Gas separation: apparatus – Degasifying means for liquid – Liquid flow slinger – spreader – deflector – disperser – or...
Reexamination Certificate
1999-07-02
2001-01-23
Smith, Duane (Department: 1724)
Gas separation: apparatus
Degasifying means for liquid
Liquid flow slinger, spreader, deflector, disperser, or...
C096S216000, C096S219000, C096S212000, C096S220000, C210S188000, C210S436000, C210S304000
Reexamination Certificate
active
06176904
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to blood filters that are used in extra corporeal blood circuits. More particularly, the invention is directed to arterial blood filters used during heart bypass surgery for the removal of particulate matter and gaseous emboli from blood that has been oxygenated and is being returned to the patient.
Blood filters are used for the treatment and filtration of blood for various applications such as cardiopulmonary bypass techniques, blood transfusions, dialysis treatment etc. Arterial blood filters are provided to trap and remove particulate matter and undissolved gaseous emboli from oxygenated blood. Typically, the arterial blood filter is one of the components in an extra corporeal blood circuit in which blood flows from a patient, through a cardiotomy reservoir, an oxygenator and finally into the arterial filter before it is returned to the patient. The arterial blood filter may be the last component of the blood flow circuit through which the blood flows before the blood is returned to the patient, and thus this filter must be durable, reliable and effective in the filtration process.
Arterial blood filters are disposable after a single patient use and must be designed for manufacture, packaging and sterilization at minimal cost. Use of low cost materials and minimization of the amount of materials is critical to the effective manufacture of an arterial filter along with simple, conventional tooling and assembly processes. A small concise design is also a critical factor in packaging costs, efficient sterilization and storage space costs related to the filter. The extra corporeal circuit, including the arterial filter, must be primed with a suitable fluid to remove air from the system prior to the introduction of blood flow; and it is therefore important that the filter have a concise internal volume to minimize priming fluid and priming time in preparation for use.
An example of an early arterial filter having a hollow tubular housing containing a concentric cylindrical filter element is shown in U.S. Pat. No. Re. 32,711 (reissue of U.S. Pat. No. 4,411,783) to Dickens et al. assigned to Shiley Inc. This patent discloses a large diameter cover on the top of the filter element having a symmetrically positioned frusto-conically shaped dome. Blood is introduced tangentially into the upper end of the device and flows over and around the dome then downwardly and through the filter element. The symmetrically positioned dome tends to produce some obstruction to the inlet of blood into the filter, and the flow over the dome tends to create some turbulence and re-circulation with the incoming flow of new blood. The inlet chamber includes a large space for re-circulation and de-bubbling of the blood and results in a relatively large internal volume that requires priming. This early design was considered to be a significant advancement over the prior art at that time, and has been widely used.
Another example of a related prior art arterial filter is described in U.S. Pat. No. 4,919,802 to Katsura, assigned to Terumo Inc. This patent discloses a tubular cylindrical housing with a concentric cylindrical filter element having a symmetrically positioned frusto-conically shaped dome similar to the device of Dickens et al. This patent particularly teaches a horizontally extended tubular blood inlet, adjacent to the cylindrical housing, to introduce blood tangentially into the upper chamber around the side of the symmetrically positioned dome to avoid any obstruction of blood flow by the dome. This patent describes improved performance in de-bubbling and laminar blood flow that does not damage any platelets of the blood cells during the filtering process. The expanded diameter inlet path would seem to require a much larger top cap resulting in more material, a more complex design, complex tooling and assembly for manufacture, and resulting in more external and internal volume and larger packaging and priming requirements.
Another example of a related prior art patent is disclosed in U.S. Pat. No. 5,632,894 to White et al., assigned to Gish Biomedical, Inc. This patent incorporates a tubular housing with a cylindrical filter element having a symmetrically positioned frusto-conically shaped dome similarly to the filter described in the Dickens et al. patent. This patent discloses a tangential tubular blood inlet extended horizontally and adjacent to the side of the housing similarly to the device described in the Katsura patent; and further teaches improves performance by inclining the tubular inlet at an angle, so that the blood is introduced into the filter around the side of the dome and at an upward angle to enhance flow within the filter device. This improvement seems to include the complexity, material and volume requirements as discussed in regard to device in the Katsura patent, plus the additional complexities and costs associated with the inclined inlet and flow path featured in the patent.
In view of the foregoing, it is an object of the present invention to provide a blood filter that has a smooth tangential inlet that is not obstructed by any internal components of the filter.
It is another object to provide a blood filter that provides smooth laminar flow in a downward spiraling vortex that provides efficient separation of any undissolved gases from the blood and does not produce any damage to the blood cells.
It is another object to provide a blood filter that is very compact having minimum external dimensions for efficient packaging and storage and minimal internal dimensions for a low priming volume and efficient blood flow.
SUMMARY OF THE INVENTION
The present invention uniquely improves upon the disclosures and teachings of the prior art in a novel manner to accomplish the desired features and performance of an arterial filter without the complexities and costs associated with those of the prior art.
The foregoing objects are accomplished by an improved compact blood filter device having a central axis suitable for use in a vertical orientation in an extra corporeal blood flow circuit for removing foreign particles and undissolved gases from blood flowing through the device, including a cylindrical body having a circular upper end and a circular lower end forming a filtering chamber therein. Further including, a hollow upper cap having a base diameter closely matched to the diameter of the upper end of the body and attached thereto, forming an inlet chamber therein in communication with the filtering chamber. The upper cap having a vertical gas outlet at the uppermost surface near the center thereof, and having a horizontal tubular inlet therein with the inlet having a horizontal axis and having the outermost edge of the wall of the tubular inlet extending tangentially from the outermost wall of the base of the upper cap. The housing further including a substantially flat circular bottom cap having a central tubular blood outlet extending therefrom and having a diameter closely matched to the diameter of the lower end of the body, and attached thereto. The device has a cylindrically shaped filter element having an upper end, a lower end, a filter surface having an outer diameter lesser than the diameter at the lower end of the body, a filter inner surface having a diameter greater than the diameter of the blood outlet, wherein the filter element is positioned coaxially within the filtering chamber of the body and is supported at the lower end thereof on the bottom cap. The inner surface of the filter element is in communication with the outlet chamber, forming an outlet chamber. The filter element is sealed and supported at the upper end and the lower end thereof by conventional means. A principle feature of the present invention is a stepped dome having a circular base with a diameter closely matched to the outer diameter of the filter element and attached to the upper end thereof, and having a hemispherically shaped upper surface extending into the inlet chamber and having a maximum diameter smaller than the diamete
Greene Jason M.
Smith Duane
Turner Roger C.
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