US 3315681 A
Description (OCR text may contain errors)
April 25, 1967 F. POPPENDI E K 3,315,681
EMPERATURE MEANS AND TECHNIQUES USEFUL FOR CHANGING T PARTICULARLY BLOOD OF FLUIDS,
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United States Patent 3,315,681 MEANS AND TECHNIQUES USEFUL FOR CHAN G- ING TEMPERATURE OF FLUIDS, PARTICULAR- LY BLOOD Heinz F. Poppendiek, 8686 Dunaway Drive,
La Jolla, Calif. 92037 Filed Aug. 17, 1964, Ser. No. 391,066 8 Claims. (Cl. 128-399) This invention relates to means and techniques useful for changing temperature of fluids and is particularly useful in so-called hypothermia surgery where it is particularly desirable that blood be changed in temperature rapidly.
The present application is a continuation-in-part of my US. patent application Ser. No. 153,317, filed Nov. 20, 1961, now abandoned.
One aspect of the present invention involves the uniform and quick heating of the blood to raise its temperature rapidly and this, in general, is accomplished by a volumetric heating of the same using a cell containing the blood through which an alternating current of higher frequency than the frequency of commercial power sources flows to thereby assure a uniform heating of the same without the effects of polarization which otherwise results in a nonuniform volumetric heating particularly so near the cell electrodes.
The term volumetric heating has reference to the particular type of heating of fluids disposed between electrodes with a current flowing between such electrodes and through the fluids such that heat is supplied by Joule heating instantaneously throughout the body.
The term Joule heating has reference to the quantity of heat generated by an electrical current flowing through an electrical resistance.
Another aspect of the present invention involves the uniform'and quick cooling of the blood when a surgical operation requires the same.
These two above indicated aspects of the present invention may be accomplished using apparatus which is adaptable for either heating or cooling purposes or by using separate apparatus for each purpose.
It is frequently desirable to change the temperature of a fluid quickly and uniformly as it flows along a given path, particularly so in so-called hypothermia surgery. In operations of this type, the patient is chilled by cooling his blood, to either slow down the body and heart functions or to introduce an anesthetized state. Once the operation has been completed, the body temperature must be raised. It has been found if the blood temperathere is a transient state in which the heart fibrillates, or quivers without completing a blood-pumping cycle. This state can be fatal; and it has been found to be avoidable by quickly raising the temperature of the blood.
Another blood-heating condition is desirable when a newly-born infant has Rh factor difficulties. At this time, the infants blood must be drained and replaced by new blood; and the new blood should be at the proper temperature to avoid thermally shocking the infant.
In the past, the blood to be heated was directed through tubing associated with a heat exchanger that warmed the walls of the tubing, and thus the blood in the tubing.
This prior-art arrangement has several serious shortcomings. Firstly, extra blood is required to fill the extra lengths of tubing, Secondly, extra pressure is needed to pump the blood through the additional lengths of tubing. And thirdly, the heat exchanger heats only the blood in contact with the walls of the tubing.
It is therefore a general object of the present invention to provide means and techniques useful in changing the temperature of fluids quickly and uniformly;
. A specific object of the present invention is to provide a heater that rapidly and uniformly raises the temperature of blood passing therethrough.
Another specific object of the present invention is to provide means andtechniques whereby fluids whose structure is sensitive to temperature may be heated rapidly and uniformly without localized heating which otherwise produces changes in the fluid structure.
Another specific object of the present invention is to provide volumetric heating means involving an electric current conducting cell for heating fluids passing through the cell, with such means obviating the necessity of using cooling means for the cell electrodes, particularly so when the fluids are of such nature that they undergo changes in composition with temperature somewhat above the desired heating temperature.
Another specific object of the present invention is to provide a heating system for this purpose wherein the cell through which the fluids pass is energized with electric currents of elevated frequency such as to avoid the effects of polarization and resulting localized heating at regions where such polarization manifests itself as a high electric resistance and thus where heating is localized.
.Another specific object of the present invention is to provide a system which is convertible for either heating or cooling purposes, with the heating or cooling, as the case may be, being accomplished efliciently, uniformly, with small pressure drop of the fluids and within a short flow path.
Another specific object of the present invention is to provide a system of this character which is particularly useful in heating fluids which are essentially colloidal dispersions of low electrical and heat conductivity such as, for example, blood and milk.
The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. This invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in connection with the accompanying drawings, in which:
FIG. 1 is a perspective view, partly in section, of a heater embodying the present invention.
FIGS. 2 and 3 are generally sectional views taken substantially as indicated by corresponding lines 2-2 and 33 in FIG. 1, with FIG. 3 illustrating also the electrical connections to the heater in a system also embodying features of'the present invention.
FIG. 4 is a perspective view, partly in section, of a modified form of the present invention in which alternately there may be either a fluid heating or a fluid cooling.
FIG. 5 is a sectional-view taken generally on line 5-5 of FIG. 4 and also illustrates electrical connections in a system also embodying features of the present invention.
FIG. 6 illustrates another formof the present invention.
FIG. 7 illustrates two graphs, one being labeled cell resistance and the other graph being designated hemolysis with in both instances the abscissae being alternating current frequencies in cycles per second and the ordinates in the first instance on the right being ohms and in the latter instance on the left, hemolysis per unit time in terms of mg. Hb/ml. plasmaxmin, i.e., milligrams hemoglobin per milliliter of plasma times minutes.
In prior art systems when the tubing through which the fluid liquid flows is in a bath of hot water, the hot water heats the walls of the tubing, and the liquid in contact with the walls of the tubing is therefore heated. This heating process is known as wall heating. It is obvious that the liquid in the center of the tube is not readily heated, and it requires turbulent flow of the liquid to bring all the fluid into contact with the heater walls. For optimum heating in the wall heating method, the tubes should have a small diameter, so that all the fluid in the tube is heated. Unfortunately, small diameter tubes require a high pressure to force the fluid therethrough. In the case of blood heating, this overloads the heart, or requires external pumps.
In contradistinction to wall heating, one aspect of the present invention contemplates volumetric heating, wherein all of the fluid in a given volume of space is heated simultaneously. Not only is this more efficient from a thermal point of view, but it obviates the need for small diameter tubes, turbulent flow, and the ancillary problem of auxiliary pumps.
Blood is not a goo-d conductor of electricity and is such that it becomes ionized upon application of voltage between electrodes between which such blood is disposed. The blood undergoes an ionization process in that electrical charges and ions are produced that are free to movetowards such electrodes. This characteristic places blood in the class of electrolytes that is, liquids that will conduct electricity therethrough in a limited manner. These ions of course have a certain mobility which signifies their capability of moving at a particular speed under the influence of an electrical field. This ionization in (the presence of certain electrical fields may result in what is termed polarization, i.e., the formation of localized regions near the electrodes which modify the further flow of current between the electrodes. The terms ionization, mobility and polarization are used above in their generally accepted meaning and as set forth in Van Nostran-ds Scientific Encyclopedia, D, Van Nostrand Company, Inc., Third Edition, 1958.
The heating system of the present invention contemplates the flow of fluids between two electrodes that are connected to a source of alternating current of frequency above the commercial power frequency of 60 cycles per second to produce a flow of electrical current through the fluids between the electrodes, thus heating the entire volume of fluids and giving rise to what is referred to as volumetric heating wherein there is a uniform heating throughout all of the fluids between the electrodes,
Referring to FIG. 1, the heater comprises a central portion 12 and two end portions 14. The central portion 12 is preferably rectangular, and electrodes 16 are positioned adjacent two opposing walls thereof. The end portions 14 are transition members, in that they change cross-section from a rectangle adjacent the central portion 12 to circular cross-sections adjacent the inlet and outlet 22.
The electrodes 16 are connected to a source of power 18, as in FIG. 3. The electrodes 16 are adjacent the larger walls of the heater 10 to achieve a maximal flow of electrical current through them minimal thickness of the fluid.
When a patients blood is to be heated, a blood vessel 24 of the blood circulatory system is severed and attached in a leak-proof manner to the inlet 20 and outlet 22 of the heater, as indicated in FIG. 2. The power source 18 is then energized so that, as blood flows from blood vessel 24 into heater 10, a potential is applied 'across the blood by electrodes 16. This potential causes an electric current to flow through the blood in a direction transverse to the flow of blood. These relative directions are illustrated in FIG. 2 wherein the flow of electric current between the electrodes 16 is indicated by the series of double-arrowed lines 8 and the direction of blood flow is indicated by the arrows 9. The heating effect is 1 R, a well-known factor, where I is the amount of electric current, and R is the resistance of the blood to the flow of electric current, 'As previously indicated, the bloods resistance, R, is quite high; and I have found that a power source that produces about 5-10 volts provides completely satisfactory results.
If a direct current source is used, the blood becomes polarized, the heating of the blood is nonuniform, and various gases which I have observed but not analyzed chemically may be produced at the electrodes, with these gases dissolving in or being carried along the blood stream. This is extremely objectionable.
To obviate this situation, an alternating current (AC) power supply 18 is used of such high frequency that produces substantially little, if any, polarization of the blood between the electrodes. As is well known, alternating current produces a heating effect in the same manner as direct current, and a direct current may be considered to be a current of zero frequency. Merely increasing the frequency of the supply current to 60 cycles per second does not obviate the problems resulting from the effects of polarization, but in accordance with important features of the present invention, the frequency is well above 60 cycles per second.
Electrodes 16 should be inert so that they do not react with or affect the blood. I have found that platinum electrodes are completely satisfactory. The electrodes may be plates or sheets that are attached to the inner surface of heater 10, or may be deposited thereon in any well-known manner.
It is preferable that each vertical cross-sectional area of the central and end portions 12 and 14 of the heater be equal to each other and equal to that of the inlet and outlet 20, 22. The arrangement assures that there is no constriction to hamper the blood-pumping action of the heart. It also assures that there will not be any appreciable air or gas space in the vessel above the blood level. In this way, the entire surface area of electrodes 16 is utilized.
Depending upon the judgment of the surgeon, the heater may be spliced into an artery or, alternatively, into a vein. Since these blood vessels are of different sizes and transmit different volumes of blood, it may be desirable to have blood heaters of different sizes.
Present-day blood heaters require about 10-20 minutes to raise the blood temperature the desired amount. The present heater can provide the same temperature rise in .about 3-5 minutes, and can warm the blood from about 50 F. to 98 F. in about two passes of the patients blood through the heater. Of course, the length of the central chamber defined by the hallow central portion 12 coacts in establishing the rate and time of heating. This rapid heating obviates the danger of fibrillation.
The blood heater 10 is preferably formed of a material that is non-reactive with blood, and does not produce coagulation, polyethylene being one such suitable material. Since various plastics, such as polyethylene, are transparent, this structure also permits the surgeon or an assistant to actually see the color of the flowing blood.
The present invention has another important advantage. Since my heater is small, light and compact, it may be brought to the patient rather than having the patients blood brought to the heater as was necessary with priorart devices.
There are times when it is desirable to raise the patients temperature to create an artificial fever. The present heater may readily be used for this purpose.
The problem of heat transfer is discussed in the following publications which are identified as follows: an article entitled Forced Convection Heat Transfer in Ducts With Volume-Heat Sources Within the Fluids, by H. F. Poppendiek, appearing in Chem. Engr. Prog. Symp. Series, vol. 50, No. '11, pp. 93404 (1954), and in an article entitled Forced Convection Heat Transfer Between Parallel Plates and in Annuli With Volume Heat Sources Within the Fluids, by H. F. Poppendiek and L. D. Palmer, appearing in Oak Ridge National Laboratory Report No. 1701, May 1954. On the basis of these publications it can be demonstrated that 5.66 times as much heat can be added to the blood per unit time when it is added volumetrically than in the case where heat is required to be transferred through a wall.
It may be readily seen that the heater has innumerable advantages over prior-art liquid heaters. Firstly, it is small, lightweight and compact. Secondly, it may be brought to the patient, thus obviating the need for piping the patients blood to a remotely positioned heater. Thirdly, the heater may be transparent, so that the color of the blood may be studied. Fourthly, it has been theo retically and practically proven that and times as much heat can be added as by conventional surface heating methods, but at no time are there hot elements that may be touched. Fifthly, the heater minimizes the danger of heart fibrillation. The heater does not introduce long thin tubes that require additional pressure and additional holdup volumes to maintain the flow of blood. And finally, the heater can provide instant heat for producing an artificial fever, or heating new blood that is being introduced into the patients body. Also, additional advantages result from the application of heating currents which are higher in frequency than the frequency of commercial power sources.
In the form of the invention illustrated in FIGS. 4 and 5, means are provided for alternately heating or cooling blood.
As illustrated, three cells 30 are provided in a single housing 26 with each cell including a pair of electrodes 30A, 30B, the electrodes 30A being each connected to one terminal of A.C. source 34, and the electrodes 303 being each connected to the other terminal of A.C. sources 34 through switch 34A.
The electrodes 30A, 3013 as in FIG. 1 are in the form of conductive rectangular plates of, for example, platinum.
The housing 26 is formed with two spaced partition members 36 and 37 of insulating material which define end walls of the cells 30 and in general define a passageway for the flow of blood between the extended openings 38 and 39 on opposite sides of housing 26.
Means are provided for cooling the electrodes in those instances where cooling instead of heating of the blood is desired, and such means involves the four like rectangular coolant passageways 42, 43, 4'4 and 45 which extend between aligned rectangularly aperture-d portions in the partitions 36 and 37, the passageways 43, 44 each being defined by electrodes 30A, 30B of adjacent cells and their corresponding upper and lower spacer strips 46, 47'. The passageways 42 and 45 are of like construction, with the space between metal plates 50, 51 and adjacent side wall of housing 26 being occupied by a corresponding filler 52, 53 of insulating material.
It will be seen that this construction provides for a blood manifold 55, 56 respectively above and below the individual cells and also a coolant manifold 59, 60 at opposite ends of the coolant channels.
Using the arrangement shown in FIGS. 4 and 5, the source of heating current is an A.C. source having a frequency above 60 cycles per second, and when heating of the blood is desired, the switch 34A isclosed and no coolant need be supplied. Coolant is supplied only when cooling of the blood is desired in which case the source is disconnected by opening switch 34A so that such cooling may occur in the absence of any heating produced as a result of current which would otherwise flow from source 34.
During the heating cycle, the blood may flow upwardly through the cells and may flow downwardly through the cells during the cooling cycle or in some instance the direction of flow may be the same in the heating and cooling cycles.
For these purposes preferably, as disclosed, the direction of coolant flow which may be a water flow is perpendicular to the direction of blood flow.
The use of an A.C. source having a frequency greater than 60 cycles per second is considered very important since, as mentioned previously, the use of DC. and an A.C. source of commercial 60 cycles per second frequency results in polarization effects manifested by localized heating at the electrodes, and in some cases the formation of gases at the electrodes. Using an A.C. source of frequency greater than 60 cycles per second, polarization effects resulting in localized heating at the electrodes are eliminated. While it has been suggested that an A.C. source of commercial 60 cycles per second be used in heating a colloidal dispersion such as milk, the necessity then arises for providing a cooling means for the electrodes, i.e. in accordance with such suggestion the electrodes should be cooled at the same time the colloidal dispersion is being heated. A further advantage resulting from the use of an A.C. source of frequency greater than 60 cycles per second is thus that in the heating of colloidal dispersions no cooling means need be used in conjunction with the heating means when such heating means is effective.
While references has been made above to the use of an A.C. source having a frequency greater than 60 cycles per second, tests have shown that more precisely the frequency of the A.C. source should not be below 200 cycles per second. While the lower limit of frequency is established by the absence of or substantially elimination of polarization effects, the upper limit of frequency is established by a different effect termed the skin effect. The skin effect is well-known among radio engineers and manifests itself as a nonuniform distribution of current through a conductor, like the electrolyte in this instance, with the current density being greater near the outer surface of the conductor. This manifestation of skin effect is in accordance with the definition of this term appearing on page 1508 of Van Nostrands Scientific Encyclopedia, Third Edition, 1958. It is desirable in this instance that there be uniform heating, i.e. the uniform distribution of heating current through the liquid between the electrodes, and thus the frequency of the A.C. source should not be so high as to result in substantial nonuniformity in current density between electrodes. For this latter reason, preferably the A.C. source has a frequency within the audio range extending above 200 cycles per second, with the upper frequency limit being established by the absence of any substantial skin effect. Practical sources having the required current or power capabilities for the present uses are found in the 400-800 cycles per sec-ond range, and for this reason and for the foregoing reasons the present invention may be practised in a good practical way using an A.C. source having a frequency lying within the range of 400- 800 cycles per second and capable of supplying approximately 1170 watts of power in those instances where it is desired to quickly elevate the temperature of approximately 10 lbs. of blood, 25 Fahrenheit, in 3 minutes, with all of the blood of an average individual passing only once through the heater. The arrangements shown in FIGS. 4 and 5 are particularly suitable for these purposes using a current density through the blood which does not exceed approximately 1 ampere per square centimeter. For these purposes, the spacing between the electrodes is preferably forty thousandth of one inch, and based on a blood resistivity of approximately ohm-centimeters, the voltage in such case is approximately 21 volts.
The above-mentioned results are indicated in FIGURE 7 which illustrates two graphs, one being a graph of cell resistance versus frequency in cycles per second and the second graph being hemolysis versus the same abscissae, namely, frequency in cycles per second. It will be seen, as alluded to above, that the cell resistance and hemolysis each remain substantially constant at frequencies above two hundred cycles per second. At frequencies below two hundred cycles per second, there is a marked rise in both cell resistance and hemolysis and this is believed due to the effects of polarization occurring at frequencies lower than two hundred cycles per second. Also, as mentioned 8 previously and as indicated in FIGURE 7, tests have indicated that there is gas generated at frequencies lower than two hunderd cycles per second but in accordance with important features of the present invention, there is no gas generation at frequencies above two hundred cycles per second.
For cooling of the same amount of blood in the same time in only one passage of the same, the spacing of those plates defining the cooling channels may also be approximately forty thousandth of one inch.
In the modification shown in FIG. 6, volumetric heating of fluids in their frozen state may be accomplished quickly and uniformly using a condenser discharge which, because of its rapidity, results in the absence of polarization effects, and hence localized heating. In this instance, the liquid which may be blood is placed in a frozen state between 'a pair of flat plate electrodes 60 and 61, with one plate electrode 61 being at ground potential and with the other electrode 60 being connected to the stationary contact 62 of a single-pole double-throw switch 63 having its other stationary contact 64 connected to the ungrounded terminal of a DC. source 66 and having its movable contact 67 connected to the ungrounded terminal of a capacitor 69. Initially, the contacts 67 and 64 are engaged to charge the capacitor 69 after which the contacts 62 and 67 are closed to allow the precharged capacitor 69 to discharge its stored energy into the frozen liquid between electrodes 60 and 61. It will be appreciated that the energy initially stored in capacitor 69 may be calculated to be that energy required to produce a predetermined amount of heat in the material between electrodes 60 and 61, and this energy may be such that it is sufficient to supply the heat of fusion required to melt the frozen liquid between electrodes 60, 61, or for that matter may be greater than the heat of fusion to elevate the melted fluid. In this case, because of the rapid transfer of energy there is no time for polarization effects to manifest itself, and thus there is a uniform heating throughout the fluid. The rapidity of such energy transfer from capacitor 69 to the fluid may be controlled using a resistance '70 connected in the line extending from switch contact 62 to plate electrode 60.
Thus, broader aspects of the present invention involve the fact that heating current should be passed through a fluid at a rapid rate which does not introduce polarization effects resulting from, for example, the migration of ions and their accumulation as space charges. In other words, the rate of current flow is believed to be related to the mobility of the ions in the fluid such that the ions are incapable of moving at the same rate as the current flow, and hence the ions are incapable of accumulating as a space charge which would manifest itself as regions of high resistance and thus regions which would otherwise be productive of localized heating.
It will be appreciated that the heating current need not necessarily be derived from what may be termed 'a sinusoidal voltage source since, for example, pulses or recurrent capacitor discharges may be used at recurrent rates outlined above, the recurrent rate being such that it is not too low as to result in polarization, but should not be so high as to introduce skin effect.
It will also be appreciated that in the arrangement shown in FIG. 6 the electrodes 60 and 61 may be spaced and held as an assembly by insulating spacers so that such electrodes may then be used as a form in which the fluid is frozen. In such case, the electrodes 60 and 61 besides serving as a container for the frozen fluid are used for making the electrical connections shown in FIG. 6.
While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover -all such changes and modifications as fall within the true spirit and scope of this invention.
I. A liquid heater system comprising: a longitudinal chamber having an inlet and an outlet whereby an electrolytic liquid may flow through said chamber; a pair of spaced-apart electrodes adapted to be connected to a source of AC. potential; said electrodes being positioned in said chamber so that liquid flowing between said electrodes may be heated by the current resulting from a potential applied to said electrodes; and a source of alternating current of audio frequency greater than 200 cycles per second connected to said electrodes.
2. A liquid heater system comprising: a chamber of substantially rectangular cross-section; an inlet; an outlet; at first transition member connected between said inlet and said chamber; a second transition member connected between said outlet and said chamber whereby an electrolyte may flow from said inlet, through said chamber, into said outlet; and a pair of electrodes adapted to be connected to a source of AC. potential; said electrodes being positioned adjacent the inner surfaces of the opposite walls of said chamber whereby the potential applied to said electrodes heats the liquid flowing through said chamber between said electrodes; and a source of alternating current of audio frequency greater than 200 cycles per second connected to said electrodes.
3. A volumetric blood heater system comprising: a chamber of substantially rectangular cross-section; a pair of electrodes positioned adjacent to the inner surface of the larger opposing walls of said chamber; an inlet; an outlet; a first transition member connected in a leakproof manner between said inlet and said chamber; a second transition member connected in a leak-proof manner between said outlet and said chamber whereby blood 'will flow from said inlet, through said chamber, between said electrodes, and out of said outlet; and a source of AC. audio potential having a frequency greater than 200 cycles per second connected between said electrodes.
4. A volumetric blood heater system comprising: a chamber of substantially rectangular cross-section; a pair of electrodes positioned adjacent the inner surface of the larger opposing walls of said chamber; an inlet; an outlet; a first transition member connected in a leakproof manner between said inlet and said chamber; a second transition member connected in a leak-proof manner between said outlet and said chamber; each vertical cross-section of said transition members and said chamber being substantially equal to the cross-section of said inlet whereby blood will flow from said inlet, through said chamber, between said electrodes, and out of said outlet, keeping said transition members and said chamber substantially full; and a source of audio A.C. potential of frequency greater than 200 cycles per second connected between said electrodes.
5. A method of heating blood which comprises: circulating blood through a chamber between spaced electrodes; and applying an audio A,C. potential having a frequency greater than 200 cycles per second across said electrodes.
6. A cell structure comprising a housing having substantially circular end portions forming a fluid inlet and a fluid outlet for the cell, said housing having a hollow central generally rectangular portion defined by oppositely disposed wall portions, and a pair of hollow transition portions each joining a corresponding end of said rectangular portion to a corresponding one of said end portions, the cross-sectional area of each of said end portions, rectangular portion and said transition portions being substantially equal, and a pair of aligned parallel extending and generally rectangular electrodes, one of said electrodes being on one of said wall portions and the other of said electrodes being on a Wall portion opposite to said one wall portion with the spacing between said electrodes being substantially less than the smaller and larger dimensions of said rectangular electrodes, said electrodes defining opposite walls of a passage for fluid flow from said inlet to said outlet, the cross-sectional areas of said end portions, transition portions and the cross-sectional area of said central portion between electrodes being each substantially the same, the larger dimension of said rectangular electrodes extending in the direction of fluid flow.
7. A housing having an inlet and an outlet, spaced partition means in said housing defining a space for confining generally the fluid flow in its pasasge between said inlet and outlet, a plurality of pairs of spaced parallel electrodes extending between said partition means with each pair defining a passageway through which fluid flows in its passage from said inlet to said outlet, said spaced partition means having aligned apertured portions, and means including said electrodes extending between said aligned apertured portions and defining channels for the flow of a liquid flowable between said apertured portions in a direction which extends perpendicular to fluid flow between said electrodes.
References Cited by the Examiner UNITED STATES PATENTS 1,668,293 5/1928 Vantuyl 21940 2,188,625 1/1940 Dufour 21940 2,934,067 4/1960 Calvin 28-214 3,064,649 11/1962 Fuson l282l4 3,154,663 10/1964 Halvorsen 128214 X RICHARD A. GAUDET, Primazy Examiner. SIMON BRODER, Examiner.