Blood recuperation device and method

The present invention relates to a blood filtration device and a method for recovering blood drained from a wound, in particular an autologous blood transfusion and the system thereto, the filtration device comprising a blood entry opening, a first filter and a second filter, wherein the first filter is located above the second filter (relative to the flow), the first filter is adapted to remove emboli and / or large matter particles from the blood received through the entrance opening and allow red blood cells to pass through, and the second filter is adapted to retain red blood cells, and the exit opening located between the first and second filters, i.e. below the first filter and above the second filter (relative to flow).

[0002] After the patient has undergone surgery, specific wounds, e.g., chest wounds after heart surgery, may be provided with drains to remove secretions from the wound, which secretions usually contain blood. You may lose so much blood that you may need a transfusion. Autologous blood transfusion, which involves administering the patient's own blood, minimizes the risk of blood transfusions from other people, so-called homologous blood transfusions, namely hypersensitivity reactions and / or donor related infections such as jaundice, acquired immunodeficiency syndrome ( AIDS), harmful effects of HLA (human leukocyte antigens) and malaria.

[0003] For autologous blood transfusion, fluid containing lost blood must be collected and blood must be recovered from it to be reintroduced into the bloodstream. This blood, which preferably is as rich as possible in healthy red blood cells or erythrocytes, must be filtered from drained blood and released or washed from impurities and / or contaminating substances prior to administration. Typical impurities in blood drained from the site of the healing wound include, but are not limited to, bone and tissue fragments, blood plugs and fat particles, as well as activated coagulation factors, plasma-free hemoglobin, denatured proteins, platelets, leukocytes and lipids.

[0004] Autologous blood purification, generally called "washing", is usually accomplished in two stages: first, the drained fluid is filtered

Relatively rough to remove large particles of litter and impurities from the blood, then the filtrate is mixed with a "washing fluid", usually saline or Ringer's solution, introduced into the centrifuge chamber to separate relatively heavy blood cells from blood plasma and relatively small and light particles such as platelets, plasma proteins and antibodies. The recovered blood is generally introduced into the bloodstream under low pressure through a leukocyte filter to further reduce the number of remaining white blood cells in the blood given during transfusion.

[0005] This cell washing technique is effective only for batches.

In addition, during washing by centrifugation, a significant number of collected red blood cells are damaged and lost to the patient. This method depends on complicated equipment that is not available when blood loss occurs over an extended period of time, e.g. 612 hours, outside the operating room, e.g. in the intensive care unit (ICU).

"Intensive Care Unit").

[0006] The improvement of this technique is ensured by the use of a two-stage filtration system that can be used for continuous or quasi-continuous washing of blood drained from a wound. Such a filtration system having the features of the preamble of claim 1. 1, is known for example from EP

0 518 975, which discloses a device for recycling autologous blood from a patient for re-administration to a patient, including aspiration means, mixing means for mixing sucked blood with a wash fluid, filter means for filtering the mixture through a thrombus plug filter and membrane filter, monitoring means for measuring volume cellular component in filtered blood, filtering means for removing excess fluid and particles from the blood, and means for re-entering the bloodstream. The membrane filter may be a conventional membrane separator with pore sizes for the cut-off fraction with a molecular weight in the range from 40,000 daltons to 400,000 daltons. However, if larger contaminants are to be removed, a plasma filter with pore sizes larger than about 400,000 Daltons and up to 0.4 μm can be used. WO-A-93/01858 discloses the maximum pore sizes of a second filter of 0.6 μm.

[0007] In order to achieve blood filtration from small impurities using commercially available membrane filters as proven by experiments, only blood having a blood cell volume or hematocrit less than about 25% should be used at a pressure difference on a membrane filter higher than about 400 mm Hg (53 kPa). In addition, the filters tend to clog, which requires an even higher pressure difference and / or even lower hematocrit for their operation. These devices can also work only when strong anticoagulants such as heparin are used during filtration.

[0008] It is desirable, especially for severely weakened patients, such as patients in intensive care units, to have a simple, reliable filtration device that can give purified blood with a high hematocrit value, e.g. 70% or even higher, for autologous blood transfusion. This will improve the recovery of patients and reduce morbidity and mortality.

[0009] Furthermore, systems that can achieve the necessary relatively high pressure differences, i.e. medium to high vacuum sources or roller pumps, may be unavailable in some hospitals, especially in underdeveloped countries.

[0010] Furthermore, it is obvious that autologous blood prepared according to the prior art may still contain impurities, such as damaged red blood cells, activated platelets or activated tissue factors that can cause complications to the patient, such as inflammatory reactions.

[0011] Thus, an improved blood filtration device and a method of recovering blood from blood drained from a wound that substantially removes such problems from the prior art are desirable.

[0012] To this end, the second filter has pore sizes in the range of about 1 to μm. Thus, because the red blood cells have an average size of about 4 μm and can form small chains or clusters up to about 10 μm, the filtration device of the present invention provides filtering means to filter relatively large impurities and to pass healthy red blood cells through the first filter, while the second filter stops these

Blood cells and permeates fluid and smaller impurities and / or contaminants.

[0013] The larger pore sizes of the second filter compared to the prior art provide a relatively low fluid flow resistance, such that the device can operate with a low pressure difference or without a pressure difference across the filter, and so that excess fluid, e.g. the washing or irrigation fluid can be effectively filtered.

[0014] Thus, a relatively simple device has been obtained that provides a filter window for the recovery of red blood cells with minimal need for additional equipment.

[0015] The pore sizes of the second filter may be in the range of about 2 to 8 μm, for example in the range of about 4 to 6 μm, for example 5 μm. The choice of size in this range allows the fine adjustment of the filter window to retain healthy red blood cells, but also to filter out relatively large impurities.

[0016] The relatively coarse second filtration step, compared to the prior art, can filter out and lose some beneficial factors in the blood, such as platelets. However, most of these platelets are activated and their number is usually small, since most of them remain in the wound itself to achieve coagulation at the site of tissue damage. Thus, an additional reduction of harmful contaminants, such as other tissue factors, and easy operation of the subject device have been found to overcompensate this effect, providing that the subject filtration device and method are a clear improvement of the state of the art.

[0017] The first filter may have pore sizes smaller than about 200 Pm or smaller than about 100 Pm, e.g. 50 Pm, for effective filtration in the first filtering step.

[0018] Also provided is a method of recovering blood from blood drained from a wound according to claim 14, in particular for autologous blood transfusion, comprising the steps of sucking or collecting in the conduit blood drained from the patient's wound, filtering the blood from the conduit in a first or coarse way to remove blood plugs and / or other matter particles from the blood, filtering the coarsely filtered blood into the second relatively accurate way to filter out small ones

Impurities and / or blood fluid and preserve the red blood cells in residue, collect the residue from the second filtering step, the second filtering step being carried out so as to retain particles having a size larger than about 1 μm and remove smaller particles.

[0019] The second filtering step may be carried out to filter and retain particles having a size larger than about 2 μm or larger than about 4 μm, e.g. about 5 μm, and to remove smaller particles, preferably the first relatively coarse filtering step being carried out to filter particles having sizes above about 200 Pm, preferably above about 100 Pm, e.g. above 50 Pm.

[0020] The present invention also relates to a kit, comprising the above-described blood filtration device, a wound secretion suction tube and a blood container, sterile packed, as well as an autologous blood transfusion assembly according to claim 1. 1.

[0021] The subject device and its operation will be better understood from the following drawings, which schematically show non-limiting embodiments.

Fig. 1 is a cross-sectional view of a blood filtration device for recovering blood from blood drained from a wound.

Fig. 2 is a cross-sectional view of the blood filtration device perpendicular along the line AA to the view in Fig. 1.

Fig. 3 is a larger scale perspective view of the second filter suitable for use in the filtration device of Fig. 1.

Fig. 4 is a cross-sectional view of the second embodiment of the blood filtration device.

Fig. 5 is a cross-sectional view of the blood filtration device according to Fig. 4 perpendicular along the line VV to the view in Fig. 4.

Figures 6-10 are cross-sectional views of further embodiments of the blood filtration device.

Figures 11A and 11B show cross sections of an embodiment of a blood filtration device having a first and a second filter contained in two separate housings.

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Fig. 12 shows a cross-sectional view of the housing with the first filter and piston.

[0022] Figs. 1 and 2 show a filtration device 1 comprising essentially a tubular housing 2, provided with a connection 3 for introducing blood into the device, an optional connection 4 for a wash fluid source, an optional vacuum connection 5 and an outlet 6 provided with a valve 6A for removing recovered blood. Inside the housing 2 there is a first filter 7, a second filter 8 and a partition 9. The housing 2 further comprises a tank 10 for filter waste and a vacuum safety valve 11. The inlet 5A of the vacuum line 5 is oriented outwards from the second filter to prevent it from sucking in filter waste.

[0023] Connections 3, 4, 5 and output opening 6 may be provided with connectors such as a standard size Luer Lock connector. Alternatively, these connections may have drains and / or wires permanently connected to them.

[0024] The vacuum safety valve 11 may be a unit of a microporous hydrophobic filter that may be permeable to gases, but not liquids, but may also be implemented differently in any known manner.

[0025] The filtration device 1, the set of drains and ducts, and possibly one or more blood containers and the specified amount of flushing fluid can be provided in one, preferably sterile packed set, which may also contain suitable means for using the drain, so that the entire a treatment kit can conveniently be provided. The parts used may be disposable to prevent inadvertent reuse of the patient or other known biological hazards associated with blood.

[0026] For recovering blood from blood drained from the wound by means of filtration device 1, a blood container is connected to outlet 6. The blood container may be an empty blood bag, a blood bag with a washing fluid or preservative fluid, or other suitable device. It can also be a device for introducing blood into the bloodstream for direct blood entry in real time.

[0027] Next, drainage 3 and drained blood containing impurities are inserted at the wound site in any suitable known manner and introduced into filtration device 1 via connection 3.

[0028] The subject device can be used in a clinical setting, connected to the wound site of a patient, or independently, i.e. separated from the patient, to filter collected blood drained from the wound.

[0029] As a first option, the blood-filled drain can simply drain the drained blood under the influence of gravity from the wound site to the filtration device when it is located below the wound site, e.g. on the floor next to the patient's bed. Drainage can be assisted by suction with a slight negative pressure inside the filtration device, e.g. obtained from an empty blood bag, or obtained from a vacuum source connected to a vacuum connection 5, e.g. using a vacuum of -30 cm H2O (-3 kPa).

[0030] In the second option, filtering can be supported by a larger vacuum which is preferably less than -200 mm Hg (-27 kPa), e.g. -120 mm Hg (-16 kPa).

[0031] After entering the filtration device 1, blood plugs and / or relatively large dirt particles are removed from the drained blood from the wound by means of the first filter 7, and smaller particles, including red blood cells, are passed through the first filter 7. Via septum 9 blood is supplied to the second filter 8.

[0032] The second filter 8 serves to retain red blood cells and to filter out smaller impurities remaining in the blood after the first filtering step.

The residue from the second filter 8 is collected at the outlet 6, and the filtrate is collected in tank 10 and is considered a waste product of the process.

[0033] As is clearly seen in the embodiment of Figs. 1 and 2, the first filter 7 has an upper surface (relative to the flow) which is convex, narrowing opposite to the direction of flow. This shape causes the outflowing drained blood to drain to the sides of the filter 7, where residues may collect, leaving a relatively clean central part of the filter surface. Thus, this feature largely prevents clogging of the first filter 7 and allows the use of smaller pore sizes than the usual 40 μm,

E.g. reduced to about 15 μm, to remove smaller impurities if desired. However, the pore size larger than 40 μm allows faster filtration and reduces the need to apply a pressure difference to the filter surface, for example by means of a vacuum.

[0034] A concave first filter 7 may also be used.

This gives the effect that residues accumulate at or near the bottom of the filter, where they can act as an additional filtering material that can reduce the speed and efficiency of filtration, but at the same time can give a higher quality filtrate, i.e. containing less impurities.

[0035] The second filter 8 has a main surface oriented at an angle to the horizontal (Figs. 1-3). The outlet 6 is located at least near the relatively lowest point or edge of the second filter. This causes the blood to flow through the surface of the second filter 8 towards the outlet 6 under the influence of gravity.

[0036] The partition 9 is arranged at an angle to the horizontal and is provided with three holes near its bottom side (Fig. 2). Thus, the septum 9 serves to direct the blood to the relatively high sides of the second filter 8 to utilize the maximum long filtering path.

[0037] The overall selectivity of the second filter 8 is determined by its pore size, and the effectively filtered size is determined to some extent by the filtration time.

[0038] The duration of the second filtering step is mainly determined by the blood flow velocity over the surface of a given filter size. The flow velocity is determined, among others by a combination of filter angle relative to level, blood viscosity and roughness or smoothness of the upper surface of the filter 8. The filtering time can be adjusted by opening or closing the valve 6A.

[0039] A suitable filter may have an upper surface that is, apart from the pores, substantially smooth on a micron scale, preferably on a sub-micron scale, e.g. such that the surface has a shiny appearance. The filter may have a hard surface or may be a woven mesh filter with smooth fibers, for example of the type used to filter beer. Such a smooth filter surface does not appear to substantially damage red blood cells and

Reduce the likelihood of mixing and retaining red blood cells in the filtered material.

[0040] An angle of orientation of the main surface of the second filter 8 relative to the level greater than about 15 degrees usually does not provide sufficient filtration with such a smooth filter, because then the blood flows down to the outlet 6 substantially without filtration.

An angle of about 6 ° ensures proper filtration of contaminants, but may leave fluid such as a washing or irrigation fluid in the residue. An angle of about 3 degrees (Figs. 1-3) ensures effective filtration of both impurities and liquids. [0041] To direct the filtered blood more efficiently through the second filter 8 to the outlet 6, the upper surface of the filter (relative to flow) is provided with guiding elements, such as folds or sidewalls, which are applied to or extend from the main surface as indicated more clearly in Fig. 3. Similarly, the filter surface may be provided with structures for distributing the filtered blood more evenly over the filter surface, if desired.

[0042] The second filter 8 may also have a conical shape or generally a convex shape (not shown). The inclined intersection (shape) of the second filter 8 with the wall of the housing 2 may form a channel directing red blood cells to the outlet 6. The partition 9 may be shaped so as to supply blood to the top or top of the second filter 8. Similar to a concave filter, the top angle of the conical second filter may be in the order of about 3 to 15 degrees, while the spherical filter may range from substantially flat to approximately hemispherical. The channel along the intersection can be tilted horizontally at an angle of up to about 15 degrees, e.g. 6 degrees or 3 degrees, for efficient filtering and guiding the blood cells to the outlet.

[0043] The washing fluid, e.g. saline solution or Ringer's solution with a high dose of anticoagulant drug such as heparin, may be introduced into the subject device for flushing filters 7, 8 and / or intermediate septum 9, and / or to assist in the collection of blood cells during the bottom of the second filter 8.

[0044] Blood and flushing fluid can be introduced into the filtration device 1 relatively close to the center of the first filter 7. This arrangement causes fluids

They rinse and clean the first filter 7 to reduce clogging and to recover as much red blood cells as possible.

[0045] When a washing fluid is used, some of it may collect in the blood reservoir and not be filtered. However, with the right choice of washing fluid, e.g. saline or Ringer's solution, it does not substantially affect the quality of the red blood cells.

[0046] Figs. 4 and 5 show orthogonal cross-sections to each other of another embodiment of the blood filtration device. Figures 6 and 7 show the embodiments of Figure 4.

[0047] In these and subsequent figures, parts having the same or equivalent functions as the parts in the previously discussed embodiment have the same reference numerals.

[0048] In Figs. 4-7, the housing 2 is provided with a bypass duct 2A, which has been shaped here as a bulge in the wall of the housing 2 (apparently shown in Fig. 5), but which can also be shaped as a separate conduit, such as a pipe or a hose, possibly with a valve. The filtration device 1 is furthermore equipped with an additional closed connection 4A for one or more sources of washing liquid, with a piston 12 having a piston head 12A and a closed outlet 13 for the filtrate from the second filter 8. The partition 9 can provide a single outlet in the bypass channel 2A so that fluid, flowing over the septum 9, bypasses the piston head 12A as indicated in Fig. 5.

[0049] The piston head 12A fits inside the housing wall 2 (for clarity, the wall 2 and the piston head 12A are drawn as separated in Fig. 5).

The piston may be provided with a flexible or resilient skirt to fit the piston head 12A tightly and provide a substantially fluid tight seal. In the embodiment shown in Figs. 6 and 7, the piston head 12A is shaped essentially to fit the top surface of the second filter

8. In the embodiment shown in Figs. 4-6 (7), the piston 12 projects through the opening in the first (second) filter. The edge of this opening may be provided with an upwardly projecting rim to prevent leakage or overflow of blood through the filter surface.

[0050] After pressing or pulling (Fig. 7) the piston downwards beyond the outlet of the bypass channel 2A, the piston head 12A will adhere to the housing wall along the entire perimeter, and thus will essentially close the lower housing.

Any, possibly all, openings leading outside or inside the housing 2, in particular below (relative to the flow) of the piston head 12A, can be closed to shut off the internal volume of the housing 2, thereby allowing fluid pressure to be applied by the piston. Thus, the piston 12 is adapted to apply fluid and mechanical pressure to the filtrate from the first filtering step, and is thus adapted to apply or increase the filtering pressure on the second filter 8. Thus, the second filtering step can be assisted. The second filtering stage can be carried out with or without additional vacuum suction via connection 5.

[0051] The piston 12 can be driven by any hydraulic, pneumatic or mechanical means. A manual drive is also possible. The piston can also be integrated into the septum 9 (not shown). [0052] For washing the filtrate of the first filter from the partition 9 and / or for additional washing (compressed) filtrate, washing liquid can be added from connections 4 and / or 4A. The filtrate from the second filter 8 can be taken out through the outlet 13, which can be assisted by equipping the housing 2 with a sloping bottom.

[0053] In the embodiments shown in Figs. 8-10, a piston 14 is provided, whose head 14A is equipped with filter material so that it acts as a second filter.

[0054] In the embodiment of Fig. 8, the filtration device 1 is equipped with an additional upper surface 15, a lower surface 16 and an additional connection

17. The upper surface 15 can form part of the partition 9, e.g. its bottom. The bottom surface 16 can be the bottom of the filter housing 2. Alternatively, the bottom surface 16 is the second filter 8.

[0055] In the embodiment shown in Fig. 8, the filtrate from the first filter 7 may be provided on top of the filter head 14A of the piston. In this case, filtration takes place as described above, now through the filter head 14A of the piston instead of the filter 8. The piston 14 can be pressed up to the surface 15 for

By increasing the filter pressure on the second filter, i.e. on the filter head 14A of the piston. Retained blood cells can be recovered through holes 6 or 17.

[0056] Alternatively, the filtrate from the first filter may be fed next to the head

14A of the piston on the lower surface 16. The piston 14 can be forced downwardly to apply pressure to the filtrate from the first filter 7 on the surface 16 and to pass fine particles through it. This process can be repeated with and / or assisted by relatively large amounts of washing fluid and / or a substantially one-way filtration process, for example by choosing a suitable, e.g. polar, filtering material. In this process, the filtration flow in the second stage takes place upwards. Retained blood cells located under a second filter located in the piston head 14A, but effectively upstream of the flow, can be recovered through outlet 6.

[0057] In the case where the second filter 8 is the bottom surface 16, the filtrate can be pressed between the two filters 8 and 14A, which increases the filtering surface. Thus, the washing and filtration efficiency of the subject device can be further increased. Then the vacuum connection 5 can be placed downstream of the second filter 8. The device 1 may also include a plurality of vacuum connectors, which allows the configuration of the device 1 to be optimized for a particular method of use.

[0058] The embodiment of Fig. 9 is a simplified embodiment of Fig. 8 in which the surface 15 is missing and the surface 16 is the bottom of the housing 2. The piston 14 is oriented upwards. This embodiment is suitable for the second mode of operation described for Fig. 8.

[0059] In the embodiment shown in Fig 10, the partition 9 has been provided with hinge means 18, e.g. a flexible part or hinge, so that the partition 9 can be closed and the flow of filtrate from the first filter 7 to the second filter can be stopped. At the same time, the baffle 9 can serve as a surface against which the piston 14 can be pressed to increase the filter pressure on the filter head 14A of the piston. FIG. 11A and 11B show the first filter 7 and the second filter 8, respectively, made as separate devices 19 and 20, respectively, i.e. both filters have been provided with separate housings 2. Both filter devices 19 and 20 are equipped with individual vacuum

Connections 5. The first filter device 19 includes an outlet connection 21 for the filtrate. A different outlet connection (not shown) may be provided for the residue from the first filter 7. The outlet connection 21 may be connected directly or indirectly, e.g. by means of a hose, pipe or other type of wire, to the inlet opening 3 of the second filtering device 20 to complete the device for blood filtration.

[0060] The individual housings 2 allow providing one or more valves between devices 19 and 20, and may allow a higher vacuum to facilitate the second filtering step, the wound site being not exposed to a higher vacuum. The pressure difference on the second filter can be increased just below the damaging red blood cells, which is believed to occur at about -5000 mm Hg (-667 kPa), with possible dependence on the filter material. Enclosures 2 do not have to be permanently connected and can be stand-alone devices.

[0061] Using separate housings 2, a piston assembly such as in Fig. 410 can be provided in one or both housings 2. For example, Fig. 12 shows a possible piston assembly for the first filter 7. In Fig. 12 the first filtering the device 19 is equipped with a piston 22 with a shaped piston head 22A. The piston head is equipped with one or more valves 23 enabling the flow of blood and flushing fluid through the piston head 22A and allowing it to be easily lifted. When lowering the piston 22, the valves 23 are pressed into the closed position, allowing the pressure on the filter 7 to increase. Instead of the valves 23, the piston head 22A may be equipped with one or more flexible membranes and / or with a flexible skirt or curtain around its circumference (or parts of it).

[0062] One or more pistons (12, 14, 22) may be used to provide a reduction in pressure suction for the upper (relative to the flow) portion of the device, potentially bypassing other sources of vacuum.

[0063] It is believed, without reference to any particular theory, that lowering the temperature reduces the ability and / or likelihood of elastic deformation of red blood cells and their passage through openings smaller than the diameter of red blood cells at rest, and may even prevent the passage of red blood cells through slightly larger openings from their diameter.

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The natural reduction in temperature from body temperature to room ambient temperature, i.e. from about 37 degrees Celsius to about 20 degrees Celsius, already causes a significant increase in filter performance because fewer blood cells pass through it.

[0064] The filtration device of the present invention may be used for several hours during which filtered blood may be left in the device on a second filter, or blood may be collected in a blood vessel.

[0065] The residue from the second filter, including the recovered blood cells, may also include white blood cells or leukocytes having the same dimensions as the red blood cells. These leukocytes should preferably be removed before reintroducing blood into the bloodstream, which can be efficiently achieved by passing autologous blood through a commercial leukocyte filter (Pall filter). [0066] Due to its relative simplicity and also because no complicated additional devices such as pumps are needed for the operation of the filtration device in question, this device can be manufactured and / or used relatively cost-effectively. This makes the filtration device well suited for use in poorer and / or less developed countries, where the risk of infection or disease, especially AIDS, during homologous blood transfusions is much higher than in highly developed countries.

[0067] The present invention is not limited to the above-described embodiments, which can be differentiated in a number of ways within the scope of the claims. For example, additional filters or devices for recovering other blood products, such as intact platelets or blood plasma, from the filtrate from the second filter may be used or added. As with the first and second filters, additional filters or devices can also be implemented in separate housings.

[0068] In addition, one or more filters may be made of a filter material that not only functions as a size sieve, but also provides a filtering effect based on biophysical or biochemical properties, such as (a) the polarity of the filtered or retained particles.

[0069] In addition, the guiding function of the partitions can also be performed by means of a funnel, a cable or by a general suitable housing design

2, e.g. by providing it with a sloping side and placing the first filter 7 and the second filter 8 spaced apart.

[0070] The operation of the piston to apply mechanical and / or fluid pressure on the filtered substance to increase the filtering pressure can also be replaced by the action of a rotary screw compressing the fluid between the screw blade and the filter by providing the housing 2 with a deformable part, such as a bellows, equipment the device in question with a flexible membrane, etc. In addition, the piston head need not be connected to the piston rod, but may be a separate device within the housing, e.g. an electromagnetically displaced disc.

[0071] In the case of sufficiently high filtration efficiency, e.g. due to filter pore size, vacuum or mechanical pressure, a filter angle greater than 15 degrees relative to the level can be selected for faster discharge of the residue to the outlet.

[0072] Furthermore, the details and / or elements shown with respect to one embodiment may be combined with those of other embodiments to provide further modification of the blood filtration device, kit and / or assembly within the scope of the appended claims.

[0073] Unless explicitly stated otherwise or clearly from the text, references to directions such as "up" or "down" refer to such orientations of the embodiments as shown in the figures, and are only given for clarification. Such references should not be construed literally or as restrictions.

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