United States Patent (19)

Transcription

1 United States Patent (19) Matson ) (51) (58) BREATHING SENSOR Inventor: Louis R. Matson, th St., Sacramento, Calif Filed: Oct. 4, 1973 Appl. No.: 403,678 Related U.S. Application Data Continuation-in-part of Ser. No. 290,340, Sept. 19, 1972, abandoned. U.S. Cl /2 R, 128/2.08, 128/208, 73/240,272/57 Int. Cl... A61b5/08 Field of Search /2 R, 2 C, 2.08, 239, 128/208; ; 272/57 56) References Cited UNITED STATES PATENTS 3,347,222 10/1967 Kohrer /2 R 11) 3,817,238 (45) June 18, ,512,521 5/1970 Jones /2.08 3,635,214 l/1972 Rand /2.08 3,695,608 10/1972 Hanson... 28/2.08 X Primary Examiner-Aldrich F. Medbery Attorney, Agent, or Firm-Ernest L. Brown 57 ABSTRACT A breathing sensor, adapted to be attached to a con duit between a source of breathing gas and an animal, said sensor comprising a substantially vertical conduit having a float therein which is movable in response to breathing of the animal, a sensor for detecting the mo tion of the float and for actuating, preferably, an audio signal. 10 Claims, 10 Drawing Figures

2 PATENTED JUN l 7,238 SHEET 1. Of 3

3 PATENTED U1897 SHEET 2 OF 3 3, seriell

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5 1 BREATHING SENSOR BACKGROUND OF THE INVENTION This application is a Continuation in Part of U.S. Pat. application Ser. No. 290,340 which was filed Sept. 19, 1972, by Louis R. Matson, and now abandoned. This invention pertains to a breathing sensor, particu larly useful by veterinarians, for sensing the breathing of animals who are under anaesthesia. A typical veterinarian performing surgery, unlike a medical doctor, frequently works alone and has to be away from his patient from time to time to answer a tel ephone or meet the owner of another animal. While away from the animal which is under anaesthesia, it is desirable that the veterinarian have a continuous moni tor on the breathing of the patient. It is instructive to consider various United States pa tents which represent the state of the art. The closest apparatus found by the inventor was that taught and shown in U.S. Pat. No. 3,635,214 which is sued Jan. 18, 1972 to William A. Rand, et. al. for a "Vi sual Pulmonary Meter.' The apparatus is a hollow cy lindrical chamber for slidably receiving an apertured piston which also functions as a damper. A patient blows into one end of the chamber and the other end has a calibrated exit regulator for selectively varying the rate at which air can escape from the chamber. The piston is effectively in series between the operator and his source of breathing gas (the atmosphere). U.S. Pat. Nos. 3,028,761 and 3,347,222 each pertain to a balloon or bellows arrangement wherein the bel lows or balloon positions are monitored by a photoelec tric apparatus. U.S. Pat. No. 3,605,729 teaches a vane which move in response to breathing of a person, together with sen sors for sensing the motion of the vane. BRIEF DESCRIPTION OF THE INVENTION The apparatus contemplated by this invention uses means forming a substantially vertical cylindrical chamber, one end of which is connected to a conduit between a gas source and an animal. The other end of the chamber opens substantially to atmospheric pres sure. In one embodiment that other end of the chamber opens into a complaint balloon. In another embodi ment that other end opens into the atmosphere. Within the vertical cylindrical chamber is a spherical float which is preferably made of light weight non hydrophilic material such as styrofoam. As the animal breathes, the pressure in the conduit between the gas source and the animal varies. As that pressure varies, the float moves up and down between two stops. A photo-sensor is used to determine when the float is at its bottom stop position, and the photo-sensor is used to produce, preferably, an aural signal indicative of the breathing of the animal. The real virtue of this device is its extreme sensitivity, for to be an effective small animal breathing monitor, it should be triggered by a force as small as the force generated by breathing of a small cat under anaesthe Sa. It is therefore an object of this invention to sense the breathing of an animal. It is a more specific object of this invention to pro vide an apparatus which is adapted to sense variations in breathing pressure in a breathing conduit which is 3,817,238 O positioned between a source of breathing gas and an animal. BRIEF DESCRIPTION OF THE DRAWINGS Other objects will become apparent from the follow ing description, taken together with the accompanying drawings, in which: FIG. 1 is a schematic view of a first embodiment of the conduits or piping used to deliver breathing gas from a gas source to an animal, showing the apparatus of this invention connected between the breathing con duit and a flexible balloon; FIG. 2 is a schematic view of a second embodiment of the conduits or piping used to deliver breathing gas from a gas source to an animal, showing the apparatus of this invention connected between the breathing con duit from one component of the breathing gas and the atmosphere; FIG. 3 is a view, partly in section, of a typical em bodiment of the sensor of this invention; FIG. 4 is a view taken at 4-4 in FIG. 3; FIG. 5 is a view, partly in section, taken at 5-5 in FIG. 3; FIG. 6 is a view taken at 6-6 in FIG. 3; FIG. 7 is a view, partly in section, of a second em bodiment of the sensor of this invention; FIG. 8 is a view, partly in section, taken at 8-8 in FIG. 7; FIG. 9 is a typical electronic circuit used with the photosensors in the breathing sensor of this invention, and FIG. 10 is a graph of experimentally determined in strument size for a styrofoam float showing the pre ferred range of the inside diameter of the cylindrical chamber of this invention plotted against the float weight. DETALED DESCRIPTION OF THE INVENTION In FIGS. 1 and 2, breathing gas is channeled, during anaesthesia, from an oxygen source 10 and a nitrous oxide source 12 through conduits 14,16 into a mixing chamber 18 and thence, through breathing conduit 20, to a throat catheter 22 which is inserted into the throat of an animal 24. Other anaesthetic gases may be used, as desired. A sensor conduit 26 is attached either to breathing conduit 16 or breathing conduit 20 to receive gas pres sure from the breathing conduit and to carry gas to the apparatus 28 of this invention. The apparatus 28 comprises a substantially vertical cylindrical element 30, shown schematically in FIGS. 1 and 2 and in detail in FIGS.3-8. A float 32 (FIGS. 3-7) is free to move up and down within the element 30, and its position is sensed, for example, by a photo-sensor 34 which cooperates with an electronic circuit 36 to acti vate a signal device 38. A typical electronic circuit 36 and signal device 38 is shown in FIG. 9. The preferred shape of the float 32 is spherical, and the preferred material of the float is styrofoam. Experi ments have shown, as set forth in FIG. 10, that spheri cal styrofoam floats weighing between 3 and 20 milli grams positioned in cylindrical chamber 30 whose in side diameter is approximately 1 millimeter greater than the float diameter are preferred for a normal range of animals. The lightest weight float used was 3 milligrams. Lighter floats are affected by static electric ity which causes them to stick to the chamber glass.

6 3 The preferred inside diameter of the cylindrical tube for a 3 milligram float, having a density of g/cc, is 6 millimeters. With those dimensions, the breathing of an 8 weeks old kitten can easily be detected. The maximum weight of the float which produces usable signals with a g/cc spherical styrofoam float is 20 milligrams. anything heavier than 20 milligrams does not move sufficiently to produce a useable signal. With the 20 milligram float, the inside diameter of the cylin drical element 30 would need to be at least 12 millime ters. The bottom line of the graph determines the mini mum inside diameter for the cylindrical element 30 to cause proper functioning of the apparatus. Anything less than the diameter specified by that line would cause undue interference between the float and the in side diameter of the element 30. If the inside diameter of the element 30 is increased above the diameter spec ified by the bottom graph of FIG. 10, it should not be increased more than one-sixth for proper operation of the apparatus. If it is increased more than one-sixth, it is found that the float tends to wander and there is ex cessive gas leakage around the float. I have found that the optimum combination for best function of the apparatus for use by veterinarians in or dinary practice wherein the most sensitive breathing is that of a small kitten about 8 weeks old, is that shown in FIG. 10 at 11 milligrams with an inside diameter of the cylindrical chamber 30 preferably at 9 millimeters but ranging up to 10 and /2 millimeters. With that opti mum sized spherical styrofoam float, a full range of breathing sensitivity for all animals normally appearing in a veterinarian's office, and also including human be ings, may be sensed. Note that with a spherical styrofoam float, the mini mum inside diameter of the cylindrical member 30 var ies with the weight of the spherical float between 6 and 12 millimeters as the weight varies between 3 and 20 milligrams. This represents a clearance of approxi mately 4 millimeter between the ball float and the glass chamber. The bottom opening of the sensor cylindrical element 30 may either be open to the atmosphere as shown in FIG. 2 or connected to a pliable balloon 40, to con serve gas, as shown in FIG. I. The details of the apparatus 28 are shown in FIGS A substantially vertical cylindrical member 30 is connected into the sensor conduit 26 with the bottom of the cylindrical member 30, typically, connected to substantially atmospheric pressure. A float member 32, which is substantially spherical, is positioned within the cylindrical member 30 with clearance for free movement of the float member 32. The float member, preferably is made of styrofoam. It may, of course, be made of other light weight material which will float up and down as the pressure varies at the top of the cylindrical member 30. The float mate rial 32 should preferably be nonhydrophilic so that moisture in the gas does not increase the weight of the float. The float member 32 is constrained to operate be tween a pair of stops 42,44 (FIGS. 3-6). In the embodi ment of FIGS. 3-6, the upper'stop 42 is a wire element which clamps over the upper lip of the cylindrical ele ment 30 as shown at 46,48. The lower stop 44 is a twisted wire element which clamps over the lower lip of the cylindrical element 30 as shown at 50, 52. 3,817, An alternative for the upper and lower stops 42,44, is shown in FIGS A pin 60 protrudes into the cy lindrical member 30. The pin 60 has screw threads 62 thereon which screw into a plug member 64 which plugs like a stopper into the cylindrical member 30. The plug or stopper 64 has ports 66 therein for the free flow of gas. A thumb screw 68 is attached to the screw 62 to adjust the position of the pedestal or stop 60. A light source 70 is positioned to direct illumination through the walls of the cylindrical member 30 into the photo-sensor 34. To that end the walls of the cylindri cal member 30 are preferably of transparent material such as glass. At least the region 72 of the cylindrical member 30 must be transparent to channel illumina tion from the source 70 to the sensor 34. When the float 32 is positioned upon the lower stop 44 or 60, the float blocks the flow of illumination from the source 70 to the sensor 34 which then, through its associated electronics 36 either activates or stops the signal device 38. If desired, the up-down position of region 72 and the source 70 and sensor 34 may be adjusted instead of ad justing the lower stop 44 or 60. To avoid or minimize channeling of illumination around the float 32 when it is resting upon stop 44 or 60, it is optionally desirable to cover the cylindrical member 30 with a light mask 80 which is transparent only in the region 72. A typical electronic circuit and signal device is shown in FIG. 9. In FIG. 9, the incoming illumination, repre sented by the arrow 82, strikes the photo-transistor 84, causing it to conduct. The output of the photo transistor 84 is connected through an emitter-follower transistor 86 to an amplifying transistor 88. The ampli fying transistor 88 is biased by a zener diode 90 and a resistor 92 to prevent spurious signals from activating transistor 88. The output of transistor 88 is channeled, through the center-tap of the primary winding of a transformer 96 to the collector of a power transistor 98. The signal is also channeled through the primary winding and an RC time delay circuit 99 to the base of the transitor 98. The RC circuit 99 causes the circuit to oscillate, producing ac signals in the secondary wind ing of the transformer 96 which actuate the loud speaker 38. The audio volume of the apparatus may be adjusted by adjusting the rheostat 100 in the collector circuit of transistor 88. In operation, as the animal 24 breathes the breathing gas, the pressure varies in the breathing conduit 20 and the sensor conduit 26. An inhaling by the animal 24 de creases the pressure below atmospheric, causing the float member 32 to rise in the cylindrical tube 30. When the float member 32 rises in the tube 30, light from the illumination source, such as a light source 70, penetrates the wall of the tube 30 in the region 72 to stimulate the photo-sensor 34. Stimulation of the photo-sensor 34 causes the transis tor 88 to conduct, producing an oscillation in the tran sistor 98 and the transformer 96, producing a tone in the loud speaker 38. As the animal breathes, the tone from the loud speaker indicates to the veterinarian that the animal 34 continues to breathe. The repetition rate and duration of the breathing are signaled by the repetition rate and duration of the tones from the loudspeaker. The dura tion and repetition rate of the tones can be interpreted

7 S by the veterinarian to tell the depth of anaesthesia of the animal. In this manner, the breathing of the animal is moni tored, and the veterinarian may interrupt the operation to attend to other duties while listening to the monitor. Should the monitor stop, it would indicate that the animal had stopped breathing, and the veterinarian should immediately return to the animal. Although the invention has been described in detail above, it is not intended that the invention should be limited by that description, but only in accordance with that description in combination with the appended claims. I claim: 1. A breathing sensor comprising: means forming a cylindrical chamber having a sub stantially vertical axis, said cylindrical chamber being connected on one end in substantial commu nication with atmospheric pressure and being con nected on the other end to a pressure source whose pressure is a function of the breathing of the user; said means forming a cylindrical chamber being transparent in at least a predetermined region thereof; a substantially spherical styrofoam float within said cylindrical chamber, said float having a diameter which is slightly smaller than the diameter of said chamber, stops at each end of said cylindrical chamber to limit the travel of said float along said chamber, the said stop on the bottom end of said chamber being posi tioned to stop said float in said transparent region of said chamber; an illumination source, positioned to deliver illumi nation to one side of said transparent region, and a photosensor responsive to illumination transmit ted through said cylindrical chamber, said float being positioned, when said float is against said bottom stop, to block passage of said illumination to said photo-sensor; and means connected to be responsive to said photo sensor for generating an audible signal. 2. Apparatus as recited in claim 1 and further com prising a light mask to limit transmission of light through said chamber to a straight line between said il lumination source and said photo-sensor. 3,817, In combination with a source of breathing gas and a breathing conduit for transmitting said breathing gas from said source to an animal; a substantially circularly cylindrical sensor conduit means open, on a first end, to said breathing con duit means to cause the pressure in said sensor con duit means to be a predetermined function of the pressure in said breathing conduit means, a substantially vertical portion of said sensor conduit means having stops at opposing ends of said por tion; a substantially spherical styrofoam float positioned between said stops and free to move between said stops; the region of said vertical portion adjacent said lower stop being transparent; a light source positioned to channellight through said transparent portion substantially perpendicular to the axis of said sensor conduit means, a photo-sensor for receiving light from said light Source, electronic means, including an electronic oscillator for producing an audible signal, connected to be responsive to said electronic means and to light from said light source impinging on said photo SeSO. 4. Apparatus as recited in claim 3 in which the sec ond end of said substantially vertical portion is in sub stantial communication with the atmosphere. 5. Apparatus as recited in claim 4 in which said sec ond end of said substantially vertical portion is opened to the atmosphere. 6. Apparatus as recited in claim 4 in which said sec ond end of said substantially vertical portion is opened into a pliable enclosure. 7. Apparatus as recited in claim 2 in which said float weighs between three and twenty grams, and the aver age clearance between said float and the inner wall of said chamber is substantially one-half millimeter. 8. Apparatus as recited in claim 7 in which said float weighs substantially eleven grams. 9. Apparatus as recited in claim 3 in which said float weighs between three and twenty grams, and the aver age clearance between said float and the inner wall of said chamber is substantially one-half millimeter. 10. Apparatus as recited in claim 9 in which said float weighs substantially eleven grams. ck k : k k