(12) United States Patent
`Cewers
`
`US006357671B1
`US 6,357,671 B1
`Mar. 19, 2002
`
`(10) Patent N0.:
`(45) Date of Patent:
`
`(54) ULTRASONIC NEBULIZER
`
`(75) Inventor: G?ran CeWers, Lund (SE)
`
`(73) Assignee: Siemens Elema AB, Solna (SE)
`
`* N'
`ot1ce:
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`Sbj
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`u ect to an 1sc a1mer, t e term 0 t is
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(21) Appl. No.: 09/489,835
`(22) Filed:
`Jan. 24, 2000
`(30)
`Foreign Application Priority Data
`Feb. 4, 1999
`
`(SE) ............................................ .. 9900369
`
`(51) Int. Cl.7 ......................... .. B05B 1/08; A61M 11/06
`(52) US. Cl. ...................... .. 239/102.2; 239/67; 239/69;
`239/71; 239/99; 239/102.1; 239/338
`(58) Field of Search ............................ .. 239/67, 69, 71,
`239/73, 99, 102.1, 102.2, 338
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,839,651 A 10/1974 Michaels
`3,918,640 A * 11/1975 Piccino et a1. ..... .. 239/102.2X
`4,300,131 A 11/1981 Mitsui et 211.
`4,319,155 A
`3/1982 Nakai et 211.
`4,641,053 A * 2/1987 Takeda .............. .. 239/102.2 X
`4,776,990 A 10/1988 Verity
`5,217,165 A * 6/1993 Takahashi et a1. ..... .. 239/102.2
`
`4/1994 Lichte
`5,303,585 A
`5,361,989 A * 11/1994 Merchat et a1. ........ .. 239/1022
`5,429,302 A * 7/1995 Abbott .................. .. 239/1022
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`EP
`EP
`JP
`
`0 151 753 A2 12/1984
`WO 93/09409
`5/1993
`0 845 663 A1 11/1997
`9-173978
`7/1997
`
`* cited by examiner
`
`Primary Examiner—Robin O. Evans
`(74) Attorney, Agent, or Firm—Schiff Hardin & Waite
`(57)
`ABSTRACT
`
`An ultrasonic nebuliZer includes a nebuliZation chamber for
`holding a liquid to be nebuliZed, the liquid being limited by
`an upper boundary Within the chamber, and a nebuliZation
`source acoustically couplable to the liquid Within the cham
`ber to provide therein an ultrasonic output at an amplitude to
`cause nebuliZation. The nebuliZation source is controllable
`to vary the amplitude of the ultrasonic output to provide a
`measurement period during Which no nebuliZation occurs,
`and a sonar device measures, during the measurement
`period, a time interval betWeen emission of an acoustic pulse
`toWard the boundary and detection of a component of the
`emitted acoustic pulse re?ected from the boundary, and
`provides an output signal dependent on the measured time
`interval for use in determining location information of the
`boundary Within the chamber.
`
`8 Claims, 2 Drawing Sheets
`
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`NEBULIZA
`TION —4
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`UNIT
`
`WATSON LABORATORIES, INC. , IPR2017-01622, Ex. 1026, p. 1 of 6
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`

`

`U.S. Patent
`
`Mar. 19, 2002
`
`Sheet 1 of2
`
`US 6,357,671 B1
`
`LL’
`8 /\
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`NEBULIZA
`TION J
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`11
`
`CONTROLLER
`UNIT
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`WATSON LABORATORIES, INC. , IPR2017-01622, Ex. 1026, p. 2 of 6
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`

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`U.S. Patent
`
`Mar. 19, 2002
`
`Sheet 2 012
`
`US 6,357,671 B1
`
`“a
`
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`NEBULIZA-
`TION /_\
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`
`FIG. 2
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`WATSON LABORATORIES, INC. , IPR2017-01622, Ex. 1026, p. 3 of 6
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`

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`US 6,357,671 B1
`
`1
`ULTRASONIC NEBULIZER
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to an ultrasonic nebuliZer
`(atomizer) and in particular to a nebuliZer of the type having
`an output controllable dependent on the level of liquid
`available for nebuliZation.
`2. Description of the Prior Art
`Ultrasonic nebuliZers are devices Which utiliZe a source of
`ultrasound, such as for eXample a pieZoelectric crystal
`oscillator, acoustically coupled to a liquid in a nebuliZing
`chamber in order to generate an aerosol of small liquid
`droplets in a space above the liquid boundary. The generated
`aerosol may be used for any desired purpose such as
`humidi?cation or medication. Such nebuliZers are often used
`as a component in a breathing circuit of a mechanical
`ventilator, Where they are employed in the delivery of
`controlled doses of anaesthetic or other additive into a
`breathing gas for supply to a patient.
`It is important, particularly in the medical ?eld, to be able
`to monitor the level of liquid in the nebuliZing chamber. This
`may be for eXample, in order to maintain a supply of liquid
`throughout mechanical ventilation or to monitor the dosage
`of liquid delivered into the breathing gas.
`One knoWn ultrasonic nebuliZer Which is provided With a
`liquid level indicator is disclosed in US. Pat. No. 3,839,651.
`This nebuliZer uses a temperature sensitive resistance ele
`ment Which is thermally coupled to the liquid Within the
`nebuliZing chamber. The current in an electrical circuit
`containing this element is dependent on the amount of liquid
`Within the chamber and is used to decrease poWer supplied
`to the oscillator and to provide a visible indication When the
`liquid level falls to a predetermined minimum. One problem
`With such a level indicator is that it is relatively insensitive
`to small changes in liquid level Which are likely to occur
`betWeen successive, or closely spaced, inspiration periods of
`a patient breathing cycle.
`
`2
`Within the nebuliZation chamber. This provides a relatively
`sensitive arrangement for identifying changes in the location
`of the liquid boundary from Which, for eXample, the amount
`of liquid Within the nebuliZation chamber may be calculated.
`Preferably, a single pieZoelectric crystal is employed as
`both the nebuliZation source and as the sonar device. This
`alloWs existing nebuliZing chambers and sources to be used
`With only modi?cations to the electronic circuitry used to
`control the crystal being necessary. Moreover, by using only
`one crystal, a major component cost saving is achieved
`compared With employing separate sonar and nebuliZation
`sources.
`A difference forming circuit is used to enable differences
`in the location of the liquid boundary to be determined. The
`determined difference, for example, may be used to monitor
`the amount of liquid nebuliZer betWeen measurement peri
`ods or to monitor the effect of different knoWn crystal
`driving currents on the liquid boundary during a single
`measurement period. Both of these monitoring modes then
`may be employed to calibrate the nebuliZation source and to
`control the amplitude or duration of the ultrasonic output
`from the source to, for eXample, more reliably provide a
`required amount of nebuliZation or to remove poWer from
`the source if a minimum liquid level is reached.
`Particularly useful is the latter mode of monitoring since
`a calibration of the output of the nebuliZation source may be
`made before generating any nebuliZed liquid.
`
`10
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`15
`
`25
`
`DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic representation of an embodiment of
`a nebuliZer and illustrates one mode of operation according
`to the present invention.
`FIG. 2 is a schematic representation of a nebuliZer illus
`trating a further mode of operation according to the present
`invention.
`
`35
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`SUMMARY OF THE INVENTION
`
`An object of the present invention is to provide an
`ultrasonic nebuliZer having a level indicator capable of
`sensing such small changes.
`The above object is achieved in accordance With the
`principles of the present invention in a nebuliZer having a
`nebuliZation chamber containing a liquid to be nebuliZed the
`liquid having an upper boundary Within the chamber, and an
`ultrasonic nebuliZation source Which is acoustically coupled
`to the liquid to introduce ultrasound into the liquid to
`nebuliZer the liquid, and Wherein the ultrasonic nebuliZation
`source is operated to emit ultrasound With a variable ampli
`tude so as to provide a measurement period during Which no
`nebuliZation occurs, and Wherein the nebuliZer has a sonar
`device Which, during the measurement period, measures a
`time interval betWeen emission of an acoustic pulse toWard
`said liquid boundary and detection of a component of the
`emitted acoustic pulse re?ected from the boundary so as to
`produce an output signal dependent on this measured time
`interval Which is indicative of a location of the upper
`boundary of the liquid Within the nebuliZation chamber.
`By controlling the amplitude of the nebuliZation source to
`provide periods Where no nebuliZation occurs, possibly by
`providing periods of Zero amplitude output, a sonar device
`Which employs echo ranging techniques may be used to
`measure the location of the upper boundary of the liquid
`
`45
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`55
`
`65
`
`In FIGS. 1 and 2 an ultrasonic nebuliZer is shoWn gen
`erally at 1. The nebuliZer 1 of FIGS. 1 and 2 has the same
`basic components but different modes of operation, Which
`modes Will be described separately for each of the FIGS. 1
`and 2.
`The ultrasonic nebuliZer 1 of FIGS. 1 and 2 includes a
`ultrasonic oscillator 2, here in the form of a pieZoelectric
`transducer, Which is located in a Water chamber 3 above
`Which is a nebuliZation chamber 4. A liquid 5 for nebuliZa
`tion is held Within the nebuliZation chamber 4 so that in use
`a space into Which nebuliZed liquid passes remains in the
`chamber 4 above an upper boundary 6 of the liquid 5. Gas
`may be introduced into the nebuliZation chamber 4, ?oWing
`from an inlet 7 to an outlet 8 through the space above the
`upper boundary 6, and removing from the chamber 4 liquid
`droplets formed during nebuliZation. A thin membrane 9
`separates the Water chamber 3 from the nebuliZation cham
`ber 4 so that ultrasonic energy from the oscillator 2 can pass
`readily therethrough With the result that the oscillator 2
`“sees” essentially only a single body of liquid, terminating
`at the upper boundary 6. An oscillator driver 10 is connected
`in an electrical circuit With the oscillator 2 and is arranged
`to drive the oscillator 2 to generate a controllable, variable
`amplitude ultrasonic signal for emission into the Water
`chamber 3. A sonar detection stage 11 is also provided in
`electrical connection With the oscillator driver 10 and With
`the oscillator 2. The detection stage 11 includes conventional
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`US 6,357,671 B1
`
`3
`timer circuitry (not shown) Which is arranged to measure the
`transit time for an ultrasonic sonar pulse to travel from the
`oscillator 2 to the upper liquid boundary 6 and back again.
`The detection stage 11 is also adapted to emit a signal
`representative of this measured transit time.
`The driver 10 and the sonar detection stage 11 are readily
`realiZable by those skilled in the art using conventional
`electrical engineering methodology and an understanding of
`the principles of their function, as provided herein.
`Acontroller unit 12, for eXample in the form of a suitably
`programmed computer, is operably connected to both the
`driver 10 and the sonar detection stage 11 and provides
`control of the driver 10 and calculates the location of the
`upper liquid boundary 6 Within the nebuliZation chamber 4
`from the output signal of the sonar detection stage 11.
`To eXplain the nebuliZer 1 of FIG. 1 and its mode of
`operation, the arroWs 13 shoW the path of the sonar pulse. In
`use the controller unit 12 provides control instructions to the
`driver 10 for generating a periodic variation in the amplitude
`of the ultrasonic energy emitted by the oscillator 2. The
`variation is such that nebuliZation periods, during Which
`high amplitude ultrasound are emitted Which are suf?cient to
`cause nebuliZation, alternate With measurement periods,
`during Which only ultrasound sonar pulses are emitted
`having an amplitude, insuf?cient to affect i.e. disturb, the
`location of the upper boundary 6 to a measurable eXtent.
`During a measurement period a trigger signal is sent to the
`sonar detection stage 11, corresponding to the oscillator 2
`being driven, to generate an ultrasonic sonar pulse. The
`trigger signal, Which may conveniently be provided either
`by the controller unit 12 or the driver 10, initiates the start
`of timing by the timer circuitry. The time measurement is
`stopped When the receipt of a re?ected component of the
`generated ultrasonic pulse is detected at the oscillator 2. This
`detection is facilitated by the use of a pieZoelectric trans
`ducer as the oscillator 2. It is Well knoWn that ultrasonic
`energy incident on such a pieZoelectric transducer 2 can
`cause detectable changes in the electrical properties of an
`electrical circuit in Which the transducer 2 is included. Thus
`in the present embodiment the receipt of the re?ected pulse
`is detected using such knoWn circuitry Within the detection
`stage 11. The pulse emission and detection optionally can be
`carried out a number of times throughout the measurement
`period and an average location determination made Within
`the controller unit 12 based on the averaged value of the
`measured transit times. The determined location may be
`used Within the controller unit 12 to provide a control signal
`Which inhibits the operation of the driver 10 When a location
`corresponding to a minimum level is detected.
`Optionally, the controller unit 12 may be programmed to
`compare the currently determined location With a previously
`determined location, having a knoWn temporal relationship
`to the currently determined location and preferably one
`made in a consecutive measurement period, so that the
`amount of liquid nebuliZed during an intervening nebuliZa
`tion period or periods may be calculated Within the control
`ler unit 12 to provide dose information. This dose informa
`tion may then be used by the controller unit 12 in the control
`of the driver 10 to regulate one or both of the amplitude of
`the ultrasound generated for nebuliZation and the duration of
`the nebuliZation period to obtain a desired dose from the
`nebuliZer 1.
`For explaining the nebuliZer 1 of FIG. 2 and its mode of
`operation, solid arroWs 14 and dashed arroWs 14‘ shoW paths
`of the sonar pulses. In use the controller unit 12 controls the
`driver 10 to provide the pieZoelectric transducer 2 With a
`
`10
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`35
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`45
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`4
`knoWn, variable amplitude driving force to generate a cor
`responding variable amplitude ultrasonic output into the
`Water chamber 3. The driver 10 is controlled to provide from
`the oscillator 2 at least one nebuliZation period, during
`Which high amplitude ultrasound is emitted suf?cient to
`cause nebuliZation, and at least one measurement period,
`during Which ultrasound is emitted at amplitudes loWer than
`are capable of causing nebuliZation.
`During each measurement period the controller unit 12
`controls the driver 10 to generate at least tWo different
`amplitudes of ultrasound to provide distinguishable and
`different locations of at least part of the upper boundary 6,
`6‘. As illustrated in FIG. 2 one output amplitude is chosen so
`as not to affect (i.e. disturb) the location of the upper
`boundary 6‘ to a measurable eXtent, for eXample a Zero
`amplitude output, and the other output amplitude is chosen
`to provide a localiZed change in the upper boundary 6. The
`sonar detection stage 11 and the driver 10 operate coopera
`tively to provide tWo measurements of transit times; one for
`a sonar pulse traveling along the path 14 Which measures the
`location of the boundary 6, and the other for a sonar pulse
`traveling along the path 14‘ Which measures the location of
`the boundary 6‘. These measurements are carried out in a
`manner analogous to that described for the transit time
`measurements of FIG. 1.
`The controller unit 12 is operably connected to the sonar
`detection stage 11 to receive outputs from the detection stage
`11 representative of the tWo measured transit times. A
`difference calculation betWeen the locations of the bound
`aries 6, 6‘ is made Within the controller unit 12. The
`controller unit 12 is further adapted to calculate the rate of
`change of location of the boundary With supplied driving
`force using the calculated difference and from the knoWl
`edge of the amplitude of the driving force supplied by the
`driver 10 to generate the tWo upper boundary locations 6, 6‘.
`From this rate of change the controller unit 12 generates an
`estimate of the driving force required to be provided to the
`oscillator 2 in order to generate a desired degree of nebuli
`Zation Within the nebuliZer 1 and controls the driver 10
`accordingly.
`Although modi?cations and changes may be suggested by
`those skilled in the art, it is the intention of the inventor to
`embody Within the patent Warranted hereon all changes and
`modi?cations as reasonably and properly come Within the
`scope of his contribution to the art.
`I claim as my invention:
`1. A nebuliZer comprising:
`a nebuliZation chamber containing a liquid to be
`nebuliZed, said liquid having an upper boundary Within
`said nebuliZation chamber;
`an ultrasonic nebuliZation source acoustically coupled to
`said liquid and operable to nebuliZe said liquid, said
`ultrasonic nebuliZation source including a control unit
`Which varies an amplitude of ultrasound produced by
`said ultrasonic nebuliZation source to provide at least a
`?rst measurement period and a second measurement
`period during Which no nebuliZation of said liquid
`occurs, said ?rst and second measurement periods
`being separated in time from each other;
`a sonar device disposed to measure, during each of said
`?rst and second measurement periods, a time interval
`betWeen emission of an acoustic pulse toWard said
`upper boundary and detection of a component of said
`acoustic pulse re?ected from said boundary, and gen
`erating respective output signals dependent on said
`time interval indicative of a location of said upper
`
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`US 6,357,671 B1
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`5
`boundary of said liquid Within said nebuliZation cham
`ber in said ?rst and second measurement periods; and
`a difference former supplied With said output signals for
`comparing said output signals to determine a change in
`the location of said upper boundary of said liquid
`Within said chamber, said difference former emitting a
`difference former output signal dependent on said
`difference, said difference former output signal being
`supplied to said control unit to control at least one of an
`amplitude and a duration of ultrasound from said
`ultrasonic nebuliZation source for nebuliZing said liq
`uid Within said nebuliZation chamber.
`2. A nebuliZer as claimed in claim 1 Wherein said sonar
`device is disposed to emit said acoustic pulse through said
`liquid to said upper boundary.
`3. A nebuliZer as claimed in claim 2 Wherein said ultra
`sonic nebuliZation source comprises a pieZoelectric trans
`ducer for emitting said ultrasound With a variable amplitude,
`and Wherein said sonar device is also connected to said
`pieZoelectric transducer for emitting and detecting said
`acoustic pulse during said measurement period.
`4. A nebuliZer as claimed in claim 1 Wherein said ultra
`sonic nebuliZation source is operated by said control unit to
`only emit, during said measurement period, ultrasound hav
`ing an amplitude Which causes substantially no disturbance
`to said upper boundary of said liquid Within said nebuliZa
`tion chamber.
`
`6
`5. A nebuliZer as claimed in claim 1 Wherein said ultra
`sonic nebuliZation source is operated by said control unit
`during said measurement period to emit ultrasound at a ?rst
`amplitude for producing a ?rst location of said upper bound
`ary and to emit ultrasound at a second amplitude to produce
`a different location of said upper boundary, and Wherein said
`sonar device detects a ?rst output signal associated With said
`?rst amplitude and a second output signal associated With
`said second amplitude, and Wherein said difference former
`uses one of said ?rst and second output signals as a reference
`signal and the other of said ?rst and second output signals as
`a measurement signal.
`6. A nebuliZer as claimed in claim 5 Wherein said ultra
`sonic nebuliZation source is operated by said control unit so
`that one of said ?rst and second amplitudes produces no
`disturbance of the location of said upper boundary of said
`liquid Within said nebuliZation chamber.
`7. A nebuliZer as claimed in claim 4 Wherein said differ
`ence former includes a memory connected to said difference
`former for storing the output signal from said ?rst measure
`ment period.
`8. A nebuliZer as claimed in claim 7 Wherein said differ
`ence former derives a difference betWeen signals received
`from consecutive measurement periods.
`
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