US3319624A - Apparatus for measuring breath volume - Google Patents

Description

May 16, 1967 J. ARP ET AL 3,319,624

APPARATUS FOR MEASURING BREATH VOLUME Filed Jan. 15, 1964 SACK Z5 COLLAPSING SOLENOID VOLUME/ W MEASURING SYRINE' '1 FLOP I .SCHMITT TRIGGER mmszn 5i p? FOLLOWER SYR/NGE I SOLENOID SCIMTT TRIGGER IN VENTORS VALVE d. LEON AEP RONALD u. GRIFFITH United States Patent ()fl 3,319,624 Patented May 16:, 1967 3,319,624 APPARATUS FOR MEASURHIG BREATH VOLUME Leon J. Arp, Ames, Iowa, and Ronald J. Griflith, Morristown, N.J., assignors to Iowa State University Research Foundation, Inc., Ames, Iowa, a corporation of Iowa Filed Jan. 15, 1964, Ser. No. 337,778

' Claims. (Cl. 1282.08)

This invention relates to apparatus for measuring breath yolume, and, more particularly, relates to apparatus for performing this function relative to an infant.

Respiratory difiiculties are not unusual with infants, particularly premature babies. It is, therefore, essential that some augmentation of the natural breathing faculty be provided, and, as an incident to this, it is necessary to .know the tidal volume. It is with the latter determinacernpanying drawing, in which:

FIG. 1 is a schematic representation of an elevational view, partially in section, of apparatus which serves to determine the volume of a selected exhaled breath of an infant; and

FIG. 2 is a schematic representation of electrical circuitry associated with the electromechanical components of FIG. 1.

In the illustration given, and with particular reference to FIG. 1, the volumetric portion of the apparatus is seen in semi-schematic form wherein the numeral 10 designates a nose mask adapted to be connected to an infant (not shown). Suitable for this purpose is the nose mask described in the copending, co-owned application of John B. Buck, Serial No. 351,182, filed March 11, 1964, and reference to that application may be made for additional details. The nose mask fits closely about the nose of the infant, minimizing dead space, yet permits the mouth to be exposed for feeding, vomiting, mucous extraction, etc. The neonatal infant normally breathes through his nose, so that the mouth covering is unnecessary as well as being undesirable.

It will be seen that the mask 11) is coupled to the conduits 11 and 12, the conduit 12 serving to provide a flow passage for inhaled air, as designated by the arrow marked 13. Air at 13 enters the conduit 12 and passes through a check valve designated 14 and thence through a trigger mechanism generally designated 15. The trigger mechanism includes a thermistor 15 sensitive to air movement. The thermistor 16, when energized, is employed to operate a rotary valve 17. In the position of the valve spool 18 seen in FIG. 1, the exhalation conduit 11 is communicated to the atmosphere via the flow passage 19. Flow in the exhalation conduit 11 is permitted in only one direction by virtue of a check valve utilizing a thin silicone rubber valve diaphragm 21.

With the appearance of a signal from the trigger mechanism 15, the rotatable valve spool 18 of the valve 17 is positioned to couple the exhalation conduit 11 to a collapsible sack device generally designated 22. Thus, as the patient exhales, air flows through the check valve 20 and the rotary valve 17 into the collapsible collection sack structure 22. All of the exhaled air is at this time contained in the sack structure 22, and when the patient next inhales, the trigger mechanism 15 delivers another electrical pulse to the electrical circuitry shown in FIG. 2. The pulse so delivered causes the rotary valve element 18 to return to the by-pass position (venting the exhalation conduit 11 to atmosphere as at 19) and energizes the solenoid 23 for collapsing the sack 24 provided as part of the sack structure 22. For this purpose, the solenoid armature is equipped with a platen 25 which is retractable" to force the sack 24 into a flattened or collapsed condition against the sack structure base 22a. The sack in the illustration given is constructed of 0.002" thick rubber and possesses essentially no resilency in the range of volumes encountered-the infant breathing volume being of the order of 5-20 cc.

The exhaled breath from the sack 24 is forced there from by the action of the platen 25 into a glass syringe generally designated 26. For this purpose, a tube as at 27 is provided to couple the sack 24 with the barrel 28 of the syringe 26. The syringe piston 29 rises appropriately to indicate the exhaled 'volume. Here, it will be appreciated that the solenoid 23 is providing the work necessary to elevate the syringe piston 29. The problem in the past in respiration :meters has been to measure accurately small volumes of breath without having the infant work against a back pressure of resistance. This is achieved in the instant invention by breathing into the sack 24, which is constructed of relatively thin rubber, and then letting the platen 25 do the work of raising the syringe piston 29. To substantially eliminate any error due to compression by virtue of acting as a syringe piston 29, the piston 29 is counterbalanced by weight 30 to a suitable pulley system generally designated 31. Thus, the displacement of the syringe piston 29 is directly proportional to the volume of air forced into it from the collection sack 24. As the syringe piston 29 rises, the string 32 of the pulley system passes over an idler pulley 33 and around a pulley 34 attached to a linear potentiometer schematically represented and designated 35. The output of the potentiometer 35 is delivered to a meter 36 for a direct read-out of the volume of the air exhaled by the patient. Alternatively or cumulatively, the read-out can be achieved through an optical system embodying a light source 38, a lens 39, and a projection screen 40 all associated with the syringe barrel 28.

The system is returned to ready condition by mechanically forcing the syringe piston downwardly by a solenoid-actuated pull-down arm 41 and opening the exhaust valve 42 for the exhaust of the air in the syringe 26. After this has been achieved and the valve 42 returned to the closed condition, the solenoid 2 3 is deenen gized to return the platen 25 to the position seen in FIG. 1.

The solenoids for pulling down the syringe piston 29 and for operating the exhaust valve 42 are represented schematically in the diagram of FIG. 2 as at 43 and 43'. Ganged switches 44 and 45 (normally closed and normally open, respectively) are operated by the displacement of the syringe piston 29 and a normally open switch 46 is closed when the platen 25 is moved so as to collapse the sack 24. Voltage is applied at the three points designated V in FIG. 2 and three Eccles-Jordan or flip-flop circuits 47, 48 and 49 are also provided, as seen in FIG. 2. The primary flip-flop circuit used in operating the apparatus of FIG. 1 is designated 49 and is seen to be electrically coupled to the trigger mechanism 15 by means of an amplifier 50, a Schmitt trigger 51, capacitor 52, emitter follower 53, and an And gate 54. The initial condition of the flip-flop 49 is such as to deliver output current to a power amplifier 55 and thence to a suitable solenoid actuator 56 operably associated with the rotary.

valve element 18 when the Read switch 57 is closed temporarily.

Closing the normally open switch 57 changes the condition of flip-flop circuit 48 to make the And gate 54 conductive as soon as a signal from the emitter follower 53 is presented to the And gate 54. When the And gate 54 simultaneously has a signal presented at both of its inputs, an output signal is delivered to the primary flip-flop circuit 49, thus changing the condition of flip-flop 49 from its start position.

The output signal from flip-flop 49 is amplified by 55 to cause the actuation of the rotary valve 17 by the electromechanical actuator 56. At this time the infant breathes out and into the rubber collection sack 24.

As the infant again inhales, the trigger mechanism '15 delivers a pulse through the circuits 50, 51, 52, 53

and 54 to change the flip-flop circuit 49 back to its start position. Having removed the signal from the amplifier 55, the rotary valve spool 18 returns to its initial by-pass condition seen in FIG. 1.

The capacitor 53 then passes a feed-back signal from the flip-flop 49 to flip-flop 48, thus causing the latter to return to its start condition. When the flip-flop 48 returns to its start condition, one of the input signals is removed from the And gate 49. .This prevents the switching of the flip-flop 49 by signals generated by the circuits 15, 50, 51 and 52 while the infant breathes during the remainder of the measuring process. Capacitor 58 also passes current to the flip-flop 47, causing application of power via the amplifier 59 to the platen solenoid 23. This causes the platen 25 to be retracted for collapsing the sack 24. The completion of this collapsing movement closes the normally open switch 46 and applies current through a delay system 69, a Schmitt trigger 61, and a power amplifier 62 to the pull-down solenoids 43 and 43. Interposed between the power amplifier 62 and the solenoids 43 and 43' is the normally open switch 45 which is closed upon initial upward movement of the piston 29. The delay system 60 is suitably constituted to provide sufiicient time for reading the meter 36 by the technician or the medical personnel attending the operation of the apparatus.

Upon actuation of the pulldown solenoid mechanism 43, the syringe piston 29 is returned to its bottom dead center position which coincidentally closes the switch 44, applying a dilferent signal via the capacitative coupling 63 to the flip-flop circuit 47, thereby removing power from the platen solenoid 23 so that the platen 25 returns to the FIG. 1 condition. The system has now completed a complete cycle and will stand-by until closure of switch 57 starts another measuring cycle.

The sequence of mechanical actions can be summarized as follows:

(1) Valve 17 opens.

(2) Sack 24 is filled.

(3) Valve 17 closes.

(4) Platen 25 collapses sack 24, forcing air into syringe 26.

(5) After sufficient time for reading the measurement, as determined by the RC constant of the circuit 60, the valve 42 opens and the syringe piston 29 is pulled down.

(6) The piston is latched in its down position and the valve 42 closed.

(7) The platen is retracted but the sack does not expand since all access ports as at 29, 42 and 18 are closed.

A more retailed description of the electrical functioning corresponding to the above-described mechanical sequence is set down below.

Operation The trigger 15, amplifier 50, and Schmitt trigger 51 produce a negative pulse each time the infant begins inspiration. These pulses are routed by the emitter follower 53 to the And gate 54 but go no further until the read switch 57 is depressed. Actuation of the read switch 57 by the operator of the apparatus causes the fiip-fiop 48 to produce an input to the And gate 54. Upon the first coincidence at the gate 54 of this input from the flip-flop 48 and the pulse from the emitter follower 53, the flip-flop 49 produces an input to the power amplifier 55 which causes rotary valve 17 to open the access to the collection chamber 22. Upon the second coincidence of a pulse from the emitter follower 53 and the input from flip-flop 48, which has remained present at the And gate 54 since its initial appearance, the fiipfiop 45 returns to its start position. This simultanously causes flip-flop 48 to return to its start position, preventing further pulses from the emitter follower 53 from passing through the And gate 54, and removes the input to the power amplifier 55. This allows the rotary valve 17 to close. Hence, the air exhaled. between the two inspirations has entered the collection chamber 22 and is now held there.

The return of the flip-flop 49 to its initial position additionally causes the flip-flop 47 to change states. When the flip-flop 47 changes states, power is'supplied to an electromagnetic spring-loaded latch 65 that holds the pulldown arm 41 firmly on the syringe piston 29' and an input is presented to power amplifier 59. The output of the amplifier 59 is power to solenoid 23 which pulls the platen 25 against the collection sack 24 to force the trapped air into the syringe 26 for measurement.

As the platen 25 reaches its final position, it actuates switch 46. The signal produced by the closing of switch 46 is delayed by the RC network 60' and Schmitt trigger 61. The time that this signal is delayed is the time in which the measurement made by the apparatus 'is displayed. The output produced by the Schmitt trigger 61 is the input to the power amplifier 62. This power amplifier energizes the exhaust valve solenoid 43' which opens the valve 42 and communicates the collection and measurement chambers 24 and 26 to the atmosphere.- This power amplifier also energizes the pulldown solenoid 43, which returns the pulldown arm 41 and syringe piston 29 to their original positions. Hence, the air that was once held in the system is forced out into the atmosphere. The return of the pulldown arm 41 to its reset position also actuates switches 44 and 45. Actuation of switch 45 interrupts power to the pulldown solenoid 43 and exhaust valve 43'. Actuation of switch 44 generates a pulse that returns flip-flop 47 to its original position. Hence, the platen 25 is released, and the electromagnet spring-loaded latch 65 catches the pulldown arm so that the apparatus is at stand-by.

While in the foregoing specification a detailed description of an embodiment of the invention has been set down for the purpose of explanation thereof, many variations in the details herein given may be made by those skilled in the art without departing from the spirit and scope of the invention.

We claim:

1. In respiratory volume measuring apparatus, a thin inelastic collapsible sack, volumetric measuring means, a conduit adapted to be coupled at one end thereof to a patient whose breath volume is to be measured, the other end of said conduit being coupled to said collapsible sack, valve means interposed in said conduit, a second conduit coupling said sack to said volumetric measuring means, valve means operably associated with said second conduit, and electromechanical collapsing means for collapsing said sack to expel a given breath volume therefrom into said volumetric measuring means.

2. The structure of claim 1 in which said collapsing means includes a base having a generally planar surface on which said sack is supported and a planar surfaceequipped platen arranged to move into juxtaposition with said base, said collapsing means including an electrical circuit for maintainingsaid platen in juxtaposition relative to said base until after said given breath volume has been expelled from said apparatus through said second conduit valve means and said second valve means is closed whereby said platen is movable away from said base without inducing expansion of said sack.

3. The structure of claim 2 in which said volumetric measuring means includes a positive displacement device and electromechanical means for returning said device to a condition of no displacement prior to moving said platen away from said base.

4. In a respiratory volume measuring apparatus, a conduit adapted to be coupled at one end thereof to a patient whose breath volume is to be measured, the other end of said conduit being coupled to a collapsible sack, valve means interposed in said conduit, a second conduit coupling said sack to volumetric measuring means, valve means operably associated with said second conduit, means for collapsing said sack, means for applying collapsing force to said sack to expel a given breath volume therefrom into said volumetric measuring means, and means for purging said volumetric measuring means of said given breath volume prior to removing the collapsing force from said sack.

5. The structure of claim 4 in which means including a time delay circuit is operably associated with said applying means and purging means for delaying the opera tion of said purging means a discrete time following the application of said collapsing force.

6. A respiratory volume measuring device, comprising a face mask, a pair of conduits coupled to said mask and providing inhalation and exhalation paths, means in said inhalation conduit responsive to inhalation of air, valve means in said exhalation conduit adapted to selectively pass exhaled air to atmosphere and to volume-measuring means, volume-measuring means coupled to said exhalation conduit and equipped with means for purging said volume-measuring means of an exhaled breath, and means including a flip-flop circuit interconnecting said responsive means, valve means, volume-measuring means and purging means for first positioning said valve means to pass an exhaled breath to said volume-measuring means in response to a signal from said responsive means, secondly for positioning said valve means to pass subsequent exhaled breaths to atmosphere in response to signals from said responsive means until said purging means purges said volume-measuring means.

7. The structure of claim 6 in which said flip-flop-including means also includes time delay means providing time to visually present the value of the breath volume measured by said volume-measuring means, and means operably associated with said volume-measuring means for visually presenting the value of exhaled breath.

the volume of said 8. The structure of claim 6 in which said flip-flop-including means includes a second flip-flop circuit coupled to a manually-operable switch, said second flip-flop and said responsive means being coupled to an and gate, said and gate being coupled to the first-mentioned flipflop for actuating said valve means, volume-measuring means and purging means in timed sequence upon simultaneous signals from said second flip-flop and responsive means.

9. The structure of claim 6 in which said volumemeasuring means includes a positive displacement device, and solenoid means in said purging means responsive to one condition of said flip-flop for placing said device in a position of no displacement.

10. Apparatus for measuring the exhaled breath volume of infants, comprising a nose mask adapted to be secured to an infants face, an inhalation conduit and an exhalation conduit coupled to said mask and equipped with check valve means, a two-position valve in said exhalation conduit adapted to selectively couple said mask to atmosphere and to a breath collection element, a breath collection element coupled to said exhalation conduit and including a base supporting a collapsible sack, a platen operably associated with said base for collapsing said sack, means in said inhalation conduit responsive to inhalation for positioning said valve in a first position to pass the subsequent exhaled breath to said sack, means including flip-flop circuits coupling said responsive means and valve for first positioning the same and thereafter for positioning said valve in a second position to pass the next subsequent exhaled breath to atmosphere, and an exhaust valve-equipped positive displacement volume-measuring device coupled to said sack, said flip-flop circuits being also coupled to said device and element for sequentially actuating said platen to collapse said sack, actuating said device to a condition of no displacement while opening said exhaust valve, closing said exhaust valve, and actuating said platen to remove collapsing force from said sack.

References Cited by the Examiner UNITED STATES PATENTS 9/1885 McDonnell 128--2.08 9/1961 Shipley 128-2. 08

RICHARD A. GAUDET, Primary Examiner. SIMON BRODER, Examiner,

Claims (1)

1. IN RESPIRATORY VOLUME MEASURING APPARATUS, A THIN INELASTIC COLLAPSIBLE SACK, VOLUMETRIC MEASURING MEANS, A CONDUIT ADAPTED TO BE COUPLED AT ONE END THEREOF TO A PATIENT WHOSE BREATH VOLUME IS TO BE MEASURED, THE OTHER END OF SAID CONDUIT BEING COUPLED TO SAID COLLAPSIBLE SACK, VALVE MEANS INTERPOSED IN SAID CONDUIT, A SECOND CONDUIT COUPLING SAID SACK TO SAID VOLUMETRIC MEASURING MEANS, VALVE MEANS OPERABLY ASSOCIATED WITH SAID SECOND CONDUIT, AND ELECTROMECHANICAL COLLAPSING MEANS FOR COLLAPSING SAID SACK TO EXPEL A GIVEN BREATH VOLUME THEREFROM INTO SAID VOLUMETRIC MEASURING MEANS.

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