Surgery – Means and methods for collecting body fluids or waste material – Material collector or receptacle having attaching means to...
Reexamination Certificate
1998-06-17
2002-01-29
Weiss, John G. (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Material collector or receptacle having attaching means to...
C604S317000, C604S319000, C604S321000, C604S118000, C604S119000, C600S573000, C600S578000, C600S579000
Reexamination Certificate
active
06342048
ABSTRACT:
TECHNICAL FIELD
This invention relates to the art of systems for recovery of physiological fluids, such as blood. In the preferred embodiment, the invention relates to a system for collection of blood during surgery and for returning the collected blood to the patient.
BACKGROUND
Systems for collection of blood during surgery for the purpose of returning the blood to the patient are known. These systems typically are vacuum systems that rely on sources of low pressure existing in the hospitals to create the suction required for collecting the blood. The collected blood may be washed by any of several known cell washing devices prior to providing the collected blood back to the patient.
Because blood cells are very fragile, they are frequently damaged during the collection process, which makes them unavailable for return to the patient. For example, cells will be damaged if subjected to excessive physical contact, such as turbulence or compression. For example, collection systems that use roller pumps cause excessive physical damage. Similarly cells subjected to pressure differentials that are too great will be damaged. Thus, blood cells subjected during vacuuming operations to exterior pressures that are too low will burst and not be available for return to the patient.
Although the use of vacuum is well known in the art, conventional systems use high vacuum (in excess of −250 mm Hg), which is throttled by simple mechanical regulators. These systems do not employ a “feed-back loop” or other sensing circuits to monitor vacuum parameters. Such systems are not optimal for collecting shed blood and are known to cause significant damage to collected red cells. Mechanically regulating vacuum to −100 to −150 mm Hg (dead end) can reduce the red cell damage greatly, but significant red cell damage occurs nevertheless and the problem is compounded by lack of understanding by the user of correct adjustment techniques.
SUMMARY OF THE INVENTION
In accordance with the invention a portable, electrically-powered blood collection system collects blood substantially without damage to the blood cells. The collected fluids are filtered and placed in a flexible bag to facilitate their return to the patient. The system is self-contained and requires only external electric power in one version and no external power in a second version. Minimal damage to the collected blood is obtained by optimization of the physical characteristics of the system. Further, the system conditions the collected blood and maintains it in a safe condition until a volume has been collected that is sufficient to warrant returning the blood to the patient. The system immediately and effectively packages the collected blood for convenient return to the patient by conventional IV administration techniques.
The blood collection system of the invention uses an electronically-controlled pump to create a low pressure flow of air to aspirate shed blood. An electronic circuit increases and decreases the vacuum parameters, such as pressure and flow rate, according to need, by sensing no load, low load and high load situations. Under a no load condition, e.g., air flow only, and a low load condition, e.g., surface suctioning air mixed with mostly foam, the system maintains a very low vacuum of about 20 mm Hg and a correspondingly small rate of air flow. Under high load conditions, e.g., where the tip of the aspiration tool is immersed in a pool of blood or is occluded, the system instantaneously increases the vacuum to about −100 mmHg. Because the flow in the high load condition is almost all liquid, the flow velocity through the aspiration path is low (Poiselle-Hagen Law). In this system, the blood being collected is never exposed to the high vacuum or velocity that would damage the cells, and laboratory testing using these control parameters has shown insignificant levels of blood damage.
The collection/suction tube of the invention preferably has a thin wall, whereby it is lightweight and easy to use. Because the vacuum level is controlled and small, however, there is little danger that the tube wall will collapse when the tip is occluded.
The system of the invention preferably includes a large-bore sucker, the opening at the tip having a diameter of between 0.285 and 0.500 inch. The bore of the sucker continues unreduced to its connection with the suction tubing, which has a nearly equal diameter, and the two components are connected by a coupler that provides an unrestricted, smooth transition between them. The large bore sucker and tubing are connected to a collection chamber equipped with an equally large bore fitting. A suitable coupler is employed to allow an unrestricted and smooth transition between the tubing and chamber fitting.
The sucker assembly described above is connected to a vacuum source capable of regulating the vacuum at very low levels. The preferred embodiment of the system regulates the vacuum between −10 mm Hg and −100 mmHg. The particular level of the vacuum is based on the demand and is governed by feedback through the sucker, tubing and collection chamber to the vacuum source. The pressure differential across a mechanical resistor in the vacuum line is sensed by pressure transducers and resulting signals are fed to a suitable electronic regulating source, which, in turn, operates the vacuum source in a pulsed mode, alternating between on and off conditions as required to maintain the desired vacuum for the particular demand condition.
With an open suction line (carrying no liquid) the resistance across the mechanical resistor is minimal and the vacuum is reduced to the minimum level. During skimming, there is increased resistance through the tubing and across the mechanical resistor, so the vacuum is slightly increased. With the collection of some pooled liquid there will be further resistance, so the vacuum level will further increase proportionately. With full immersion of the sucker tip in liquid, the vacuum resistance through the system will be at a maximum level, and the vacuum will then be controlled to be the largest level of −100 mmHg.
A general observation of fluid mechanics is that the rate of fluid flow through a tube is a function of the 4
th
power of the radius of the tube. Thus, a slight increase in the internal diameter of a tube results in a significant increase in the flow rate, all other conditions being equal. Recognizing this relationship, the system of the invention utilizes larger bore tubing to permit lower operating vacuum levels, which minimizes damage to the collected blood and avoids issue trauma. Increasing the tubing diameter in accordance with the invention more than compensates for the reduction in vacuum levels by providing a larger than expected flow rate for these vacuum levels. The low vacuum levels used by the system of the invention could not provide flow rates acceptable to surgeons with standard bore suckers. Thus, the combination of the large bore sucker, tubing and connectors with lower vacuum levels is important.
Because the tubing has a larger bore, fluid moves through the tube more slowly while still achieving the desired flow rate. This is advantageous because less damage is caused to slowly moving blood than to faster moving blood. Another advantage is that the less-restricted pathway of the large bore system significantly reduces the potential for clogging the tube with debris during the surgical procedure. There are two reasons for this. First, the increased diameter has the ability to pass more potentially-clogging particles and, second, the unrestricted path allows potentially clogging solids to pass all the way through to the collection chamber.
The low pressures of the system (i.e., the maximum of −100 mmHg) also reduces or eliminates trauma to tissues and also reduces the tendency of the suction to “grab” the tissue, known as invagination.
Yet another advantage of the small negative pressures employed in the invention is that the tubing may be made of thinner, more flexible materials. Prior art suction t
Ellsworth James R.
Verkaart Wesley H.
Bogart Michael
Clark & Brody
Harvest Technologies Corporation
Weiss John G.
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