds of the pumps. The control system includes a central processor that receives input data from the sensors and the pumps to regulate the apparatus. The central processor will regulate the venous pump to maintain a specified outflow rate. The central processor also will maintain a desired average transmembrane pressure while the venous pump rate remains constant. The central processor calculates the average transmembrane pressure based on the measured filter input and output pressures. The central processor regulates the arterial pump speed as necessary to achieve the desired transmembrane pressure, while the venous pump rate is held steady.”

ECMO: Extracorporeal Membrane Oxygenation

BACKGROUND OF THE INVENTION (this generalized description is a lesson in itself)
“The present invention relates generally to the field of extracorporeal circulation of bodily fluids. More particularly, it relates to circulation and processing of blood outside the body. Still more particularly, it relates to regulating the rates and pressures of blood flowing through an extracorporeal processing circuit.

The human body is a complicated organism. It carries out a myriad of functions and processes around the clock, day-in and day-out. Sometimes the body is unable to perform vital tasks completely or adequately. Circumstances sometimes require medical treatment to assist or replace bodily functions. Medical science has devised various machines and equipment to help the systems of the body meet the demands placed on them in ordinary and extraordinary situations. One system extremely crucial to proper operation of the body is the cardiovascular system.

The cardiovascular system includes the heart and all the blood vessels in the body. The heart provides force to pump blood through the system. The arterial system connects to the heart and fans out in increasingly smaller vessels to the far reaches of the body, linking ultimately to capillaries. Capillaries are the smallest vessels in the cardiovascular system. Capillaries form minute networks throughout the body’s tissues. The capillaries eventually connect to veins. Veins, constituting the venous system, lead finally back to the heart.

Blood is a highly complex fluid. It contains, generally, plasma and cells. The cell component comprises red blood cells, white cells, and platelets. Plasma is mostly water with a tremendous variety of solutes. These solutes include inorganic components, metaboli nutrients and byproducts, and a host of plasma proteins.

Blood flows from the heart to the arteries, then to the capillary network. The blood brings nutrients and oxygen to the cells of the body. All cells need these substances to live. The blood also gathers carbon dioxide and other waste products resulting from the body’s matabolism. These wastes must be removed to allow cells to continue functioning. The returning blood collects in the veins and flows back to the heart. This returning blood carries the collected waste. The kidneys treat the blood to remove such waste products. These wastes, if left in the blood, would ultimately be fatal. Kidneys perform the vital function of cleansing the blood. Lungs likewise help to rejuvenate the blood. The major function of the blood’s red cells is to transport oxygen from the lungs to body tissues and to help transport carbon dioxide from the tissues back to the lungs. The heart pumps returning venous blood to the lungs. The lungs contain semipermeable membrane tissue that allows gases to migrate across it. Carbon dioxide passes from the blood into the lungs to be exhaled, while oxygen in the lungs is absorbed by the red blood cells. This newly oxygenated blood then returns to the heart for subsequent re-circulation through the cardiovascular system.

The process of circulating, cleansing, and oxygenating of the blood, then, is essential to life. The natural mechanical and biochemical systems of the body, when operating properly, perform these tasks best. Sometimes, though, a medical patient’s condition prevents proper functioning of the blood system. The ability to supplement or replace the blood system then becomes crucial to the patient’s survival.

Existing extracorporeal circulation apparatus for treating blood generally remove and collect a patient’s whole blood, circulate the blood through an extracorporeal circuit, and return the treated blood to the patient. Depending on the specific application, the treating involves filtering, removing some component(s) from the blood, or oxygenation. Various techniques and apparatus have been used in different blood treatment applications.

Heart-lung machines used during surgery pump and oxygenate blood, in place of a patient’s heart and lungs. Existing oxygenators suffer from imprecise control and inefficient operation. Blood flows through semi-permeable hollow fibers or channels inside semi-permeable membranes. Utilizing at least one pump in series with the oxygenator, the blood is pressured sufficiently to flow in the form of thin film layers along the membrane walls, thereby maximizing the flowing surface area. The partial pressure of oxygen on the exterior of the membrane walls is kept sufficiently high for the red cells of the venous blood to absorb the oxygen; similarly, the partial pressure of carbon dioxide on the membrane exterior is low enough to allow the venous red cells to discharge carbon dioxide. Oxygen on the membrane exterior migrates across the membrane for absorption by the blood, and carbon dioxide exits the blood and migrates to the membrane exterior. Inadequate control of the transmembrane pressure, however, often requires recirculation of the blood through the circuit after initial oxygenation. What pressure control exists is merely regulation of pump speeds as an indirect, and inaccurate, means for maintaining hoped-for pressure differnentials. There is no true, direct control of oxygenation based on transmembrane pressure. Instead, direct observation of blood colors and pressures ordinarily helps ascertain if blood leaving the system has been properly oxygenated. Such crude operational methods demonstrate the need for improved, effective, efficient control of blood oxygenating apparatus.

It is apparent that extracorporeal circulation and treatment of blood is a necessary, vital process for a wide range of medical treatments. Known apparatus for performing this process have suffered from numerous inefficiencies, operational problems, inadequate regulation, and economic disadvantages. A serious need has existed for an efficient, simple, controllable, yet economical means for circulating and treating blood outside the human body.”  (end of lesson; quiz Friday)

SUMMARY OF THE INVENTION (edited)

“Accordingly, there is provided herein a new and improved method and apparatus for the extracorporeal circulation and treatment of blood. The extracorporeal circulation apparatus of the present invention comprises means for circulating and means for treating blood, with a control system for controlling the circulating means so as to determine the results and output of the blood treatment.

The present invention provides for the first time an apparatus and method for directly, precisely, and continually controlling either transmembrane pressures or membrane filtration. Two pressure sensors, one on either side of a filter, provide a simple yet complete means for monitoring the crucial pressures at the filter. Two pumps, one also on either side of the filter, provide separate means for controlling the output flow rate and the flow and pressures at the filter, independently of conditions elsewhere in the extracorporeal circuit. A control system enables precise, predictable, dependable regulation of the apparatus with continual feedback from and adjustment of the apparatus. An apparatus embodying the invention provides all these advantages while being capable of use with standard, inexpensive, readily available filtering devices. Application of the principles of the invention can improve equipment reliability, lower costs, avoid waste of valuable substances, and reduce risks of disease.

These and various other objects and advantages of the present inventon will become readily apparent to those skilled in the art upon reading the following detailed description and claims and by referring to the accompanying drawings.”

DESCRIPTION OF THE PREFERRED EMBODIMENT (edited)
“Extracorporeal circulation of blood generally involves removal and return of a patient’s blood, with some appropriate treatment of that blood. Typically, treatment includes flowing the whole blood through some filtering means to remove undesirable components from the blood. One common type of filter has a microporous or semipermeable membrane that selectively filters these undesirable components. The blood flows under pressure through an interior space enclosed by the membrane.”
OPERATION OF THE APPARATUS (edited)

“The present invention, therefore, further provides a reliable, precise means for predicting, determining, and regulating the rate of filtration of components through the membrane walls of the filter 142. Prior art apparatus have failed to provide means for continually monitoring and controlling the component filtration rate with such a degree of precision and regularity. The present invention provides an apparatus for directly measuring and regulating filtration rates. This capability provides a powerful tool for predicting and monitoring a variety of medical procedures, including autotransfusion, dialysis, plasmapheresis, and other treatment methods.”

OXYGENATION APPARATUS (edited)

“…This transmembrane pressure ensures that the flowing blood properly forms thin films along the membrane interior. The thin films of flowing blood provide maximum surface area for optimum oxygenation of the blood. By optimization of the pump rates and the oxygen flow rate, oxygen and carbon dioxide can most efficiently migrate across the membrane to be absorbed and discharged, respectively, by the red cells of the blood. The invention thus considerably enhances the efficiency and effectiveness of heart-lung machines by providing a precise and predictable means to control transmembrane pressure and flow rates while oxygenating blood.”



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