SUSPENSION CLEANING

Abstract

A method of cleaning a contaminated surface, such as cleaning the elongate interior lumen of an endoscope contaminated with flesh, bone, blood, mucous, faeces or biofilm, said method comprising the steps of: providing a suspension of solid particles in a liquid to said contaminated surface, and flowing said suspension along said surface thereby to remove contaminant from the surface. The suspension is preferably a paste, where the solid material may be e.g. crystals of a salt, silicon oxide or organic material. The paste preferably has a solid fraction between 5 and 55%. A rheology modifier may be present.

Claims

1-37. (canceled)

38. A method of cleaning an interior surface of an elongate lumen, comprising: providing a suspension of solid particles in a liquid; and iteratively pulsing the suspension of solid particles in the liquid through the elongate lumen to remove contaminants from the interior surface.

39. The method of claim 38, wherein the elongate lumen is at least one of an air or water channel of an endoscope.

40. The method of claim 38, further comprising: after iteratively pulsing the suspension of solid particles in the liquid through the elongate lumen, flowing a liquid without any portion of the suspension of solid particles in the liquid through the elongate lumen to rinse the interior surface.

41. The method of claim 38, wherein the solid particles are salt crystals.

42. The method of claim 41, wherein the salt crystals are crystals of sodium bicarbonate, potassium bicarbonate, sodium phosphate, potassium phosphate, sodium nitrate, potassium nitrate, sodium benzoate, potassium benzoate, borax, calcium carbonate or mixtures thereof.

43. The method of claim 38, wherein the solid particles are particles of water insoluble material.

44. The method of claim 38, wherein the liquid is selected from a group consisting of a saturated solution of a salt, a water/alcohol mixture, a water glycol mixture, and a water glycerol mixture.

45. The method of claim 38, wherein iteratively pulsing the suspension of solid particles in the liquid through the elongate lumen comprises: providing a portion of the solid particles in the liquid from a cartridge; and applying at least one flow of fluid to accelerate the portion of the suspension of solid particles into the elongate lumen.

46. The method of claim 45, wherein applying the at least one flow of fluid comprises: applying a first flow of fluid and a second flow of fluid.

47. The method of claim 38, further comprising: mixing the solid particles with the liquid in a cartridge.

48. The method of claim 47, further comprising: drawing a portion of the solid particles in the liquid from a cartridge.

49. The method of claim 38, wherein iteratively pulsing the suspension of solid particles in the liquid through the elongate lumen comprises: pumping a portion of the solid particles in the liquid from a cartridge.

50. A method of cleaning an interior surface of an elongate lumen, comprising: providing a suspension of solid particles in a liquid; flowing a plurality of portions of a suspension of solid particles in a liquid through the elongate lumen; and interspersing one or more fluid only flows between at least two portions of the suspension of solid particles in the liquid.

51. The method of claim 50, further comprising: after flowing a plurality of portions of a suspension of solid particles in a liquid through the elongate lumen, flowing a liquid without any portion of the suspension of solid particles in the liquid through the elongate lumen to rinse the interior surface.

52. The method of claim 50, wherein the solid particles are salt crystals.

53. The method of claim 52, wherein the salt crystals are crystals of sodium bicarbonate.

54. The method of claim 50, wherein interspersing one or more fluid only flows between at least two portions of the suspension of solid particles in the liquid comprises: interspersing one or more liquid only flows between at least two portions of the suspension of solid particles in the liquid.

55. The method of claim 50, wherein interspersing one or more fluid only flows between at least two portions of the suspension of solid particles in the liquid comprises: interspersing one or more gas only flows between at least two portions of the suspension of solid particles in the liquid.

56. The method of claim 50, wherein interspersing one or more fluid only flows between at least two portions of the suspension of solid particles in the liquid comprises: interspersing one or more mixed gas and liquid flows between at least two portions of the suspension of solid particles in the liquid.

57. The method of claim 50, wherein flowing a plurality of portions of a suspension of solid particles in a liquid through the elongate lumen comprises: separately drawing each of the plurality of portions of the solid particles in the liquid from a cartridge.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] FIG. 1 shows a suspension or paste cleaning prototype.

[0050] FIG. 2 shows an alternate suspension or paste cleaning prototype.

[0051] FIG. 3 is shows an arrangement used to produce standardised biofilm deposits in a lumen.

DESCRIPTION OF THE INVENTION

[0052] The present invention in it broadest form relates to passing a suspension of solid particles in a liquid through the lumen of an endoscope for the purposes of mechanically cleaning the endoscope channel of bioburden, which includes residual tissue such as flesh, bone, blood, mucous and faeces remaining after diagnostic or surgical procedures. The present invention also relates to the use of suspensions to remove biofilm.

[0053] The invention will be described with reference to the use of a flowable, conveyable paste for lumen cleaning. Based on the teaching of the present invention it will be understood by those skilled in the art of that the invention may be embodied in other forms and may utilise other liquids and other particles in the cleaning of endoscope lumens and other instruments without departing from the concepts herein described.

[0054] For instance, the methods of the present invention are useful in cleaning other lines susceptible to contamination. Particularly, the methods of the present invention are useful in cleaning water lines, such as those used in the food, beverage, manufacturing or airconditioning industries. Such lines are very susceptible to biofilm contamination.

[0055] In an embodiment the suspension comprises solid particles in a carrier fluid in the form of a paste. The carrier fluid is selected to not dissolve, or to only provide minimal dissolution, of the solid particles, and to provide a suitably stable suspension of the solid particles. Suitable carrier fluids include water/alcohol mixtures, water glycol mixtures or water glycerol mixtures. If the solid particles are a water-soluble salt, then a saturated aqueous solution of the water-soluble salt can be used as a carrier.

[0056] The invention using pastes is described with reference to specific examples, however, it will be appreciated by those skilled in the art that the process is, in very large part, a physical process rather than a chemical process, so the exact chemical nature of the components is not critical, but rather, the resultant physical properties of the mixture that arise from the interrelationship of the components. The physical properties of the mixture that are believed to give rise to the desirable cleaning effect include: the paste yield stress; the viscosity in the range of shear rates that are present when cleaning; if viscoelastic properties are present, then by how much; the rate of any shear thinning or thickening properties.

[0057] The nature of the particles, including crystal size and morphology, have also been shown to contribute to the cleaning effect.

[0058] The solid particles may be for example salt crystals. Suitable types of salt crystals include, but are not limited to, sodium bicarbonate, potassium bicarbonate, sodium phosphate, potassium phosphate, sodium nitrate, potassium nitrate, sodium benzoate, potassium benzoate, borax, calcium carbonate or mixtures thereof.

[0059] Again, the density, size and morphology of the salt crystals can be selected for optimal cleaning.

[0060] The invention will be described with reference to the conveyable paste being conveyed by pumping (i.e pushed) but a conveyable paste may equally be conveyed by way of reduced pressure or suction (i.e. pulled).

[0061] Preliminary studies indicate that particles that are too large are difficult to pump and do not provide sufficient granularity to evenly scour the entire tube wall, whereas particles that are too small tend to exhibit more fluid like properties, rather than the necessary solid abrasion required. Particles will ideally be within the range of 1 to 250 microns, and more particularly, 10 to 50 microns.

[0062] In addition to salts, other particles, such as hard plastic objects, silica, ceramics etc can be used as the suspended solid, although caution needs to be exercised as the use of excessively hard particles may damage the endoscope lumen.

[0063] When a paste is used, the solid fraction is between 30 and 70% w/w, more particularly between 30 and 50% w/w and even more particularly between 40 and 50% w/w.

[0064] The paste needs to be flowable and it is desirable to have a viscosity that allows good flowability in combination with suitable abrasive properties. 50,000 to 100,000 cP (centipoise) at ambient temperatures (similar to toothpaste) is a suitable viscosity. If necessary, rheology modifiers, such as polyvinyl alcohol, polymers or gums can be added to change the rheological profile of the paste, such as by increasing viscosity, and assist in the formation of a stable system.

[0065] One particularly useful paste has been found to be that made from ⅓ sodium benzoate, ⅓ sodium bicarbonate and ⅓ water by weight. Sodium benzoate has a solubility of around 50 g/100 mL in water and sodium bicarbonate has around 6.9 g/100 mL. The water thus becomes a saturated salt solution as carrier fluid. A significant residual solid component of each of the bicarbonate and benzoate crystals remains present to produce a suitable paste.

[0066] In one embodiment, the paste is premixed and provided contained in a cartridge. The cartridge containing the premixed paste is placed in line with the endoscope lumen and simply pumped through the lumen under pressure. This embodiment is shown in FIG. 2.

[0067] The embodiment in FIG. 2 shows apparatus which contains two separate cartridges, a thick (relatively viscous) paste cartridge, 101 and a thin (relatively non-viscous) paste cartridge 102. The paste is forced from the cartridges by engagement with plungers or similar driven by respective linear drives 103 and 104. Paste from each cartridge flows under pressure down line 105 and 106 respectively, to valve 107. Valve 107 allows for the selection and/or mixing of the thick paste from 101 or the thin paste from 102 as desired.

[0068] The selected paste or selected paste mixture flows down line 108 to valve 109 and through line 110, where the pressure is sensed by pressure sensor 111. The pressure sensor ensures that the paste flows at an optimal speed, i.e., as fast as practicable without approaching too closely the pressure limit of the endoscope lumen. The pressure sensor can be connected to a feedback or control mechanism to shut off the linear drives should the pressure begin to approach levels that may damage the endoscope.

[0069] The valves 112 and 113 can be maintained in configurations as to control the flow of the paste through the various channels 114, 115 and 116 (suction/biopsy, air/water, forward water jet etc) of the endoscope as desired.

[0070] The apparatus in disclosed FIG. 2 is also configured to provide a wash with water, an enzyme cleaner or other detergent after the physical clean of the paste has been completed. When the paste cleaning is finished, valve 109 is closed to the flow of any paste or paste mixture, but is opened to be in fluid communication with valve 118. Valve 118 is in turn in fluid communication with diaphragm pump 119 which, pumps a ready to use aqueous solution of enzyme from tank 120 along the lines to endoscope channels 114, 115 and/or 116 as desired. The pressure sensor 111 in this case can be used to ensure the aqueous enzyme solution is not pumped through the endoscope channels at excessive pressures.

[0071] The paste flows down the desired lumen channels of the endoscope and may be discharged via an exit line into a drain.

[0072] The concentration of enzyme solution in tank 120 can be regulated by controlling the addition of enzyme from enzyme concentrate reservoir 121 by peristaltic pump 122 and water, through water inlet 117. The temperature of the enzyme system can be independently optimised by the inclusion of a heating circuit that includes the tank 120 and an-in line heater 123. The aqueous enzyme solution can be cycled through the heater until the desired temperature in tank 120 is achieved. A thermocouple 124 ensures that the ready to use enzyme cleaner in tank 120 is maintained at optimal active temperature before use. Float switch 125 ensures the liquid level in the reservoir tank is maintained within the proper operational limits.

[0073] The aqueous enzyme solution passes through the channels of the endoscope and may be discharged via an exit line into a drain.

[0074] It will also be seen that by selection of the various valve positions that water from inlet 117 can be passed via line 110, where it can be used at a measure pressure to rinse residual cleaning paste or aqueous enzyme.

[0075] The paste is pumped down the lumens at the maximum pressure permissible by the endoscope manufacturer. A typical maximum allowable air or water pressure for aerating or irrigating endoscope channels is 0.5 MPa (5 kgf/cm.sup.2, 71 psig). At this pressure, the flow rate for the paste is less than 10 cm/s, which is considerably less than the flow rate of water used to flush the channel.

[0076] After passing through the lumen, the paste is discharged into a drain along with the dislodged contaminants. The paste can be further diluted with water to remove soluble components and allow any insoluble or precipitated components to be isolated, for example, by filtration or centrifugation, which can also allow capture of removed residual material dislodged from the lumen. The residual material can be removed and treated as biological waste. The other residues can be further sterilised if desired and discharged as necessary.

[0077] In one embodiment, the paste may be made to flow in a single direction at a constant rate. Alternatively, the flow may be pulsed, that is, the paste moves, rests for a period and then continues to move in the same direction, with that being repeated. Alternatively, in another embodiment, the flow of the paste at times is intermittently reversed, creating a back and forth scrubbing motion of the solid particles which aids in removing any residual bioburden or biofilm that may have been flattened in a particular direction by the flow of the paste in the primary direction (from the reservoir towards the discharge point of the endoscope). In yet a further embodiment, the flow may be fed through the endoscope in a manner interspersed with one or more other liquid, gas or paste flows. For instance, a chemical clean may be included between paste flow phases to assist in the removal of residues.

[0078] The paste is passed through the endoscope for a suitable time to remove the biological material, depending upon the initial level of contamination and the construction of the endoscope. Once the paste cleaning has finished, the lumen of the endoscope can be flushed with water and air dried, or dried in any other suitable manner.

[0079] The paste may also contain chemicals to alter its characteristics. For example, non-solvents for the salt, such as alcohols and glycols may be used. Other agents, such as surfactants, disinfectants, residual treatments etc may also be added to the paste for beneficial effect. If used, these can be added through either tank 2 or 20, or via another tank directly into the mixing ratio valve 24.

[0080] Of course, in the present invention, slurries of insoluble materials, such as polymer or silaceous particles may be used. Although these would be expected to show similar beneficial effects, they do suffer from the drawback that the solids cannot be readily dissolved, a factor which in the case of the present invention assists greatly in their removal in subsequent rinsing, disinfection and drying steps, as well as facilitating their disposal.

Experimental

[0081] 1. Test Soils and Contaminants

[0082] The removal of bioburden from endoscope lumens was modelled using a variety of standard and customised test soils applied to the inner surfaces of teflon or other suitable tubing in order to mimic the inner lumens of endoscopes. The soils were pumped into the tube or manually applied to the inner surfaces of the tubes and allowed to dry or bake onto the surface as required. In addition to modelling soils, the present inventors also employed standardised protocols for biofilm for testing and residual protein.

[0083] The procedures for soil preparation, as well as the fixed protein and biofilm contaminations are as follows:

[0084] A. Soil 5B (Pumped Soil)

[0085] Soil 5B is a standardised pumped test soil for use in experiments in the cleaning of medical devices.

[0086] Ingredients:

[0087] 3 g hog mucin

[0088] 5 ml horse blood

[0089] 1.5 ml deionised water

[0090] 50 ml egg yolk

[0091] 3.0 g of mucin was mixed with 5 mL of horse blood and stirred until smooth, 1.5 mL of deionised water was added and the mixture again fully stirred. 5×10 mL batches of egg yolk were added to the mixture while stirring. The mixture was stored in a cool dry environment in a closed container.

[0092] Teflon tubes (ID 4.25 mm, OD 5.1 mm, 10 cm long) were inoculated by pumping the soil into the tube with a syringe, holding the soil in position for 5 seconds and then pumping the soil back into the syringe.

[0093] The inoculated tubes were fixed in place inside a small container. The container was then placed on top of a rotational mixing apparatus situated inside an incubator. The tubes were rotated at medium speed in the incubator for 30 minutes at 40° C. The tubes were then connected to a 4-port air pump machine (eight tubes at a time via four T-Pieces) within the 40° C. incubator. The tubes were held in the incubator for a further 15 minutes at low airflow. Any tubes that leaked during the airflow stage were discarded. The tubes were stored in a cool dry environment.

[0094] B. Soil 5D (Brushed Soil)

[0095] Soil 5D is a standardised brushed test soil for use in experiments in the cleaning of medical devices.

[0096] Ingredients:

[0097] 3 g hog mucin

[0098] 5 ml horse blood

[0099] 1.5 ml deionised water

[0100] 50 ml egg yolk

[0101] 3.0 g of mucin was mixed with 5 mL of horse blood and stirred until smooth, 1.5 mL of deionised water was added and the mixture again fully stirred. 5×10 mL batches of egg yolk were added to the mixture while stirring. The mixture was stored in a cool dry environment in a closed container.

[0102] Teflon tubes (ID 4.25 mm, OD 5.1 mm, 10 cm long) were inoculated one at a time. A small brush was dipped into the soil and then passed through the inside of the tube several times from each direction until an even coating is achieved. The brush was removed along with any soil that builds up around the ends of the tube and any that is on the exterior of the tube.

[0103] For the purposes of the present invention, soil was applied to attain a target weight of between 0.0685 g and 0.0925 g.

[0104] The inoculated tubes were placed in an incubating oven for 5 minutes at 40° C. Advantageously, the tubes were used immediately. If necessary, the tubes could be stored during down time in testing in a zip-lock bag with as much air removed as possible.

[0105] C. ATS2015

[0106] ATS2015 is a commercially available artificial test soil used as to model, available from Healthmark Industries Co. It contains haemoglobin, protein, carbohydrate lipids and insoluble fibres and is used as a standardized test soil in proportion found on clinically used medical devices, including specifically flexible endoscopes.

[0107] Ingredients:

[0108] ATS2015 dry powder—0.0905 g per mL final volume

[0109] Defibrinated blood (sheep)—0.2 mL per mL final volume

[0110] Sterile water—1 mL per mL final volume

[0111] Water was added to the ATS 2015 dry powder and vortexed/shaken for 10 minutes or until completely mixed. The foam was allowed to settle for 20 minutes. The blood was added and mixed gently.

[0112] When preparing ATS2015 soil for biological testing, a microbe containing suspension was added after the dry powder had been dissolved. The amount of water used to introduce the microbe suspension was noted in advance, so the final volume of sterile water was still only 1 mL

[0113] The reconstituted mixture could be satisfactorily stored in an air-tight container at 2-5° C., away from light and heat for up to two weeks.

[0114] Soil was pumped into Teflon tubes (ID 4.25 mm, OD 5.1 mm, 10 cm long) using a syringe. The tube was completely filled soil. The tubes were held vertically to allow draining, with a small volume of air applied to the top of the syringe at the completion of the draining process. The inoculated tubes were allowed to dry on a bench at room temperature (15-25° C.) for 1 hour. Cleaning tests were conducted within 1 hour of preparation.

[0115] D. Black Soil

[0116] Black soil is a standard test soil described in ISO/TS 15883-5:2005(E) useful in experiments relating to the cleaning of medical devices.

[0117] Ingredients:

[0118] 30 g unbleached plain wheat flour

[0119] 15 g water soluble wallpaper adhesive powder

[0120] 1 hens egg (60-65 g)

[0121] 10 ml black ink (water tolerant/permanent, Indian ink)

[0122] 240 ml water

[0123] The ingredients above were mixed together to form a uniform thick paste. The paste could be used immediately or stored in an air-tight container at 2-5° C. for up to one month.

[0124] Black soil at room temperature was pumped into Teflon tubes (ID 4.25 mm, OD 5.1 mm, 10 cm long) via a syringe. The syringe plunger was rapidly withdrawn to extract excess soil such that there was a thick, uniform coating of soil on the inside of the lumen with an unbroken air-path from one end of the tube to the other. Unsuitable tubes were refilled or discarded. The inoculated tubes were allowed to dry on a bench at room temperature (15-25° C.) for 30-35 minutes and used within a subsequent 30 minute period.

[0125] E. Edinburgh Soil

[0126] Edinburgh soil is a standard test soil described in ISO/TS 15883-5:2005(E) for use in experiments in the cleaning of medical devices.

[0127] Ingredients:

[0128] 100 ml fresh egg yolk

[0129] 10 ml defibrinated blood (horse or sheep)

[0130] 2 g dehydrated hog mucin

[0131] The above ingredients were mixed together to give a liquid of uniform consistency. The liquid was used immediately or stored in an air-tight container at 2-5° C. for up to a week.

[0132] Soil at room temperature was pumped into Teflon tubes (ID 4.25 mm, OD 5.1 mm, 10 cm long) via a syringe. The tubes were held vertically to allow excess soil to drain. The last traces of bulk soil were removed using a syringe to push a small amount of air through the tube. The inoculated tubes were allowed to dry on a bench at room temperature (15-25° C.) for between 30 and 120 minutes.

[0133] F. Fixed Protein

[0134] Ingredients:

[0135] 1% glutaraldehyde

[0136] 1% horse serum

[0137] Equipment:

[0138] 1% horse serum was pumped through a Teflon tubes (ID 4.25 mm, OD 5.1 mm). The volume used was 2×tube volumes. After 20 minutes, 2×tube volumes of 1% glutaraldehyde was pumped through the tube. After 10 minutes, the process was repeated. Altogether, there were five cycles of horse serum followed by five cycles of glutaraldehyde. The tube was then washed with 10 tube volumes.

[0139] The tube was stained for protein as disclosed below, and could be cut into 10 cm lengths.

[0140] G. Biofilm

[0141] This procedure outlines the preparation and growth of biofilm of Pseudomonas aeruginosa ATCC15442 in tubes for use in experiments in the cleaning of medical devices.

[0142] Pseudomonas aeruginosa ATCC15442 culture was grown overnight in Synthetic Broth+Glucose (5 mL) at 37° C. The microbial inoculant concentration was determined by % transmission by spectrophotometry at 580 nm wavelength. The level of inoculum was also determined by historical data.

[0143] All apparatus were sterilised before use and the conditions used were aseptic. Teflon tubes (ID 4.25 mm, OD 5.1 mm, up to 5 metres long) used for inoculation were sterilized in an autoclave.

[0144] 5% TSB (tryptic soy broth, equates to 50 mL/L) in 1 L of sterile distilled water was inoculated with ˜0.2% of P. aeruginosa isolated culture. The exact volume of microorganism added was dependent on the % Transmission). The inoculated growth medium was placed into a 1 L Schott bottle, which was stirred.

[0145] The setup, which shows the water cycling in the closed system immersed in the waterbath, is shown in FIG. 3

[0146] The inoculated media 200 was then pumped via pump 201 at the lowest available flow setting (˜5 L/min) such that the growth media was transferred from the Schott flask 202, through teflon tube 203 to be inoculated and then back into the Schott flask. The Schott flask 202 and teflon tube 203 were immersed in a water bath 204 at 30° C., such that the inoculated grown medium was contained below the level of the water bath and always maintained at 30° C. by heater 205. The apparatus was checked to ensure that there were no bubbles in the teflon tubing and that the inoculated grown medium was in contact with every part of the internal of the tube as it flowed through.

[0147] Growth Cycle:

[0148] After 48 hours, the pump was stopped and the growth medium was allowed to empty from the tube at a slow rate. The growth medium was replaced, the tube refilled and the pump restarted

[0149] After a further 72 hours, the tube was again drained and the growth medium replaced. The pump was restarted and allowed to run for a further 48 hours, after which the tubing was removed and drained and was ready for testing. The inoculated tubing could be stored overnight at ˜4° C. The tubing could be cut to desired lengths and tested.

[0150] 2. BioBurden Test Protocols

[0151] Testing for the presence of residual bioburden in the enclosed parts of medical instruments is challenging. In consequence, there is little available in the way of established protocols for assessing either the quantity or the activity of biological residue. The Applicant has developed the following tests which enable rapid and reproducible quantification of biological residues.

[0152] 2.1. Procedure for Determination of Cleaning Efficacy by Weight.

[0153] The following procedure is used on each sample, with at least 2 replicates: [0154] Step 1. The unsoiled item is weighed.

[0155] Step 2. Test soil is applied to the item.

[0156] Step 3. The soiled item is weighed. Items with more than ±10% deviation from mean mass were not used for testing but retained for % dried calculation. At least one soiled item was retained as a standard for % dried calculation.

[0157] Step 4. The cleaning experiment on the item was conducted. After cleaning, the item was allowed item to drain

[0158] Step 5. Cleaned tubes and soiled standards were placed in a container containing dry silica in an oven at 56° C.

[0159] Step 6. The dried item was weighed after 1 day.

[0160] Step 7. The dried item was weighed after 3-5 days. Weighing was repeated until dried items attained a constant weight. (Drying time depends on the amount and distribution of soil in the item, the extent of moisture present and the air accessibility of the soil).

[0161] Step 8. The mass of soil removed by cleaning was obtained by the following formulae:

[0162] The mass removed by drying, per unit-mass of initial soil, from the drying control tubes was calculated by the following equation and their average determined:

DryCal=M.sub.init soil/(M.sub.tube dry−M.sub.tube unsoiled)

Where: M.sub.init soil=(M.sub.tube soiled−M.sub.tube unsoiled)

[0163] The percentage of soil removed is then calculated by the following equation:

M.sub.soil removed=(M.sub.init soil−((M.sub.tube dry−M.sub.tube unsoiled)*DryCal.sub.ave))/M.sub.init soil

[0164] 2.2 Procedure for Protein Staining of Lumens

[0165] The following procedure was used to stain protein residues for visual inspection:

[0166] Ingredients:

[0167] 50% Methanol or EtOH

[0168] 10% Glacial acetic acid

[0169] 0.5% Coomassie G-250 (dehydrated)

[0170] 40% H.sub.2O

[0171] The above ingredients were combined and mixed well.

[0172] The stain was drawn into a syringe and filled into the tubes to be tested for residual protein. The tubes were then flushed with water until the solution colour exiting the tube was clear. Residual protein could be detected in the locations where the tube remained blue.

[0173] Uncontaminated tubing was subjected to the staining process and used as a control.

[0174] 3. Cleaning by Paste

[0175] A number of 1 mm PTFE lumens were contaminated with protein as per the protein contamination procedure disclosed above.

[0176] A variety of commercial paste cleaners were forced through the lumen with the aid of an electronic caulking gun. After cleaning, the lumens were rinsed and the interiors stained with Coomassie blue to determine the presence of residual protein.

[0177] Flowable commercial cream cleaners demonstrated qualitative efficacy in reducing the presence of material stained blue relative to control staining. Cleaners that were too viscous or tacky were not sufficiently pumpable through small lumens at pressures within the range tolerable for endoscopes.

[0178] Further experiments were conducted on different pastes to determine the effect of crystal morphology, carrier fluid properties (such as viscosity) and solid fraction (ratio of solids to liquid phase) rheology of the paste/slurry and importantly, the cleaning action achievable in narrow, elongate lumens. In order to allow for proper comparison cleaning pastes, and apparatus designed to provide a continuous, measured flow of paste was constructed based around an electric caulking gun.

[0179] The pastes were prepared according to the table below. The ingredients were added to paddle blender bags and mixed in a paddle blender until a homogeneous consistency was achieved.

[0180] The paste is then pumped through 10 cm lengths of teflon tube, ID 4.25 mm, OD 5.1 mm. As the paste exits the tube it is collected in a beaker and the mass recorded.

[0181] This process was done twice for each paste; once to determine the removal of Soil 5B and again to determine the removal of fixed protein.

[0182] 3.1 Soil Removal by Paste

[0183] After the passage of the paste through the 10 cm lengths of teflon tube, ID 4.25 mm, OD 5.1 mm, each tube was rinsed gently but thoroughly with water, with the aim of removing all the paste but not removing any further soil.

[0184] Once the cleaning process was carried out, each of the thus cleaned test lumens and the drying control lumens was dried over 48 hours at 56° C. and their weight recorded.

[0185] The mass removed by drying, per unit-mass of initial soil, from the drying control tubes is calculated by the following equation and their average determined:

Dry.sub.Cal=M.sub.init soil/(M.sub.tube dry−M.sub.tube unsoiled)

[0186] The percentage of soil removed is then calculated by the following equation:

M.sub.soil removed=(M.sub.init soil−((M.sub.tube dry−M.sub.tube unsoiled)*Dry.sub.calave))/M.sub.init soil

[0187] Microscope photographs were taken of samples of the pastes to gain information on the crystal sizes and shapes.

[0188] The results are summarised in the table below:

TABLE-US-00001 % Soil Removed Pumping (drying Protein Cleaning General No Paste Voltage (V) adjusted) Comment Comments 1 Borax 58.94% — Small spots of The paste was too Polyethylene Glycol blue left thick to be (300 Mw) 32.85% Brij35 pumped 2.46% Water 5.75% 2 Sodium Bicarbonate 6 36.7 Slight blue haze 69.33% Polyvinyl left Alcohol (90-100k Mw) 1.53% Water 29.14% 3 Sodium Bicarbonate 6 17.9 Small spots of Could have been 64.33% Polyethylene blue left pumped at a Glycol 35.67% faster rate 4 Sodium Bicarbonate 6 55.0 Little to no effect 59.28% Glycerol 40.72% 5 Sodium Bicarbonate 15 65.9 Almost no blue Almost too thick, 63.91% Glycerol 36.09% left nearly broke syringe 6 Sodium Bicarbonate 15 2.8 Little to no effect 64.15% Xanthan Gum 0.47% Water 35.38% 7 Jiff 15 20.9 First 3rd Cleaned, no effect after 8 Sodium Bicarbonate Far too fluid to do 64.27% Brij35 10.72% any cleaning Water 25.01% 9 Sodium Bicarbonate Far too fluid to do 58.84% Polyvinyl any cleaning Alcohol (90-100k Mw) 2.06% Water 39.10% 10 Aluminium Oxide 45% The paste was far Polyethylene Glycol too thick to be (300 Mw) 55% pumped 11 Calcium Carbonate 15 60.4 No noticeable 30.05% Glycerol cleaning 69.95% 12 Calcium Carbonate 15 42.0 No noticeable 36.38% Glycerol cleaning 63.62% 13 Calcium Carbonate 15 18.2 43.94% Polyethylene Glycol 56.06% 14 Calcium Carbonate 15 14.6 No noticeable 39.19% Polyethylene cleaning Glycol 60.81% 15 Calcium Carbonate 15 23.3 No noticeable 47.36% Polyvinyl cleaning Alcohol (90-100k Mw) 2.63% Water 50.01% 16 Calcium Carbonate 12 21.3 No noticeable 49.19% Polyvinyl cleaning Alcohol (90-100k Mw) 2.54% Water 48.27% 17 Calcium Carbonate 15 19.3 No noticeable 45.36% Xanthan Gum cleaning 0.54% Water 54.10% 18 Calcium Carbonate 15 42.2 A slight 49.78% Xanthan Gum cleaning effect 0.50% Water 49.72% 19 Sodium Bicarbonate 15 50.9 Almost perfect Looked like 40.59% Glycerol cleaning decent cleaning 59.41% for a relatively small paste volume 20 Calcium Carbonate 15 6.5 No noticeable Extremely thick 48.25% Water cleaning paste, syringe 51.75% plastic warped

[0189] The carrier fluid can make a large difference in the behaviour of the cleaning suspension or paste. An example of this is Paste No. 3 and No. 5 both contained similar percentages of Sodium Bicarbonate, only in different carrier fluids and No. 3 was extremely fluid whereas No. 5 was extremely thick and had the greatest cleaning efficacy by soil mass removed.

[0190] Under all conditions Aluminium Oxide appeared to be unsuitable. This is believed to be due to the extremely small particle size.

[0191] Similarly, commercially available borax was also unsuitable due to clogging. This is believed to be due to the relatively large crystal size, which and may be addressed by milling the borax down to a smaller crystal size before mixing up the slurry.

[0192] The results raise the possibility that the exact mechanism of cleaning for soil is different from that for removing fixed protein. Paste No. 3 removed only 17.0% soil by mass, however, that same paste was very effective, on visual inspection, in removal of the protein

[0193] Paste No. 11 produced the greatest result in terms of soil removal with 60% of the soil cleaned.

[0194] While Paste No. 19 removed only 50% of the soil it had a greater efficacy per gram of paste used (2.03% per gram)

[0195] Paste No. 19 also proved much better at cleaning fixed protein than Paste No. 11

[0196] Sodium Bicarbonate in Glycerol paste was particularly useful.

[0197] The differences between Paste No. 1 and Paste No. 19 are interesting as they have the same carrier fluid but different solid particles and while they both clean soiled tubes similarly, their efficacy when cleaning fixed protein is very different.

[0198] 3.2. Paste Cleaning-Initial Volume Testing

[0199] Initial testing has shown that a small volume of paste can clean a significant amount of soil 5B and also that using a larger volume increases the efficacy, with the potential to clean the tube entirely.

[0200] ID 4.25 mm, OD 5.1 mm ID PTFE tubing was contaminated with soil 5B as described above. Two specific pastes were prepared:

[0201] 1) Sodium bicarbonate (120.24 g)+Glycerol (80.86 g)=59.79% sodium bicarbonate % w/w. [0202] 2) Sodium Bicarbonate (128.56 g)+PEG 300 (71.93 g)=64.12% sodium bicarbonate % w/w.

[0203] These were pumped through the tubing at 15V. The amount of paste used was recorded.

[0204] The 59.79% sodium bicarbonate in glycerol created a significant amount of back pressure with this paste when a larger volume of was used. The soil initially appeared to be removed well, however as more paste went through the tube, less soil was removed, and the final portion of pumped paste did not appear to remove any soil additional soil.

[0205] 64.12% sodium bicarbonate in PEG was very smooth running. The initial portion of paste cleaned well but as with the paste above, the cleaning efficacy tailed off as more paste was used.

[0206] Thus, simply increasing a quantity of cleaning paste through a lumen is not sufficient to ensure that a desired cleaning outcome can be obtained.

[0207] 3.3 Paste Test—Detailed Solids Removal

[0208] A detailed examination of the most suitable pastes was conducted.

TABLE-US-00002 Paste Wet soil Wet soil Wet soil Ave Wet Paste used (g) (g) left (g) left % soil left % ⅓ Sodium Benzoate 29.1000 0.32 0.0017 2.10 0.51 ⅓ Water ⅓ Sodium Bicarb ⅓ Sodium Benzoate 31.5100 2.56 −0.0001 −0.14 ⅓ Water ⅓ Sodium Bicarb ⅓ Sodium Benzoate 37.5900 4.92 −0.0004 −0.42 ⅓ Water ⅓ Sodium Bicarb 50% Sodium Benzoate 32.2200 2.78 0.0035 4.41 2.37 50% Water 50% Sodium Benzoate 19.0500 4.67 0.0027 3.26 50% Water 50% Sodium Benzoate 22.6200 6.41 −0.0005 −0.55 50% Water 68% Sodium Bicarb 70.2700 9.49 0.0028 3.85 4.71 in Propylene Glycol 68% Sodium Bicarb 75.7700 0.32 0.0035 4.34 in Propylene Glycol 68% Sodium Bicarb 63.8900 13.12 0.0042 5.94 in Propylene Glycol Water Flush 51.6600 8.37 0.0184 24.89 24.89 Water Flush 51.6600 10.23 0.0112 15.54 15.54 Water Flush 51.6600 14.48 0.0197 21.38 21.38

[0209] The pastes were all significantly more effective than a water flush at removing contaminants.

[0210] 3.4 Paste Test Results—Protein Removal

TABLE-US-00003 Paste used Image 68% Sodium Bicarb in 73.9200 excellent Propylene Glycol 68% Sodium Bicarb in 77.2100 excellent Propylene Glycol ⅓ Sodium Benzoate 23.8400 excellent ⅓ Water ⅓ Sodium Bicarb ⅓ Sodium Benzoate 34.3600 good ⅓ Water ⅓ Sodium Bicarb 50% Sodium 27.1700 good Benzoate 50% Water 50% Sodium 21.3000 good Benzoate 50% Water

[0211] The pastes used in the above table were found to be suitable for the removal of residual protein.

[0212] In general pastes comprising almost equal quantities (w/w) of sodium benzoate, sodium bicarbonate and water were found to give good cleaning. That is, a range of pastes comprising 25-45% sodium benzoate, 25-45% sodium bicarbonate and 25-45% water were all suitable for cleaning endoscope lumens. The amount of each component used could be independently varied, provided all three quantities stayed within the stated quantities.

[0213] One particularly beneficial formulation comprises sodium benzoate, sodium bicarbonate and water in the respective ratios 27:35:38 w/w.

[0214] In these preferred formulations, the sodium bicarbonate particles used all had a particle size below 0.15 mm. A range of particle sizes of sodium benzoate were tested between 1 mm and 0.15 mm. In general, the smaller particles appeared to provide better results. However, it was observed that if these three component (bicarb, benzoate and water) mixtures were allowed to stand for some time between mixing and use, the differences in sodium benzoate particle size became less pronounced.

[0215] 3.5 Visual Inspection of Soil Removal.

[0216] Endoscope lumens are of extremely long length in relation to their diameter, which is a factor contributing to the difficulty in their cleaning. In order to better model the cleaning processes in such elongate systems, the cleaning processes were carried out in an endoscope that was specially constructed to have a semi-transparent Teflon tube as a lumen configured to connect with all the internal passageways and having all the necessary external connections and ports present in a commercial endoscope, but without the external casing. This enabled the cleaning of the lumen to be visually examined. The lumen of the uncased endoscope was approximately 1700 mm in length and 4.0 mm inside diameter.

[0217] The visible inner workings of the endoscope were particularly useful in examining the efficacy of the suspension methods of the present invention, and in particular, the paste method. Because the paste is white, it provides a clear visual contrast with the dark red or brown soil present in the lumen. The white paste displaces the red soil from the interior lumen, changing the exterior appearance of the Teflon tube as it does so. This enables the progress of the cleaning along the tube to be monitored readily. When the soil is fully removed, the tube is white in appearance and can be compared against a control, which contains the paste in an unsoiled lumen. This can be monitored visually, although colourimetric measurements can be made on the paste exiting the lumen to determine whether the paste contains any removed soil. In such a case, the paste continues to be pumped through the lumen until no further discolouration due to contaminants is detected. The paste was passed through the lumen at a pressure of 35 psi for around 4 to 5 minutes for a total volume of around 60-100 ml of paste, which is a volume similar to the total volume of the lumen.

[0218] The pastes of the present invention, in particular, the pastes comprising 25-45% sodium benzoate, 25-45% sodium bicarbonate and 25-45% water, were all highly effective in removing the various artificial soils from the interior of the lumen wall as determined by visual inspection.

[0219] After the required volume of paste had been applied, water could be passed through the lumen to remove the paste. The water can be used immediately after the paste, and in direct contact with the paste, to continue the flow through the lumen. The wash phase typically required around 30-60 seconds to remove all of the paste and return the lumen to a useable condition.