Title:
REBREATHING APPARATUS FOR ANESTHESIA
United States Patent 3612048


Abstract:
A device for recirculating air to a patient combining the simplicity of the to and fro type of apparatus with the advantages of the circle type. Dead space is avoided by use of two venturis which enhance flow rate through a canister of carbonic gas-absorbing material. The absence of valves lowers resistance and increases efficiency.



Inventors:
TAKAOKA KENTARO
Application Number:
05/012598
Publication Date:
10/12/1971
Filing Date:
02/19/1970
Assignee:
KENTARO TAKAOKA
Primary Class:
Other Classes:
128/205.12, 128/205.17, 128/205.28
International Classes:
A61M16/10; (IPC1-7): A61M17/00
Field of Search:
128/188,185,195,202,205,211,145.7,191,191A
View Patent Images:
US Patent References:
3200818Breathing apparatus1965-08-17Johannisson
3097642Face mask1963-07-16Russell
2891542Infant anesthetic machine1959-06-23Pentecost
2352523Apparatus and method for artificially inducing breathing1944-06-27Emerson
2325049Breathing apparatus1943-07-27Frye et al.
0802339N/A1905-10-17



Foreign References:
FR569201A
FR1298409A
DE277995C
DE318786C
IT277961A
NL78842A
Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Howell, Kyle L.
Parent Case Data:


CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of my copending application Ser. No. 596,266, filed Nov. 22, 1966, now abandoned and entitled REBREATHING APPARATUS FOR ANESTHESIA.
Claims:
What is claimed is

1. A rebreathing apparatus for the recirculation to a patient of air or air plus an anesthetic combined with fresh gases from a source of gases, of the type in which carbonic gas is removed from the gases exhaled by a patient, comprising: a canister adapted to contain carbonic gas-absorbing material for purifying gases passing through it; two hollow end parts mounted on opposite ends of the canister, one end part being fitted with a gas reservoir means and the other end part including an offtake tube connected to means adapted for delivery of gases to a patient; an inlet tube on said one end part for admitting fresh gases under pressure and an outlet tube on said one end part aligned with the inlet tube, the inlet tube having an inwardly tapering orifice forming a venturi within the one end member for drawing gas circulated through the canister into a stream flowing from the inlet tube to the outlet tube; means in communication with said other end part permitting controlled escape of gases from said other end part; and conduit means extending from the outlet tube to the other end part adjacent the offtake tube for supplying a patient with recirculated gases mixed with fresh gases.

2. Apparatus according to claim 1 wherein said conduit means is a flexible tube extending longitudinally alongside the canister connected to said outlet tube and to an intake tube on said other end part, the intake tube lying perpendicular to the offtake tube.

3. Apparatus according to claim 2 wherein said intake tube has a tube portion extending within said other hollow end part, the tube portion having an opening directed toward the canister thus providing a second venturi for enhancing circulation.

4. Apparatus according to claim 1 including a perforated element extending transversely across the inside of the canister and a spring means for biasing the perforated member toward said other end part for compacting carbonic gas-absorbing materials within the canister.

5. Apparatus according to claim 1 wherein the canister is cylindrical, and the hollow end parts include truncated conical extensions terminating in hollow cylindrical members.

6. Apparatus according to claim 5 wherein said offtake tube extends perpendicularly from the hollow cylindrical member of said other end part.

7. Apparatus according to claim 1, wherein an inner end of said inlet tube and an inner end of said outlet tube are interfitted within a space defined inside said one hollow end part, a small chamber being defined by said outlet tube adjacent the point at which said inlet and outlet tubes are interfitted, said small chamber being in communication with the space defined within said one end part whereby recirculated gases may flow into the chamber from said space.

8. Apparatus according to claim 1 wherein said means permitting controlled escape of gases includes and exit valve having a plurality of apertures, the valve being selectively adjustable to bring one of said apertures into registry with an exhaust passage from said other end part for selectively controlling gas pressure to a patient.

9. Apparatus according to claim 1 wherein said gas reservoir means is an inflatable breathing bag.

10. Apparatus according to claim 1 wherein said canister includes two transversely extending perforated plates for containing said absorbing material therebetween, each of said plates having a centrally disposed baffle for preventing channeling of gases through the absorbing material.

Description:
BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rebreathing apparatus for use in anesthesia to provide a continued supply of air or an anesthetic gas mixture to a patient by purifying and returning exhaled gases to a patient mingled with freshly supplied gases.

2. Description of the Prior Art

There are two well-known types of rebreathing devices in the art of anesthesiology. Since exhaled gases in both such types of rebreathing devices include means for removing carbonic gases by absorption, these rebreathing devices are commonly called "absorbers."

The type of rebreathing device known as a "circle" absorber comprises two tubular branches connected by a Y-piece to a fitting or mask through which the patient breathes, with exhaled gases passing through one branch to a carbonic gas removing element, and recycled gases for inhalation flowing to the patient through the other branch.

In the circle-type absorber two directional valves are necessary to control gas circulation. Because of the resistance such valves present, it is necessary that different models of a circle absorber of any given design be provided, one model being adapted to use in the anesthesia of children.

The second type of rebreathing device is called the "to and fro" or "pendular" absorber. The construction of the to and fro absorber is simpler than that of the circle absorber, but there are serious disadvantages to its use.

In both types of absorber carbonic gas is removed by passage of exhaled gas through a canister of CO2 absorbing material, such as crystalline soda lime. In the to and fro type of absorber gases pass back and forth through the CO2 absorbing material. As the granules of absorbent material become saturated with CO2 some intergranular space in the canister is exhausted. This henceforth useless space is called "dead space." Since the tidal volume, or volume of air or gases breathed in and out by an infant or child is much less than that of an adult's respiration, the amount of "dead space" in the device is critical, and devices of varied sizes must be used for the various age groups to avoid endangering the life of the patient.

SUMMARY OF THE INVENTION

The rebreathing apparatus of the invention comprises a cylindrical canister for CO2 absorbing material, fitted at each end with a truncated conical cap. One cap has a fitting for a breathing bag and an inlet for gases under pressure, and the other has a tubular extension provided with a right-angle mask elbow for direct connection to a breathing mask or endotracheal tube.

The device differs from the to and fro absorber in that a bypass hose or tube extends externally of the canister for circulatory flow of pure gases from the bag end to the patient end of the system. A venturi is provided near each end of the bypass tube. At the inlet end, gas admitted has its velocity increased, flowing rapidly through the bypass tube after picking up purified gases leaving the canister. At the patient end a second venturi directs the flow of expired gases into the canister and compensates for pressure differences so that the system presents virtually no resistance to respiration.

A selectively adjustable exit valve at the patient end of the system permits control of the venting of excess gas, thereby keeping the breathing bag semiinflated without any need for precise inflow adjustment.

Thus absorption efficiency is increased by a high-velocity circulation of gases, eliminating canister dead space. The capacity of the CO2 absorbing material is uniformly exhausted. Thus the system provides the advantages of a circle absorber while retaining the simplicity of a to and fro absorber.

It is accordingly an object of the invention to provide a rebreathing device for anesthesia characterized by efficient CO2 absorption and maximum reduction of apparatus dead space.

A further object is to provide a semiclosed rebreathing system for economy of anesthetic agents and which allows spontaneous, assisted or manually controlled ventilation.

Another object of the invention is to provide a versatile, portable rebreathing apparatus having minimal respiratory resistance due to the absence of inspiratory and expiratory valves.

Other objects and advantages of the invention will become apparent from the following detailed description, taken together with the accompanying drawings illustrating a specific embodiment of the rebreathing device.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in perspective of a rebreathing device in accordance with the invention;

FIG. 2 is an enlarged sectional view of the apparatus of FIG. 1 with some parts omitted;

FIG. 3 is a side view of the apparatus of FIG. 1 taken along a line perpendicular to FIG. 2 with some parts shown in section and some parts omitted;

FIG. 4 is a detail view of an adjustable exit valve of the apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the rebreathing device of the invention is generally indicated by the reference numeral 10. A generally cylindrical canister 11 having truncated tubular end pieces 12 and 12a is adapted to contain a quantity of carbonic gas absorbing material, such as that distributed under the trademark SODASORB. As shown, the canister 11 and end pieces 12 are of sheet metal, but the canister might also be of synthetic resinous material, such as Lucite. A reversible canister might be employed, if desired.

Referring now to FIG. 2, it can be seen that the lower end part 12a is removably secured to the canister 11 by a knurled ringlike fitting 13 within which an annular gasket 14 is fitted to seal the joint against gas leakage. The upper end piece 12 may be permanently secured to the canister 11 as shown. This arrangement permits removal of the canister 11 for refilling with CO2 absorbing material.

The inlet end of the device, shown lowermost in FIGS. 2 and 3, includes a male bag holder fitting 15, generally tubular in shape with an outwardly directed lip 16 for engaging a breathing bag, the fitting tapering inwardly beyond the lip 16 at 17. Mounted within the fitting 15 and extending outwardly therefrom is a basketlike element 20 for insertion into a breathing bag to keep the bag's mouth open for entry and exit of gases.

As best shown in FIG. 3 the bag holder 15 is formed as an extension of a generally tubular member 21, mounted on and extending into the lower conical end piece 12a. The member 21 has a central cavity 23. The member 21 is secured to the end piece 12 by a sleeve 22 fitted into the end piece.

The sleeve 22 receives inwardly the tubular member 21 and tightly seals the connection against gas leakage.

A gas inlet and circulation element 24 extends transversely through the tubular member 21.

The element 24 serves as inlet conduit for input anesthesia gases and/or air and as an means for mixing input gases with recycled purified gases.

One end of the element 24 is formed generally as a nipple 25 for connection to a connective tube. A tapering passage 26 through the nipple 25 is fitted with a porous filter element 27 for cleaning the input gases. As clearly shown, the passage 26 has a gradually stepped, inwardly narrowing taper, terminating in a very narrow passageway at 30, centrally of the chamber 23, serving to greatly increase the velocity of input gases.

Interfitted with the inner end of the inlet element 24 adjacent the end of the passageway 30 is the inner end 31 of a generally tubular outlet element 32 for the mixture of input gases and recycled gases. Like the element 24 the outlet element 32 is formed as a nipple at 33 for connection to a bypass hose or other conduit 34 shown in FIG. 1.

A generally conical central orifice 35 through the outlet branch element 32 has a gradual outwardly widening taper. The orifice 35 of the outlet branch 32 is aligned with and in registry with the central orifice 26 of the inlet branch 24. Adjacent the point where the orifices 26 and 35 approach each other the stream of gases flowing rapidly therethrough contacts the gases within the chamber 23, thereby acting as a venturi to suck in gases from the surrounding chamber 23.

As shown in FIG. 2, the narrowed inner ends of the orifices 26 and 35 open into a small chamber 31 formed within the outlet branch element 32. The small chamber 31 is in communication with the surrounding chamber 23 by way of a plurality of openings 31a formed through the wall of the outlet branch element 32. Thus, as stream of rapidly flowing gases from the constricted portion 30 of the inlet orifice 26 pass toward and into the outlet orifice 35 the venturi effect in the small chamber 31 draws purified gases from the chamber 23 into the rapidly flowing gas stream through the openings 31a.

The inlet branch element 24 and the outlet branch element 32 have outer diameters smaller than the diameter of the tubular chamber 23 so that gases may flow freely to and from the breathing bag through the chamber 23. As shown in FIG. 2, the inner end of the inlet branch element 24 is threadly received within the inner end of the outlet branch 32 for easy assembly and disassembly.

At the opposite end of the canister 12, i.e., the patient end of the apparatus, the conical end piece 12 is threadedly secured to a generally cup-shaped end piece 40 into which a transversely extending circulation tube 41 is fitted. The circulation pipe 41 is formed as a nipple at 42 is fitted. The circulation pipe 41 is formed as a nipple at 42 to receive the "patient end" of the bypass tube 34.

At right angles to the circulation pipe 41 and transversely oriented with respect to the end piece 40 is a mask elbow 43, threadedly secured to the end piece 40. A sealing gasket 43a serves to prevent leakages at the joint. Both the mask elbow 43 and the circulation pipe 42 have axially extending passages in communication with a generally cylindrical chamber 44 formed within the end piece 40. The chamber 44 opens on to the conical end piece 12 so that gases may flow freely therethrough to the canister 11.

The circulation pipe 42 is tubular and has its end in abutment with a wall of the end part 40. An aperture 45 through the wall of the circulation pipe 42, directed toward the canister 11, permits gases flowing through the end pipe 42 to enter into the chamber 44. Since the gases flow rapidly through the restricted aperture 45 into the larger chamber 44 the venturi effect operates, inducing gases in the chamber 44 to tend to flow towards the canister 11. This second venturi overcomes resistance to patient respiration.

The mask elbow 43 has double generally annular walls, an outer wall 50 and an inner wall 51, formed with a slight double conical taper for easy connection either to a conventional breathing mask for a patient, as shown in FIG. 1, or for connection to an endotracheal tube.

As shown in FIGS. 2, 3 and 4, there is an exit valve 52 at the base of the cuplike end part 40. The valve 52 has a disc 53 rotatably secured at its axis to the end part 40 by a pin 54. Five exit apertures 55, two of which are shown in the FIG. 3 at 55a and 55b , pass through the valve disc 53 at radially spaced locations, so that by rotation of the disc 53 any one of the apertures 55 can be brought into registry with a passage 56 extending through the base of the end part 40 from the chamber 44. Each of the exit apertures 55 is of a different diameter, so that by bringing a selected one of the apertures 55 into registry with the passage 56, a particular rate of flow of exiting gas can be achieved.

A spring and ball check device 57 mounted in a recess in the end part 50 cooperates with spaced depressions in the back of the valve disc 53 to lock the valve 52 in the chosen position.

The canister 11, as shown in FIG. 2 is adapted to securely contain a quantity of closely packed granules of a carbonic gas-absorbing substance. Since suitable-absorbing materials tend to become reduced in volume with use, a spring-biased mechanism is preferably provided to hold the absorbing material. A perforated disc or screen 60, slidably fitted within the canister 11, has a centrally positioned baffle plate 61 to which the narrow end of a generally helical spring 62 is received between a pair of annular lips or flanges 65 extending outwardly from the sleeve 11 within the conical end piece 12a.

The patient end of the canister 11 is fitted with a perforated plate or screen 66 for containing the carbonic gas-absorbing material while permitting passage of gases to and through the absorbent material. A second baffle plate 67 in the form of a flat disc is secured at the center of the perforated disc 66 in alignment with the baffle plate 61. The two baffles 61 and 66 prevent gas from following a direct course through the middle of the canister 11, since such channeling results in inefficient nonuniform consumption of the absorbing material.

The breathing bag 70, shown in operating position secured to the bag holder 15 in FIG. 1, is of the conventional pecan shape and is preferably of lightweight elastic material. FIG. 1 also shows a conventional respiratory face mask 71 in operating position secured to the mask elbow 43.

The inlet branch element 24 may be provided with a small transversely extending nipple 24a for connection to a pressure-measuring manometer for determining the flow through the rebreathing devices.

MODE OF OPERATION

In ordinary operation the inlet branch 24 is connected to a source of air or anesthetic gases under pressure and a face mask or other means supplying gases to a patient's respiratory circuit is connected to the elbow 43.

As the patient exhales the exhaled gases pass into the chamber 44 and thence through the carbonic gas-absorbing material in the canister 11 to be either recycled to the patient through the bypass tube 14 or held in the breathing bag 70, which serves as a gas reservoir.

Gas entering the inlet branch 24 is diluted with exhaled air from which carbon dioxide has been removed by its passage through the carbonic gas-absorbing material in the canister 11. This effect is produced by the action of the venturi at 31 where gases from the chamber 23 are drawn through the apertures 31a into the swiftly flowing stream passing from the inlet branch 24 to the outlet branch 32.

Preferably the dimensions of the system are so elected that the hydrodynamic forces active at the venturi result in a 10 : 1 dilution of input gas by gases to be recycled. Thus a flow rate of 20 liters per minute has been achieved with an input rate of 2 liters per minute.

The mixed stream of input gases and gases recycled from the patient's breathing circuit then passes through the bypass conduit 34 to the chamber 44 at the patient end of the device. Here the action of the second venturi removes expired gases from the mask of the patient by suction produced in the swift flow of recycled gases through the narrow aperture 45 into the upwardly widening chamber 44.

The action of this second venturi balances the flow so that there is negligible resistance even to the breathing of newborn infants.

A constant rapid velocity circulation of gases is maintained through the system, regardless of whether the patient is inspiring or expiring. This results in higher absorption efficiency by eliminating canister in circulating through the system the temperature of inhaled gases is kept low.

The patient always inhales CO2 -free gas because of the absorption efficiency of the system. Exhaled gases are quickly swept into the canister by the flow through the second venturi so the patient does not rebreathe unpurified gases.

Pressure in the system is easily controlled without any necessity for repeated adjustments of the rate of input flow. Any excess gas can be vented out at the desired rate through the exit valve 52 by opening the valve to one of its five open positions.

In inducing narcosis in a patient the input flow of gases and anesthetic is diluted to a concentration of one-tenth that of the supply by the rebreathed gases. Gradually but steadily the concentration of anesthetic in the gas mixture increases as the gases with entrained anesthetic are recycled to the patient. Induction is smooth and quick.

The absorber can be used in combination with commercially available vaporizers such as the Takaoka Universal Vaporizer for maintaining anesthetic concentration constant during spontaneous, assisted or controlled ventilation.

The semiclosed nature of the system of the invention results in economical consumption of anesthetic agents while assuring easy pressure control. Any gaseous or volatile anesthetic agent compatible with the material used for the absorption of carbonic gases can be administered with the device of the invention.

The rebreathing device of the invention is particularly suited to use for pediatric and neonatal anesthesia.

It will be apparent to those skilled in the art that various modifications and substitutions can be made in the rebreathing apparatus disclosed herein without departing from the spirit and scope of the invention.