Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1997-09-22
2001-11-06
Yasko, John D. (Department: 3306)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S004010, C604S035000
Reexamination Certificate
active
06312414
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for suctioning blood and for separating blood and gas and particularly to moving blood through a non-rotating centrifuge for separating blood and gas.
When blood is drawn from a patient, in particular from the site of a wound which may result from a surgical operation or an accident, and this blood is then to be used again for the same patient or for another patient, the blood must be again separated as soon as possible, and as close as possible to the place of removal from the patient, from the air which may have been drawn into the blood at the place where it was drawn is from the patient. Blood which contains air must under no circumstances be administered to a patient. Furthermore, blood is damaged by inclusions of air the longer air which has been drawn-in remains in the blood, and the more the air is mixed with this blood over the blood-removal path.
The quality of blood can be impaired among other things by the amount and length of presence of air or other gases in the blood; by suction or pressure forces on the blood; by frictional forces of the blood in flow paths, and by deflections of the flow of blood and turbulence in the blood.
Upon the degassing of blood, a distinction must be made between different uses, since they have different purposes and different conditions.
In a first case of use, blood is degasified while it is drawn in relatively small and strongly varying amounts from a patient, in particular through a suction tube from the site of a wound which may have been caused by an accident or an operation. Vacuum for drawing the blood is produced by a suction pump, generally a roller pump. The suction pump not only draws off blood but frequently also draws off air at the place where blood is being removed from the patient. The amount of air which is drawn off is relatively large, as compared with the amount of blood being drawn off, for instance five parts of air to one part of blood (parts by volume). The blood-removal rate is relatively low, for example 100 to 600 milliliters per minute, and it varies greatly. The suction flow speed of the blood is also relatively low and varies greatly.
The air bubbles contained in the blood are frequently relatively large. Their size ranges from the micrometer range to the millimeter range. The present invention concerns this field of use, namely degasifying blood while it is being drawn off from a patient.
The second case of use concerns administering blood to a patient, for instance upon dialysis or after a large loss of blood in an accident. Blood which is administered to a patient cannot be fed by suction but can only be administered to the patient by the pressure of a pressure pump. The blood rate, for instance three liters per minute, and the speed of conveyance of the blood are relatively high and substantially constant. The amount of air in the blood is, however, slight, for instance only 50×10
−6
parts by volume of air to one part by volume of blood. The air has the form of only very small bubbles in the micrometer range.
The third case of use concerns the handling of blood outside a patient and independently of the patient. Here, similar to the second case, there are substantially constant blood flow quantities and constant speeds of flow of blood.
For the first case of use, U.S. Pat. No. 3,785,380 discloses a blood removal device which consists of a cylindrical housing in which microporous filter material is present for filtering air bubbles and other impurities out of a stream of blood drawn off from a patient, a blood suction tube at a front end of the housing, and a blood suction line at the rear end of the housing.
Literature concerning the second case of use includes GB-A-2 063 108 which shows a blood degasification device for removing bubbles of gas which can be so small as to lie in the micro range, for instance having a diameter of only 40 microns. This blood suction device has a vertically arranged cylindrical cyclone chamber, with a tangential inlet at the upper end of the chamber, and a blood outlet at the
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lower end of the chamber arranged tangentially opposite the direction of rotation of the cyclone. An air vent tube extends in downward direction in the axis of rotation of the cyclone to a level below the blood inlet into the cyclone chamber. A second venting means is in the form of a radial hole in an upper extension of the cyclone chamber above the blood inlet. A second tube extends through the entire cyclone chamber along the axis of rotation of the cyclone and through a part of the first mentioned tube. The second tube serves so that air bubbles collect on its outer surface and can rise upward. German DE-A-43 29 385 describes an air separator which is an improvement on the one described in the above described GB-A-2 063 108. In the German publication, the blood inlet and blood outlet are arranged axially to each other at the ends of a cylindrical eddy chamber which face each other. The blood inlet is formed by a guide blade body and there is a filter candle in front of the blood outlet. Ascending bubbles of blood enter into a section of the eddy chamber which is located above the guide blade body and in which an air cushion is formed which is vented by a hole. German DE-C-36 41 644 shows a blood flow chamber having a blood inlet at the mid-height of the chamber and a blood outlet channel immersed in the flow chamber. Air bubbles contained in the blood can rise upward only due to the Archimedean buoyancy force.
Furthermore, German DE-C-36 24 363 and U.S. Pat. No. 5,451,321 show devices with microporous filter material for filtering gas bubbles or other blood impurities out of a stream of blood.
SUMMARY OF THE INVENTION
The object of the present invention is substantially to reduce the aforementioned impairments in the blood caused upon drawing blood from a patient. Another object is to do this by a low weight, inexpensive apparatus which is easy to operate.
This object is achieved with an apparatus having a non-rotating centrifuge chamber with a vertical axis and with a blood inlet above and a blood outlet below, wherein blood enters tangentially, flows around the chamber and exits the outlet. The apparatus is widened above the centrifuge chamber to produce an enlarged gas space wherein gas from the blood flow can separate and be drawn off through a gas outlet. The apparatus is developed and sized to be carried in one hand and includes a hand grip for that purpose. The blood inlet channel is connected at or is the rear end of the blood suction tube.
The centrifugal chamber is preferably funnel shaped, wide toward the upper end inlet and narrowing toward the lower end outlet. The blood inlet suction channel is angled at an angle, open at the top, of less than 90° to the axis of rotation. For compactness, various elements may be in or may run through the hand grip of the apparatus, those elements including the centrifuge chamber and various blood or gas flow channels.
The invention has following advantages: The blood suction apparatus can be arranged close to a patient. It is very light in weight. It can be produced at low cost by the use of commercial tubes. It is simple to handle and not fatiguing for the operator. The invention utilizes the centrifugal forces of a cyclone flow for the removal of gas bubbles of all sizes. The gas removal suction action is applied on the rotating blood from above, and the Archimedean buoyancy forces simultaneously and in a manner support each other, so that with even only a weak suction of a suction pump, gentle and at the same time effective separation of the gas phase from the blood phase takes place.
If, in accordance with the invention, the cyclone chamber has the shape of a funnel which becomes narrower from the blood inlet to the blood outlet, then the centrifugal kinetic energy of the cyclone flow is better maintained from the blood inlet to the blood outlet than in the case of a non-funnel-shaped cylindrical chamber. Even with small quantities of blood flow and low
Brockhoff Alexander
Plechinger Hans
Beck & Tysver P.L.L.C.
Yasko John D.
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