US 2318380 A
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Description (OCR text may contain errors)
May 4, 1943. w. s. oAvls ETAL METHOD OFy STERILLING* AND PACKAGING SU'I'URS4 AND THE LIKE FiledAug., 8, 1941 4 Sheets-Sheet 1 j@ l lll lII Ewa c" k i Il ill ss u @zu D77o Vacuum Pump 6 F//er www: 57 59 F//vef- /fvoxcr/f 7a.( .34
f (s2-nw# F//fef 5 da Z562 Lsa-f/ C'ffae '7, @eda's y a MW May 4, 1943. w. s. DAVIS Erm..
METHOD 0F STERILIZING AND PACKAGING SUTURES AND THE LIKE Filed Aug. a, 1941 4 Sheets-Sheet 2 MNN May 4, 1943. w. s. DAVIS Erm..
METHOD 0F STERILIZING AND PACKAGING SUTURES AND :THE LIKE Filed Aug. 8. 1941 4 Sheets-Sheet 3 WSN wNN
May 4 3943 w. s. DAVIS Erm. 293%,380
METHOD OF STERILIZING AND PACKAGING SUTURES AND THE LIKE Filed Aug. 8, 1941 4 Sheets5heet 4 Patented May 4, 1943 mamon Walter A S.
F STEBILIZING AND PACKAGING SUTURES AND THE LIKE Davis, San Bernardino, and Charles T.
Davis, Los Angeles, Calif.
application August s, 1941, serial No. 5,912
- 1 claim. (ci. 12s-335.5)
'I'he present invention relates tomethods of sterilizing and packaging sutures and'the like. While the complete and longer processes described herein are particularly adapted for the sterilization and packaging of sutures. we desire it to be understood that our methods of sterilisation are capable of being used for sterilizing any kinds of products more eiiectively than the methods of the prior art.
One oi' the specic embodiments of a process embodying the invention is the subject of our prior application Serial No. 284,388.1iled July 14, 1939, ,which issued as United States Patent No. 2,253,287, on yAugust 19, 1941, of which this application is a continuation-in-part.
The products s made` according'to .said process with apparatus constructed according to the invention has been made the subject of another application which is also a continuation-impart of the parent application just mentioned and which is entitled Suture packages," Serial No.
388,948, led April 17, 1941.
The present application relates particularly to the various modified forms of processes broadly or specically not covered by-our prior patent above-mentioned.
' One of the objects of the invention is to provide improved processes by means of which the improved suture packages of the copending ap plications may be made in a very economical and eiilcient manner with a minimum amount of manual labor and with a minimum of possibility of any kind of contamination of the suture or introduction of any spores or bacteria in the package. Y Y
Another object is the provision of an improved process for handling suture packages by means of which the sutures may be preserved in a sterile condition for long or indmnite periods oi time until they are to be used and by means of which the sutures are 'maintained in the best possible condition for use.
Another object of the invention is the provision of improved processes for handling suture packages, which processes are equally adaptable for use in packaging all kinds of sutures of either the boilable or non .boilable type.
' Another object of the invention is the provision of improved processes for sterilizing and packaging sutures or other articles by means oi which the sutures or other articles may be more adequately sterilized than by any ofthe processes of the prior art through the application simultaneously of vacuum and heat to the products that are sterilized.
vision of improved methods for treating sutures Another object ofthe invention is the proi vision of improved processes adapted to be used for sterilizing sutures and other articles while in suitable containers lwhich may be iilled with a preserving iluid under aseptic conditions and which may then be hermetically sealed while in a sterile condition without any possibility of bacterial contamination.
Another object of the invention is the provision oi improved methods for handling sutures by means of which a constant record may be kept of the various batches of sutures which have been treated and of the vacuum and temperature conditions to which they have been subjected so that the sutures may be permanently identiiled with their treatment and samples selected at random may be tested and identiiied with the complete batch to make sure that all of the sutures of everybatch have been subjected to proper treatment and have been found substantially perfect in characteristics after completion.
Another object of the invention is the proand other products by means of which the subject-matter for treatment is handled in a bac-- teriologically closed system so that the possibility v of introduction of contaminating yiniiuences or bacteria or their spores is reduced to a minimmn.
Another object of the invention is the provision of improved processes of the class described in which provision is made for the sterilization of the passage through bacteria-prooi iilters of every element such as preserving duid or air introduced into the system so that the system is closed bacteriologlcally vagainst the introduction of bacteria or their spores.
Another object of the invention is the provision of improved processes in the sterilimtion ;and packaging of sutures characterized by the following advantages:
1. 'rne sterility of the sutures-is assured bythe use of the closed system oi.' the invention:
2. The product of the process has the desirable characteristics of both boilable and non-boilable types of ordinary gut but has none of the dei of either;
3. The sutures are characterized by absence of tissue reaction; A
4. The sutures are very nexible and have a very soft character While still having a high tensile strength;
5. The knots made Awith such sutures or ligatures are stronger and hold more securely;
sf'rnefunmammestrengthastri-azucare-'V 'tained notwithstanding the llplitin of 8. high sterilizing temperature for a considerable period of time; v
7. The system of records of the actual ternperatures and vacuum to which the sutures have been subjected provides a check on the sterility;
8. The sutures are conveniently removable and the tubes are adapted to break more cleanly than devices of the prior art.
Another object of the invention is the provi-l sion of an improved process of sterilization by the simultaneous use of vacuum and heat which is adapted to kill the most resistant micro-organisms at temperatures greatly below those required when heat is used alone, thereby making it unnecessary to subject products which are to lbe sterilized to such high temperatures as had to be used when vacuum was not employed.
Another object of the invention is the provision of improved processes adapted to be used for making various types of improved suture packages each of which has important advantages in its own ileld.
Other objects of the invention will be apparent from the following description and the accomdrawings in which similar characters of reference indicate similar parts throughout the several views.
Referring to the drawings of which there are four sheets:
Fig. 1 is an enlarged elevational view of a suture package which has been subjected to treatment by the apparatus constructed according ,to theinvention and which may be regarded as an intermediate product ready for immediate use in the hospital.
Fig. 2 is another similar view of a suture package treated according to the invention with the present apparatus as it appears after the glass tube has been sealed so that the suture and package are in condition to be shipped or stored for a long period of time without possibility of contamination.
Further infomation as to other products which may` be made according to the invention may be had by reference to the copending application Serial No. 388,948, iiled April 17, 1941, entitled Suture packages, or the copending application on Sutures and methods of packaging and sterilizing the same, Serial No. 284,388, filed July 14, 1939, Patent No. 2,253,287 issued August 19, 1941.
:,siaaso Fig. 9-is a transverse `sectional view taken on the plane of the axis of thetube; and
Fig. l is a longitudinal sectional view of another modiiled form of suture-package comprising a glass tube having a frangible portion-intermediate its ends formed by 'pinchingthe walls of the tube together while they are hot.
In order that the processes and their characteristics may be understood, we shall first `describe several types of products adapted to be packaged or prepared according to the processes of the invention.
Referring to Figs. 1 and 2, the suture packages there illustrated are indicated in their entirety Fig. 3 is a diagrammatic 'sectional view show- 4 ing one simple form of apparatus adapted to be used in carrying out the methods of the present invention.
Fig. 4 is a similar diagrammatic sectional view of a modified form of apparatus which is especially. suitable for use in sterilizing and packaging the boilabletype of sutures although it is not limited to use on such sutures.
Fig. 5 is another similar diagrammatic sectional view of a modified form of apparatus especially suitable for preparing the non-boilable type of sutures although not restricted to nonboilable sutures.
Fig. 6 is a side elevational view of another modiiied form of product which is provided' with an improved form of illters;
Fig. 'I is a vertical sectional view taken through a suture package of the ty-pe of Fig. 6. taken on the piane passing through the axis of the tube;
Fig. 8 is another modiiied form of suture package. particularly adapted i'orv military use and shown in plan:
by the numeral III in Fig. 1 and II in Fig. 12. This package comprises a glass tube I2 which Is closed with a rounded end portion I3 and which has a restriction Il formed intermediate the ends and in position to engage the suture reel I5 at its upper end. This restriction consists of an inward bend in the wall of the glass tube extending fully around the periphery of the tube and the outer wall of the tube is preferably ground away at the base of the groove I8 which' forms the restriction so that there is a flattened wall portion I1 which is thinner all the way around the tube.
The combination of the restriction and the' thinner wall 'at that point so weakens the tube that it can be broken off squarely, preferably after being wrapped in a towel. Yet there-is no danger of the-tube breaking intransit when properly packed because the wall of the glass tube is notl cracked or nicked and the tube is relatively strong except against the application of such a bending force at the right point.
The upper end of the glass tube I2 in Fig. 1 is open but after the suture has been placed therein; it is plugged with a sterile plug I8 of fibrous material such as cotton, preferably about iiveeighths of an inch in length and having a tight 'frictional ilt in the bore of the tube so that the interior of the tube is closed against the entrance of bacteria or Vtheir spores. This cotton vplug makes the tube a closed system against entrance of bacteria or their spores. The porous plug should iirmly contact the inner wall of tube for, preferably, about five-eighths of an inch.:
We desire it to be understood that the term suture" as employed in the application and claims is synonymous with the term ligature" as the same material may be usedvboth for sewing wounds or tying knots about various types of-tissue.
'l'he suture I8 may consist of any suitable type of suture and itis preferably coiled helically about the reel I5 in a plurality of coils with the upper end projecting from the reel in such a direction that it extends into the upper part of the tube l2.
I'he reel may consist of one or more pieces of iiat indurated fiber so long as it is formed with a central groove and upwardly projecting guide ilanges on each side of the coiled suture I9. Various types of reels have been disclosed in the aforesaid prior application on Suture packages. Serial No. 388,948, and in the aforesaid parent application Serial No. 284,388, any -of which may beemployed.
There maybe a suitable clearance between the reel and the walls of the tube even at the restriction but the suture is not tightly coiled on the reel but forms an easy bend at each end of the reel so that the suture coils expand in the tube i2 beiow the restriction u tov retain coiledsutineinthat endofthetube.
asiasso The sutures may be of the boilable or nonsuture is substantially all immersed.
The length of the glass tube l2 is preferably such that there is space between the free surface of the preserving iluid 9 and the plug Il sothattheglasstubemaybesealedoflfhermetically at this upper portion without removing the plug I8.
We have foimd that sutures which have been suitably treated and sterilized according to the methods of our invention and with our apparatus may be preserved for a long period of time without contamination merely by means of the illter plugs I8.` Therefore, the embodiment of Fig. 1 may be regarded as a finished product, for some purposes, and in somev hospitals where it is not necessary to ship the product, shorter tubes may be used' and closed with' cotton plugs and kept in this condition as illustrated in Fig. 1 until used.
Whenever the sutures are to be preserved indeiinitely or packaged for shipment, the glass tube is preferably sealed on hermetically as shown in Fig. 2 and this is accomplished by application of heat to the tube between the plug Il and liquid 9, the tube being rotated and drawn out until the glass melts and is severed and the end of the tube is thus closed and takes a substantially spherical form as shown in Fig. 2. The severed end of the tube and plug may then be thrown away.
The foregoing two embodiments are merely exemplary of two of the forms which the packaged sutures may take, others of which are disclosed in the compending applications abovementioned.
Referring to Figs. 6 and 7, the suture package -shown in these views may be in all respects simmersed in any tubing iiuid and after sealing the package may be ilattened out so as to make it Voi? better form for packing. Such packages are particularly adapted for military purposes because they can be packed, `carried and shipped with less possibility of breakage than the packages which compriseiglass tubes. v
Other advantages of this package are that the containers are unbreakable, they are compact and a larger quantity may be carried in a given space, the sutures and their containers may be boiled along with the instruments, and the containers are waterproof, so that they may be subiected to various kinds of abuse without possibility of introduction of micro-organisms into the Y, containers.
ilar to that of Fig. 1, except that the open end of the glass tube I2 is closed with a iilter 18a of I a different construction This may comprise a closure of porous iilter paper which is ilrmly secured on the endV of the tube by means of a tight cotton thread, wire, or, for example, a paper band I8b of paper which is glued to the lter paper Ilaandtothetube I2byagumwhichis insoluble in water or in any of the tubing fluids employed. 'i
Referring to Fig. 8, this is an elevational view of a package lil ior sutures or other material such as antiseptic gauze, comprising 1a tubular container I5I of metal, such as tin foil, one end of' which is nattened out, folded over, and sealed by means of heat, and the other end of which is left open and plugged with a plug I8 of the sametypedescribedwithrespecttoFig. l.
This'package may be subjected to the same treatment es described with respect to the packmay be cutoff along the line |53 and thrown i away with the plus l8- 'rhese'containers are preferably provided sutures or antiseptic gauze or any other article intended to be kept sterile without being im- For example, the sterilization with -dry heat Referring to Fig. 10, this is a view similar to' Fig. 1, of another form of suture package in which the glass tube I 2 is provided with a restrictionil! of different shape by merely pinching the two walls of the tube together while hot to form two grooves, the bases of which are substantially parallel. This may be done'with a tool similar to a pair of accurately spaced parallel rods, thus providing a restricted portion which is particularly adapted to be broken when bent in the direction of the nari-cwest dimension of the pinched part of the tube.
This tube may then also be provided with a wall of reduced thickness at the base of each groove. This modication is of particular value where large-diameter tubes are'used.
In order tthat the processes embodying the invention may be most conveniently practiced, we shall now describe various types of apparatus which may beA used in carrying out these proceSSeS.
Referring to Fig. athis is a diagrammatic elevational view of one form of apparatus adapted to be used for packaging sutures according to the invention .In this embodiment In indicates one of the suture packages `of Fig. 1 lled with a reeled suture and plugged with a cotton plug I8 as described with respect to Fig. 1 but not yet supplied with its preserving'liquid 9. Whileonly one of these tubes is shown, it should be understood that a multiplicity of tubes and vsutures can be treated at the same time and in fact a very large other embodiments of the invention, glass, porcelain or earthenware jars have been used for sup- Porting thesuture-iilled glass tubes in vertical position inside the jar and the jars may be piled in the sterilizing chamberin the same manner the racks with their upper ends open.
20 indicates Ya sterilizing chamber provided with a cover 2l adapted to be secured by bolts or other fastening means in such manner that the chamber 20 can be hermetcally sealed.A The sterilizing chamber 2l is housed entirely within a suitable oven 22 which may be heated with elec-V Y tricity or gas, but which is preferably of the elecg trical heating type- The oven 22 isV adapted to heatthesuturepackages Iinthesterilizing chamber 20 to the desired tempera- 'ture'which may be maintained for such a period of time that all of the bacteria and their spores are killed.
The controls for the heating apparatus are preferably such as to maintain the oven at the predetermined temperature desired automati-l cally.
The sterilizing chamber is provided with a pipe 23 having a valve 24, the actuatinghandle o'f which extends out through the wall of the oven. The further extension 25 of this pipe leads to a suitable vacuum pump preferably adapted to maintain a very high vacuum such as for example 29 or 291/2 inches of mercury or better. y
The sterilizing chamber 20 is also provided with another pipe or conduit 26 controlled by another similar valve 21 and having its extension 28 leading to a sterilized bacteria-proof air filter 29.
'I'he sterilizing chamber is also provided with a conduit 30 which extends into or to the bottom of the sterilizing chamber and which is provided with a valve 3| and a bacteria-proof filter 32. A pipe 33 leads from the bacteria-proof lter 32 to a tank 34 containing the preserving liquid with which the tubes are to be partially filed, such as alcohol, toluene or xylene.
The tank 34 is provided with a conduit 35 controlled by a'. valve 36 and the conduit 35 also leads to another or the same vacuum pump previously the tank 34. Another conduit 31 provided with a valve 38 extends from the tank 34 to a bacteriaproof air lter 39 which is open to the air at its lower end.
The oven 22 is preferably provided with devicesh for indicating temperature of the oven while the sterilizing chamber is preferably provided with devices for indicating both the internal temperature in the chamber 20 and the vacuum and for recording continuously the temperature and vacuum throughout the period of sterilization. These indicating devices are designated by the member 40 in the sterilizing chamber 2|! connected by member 4I to the indicator or dial and recording mechanism indicated at 42.
The operation of the apparatus of Fig. 3 is as follows: After the sterllizing chamber has been filled with the tubes I2 containing sutures and lter plugs, the valves 3l and 21 may be closed and the cover 2| clamped down tightly so that the sterilizing chamber is hermetically sealed. 'I'he temperature of the oven 22 may then be raised gradually to the desired sterilizing temperature and simultaneously the air may be pumped out of the hermetically sealed sterilizing chamber 20 to produce a vacuum by means of the pump connected to the conduit 25, the valve 24 being open.
We have discovered that the simultaneous action of vacuum and sterilizing heat will elect sterilization more eiliciently and more quickly and will kill bacteria and their spores that might resist the application of heat alone. The use of the vacuum introduces the element of an insulation space around the subject-matter to be sterilized so that there may be a greater time lag between the time when the oven 22 or chamber 2l reaches the sterilizing temperature and the time when the sutures reach the desired temperature, but the vacuum pump removes from, the
sterilizing chamber the air,and most of the destroyed bacteria and their spores and the present apparatus is'adapted to carry out a new method of sterilization by simultaneous application of vaccum and heat.
liter the sterilization has been carried on for described so that a vacuum may be created in a sumcient length or time, such as for example a. temperature of 300 F. for a period of Vthree hours or more, the entire contents of the chamy ber 20 will be completely sterile. The temperature attained at the innermost portion of the chamber 2|| is constantly measured and preferably recorded by the recording mechanism 42 and a similar record is preferably kept of the vacuum applied.
After the sterilization has been effected, the valve 24 is closed and the valve 21 is opened slightly in order to break the vacuum gradually. Then sterile air, taken from the interior of the oven 22 through the bacteria-proof filter 29, enters the sterilizing chamber 2l. This is prei'- erably continued until the pressure in the sterlhzing chamber is substantially atmospheric pressure andthe valve 21 is then closed. l
Thereafter the valve 3| may be opened, thus establishing connection between the tank 34 which contains sterile alcohol or some other suitable preserving liquid and a vacuum is applied to the sterilizing chamber 2l by means of the pump attached to conduit 25 with the ,valve 24 open.
In other embodiments of the invention, pressure may be applied to the liquid in the tankA 34 by means of a pressure pump attached to pipe 35 and the liquid forced into the sterilizlng chamber 2l while the valve 21 is open, permitting n the airto be forced out of the chamber 2l. -Thls' is continued until there is a sufficient amount of liquid in the chamber 2B to cover the open ends of all the tubes I2 and to provide enough liquid to fill the tubes to a predetermined level. While the plugged ends of all the tubes are covered with preserving liquid, the liquid does not at this time pass into the tubes on account of the pressure of the air inside the tubes.
In some embodiments of the invention where the tubes are packed in porcelain jars or other containers, the cover 2| of the chamber 2l may be removed and the jars nlled with the preserving liquid by pouring into the jars until the glass tubes are submerged to a predetermined degree. Thereafter the cover-2| may again be applied and the apparatus is ready for the rest of the steps of the process which Vmay be carried out in the.
same way whether the chamber 20 is filled with liquid or the jars are nlled with liquid.
It should be noted that although-the removal preferred practice of the process and operation of the apparatus, the cover 2| is not removed, thus keeping the sterllizing chamber in a sterile condition at this time.
When a sufficient amount of liquid has entered the chamber 20, the valve 3l may be closed, shutting oi the connection between the preserving fluid tank 34 and the sterilizing chamber 2l, and with the valve 21 closed, valve 24 may be opened and air again exhausted from the chamber 2|I to a predetermined degree of vacuum. This causes the' air in the tubes I2 to expand and the air passes out of the tubes through the'lter plugs I8 and bubbles up through the preserving liquid. v
It is found that such glass tubes vary slightly in their internal diameter but they are all of substantially the same length. The product is more salable and more desirable if the preserving liquid is brought to substantially the same This precise degree of vacuum depends upon the external atmospheric pressure and the eil'ect se'- cured depends upon the net difference in pressure between the outside and inside of the chamber 2l. This, for example. may be 15% inches of mercury in a vtube of the type illustrated.
Thevalve 21 may then be opened slightly in order to break the vacuum slowly in the chamber 2l. If the vacuum is broken too quickly, the increased pressure in the chamber on the liquid may cause all of the cotton plugs to shoot to the bottom from the open end of the tube, that is, down to the suture or restriction.
If the vacuum Yis broken gradually, the gradualiy increased pressure onV the liquid in the chamber 20 will cause the liquid to fllter through the plugs into the tubes gradually so that the plugs will not be displaced.
After the valve 21 has been partially opened and a short period of time has passed. the preserving liquid will have filtered into all of the tubes I2 to substantially the same level.
In some embodiments of the invention a pressure pump may be connected to the bacteria.- proof illter 29 and pressure may be applied to the liquid in the chamber 20 at this stage instead of applying a vacuum and breaking the vacuum. The net result is brought about by the diiferential ofpressure between the air in the tubes and the air in the chamber to illl the tubes to a predetermined level. In either case, after the tubes have been filled to a predetermined level, atmospheric pressure is again reestablished in the chamber 20 and the cover may be removed.
The :lars containing the tubes and liquid may then be removed from the tank 2l and the excess liquid poured oiI from the jars or, in case racks are used, the excess liquid may be drawnv oil' from the tank 2li before removing the cover, by opening the valve 3| and applying suction to the tank 34 through pipe 35 with valve 3| open. The purpose of the-valve 38 on tank 34 is to permit the ingress of air through the illter 38 when liquid is being drawn from the tank I4 into'the chamber 2li.
The cotton-plugged tubes u containing the sterile sutures immersed in preserving liquid may then be permitted tosit in the oven for a predf termined period of time such as over night until the alcohol in the plugs I8 has evaporated or the alcohol-wet plugs I8 may be ignited and permitted to burn until all the alcohol burns o. 'Unless this is done, when heat is applied to the tube l2 between the preserving liquid and the plug Il,
the vaporization of the alcohol would produce pressure within the tube, blowing out the glass and this would introduce dimculties in the sealing of the glass tube.
'I'he glass tubes may then be sealed `between the plug and the suturewithout removing the plug and the end of the tube and the plug may be thrown away.
LReferring to Fig. 4, this is a similar diagrammatic sectional view of an improved form of apparatus having additional advantages over those shown in 218.3. In the apparatus of Fig.
lwith the sutures.
had to be employed for ensuring the sterility ofy ber.
3 the preserving fluid was preferably ethyl alcohol and the tubing iluid was not heat-sterilized Consequently, other means the fluid. The ethyl alcohol in that case was denatured by means of the addition of mercury which made the iluid bacteriologically safe and sterile.
There are, however, a small percentage of patients who have an allergy to mercury and the use of mercury for this purpose is undesirable. In the apparatus of Fig. 4 its use is avoided by employing apparatus in which the sterility of the iluid is accomplished without the use of mercury or any other germicidal substance. This is accomplished by includinga special tank for the tubing iluid in the same oven so that the tubing iluid is subjected to substantially the same degree of heat as the sutures.'
This apparatus is particularly suitable for use when sterilizing the boilable type of sutures. In such case the tubing iluid is preferably waterfree hydrocarbon of comparatively high boiling point. Being without moisture content, the ef- `feet of this tubing fluid on the micro-organisms is the same as dry heat of an oven, which is not nearly so effectual as wet heat at equivalent temperatures, and therefore it withstands, and requires, a high degree of heat for sterilization. v
Therefore, the iluid to be rendered sterile must be subjected to as much heat as is used in sterilizing the sutures. Having a high boiling point; this can be done without creating' a dangerously high pressure within the iuid sterilizing cham- When the non-boilable type of sutures are to be prepared with the saine apparatus,l thetubing duid chamber must be constructed in such manner as to withstand the high pressures which would be created by heating the alcohol or other low boiling fluids to such a temperature as 356 F.
'I'he apparatus of Fig. 4 also preferably includes an oven 22 which may be provided with the same sterilizing chamber 20 having a cover 2|. The oven may be heated by means of hot air which is heated in an electric heater 46 contained ln housing 4l which-has a conduit 4l communicating with the upper part of the interior of the oven 22.
The housing 46 of the heater 45 has an outlet conduit 4I connected with the inlet 49 of a centrifugal blower 50 the outlet of which is con nected by conduit 5| to the lower part of the interior of the oven 22. f
The amount of hot air delivered by this apparatus is such that the circulation of hot air by mere convection becomes a negligible factor and the air is taken of! the top of the oven, heated, and blown into the bottom of the oven in large volume so as to heat the oven to a substantially uniform temperature.
The temperature inside the oven is substantially that of the temperature of the air passing out of the upper conduit 4l and this conduit is preferably provided with a suitable temperature responsive mercury' bulb or other thermostatic electric switch i2 connected by a cable I3 having suitableconductors to the conductors ofthe cable I4 leading to the electric heater 45.
The electric heater may have a plurality of ranges of heat provided by switch contacts for cutting in dinerent sections of the heating cous so that the oven may be maintained'at substantially constant temperature determined by the setting of the thermostatic switch 52 at a temperature controller 55.
The oven may also be provided with an angle thermometer having its mercury bulb located in- 54 F. between the temperature inside the oven 22 and that at the center of the sterilizing chamber 20.
There is also a time lag of several hours between the time when the operating temperatureA is reached in the oven 22 andthe desired operating temperature is reached inside the sterllizing chamber -2li.4 Thus. the temperature of the air circulated in and about the oven chamber 22 must y be about 54 higher than that inside the chamber 20, the exact amount being determined by means of the readings of a temperature recorder 51 which has a clock-driven dial upon which an inked pen constantly indicates graphically the temperature existing on the insidevof the sterilizing chamber 29. This temperature recorder is connected by a suitable capillary tube 58 with a mercury bulb 59 located inside the vacuum chamber 20 and preferably adjacent the center and the lower part since the upper part and outside are apt to be hotter.
The vacuum chamber 20 in this case is preferably formed with a partially spherical bottom wall GII draining. toward a centrally located well 6i in which is located the end of a pipe 52 used for emptying the tubing liquid from the vacuum tank 20 and for iilling the tank. A
A valve 3| again controls the conduit 90 which,
' however, in this case leads to the sterilizing tank 34 located'in the oven 22. Here again the conduit 20 extends down into the tank with which it has a sealed connection to a point adjacent the bottom of the tank so that practically all of the uid in the tank 34 can be used.
Vacuum tank 20 is again provided with the valve 21 controlling the conduit 26 leading to a bacteriaproof lter 29. The sterilizing tank 24 for thetubing fluid may be provided with a gauge glass 63 which indicates the height of fluid in the tank and may be used as an indication of the amount which has been drawn from this tank into the vacuum tank 20.
The tubing fluid tank 34 is also provided with a bacteria-proof nlter 64 communicating with the tank through a valve 65, the other end of the nlter `being open to the air inside the oven 22 like the filter 29.
All of these iilters may consist of compact .plugs or bodies of sterile cotton closely packed in a cylindrical container. They are, `of course. maintained in sterilized condition by the sterilizing temperatures in the oven.
The tubing iiuid tank 34 has its interior in communication with a pipe U6 which may lead from its upper end to a valve 61 and thence to a T cone nection 69. The T connection has one opening connected by means of a pipe 69 to a yhelically coiled pipe 10 located in an insulated chamber 1| and peered with send carbon dioxide.
The lower endof the helically coiled pipe 19 is open and -the object of the unit'1l is to condense any moisture which may be present in the air and to erect a drying of the .sir before it gets te the vacuum air pump 12 which is connected to the hermetically sealed chamber 1| by pipe 12.
The vacuum air pump 12 is driven by motor 14 through belt 15. The other end of the T connection $8 is connected by a pipe to a valve 1I which connects with another T connection 11 to a pipe 18 leading to the interior of the vacuum chamber 20. f
The other end of the T connection 11 has a pipe 19 leading to a vacuum recorder Il which is essentially a pressure gauge provided with a com'- bined indicator and pen and with a clock-driven dial for indicating pressure or vacuum so that the vacuum in the chamber 20 or other pressure conditions are constantly indicated and recorded on the dial.
A diierential manometer 9| has one end of its U tube connected to the pipe 19 and is provided with a scale 82 located between the legs of the manometer and adapted to indicate the difference in the external and internal pressure by means of the difference between the elevations of the two columns of mercury in the manometer.
With this arrangement it is not necessary to make a separate reading of the air pressure at the time the proper vacuum is determined to effect a filling of the tubes with tubing iluid. The manometer gives the diierence in pressure with relation to the external air pressure and eliminates the necessity for calculation. For example, it might show a diierential of 15% inches of mercury necessary for the nlling of tubes with tubing fluid to a point just above the restriction.
indicates a thermostatic limit switch for the electric heater so that if the temperature conditions in the electric heater exceed thislimit, such as for example through a breakdown of the blower, the heater will be turned off and damage to' the mechanism prevented.
The tubing fluid tank 34 preferably communi-- cates through a pipe and Vvalve I4 with a bacteria-proof iilter l5 preferably of the Berkefeld or similar type. Filter 85 communicates through pipe I8 with the interior of a standard commercial drum I1 of the tubing fluid, the pipe Il preferably extending to the bottom 0f the in-v side of the drum and having liquid-tight connection with the top of the drum.
A pipe 88 leads from the top of the interior of the drum to a bacteria-proof air filter il and thence to another pipe 90 which is cone nected to the air pressure pump 9| driven by motor 92 by means of belt 93. In this case the wire racks for supporting the suture tubes I2 in the vacuum chamber 2l are indicated by the' numeral 94 and they are preferably circular, having a multplicity of frame members for engaging the tubes which may be arranged in circles. the center of each rack having an opening to accommodate the pipe 62.
The vacuum chamber 20 preferably has its cover provided with a ground metal surface for engaging a similar surface on the tank so as to assure a vacuum-tight joint.- While it is true that there is a possibility of leakage through the multiplicity of dierent valves employed in .the apparatus, the continuous operation of the vacuum pump during the sterilization takes care of the leakage which might occur at these valves or at any other jointsand assures the maintenance of a relatively high vacuum of 29 or 29% inches of mercury or more.
94' indicates a union joint which facilitates the e disconnection of the pipes from the cover 2| before the cover is removed from the vacuum tank.
The method of manipulation of this apparatus is substantially the same as that described in respect to iEig. 3 except that it is necessary to Y operate the pressure pump 9i to place pressure on the tubing-huid in the drum 81 while the valves Il and are open so as to force an adequate supply of tubing iiuid into the tubing iluid sterilizing tank 3l before the process of sterilization is begun. Then the tubing fluid is sterilized simultaneously with the sterilization of the sutures in the vacuum chamber 20 except that the sutures are subjected to both vacuum of from 29 to nearly 30 inches of mercury to the sutures at .the same time the sterilizing temperatures are applied, contributes to the excellence of the product. Another difference in the operation of th apparatus of Fig. 4 over that of Fig. 3, although both may be operated in the same way, is in the fact that vacuum is preferably applied to the vacuum chamber 20 for a period of about two hours before the application of heat.
This vacuum extracts from the suture material the greater portion of its water of constitution without the application of heat. This avoids the case hardening of the suture strands and the nished sutures are more flexible than if they are case hardened by the application of heat without subjecting the sutures to vacuum Animal sutures, such as gut and tendons, are composed of a colloidal substance, collagen. When heat is applied to collagen before the extraction of most of its moisture, it is converted into gelatin which hardens it and reduces 'its tensile strength and the degree of its conversionyinto gelatin is reduced to a minimum by the initial application of vacuum without heat.
'Ilhe air drying imit 1I of the present apparatus also prevents the drawing of any water or other iluid into the vacuum plnnp which might cause damage to the vacuum pump.
The sutures may then be subjected to the action of combined vacuum and heat, thetemperature being gradually increased imtil the re-v corder indicates about 302 F. inside the vacuum sterilizing chamber 20 and this temperature may be maintained, for example. for a period of three hours at the end of which period the temperature may be gradually decreased and reduced in the oven by shutting off the electric heater 45 while continuing to operate the blower 50 which causes air at room temperatm'e to circulate through the oven 22 while the lid has been removed from the even.
In other cases the oven may be left to cool l over night or for a predetermined period of time before the next step is taken in the manipulation a fluid well above 'the tops of the uppermost layer of tubes such as, for example, to a point three inches below the outlet where the vaclmm pipe 18 is attached to the vacuum chamber 20.
The degree of vacuum inthe chamber 20 which is produced after the chamber is iilled with tubing iluid is read at the manometer 8| and the pump is operated continuously until the desired degree oi vacuum is reached. It should also be noted that whenever the vacuum pump is turned oif, the valves 81 and 16 are closed iirst in order that when the pump is standing still, the oil in the pump may not be drawn into the conduits leading to the vacuum chamber 20.
Thenthe chamber 20 is again restored to atmospheric pressure and the surplus fluid is re-' moved into the tank 34 wh'ere the gauge glass 63 will incidate its usual height of liquid when all has been removed from the vacuum chamber 20.
Referring now to apparatus of Fig.v 5, this apparatus is particularly adapted'to be used for preparing the non-boilable type of sutures. It is distinguished from that of Fig. 4 in that the sterilizing chamber for the tubing uid of low boiling point such' as ethyl alcohol which is used for non-boilable sutures, is sterilized by heating in a separate liquid heating bath or oven.
This bath or oven is heated by a separate heating unit to the degree of temperature which is required and which need only be suiiiclent for sterilization of the'tubing uid, which is not subjected to as high a temperature as the sutures for sterilization. Here again, although the apparatus is particularly adapted for preparation I of non-boilable sutures, it is not limited to that type as the tubing iluid sterilizer may be operatedat a higher temperature for sterilizing the higher boiling fluids that are used for boilable sutures. In the embodiment of Fig. 5, the apparatus is provided with two sterilizing tanks 95l and 98 adapted to receive a heating bath' 91 or 98 sur rounding the suture sterilizing chamber 20 and the tubing liquid sterilizing chamber 3l, respectively. Similar parts in this apparatus have been indicated by similar numerals to those used in Fig. 4. In this case the medium for carrying the heat from the heater to the vacuum chamber 20 and sterilizing tank 3l may consist of a bath `of glycerin or a bath of oil instead of circulating hetairasinnigA.
99 indicates a thermostatically controlled valve which is operated responsive to the temperature in the bath 91 by means of a thermal at its lower end t6 the inlet of a liquid circulating pump |05 which has its outlet connected to the interior of the tank by pipe I 06. Outlet pipe-|00 preferably leads to the bottom center of the tank 95 and discharges upwardly through an elbowl or a bifurcated fitting so that the heated liquid flows upward on all sides of the vacuum chamber 20.
The same arrangement is utilized in maintaining the heat ofthe bath 98 in the tank 96 for heating Athe sterilizing ch'amber 34 for tubing uuid. There the numeral m indicates ,the ther-- mostatically actuated valve, the capillary tube, |09, the thermal bulb, III, tl'ieheater pipe, III,
the bath intake pipe, H2, the heater coil, H3, the coil outlet pipe, ||4, the liquid circulating pump, and I| the discharge pipe leading to the interior of bath 38.
The outlet pipe from the vacuum tank 2l in this case isl the pipe vcommunicating with the pipe IIB, and communicating with the lowest part of the bottom ofthe chamber which pipe ||6 leads to the two parallel conduits ||1 and ||8. Conduit ||1 has the valves H3, |20 on both sides of a meter |2|. Conduit ||8 has the valves |22, |23 on both sides of a Berkefeld lter |24.
Thus, the liquid passing into the vacuum chamber 2l may be metered when it is passing into the chamber, but when it passes out of the chamber, it may be passed through the iilter 52 to filter out the cotton fibers.
The uid liquid supply in chamber 34 may thus always be kept in a state of perfect clarity and the chamber may be kept free of any accumulation of such fibers which are sometimes very ilne and even microscopic.
The pipe |25 leading from the conduits H1, H8 also leads into the bottom of the tank 34 through a T connection and conduit |26 and it may be continued on through the valve |21 to a bacteria-proof lter |28 of the, same type and through a pipe |23 leading into the standard drum of tubing liquid through a liquid-tight connection with the top of the drum.
metically closed chamber, the tubes beln'g securely stopped with bacteria-proof plugs, The tubing uid used has been previously sterilized by heat at the same time as the product and it is introduced into sterile tubes through the sterilizing plugs while the tubes are still within the hermetically closed sterilizing chamber.
The tubes are then sealed without removal of V the plugs and therefore this apparatus is capable of producing a product which could not be other than sterile. The system is so positive and deflnitely predetermined that it does not require the I services of an operator skilled in a knowledge of The drum is preferably connected to a conduit leading to a bacteria-proof air lter |30 which is connected to conduit |3| leading to the air pressure pump |32 so that air pressure may be used for forcing the tubing liquid into the tank 34 when the valve |21 is open.
The tank 34 for sterilizing tubing fluid may also be provided with a pressure recorder |33 adapted to indicate constantly the changes of pressure on a dial by means of a pin. This pressure recorder is essentially a. pressure gauge with indicating mechanism and its bellows may be connected by a capillary tube |34 with' the interior of the chamber 34.
A temperature recorder |35 has a capillary tube |36 leading to a mercury bulb |31 located centrally in the chamber 34 to record constantly on the dial in the same way the changes intemperatureof the tubinguid so as to make a record of its sterilization.
The dials of all these recording instruments have scales and indications of the time as well as indications o f the pressure or temperature. The recorders draw a curve which indicates these values at all times when the apparatusis operating.
The vacuum tank 2l for sterilizing the sutures may also be provided with a pressure pump |33 connected by pipe |33' to the interior of the tank through a valve |33.
The manipulation of this apparatus is substantially the same as that of the apparatus of Fig. 4 except that th'e tubing fluid is sterilized at a different temperature which, while sumcient to sterilize the tubing fluid, would not be suilicient to sterilize the sutures. Due to the y presence of water in alcohol, there takes place in the sterilization .what may be called moist heat sterilization which is effective at temperatures upward of 212 F.
The present apparatus constitutes a'bacteriaclosed system in which there is no possibility of accidental contamination of the product. The sterilization by heat is carried out in an herbacteriology.
Furthermore, the sutures prepared by this process possess better flexibility than when they are prepared by the methods of the prior art and the original tensile strength of the sutures is preserved. l Y
At no point in the handling of the product is it necessary to employ aseptic technic in handling the sterilized tubes.. So long as the plugs are in the tubes, no bacteria can enter.
It should be noted that the valves through which the tubing liquid flows are located withinv the sterilizing oven and this is also true of the ar lters which are adapted to be sterilized by the oven except the piping, filter |24 and meter |2| whichv have to be sterilized on their inside' by other means.
In addition to the fact that all of the air admitted to the system has to Pass through bacteria-proof air filters, this air cannot gain access to the sutures in the tubes until it passes through still another sterile and bacteria-proof lter comprising the plugs and the tubes.
By means of the recording instruments of temperature and vacuum and of the numbering of the sutures by means of numberedslips placed in the tubes I2', a constant checkand record may be kept of the treatment to which any suture has beensubjected. Samples of the sutures from every batch may-be tested for sterility after the process is completed and the results may be taken as an indication of the sterility of the complete batch.
` Should any trouble occur, or any complaint be made regarding sutures ,from any batch, all of the rest of the sutures of that batch may immediately be segregated by reason of the fact that they also are numbered and further check may be made to convince the complaining parties of the fact that the sutures were sterile.
' The various processes which may be carried out according to the invention with the foregoing types of apparatus or other apparatus, are briefly summarized as follows:
Any of the various types of apparatus shown in Figs. 3, 4 and 5 may be used for sterilization of various articles by the simultaneous application of heat and vacuum; We have discovered that when vacuum is .used simultaneously with the application of heat, it is not necessary to apply heat at as high temperatures as may be required when there is no vvacuum employed for sterilization for destruction of micro-organisms.
The simultaneous action of vacuum and heat tends to destroy the micro-organisms with greater facility and certainty than the mere application of heat. We have not been able to arrive at any certain explanation of the action of the Vvacuum and heat together on the micro-organisms, but it'is certain that the destructive action of both of these factors is much greater than either one applied alone.
In addition to the' destructive action of the heat, the vacuum removes from the vicinity of the subject of sterilization, the destroyed microorganisms and it is believed that the vacuum also aids in the destruction of micro-organisms which are not able to withstandthe low pressures or absence of pressure incident to production of a vacuum.
While we prefer to utilize a relatively high vacuum of 29 or 291/2 inches or more, we desire it to be understood that good resultsA may also be achieved by the use of lower degrees of vacuum simultaenously with sterilizing heat. Thus, the method of sterilization comprising the simultaneous subjection of the product to be sterilized to vacuum in an hermetically closed container with the application of heat to a temperature of 150 C., or more, for a period of three or more hours, may be utilized for various types of products.
In some embodiments of the invention the sutures may be placed in the glass tubes and subjected to sterilization by the application of heat after the tubes have been closed by means of a porous plug I8 or a filter paper I8a without the application of vacuum. Some sutures may be packaged and sealed oi as shown in Fig. 2 without utilizing any fluid within vwhich the suture or other product is immersed. In such case the various steps of lling the sealed container with tubing uid, then producing'a predetermined degree of vacuum and again breaking the vacuum to ll the tubes with iluid, may be omitted.
One form of the methods embodying the invention comprises the support of the suture Iilled tubes in jars of glass or porcelain which jars are then placed in an hermetically sealed container. In such case it may be necessary to remove the cover of the container after the sutures have been sterilized by application otheat or the simultaneous application of heat and vacuum.
The jars can then be iilled with sterile tubing tluid by pouring it into the jars until the tubesv` steps may be taken to cause the tubing iluid to lter into the tubes through the lter plugs or papers.
While we have illustrated a preferred embodi- 10 ment of, our invention, many modications may be made without departing from the spirit of the invention, and we do not wish to be limited to the precise details of construction set forth, but desire to avail ourselves of al1 changes within the scope of the appended claim.
Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States, is:
u The process of making sterilized packaged sutures which comprises winding a suture on a reel, placing' the reeled suture into a glass tube open at one end, plugging that end with a plug of cotton, placing the glass tube in a vessel capable of being evacuated and evacuating air therefrom While subjecting the vessel to a temperature suiiiclent to thoroughly sterilize the entire contents of the vessel, cooling the vessel and its contents and restoring atmospheric pressure therein, introducing an aseptic liquid into the vessel until the tube therein is completely immersed and the level of said liquid is well above the cotton plug, partially exhausting air from the vessel to lower the pressure of the air in the tube, allowing air to enter the vessel to restore atmospheric pressure therein whereby to cause said liquid to lter through the cotton plug and partially ll the tube, removing the partially lled tube from the vessel, and then hermetically sealing the glass tube.
WALTER S. DAVIS.
CHARLES T. DAVIS.