In the field of surgery, it is well known that blood is collected from a patient for various reasons. The blood that is collected is commonly centrifuged in order to separate the red blood cells from fluid in the blood, with the fluid being disposed. The final product of concentrated red blood cells is then re-introduced into the patient's blood system in order to thicken the blood. Specifically, the percentage of red blood cells in the blood, the hematocrit level, is increased.
Conventional collection bowls currently in use define a fixed volume. A typical collection bowl 10A is illustrated in FIG. 1. The bowl 10A includes an outer wall 14A and an inner wall 16A, with a particular volume defined therebetween and within which the blood is collected and centrifuged. Waste fluid is expelled and the red blood cells are kept within the volume. The inner wall 16A and outer wall 14A are fixed in relation to each other such that the volume within the bowl 10A is fixed. The inner wall 16A may be configured with a stepped frusto-conical shape as illustrated in broken lines, or with a frusto-conical shape as illustrated with solid lines. In either configuration, the volume within the bowl 10A is determined by the configuration and dimensions of the inner wall, and cannot be changed with the particular bowl 10A being used. Although various sizes may be chosen, the bowl 10A must be fill prior to re-introducing the red blood cells into the patient's blood system. Thus, if a surgical procedure is completed such that no more blood is to be collected, and if the collection bowl is not full, any red blood cells that have been collected are disposed. In another scenario, the red blood cells may be required during a surgical procedure, but not available because the collection bowl 10A is not yet full. In such an instance, the surgeon must wait until the appropriate amount of blood is collected such that it may be processed and the red blood cells harvested.
Other devices have been produced for separating components in a fluid using centrifugal separation. Typical of the art are those devices disclosed in the following U.S. Patents:
______________________________________ Pat. No, Inventor(s) Issue Date ______________________________________ 260,412 E. E. Quimby July 4, 1882 3,930,609 K. Nelson Jan. 6, 1976 4,530,691 R. I. Brown July 23, 1985 5,186,708 K. Stroucken, et al. Feb. 16, 1993 5,306,423 G. Hultsch Apr. 26, 1994 5,405,308 T. D. Headley, et al. Apr. 11, 1995 5,441,475 S. Storruste, et al. Aug. 15, 1995 ______________________________________
Of these devices, Quimby ('412) discloses a centrifugal separator for the separation of starch from liquid matter. The separator has a removable rim such that starch may be removed. Although the outer wall is movable with respect to the stripping disk, the volume within the separator, during operation, is not variable.
The device disclosed by Nelson ('609) is a centrifuge designed to prevent the admission of air into the bowl during discharge of sludge in order to maintain a normal liquid level. Nelson does not disclose a means for varying the volume defined within the centrifuge, regardless of whether or not it is in use.
Stroucken, et al. ('708), teach a centrifugal separator having a rotor body with a movable wall. The rotor of the '708 device includes two axially separated end walls and a surrounding wall disposed between, and separate from, the two end walls. The surrounding wall may be moved axially with respect to either or both end walls and is capable of elastic deformation in response to liquid pressure in the separation chamber. However, Stroucken, et al., do not teach a means for varying the volume within the separating chamber, especially to reduce the volume during operation of the same.
The device disclosed by Hultsch ('423) is a discontinuously operating filter centrifuge. The '423 device is constructed such that liquid is discharged from a filter cake, the filter cake being discharged from a filter bag when shifting out of the mouth of the drum, thus enabling the inspection of the interior of the drum. Hultsch, as in the above references, fails to teach a variable volume collection receptacle, and especially a receptacle whose volume may be reduced during operation of the centrifuge.
Headley, et al. ('308), disclose a disposable centrifuge rotor and core for blood processing whereby a plurality of projections extend into the processing region to minimize formation of fluid Coriolis waves. The '308 device is used in conjunction with a fixed volume centrifugal separator. Thus, Headley, et al., do not disclose a variable volume bowl.
The '475 device disclosed by Storruste, et al., includes a separation chamber housing split into what are described as mating, unhinged clamshell sections. Although the two sections are movable axially away from each other, such movement is provided for discharge of material from within the separation chamber. As with the previous devices, the '475 device does not provide for variance of the volume within the separation chamber, and especially does not allow for the volume within the chamber to be reduced during operation of the centrifuge.
The '691 device disclosed by Brown is a centrifuge having a movable mandrel for varying the volume within a blood processing chamber. The '691 device employs a chamber which, upon application of a force, conforms to the shape of a chamber cover and the mandrel. However, in the configuration disclosed by Brown, a volume of the blood being processed is necessarily situated in the center of the bowl, co-linear with or near the axis of rotation. Therefore, without some circulatory incentive, that blood will remain substantially unprocessed, as it is not being subjected to any centrifugal forces.
Therefore, it is an object of this invention to provide a means for varying the volume within the separation chamber of a centrifuge in order to accommodate variations in the volume of fluid collected such that, in the instance of collected blood, the desired component may be removed from the fluid and used as needed.
It is a further object of the present invention to provide a variable volume cell saver bowl for use in collecting red blood cells from blood collected during surgery for re-introduction into the patient in order to elevate the hematocrit level of the patient, the bowl volume being adjustable during operation of the device to accommodate various volumes of blood collected.
As a result, it is a further object of the present invention whereby the volume within the separation chamber may be reduced such that lower volumes of blood collected may be immediately centrifuged to collect whatever red blood cells are present.
Still another object of the present invention is to provide a variable volume cell saver bowl which defines an interior processing volume configured to displace the blood to be processed away from an axis of rotation of the bowl, thereby insuring proper processing of substantially the entire volume of blood introduced therein.