CA2232546A1 - Pressure control in cpap treatment or assisted respiration - Google Patents
Pressure control in cpap treatment or assisted respiration Download PDFInfo
- Publication number
- CA2232546A1 CA2232546A1 CA 2232546 CA2232546A CA2232546A1 CA 2232546 A1 CA2232546 A1 CA 2232546A1 CA 2232546 CA2232546 CA 2232546 CA 2232546 A CA2232546 A CA 2232546A CA 2232546 A1 CA2232546 A1 CA 2232546A1
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- Canada
- Prior art keywords
- pressure
- flow generator
- turbine
- breathable gas
- control means
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0057—Pumps therefor
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0057—Pumps therefor
- A61M16/0066—Blowers or centrifugal pumps
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T137/00—Fluid handling
- Y10T137/2496—Self-proportioning or correlating systems
- Y10T137/2544—Supply and exhaust type
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T137/00—Fluid handling
- Y10T137/8593—Systems
- Y10T137/86493—Multi-way valve unit
- Y10T137/86558—Plural noncommunicating flow paths
Abstract
The pressure of breathable gas exiting a flow generator (10) is controlled by adjusting the efficiency of the flow generator. In one embodiment, a baffle plate (44) of a control element (40) can restrict the open entry area of a motor (16) driven turbine (18) of the flow generator. In another form, the degree of opening of the mouth of the flow generator inlet (20), and hence the pneumatic impedance, can be controlled, as in a similar manner can the impedance outlet (22).
Description
WO 97/10868 PCT/AU~6i~-Y~
PRESSURE CONTR'OL IN CPAP TREATMENT
OR AS~ ;Ll RESPIRATION
Field of the Tnvention This invention relates to d~*)dl~LUs and methods for the control of pl~s~ule in t'ne a~lmini~tration of continuous positive airway ~res~ure (CPAP) tre-~nt-nt or ,7csi~t~
es~ldlion.
R~rlu~rolln~l of t'nP Tnvention The ~cl.,.i"i~.dtion of CPAP is common in the L~~~ "f of Obstructive Sleep Apnea (OSA) syndrome and Upper Airway Resi~L~ce ~y~dlo~l~e. It has been poshl1~tf~ that CPAP Ll~ effectively acts as a ~P~ f ic splint of a patient's upper airway by providing air or breathable gas at a pressure elevated above atmospheric pl~:s:,ule to the e~ re of ~he patient's airway. Treatment pl~ UlCS in the range 4-25 cm H20 are commonly enc~u"L~,led.
Common to all forms of CPAP apparatus is a mask worn by a patient having connPction via a flexible air delivery tube to a flow g~lle,ator. Most often, the flow gt.,~Lc,r is driven by an electric motor that is under the control of a motor controller.
In tnis specification lert:-~-,ce to a "mask" is to be understood as inrl~l~ling a nose mask, a mouth mask, a nose and mouth mask in cc",ll~ aLion, nasal prongs or nasal pillows, or a full face mask.
CPAP L~t:dL~ent can be in a number of forms, including (i) the m~;.,f~"~"~e of a constant tre~nnPnt p~CS~ulc level, (ii) alL~lllaLil,g between two constant levels in ~yncll~ lll with the inspiratory and expiratory phases of l~yhdLion ("bi-level CPAP"), and (iii) having an autosetting level in accordance with a patient's therapeutic needs. In all of these cases there must be control over the ples~ of air or breathable gas supplied to the patient's airway.
In one form in the prior art, control over the tre~nnPnt pressure is achieved byspeed control of the electric motor driving the turbine (or fan) that together co~LiLuk:
~U~Slll Ul l~ SHEET (Rule ~6) , CA 02232~46 1998-03-18 WO 97/10868 PCT/AU9~_5~.S
PRESSURE CONTR'OL IN CPAP TREATMENT
OR AS~ ;Ll RESPIRATION
Field of the Tnvention This invention relates to d~*)dl~LUs and methods for the control of pl~s~ule in t'ne a~lmini~tration of continuous positive airway ~res~ure (CPAP) tre-~nt-nt or ,7csi~t~
es~ldlion.
R~rlu~rolln~l of t'nP Tnvention The ~cl.,.i"i~.dtion of CPAP is common in the L~~~ "f of Obstructive Sleep Apnea (OSA) syndrome and Upper Airway Resi~L~ce ~y~dlo~l~e. It has been poshl1~tf~ that CPAP Ll~ effectively acts as a ~P~ f ic splint of a patient's upper airway by providing air or breathable gas at a pressure elevated above atmospheric pl~:s:,ule to the e~ re of ~he patient's airway. Treatment pl~ UlCS in the range 4-25 cm H20 are commonly enc~u"L~,led.
Common to all forms of CPAP apparatus is a mask worn by a patient having connPction via a flexible air delivery tube to a flow g~lle,ator. Most often, the flow gt.,~Lc,r is driven by an electric motor that is under the control of a motor controller.
In tnis specification lert:-~-,ce to a "mask" is to be understood as inrl~l~ling a nose mask, a mouth mask, a nose and mouth mask in cc",ll~ aLion, nasal prongs or nasal pillows, or a full face mask.
CPAP L~t:dL~ent can be in a number of forms, including (i) the m~;.,f~"~"~e of a constant tre~nnPnt p~CS~ulc level, (ii) alL~lllaLil,g between two constant levels in ~yncll~ lll with the inspiratory and expiratory phases of l~yhdLion ("bi-level CPAP"), and (iii) having an autosetting level in accordance with a patient's therapeutic needs. In all of these cases there must be control over the ples~ of air or breathable gas supplied to the patient's airway.
In one form in the prior art, control over the tre~nnPnt pressure is achieved byspeed control of the electric motor driving the turbine (or fan) that together co~LiLuk:
~U~Slll Ul l~ SHEET (Rule ~6) , CA 02232~46 1998-03-18 WO 97/10868 PCT/AU9~_5~.S
the flow ge~ alol. In the case of bi-level CPAP, the motor must be able to ~ecelPra (or decelerate) respectively to double (or half) its operational speed within about 100 ms. For typical CPAP treatment, this equates to the need to supply (or sink) approximately twice the steady state electrical power within the noted time interval.
Disadvantages in motor ~e~ allce associated with the rapid transitions in speed are, for example, noise due to m~gn.otostrictive effects and bearing vibration, and increased thPrm~l dissipation re4uh~ll~llL~. Lower noise will increase patient compliance with the tre~tm~-nt Fig. 1 shows, as a cross-sectional view, a conventional flow gell~,a~ol 10 10 comprising a chamber 12 that is segregated from the casing 14 of the CPAP a~pa-dlus.
The casing 14 houses the control cil~;uiL~y (not shown) associated with the flowg~ lc Lol 10. The flow generator further is culll~-ised by a motor 16 driving anin-lucefl flow centrifugal turbine (impeller) 18, which induces the flow of air or breathable gas by an air inlet 20 to pass the air or breathable gas under ~.es~ult: by an 15 air outlet 22 to the air delivery tube (not shown) and so to the mask (also not shown).
The turbine 18 has radially directed impeller blades 24. The alternate use of axial fans is known also in CPAP appd dLus.
Another form of controllable flow generator involves operation of the driving motor at a COl~.LdllL speed, and venting or bleeding-off excess air from the output side of the turbine. As shown in Fig. 2, the ~urbine 18 is conn~octed to a plenum ch~mher 30 by a supply pipe 32. The plenum chclllbe. has a controllable spill valve 34 operable to indexingly open and close an opening 36 in the chamber wall to allow the venting of air to atrnosphere so as to achieve the desired output p.es~u.e at the air outle~ 38.
Such an arrangement also has disadvantages. Firstly there is excessive noise due to the venting of air when the LleaL~ t pressure is adjusted. This is particularly the case for each expiratory event during bi-level CPAP tre~tmt-nt when the treatment Ule typically is reduced from 16 cm H20 tO 6 cm H20, and thus over one half of the pressure head of the air within the plenum chamber 30 must be vented by the spill ~ ~ - ~
WO 97/10868 PCT/AU~ 86 valve 34. It is also diffl~lllt to m~int:~in precise ~lC~ l P1C~7~ regulation, since small variations of the spill valve position give relatively large variations in tne ples~ul~ at the air outlet 38. This configuration also leads to an il,hclellLly low m~ximllm flow rate which can culllplolllise the efficacy of CPAP Lle~ In particular, the spill valve 34 works by increasing outlet flow from the plenum ch~...'r.e 30, thereby increasing tne pressure drop in the supply pipe 32 and the turbine 18, thus ~llu~illg the p~ UlC in the plenum chamber. The combined p..~ ic i...pc~.r~e of the supply pipe 32 and the turbine 18 limit the m~ximnm achievable flow rate into the plenum chamber 30, and so to the patient, on sllhseqll~nt closure of the spill valve 34.
An example of another prior art arrangement that operates on ~e output ûf tne flow generator can be obtained from Intern~tion~l Publication No. WO 90/14121 (PCT/US90/02800), in the name Puritan-BenneK Corp.
As is noted, the invention also has application to ~palaLuS for the provision of~.csi.~te~1 lci,~i,aLion. Use of the terrn "assisted respiration" is to be understood as elllbrdci lg both ventilators and ~ei~ilarul~. Ventil~tors can broadly be ch~.d~ ed as providing for patient ventilation in a volume cycled mode, and do the worl~ of br~aLllillg for the patient. Re~pild~ùl~, on the other hand, may or may not do the complete work of breathing for a patient, and are characterised by their bi-level operation, with a large tre~trn~t ~ UlC diLr~.ellLial between il~ildLion and expiration and a high ilLsLJilaLol y ~le~ ll pie;,~ult:, which may reach 3040 cm H20 ni.~losure of th~ Tnvention It is an objective of the present invention to overcome or at least ameliorate one or more of the problems associated in the prior art The gist of the invention is to provide control of output pressure by controlling the efficiency of a flow generator or its component turbine Thererol~, tne invention broadly discloses a controllable flow g~ .a~Ol for the supply of breathable gas in the a~l--,i"i.~;l-dLion of CPAP tre~tm~nt or assisted W O 97/10868 PCT/AU~ S8 lc~ildtion, the flow gelle.aLor Cu~ iSillg: a motor coupled to drive a turbine, an inlet for breathable gas in col.ll".ll-ir~lion with the turbine, an outlet for the supply of said breathable gas at a ~lle;~UlC elevated above atmospheric ~lc~ule, and means to control the efficiency of the flow generator and thus the ~l~s~ulc of breathable gas exiting the flow generator.
In this specification the term "efficiency" in relation to a flow gcllel aLor or to the component turbine is to be understood as the ability to ~les~ulise a mass of air at a given flow rate and a given ples~ulc.
In one ~lcÇcl.cd form the control means controls the efficiency of the turbine, 10 and most preferably comprises adjustable pitch turbine blades or turbine louvres. In another ~rercllcd form, the control means controls the breathable gas available to the turbine. Alternatively, it controls the gas available to the inlet. Further, the control means can control the impe~nre of the outlet. The flow ~cn.,~lor can further comprise ~l~s:iurc sensor means for sensing the ~lc~ule of air or breathable gas exiting 15 the flow gel~àlol by the outlet, said sensed ~ ule being provided to said control means, and said control means further operable to compare said sensed ~ ,S:jUlC with a set pressure to m~int~in said exiting ~ u~e substantially the same as said set plC~ ulc by controlling the efficiency of the turbine in accordance with the result of said comparison.
The invention further discloses a controllable flow gel~.aLor for the supply of ;,~ulised breathable gas in the ~(I",;";!~L.alion of CPAP tre~tm.ont or ~csicte,l c~ilaLiom, the flow gellclalol conl~lisillg a motor coupled to drive a turbine, an inlet for breathable gas in cu~ tion with the turbine, an outlet for the supply of said breathable gas at a plcs~ulc elevated above atmospheric pl,s~ulc, and control means for 25 controlling the breathable gas available to the turbine and thus the ~leS~ C of breathable gas at the outlet.
Advantageously, the control means acts to restrict the flow generator inlet.
The restriction can be over a range of inlet opening. The range can be between the W O 97/10868 PCT/~U96/00586 inlet fully open and partly or fully closed. For an operational rotational speed of said turbine, the limits of t'ne range relative to inlet when open and at least partly closed respectively CO1LeS~OIId to tne highest outlet pressure and the lowest outlet ~)~C:i''Ul~ of supplied air or breathable gas.
In a ~ref~llGd form? the control means can comprise means for closing at least a portion of a mout'n of said inlet. Alternatively, said control means can comprise a controllable vane for at least partly restricting said imet.
~lt.orn~tively, the control means acts to adjust the Grre~;livG entry area of the turbine impeller open to the inlet. The adjllctm~nt can be over a range. The range can be between the total effective entry area of the turbine open to the inlet and partial or zero effective entry area of the turbine open to the inlet. For an operational rotational speed of said turbine, the limits of the range relative to said total ~fre~;Live surface area and at last partial crr~.;liv~ entry area respectively correspond to the highest outlet sule and the lowest outlet ples~ulc of supplied air or breathable gas.
In a pl~rGlled form, the control means can comprise a positionally adjustable baffle that can block-off at least a portion of the effective moutn area open to the imet.
In one particular plGrGlled form, the control means acts to cause the l~pe~li..gseq~-.onti~l supply of breathable gas at said outlet at a first higher ~re~.~ulG and a second lower pressure. The flow generator can further comprise pLC;,~ule sensor means for sensing ~l~s~ul~: at said outlet, said sensed ~les~ule provided to said control means1 and said control means further operable to eolll~ale said sensed ~ s~ule with a set pl~s~ule to m~int~in said outlet ~7l~ iule subst~nti~lly the same as said set ~l~,SSUlc by control of the breathable gas available to the turbine in accoldallce wit'n the result of said colllp~lison.
The invention further discloses CP~P tledLIllellL a~aldlus conl~ .ing a patient mask, an air delivery tube conn.octe~l at one end to the mask, a flow generator conn~ctP-I to the otner end of the air delivery tube and collll)lisillg a motor coupled to drive a turbine at an operational rotational speed, an inlet to receive breathable gas, an outlet for the supply of said breathable gas to said air delivery tube at a pl'cS~.ule elevated above atmospheric ~Le;~ r~ and control means for controlling the breathable gas available to the turbine and thus the ~lcs~ule of breathable gas at said outlet.
In one plcfcllcd form the control means acts to restrict the flow gellclaLo imet. Alternatively, the control means acts to adjust the ~frccLivc area of the turbine open to the inlet.
The a~alalus can further comprise a path for patient exh~l~tion from said outlet by-passing the turbine. The exhalation path can vent to atmosphere or recirculate to said imet.
0 Advantageously, the CPAP ap~a,àLus can be for the ,~ L~dLion of bi-level CPAP ll~ nl.l-r~ and the control means is operable between two states ,c~,~ecLi~cly corresponding to a desired patient h~ilàl~lyll~aLlll~llL~leS~ul~, and the reduced desired patient e~i,dLol y treatment ~C~Ul~ .
Advantageously, the CPAP apparatus can be for the a~lminictration of a trP~tmPnt L~ .Ul-, adju~.~il,g in accordance with patient need, whe~cill the control means has a contim-~lly adjusting current set level col,~Jonding to the desired tre~.tmPnt ~les~,urc, and causes the outlet level to be controlled to m,.im,.in the ~)leS~.Ulc at the desired level.
The CPAP apparaLus can further comprise pressure sensor means for sensing ~re~ulc at said outlet or at a point in said air delivery tube or in said mask, said sensed pl~,s~iule provided to said control means, and said control means further operable to e~Jlllpare said sensed ~lc~ule with a curlent set pies~ c to m~int~in the trP~tm~t ~"es~u,e sl~bst~nti~lly co,~LanL at the desired level in accordance with the result of the cc,lllpal iSOll.
In another preferred form, the CPAP tre~rmPnt apparatus can be operable to m~int~in the Lle~ pressure at said mask substantially constant by continuous control of said control means.
WO 97/10868 PCT/AU~5./~ 6 The invention yet further ~ closes a method for control of the F~l~,SSurt: of breathable gas delivered by a flow ~ ene.dL~Jl in the ~r~ l dtion of CPAP L~G~
or ~si~ted lc~pildLion, said method CO~ iSi~g the steps of operating said flowg~llelalol at an operational rotational speed whereby said breathable gas enters the turbine by an inlet of the flow gellel~Lur and exits the turbine at a l,r~s~ule elevated above atmLospheric pressure, and controlling the breathable gas available to thLe turbine and thus the exit plcs~ule.
All the above allallgelllents limit the through-put of breathable gas thLrough thLe flow generator, colll~ar~d with prior art. arrange~ llLs which provide for ~ UlC10 control by spilling excess gas, thLereby resnltin~ in concomitant increase in acoustic emissions and motor power re~uh~lllellL~. Embo~i...f ~ of the invention as defined can provide a controllable flow generator or CPAP a~alalLIs that provides one or more of thLe advantages of lower power, lower acoustic noise, higher m~ximnm air flow and improved ~ S~We control in CCll~dliSOJLl with prior art alldn~elllellL~. In one or more embo~iimpnt~ thLe power supply for thLe flow generator can halve its rating, thus reducing cost, heat dissipation and occupied volume.
It will be understood that all references to "tre~tml-nt pleS~ul'e''inCIULde a continuous pLeS~UlC that can vary with time if desired in accoldallce with L
needs, and therefore is not n.ocess~rily of a constant level.
Rrief rlescriptio~ of the nrawir~
A llUlllbel of emboriimpnt~ of the invention now will be described with reference to the accolllpallyhlg drawings, in which:
Figs. 1 and 2 show exarnples of controllable flow gellel~t~ in the prior art;
Figs. 3-5 show a first embodiment of a controlled flow gene,d~ol in accordance with the present invention;
Figs. 6 and 7 show another embodiment of a controlled flow generator;
Figs. 8 and 9 show a yet further embodiment of a controlled flow gelleldt(JI, W O 97/10868 PCT/AU96,'~ 6 Figs. 10 and 11 show a yet further embodiment of a controlled flow generator;
Figs. 12a and 12b respectively show a cross-sectional and plan view of a further embodiment of a controlled flow generator;
Fig. 13 shows a variation to the controlled flow genela~ur shown in Figs. 12a and 12b;
Fig. 14 shows a yet further embodiment of a controlled flow ~ellel~Lol, Fig. 15 shows an embo-iimPn~ of a controlled flow gel~aLuI inrl~ an gell~e~t for ~ ti~n;
Fig. 16 shows an alternative arrangement for ~rtll~tion of the controlled flow o generator of Fig. 15;
Fig. 17 is a sch~m~tir block diagram of CPAP ~I~/paldLUS in~lllriing any one of the controllable flow generators of the preceding figures;
Figs. 18a and 18b show a cross-sectional view of a further embodiment of a controlled flow ~,e.l~.atol, Figs. 19a and l9b show a sc~ view of a yet further embodiment of a controlled flow g~ aLor, Figs. 20a-20d show examples of ~ e transition functions; and Fig. 21 shows a graph of ~.ei,~ule versus time for the flow ~ el~,~tul of Figs.
12a and 12b.
nescrirtion of Preferred F,mbo~lim~t~ ~n(1 Rtost Mode A llulllber of controllable flow generator arrangell~..ls will be described, and it is to be understood that each and every arrangement can readily be incorporated into the CPAP a~al~Lus m~mlf~ctllred by the present applicant, including the applicant's Sullivan ~ III, Sullivan ~ V, VPAP n' and Autoset su l~chintos.
While the embo-lim~-nt~ to be described refer to CPAP tre~trn~nt, it is to be understood the invention equally is applicable to apparatus for ~si~t~d respiration tre~tm.ont Where a~ u~liale, the same lcr~rel1ce numerals have been used to ;".li~ a component part in common with other embo~1i.,.~.~lx, or with the prior art.
The embodiment shown in Figs. 3 to 5 differs from the prior art all~ngelll~,llL
shown in Fig. 1, in that a control element 40 is located in the air inlet path of the inlet 20 proximate the turbine impeller blades 24, and is comprised of a shaft 42 ending in a baffle plate 44. The control elemPnt 40 is caused to move vertically within a defined range by any convenient actuator (not shown) to change the erf~ ive entry area of the turbine impeller blades 24 open to the inlet 20. Generally, this controls the air or breathable gas available to the turbine 18, and more generally the efficiency of the flow o g~ tor. The baffle plate 44 may have a small clearance b~Lweel1 its ends and the blades 24 (or blade housing) of the turbine 18. Equally, the baffle plate 44 could be in contact with the turbine 18 to rotate together with the turbine 18.
In operation of the flow g~J-~ldlol 10, the motor 16 causes the hlrbine 18 to rotate at a near con~t~nt operational speed concomitant with, or slightly higher than, the m~ximllm required Llc~ 3,es~u,c; to appear at the patient mask. In Pig. 4, the baffle plate 44 is located at its lower-most extent, thereby not l~ ;lhlg the flow of air from the inlet 20 to the turbine impeller blades 24. This l~pl~,selll~ the m~ximllm pressure at the outlet 22, typically 20-30 cm H20 for CPAP tre~tmP~t Fig. S shows the sit~ ti~n where the baffle plate 44 is arranged to be at its top-most extent of the range, whereby ~e air or breathable gas available to the ~urbine impeller blades is almost zero, in that the effective surface area of the blades 24 open to the inlet 20 is pr~rtir~lly zero. Again, Ihe motor 16 is driving the turbine 18 at the same operational rotational speed, in which case a near zero positive ~ S:~Ult; (or at least a very low positive p-~:s~u,c) occurs at the outlet 22. In practice, this a~ gellle would lc~ sell~ a positive plei,~ul~ at the outlet 22 of approximately 0-2 cm H20. A
seal also may be provided at the top of the fan to ensure complete baffling by cooperation of the seal with the baffle plate 44 to avoid leaks around the edge of the baffle plate.
W 0 97/10868 PCT/AU~S~'~OS~'Ç
-10- .
Thus by control of the control element 40, the flow gen~dLul's efficiency can be controlled, and different flow generator outlet (and therefore mask) ~'e~ P~II
S5uleS can be obtained. As will be a~pare~lL, two l)res~.ules can be a~l~u~!liaL~ly selectP~l for implc"l~.lLdLion of bi-level CPAP by control of the baffle element 40. The higher i,~.l,i,ato. y pressure corresponds with a lower position for the control clf -... l.
40, while the lower expiratory ~eS'.~ corresponds with a higher position of the control elern~nt 40.
The ~ctl~ti~ n devices coupled ~o the control element 40 have co~ on with bl~d~ g detection circuitry that detects transitions between patient ilL~ Lion and o expiration, so that control over the movement of the baffle element 40 can be in ~yllcl~ ism with the patient's respi,dlion phases. The present applicant's VPAP
apparatus has such bleaLl~illg ~letPctiQn Ci~;uiLl y.
Importantly, and as noted in Fig. 5, on patient expiration, a low h,~eda"ce e7~h~l~tion path 46 is provided, otnerwise the benefit of a reduced L~ ...ure during expiration may be nPg~tP-l by the patient being required to do excessive work during expiration. The expiration path 46 occurs between the outlet 22 and the inlet 20 by means of t'ne open space around the sides and top of the turbine 18, cledlillg a ready path to atmosL~hele. Without the expiration patn a back l,re..~.u,~ would be formed on patient expiration that would restrict the lowest L~e~l."~"l p,e~..u,e achievable, that being particularly il"polL~l~ to expiration ll~dL,~ L pressure in bi-level CPAP where an expiration ilc~l.llr-l~l ples.~ure of 4 cm H20 is not uncommon. Ideally, the back 7~7Ul~ on expiration should be limited ~o 2 cm H2O through the provision of the e~h~l~tion path 46. A low impedance exh~l~tion path is ~ f~.led not only for bi-level CPAP tre~tmPnt, but also for single level CPAP where, although the ~,es~.u,~ remains col~.L~llL, tnere should not be undue impedance to opposed flow due to patient expiration.
Figs. 6 and 7 show another embodiment of a controllable flow generator 48, in which the supply of air or breat~hable gas to the inlet 20 is controllably restricted (and W O 97/10868 PCT/A~ 86 thus the flow gel~.aLc~r efficiency reduced) by a choke 50 formed by a shaft 52 ending in a choke plate 54. Therefore, by the proxirnity of the plate 54 to the entrance to the air inlet 20~ the air or breathable gas available to the turbine 18 can be controlled. As shown in Fig. 6, the choke plate is remote from the opening to the air inlet 20, hence s there is no ,c~Lli-;Lion of the flow of air or breathable gas into the inlet and to the turbine 18. This represents the situation of the m~ximllm ll~,aLIl~ell~ pl~S~iult: for a given operational rotational speed of the turbine 18. The situation shown in Fig. 7, where the choke plate 54 is seated against the mouth of the air inlet 20 to restrict any flow of air or breathable gas to the inlet, ~ cse~ the lowest possible ~
pressure for the turbine 18 operating a~ or near the same operational rotational speed.
Clearly, ~ pressures intermediate of the limits represented by the arran~llle shown in Figs. 6 and 7 are achieved by vertical lllo~ llL of the choke shaft 52 to provide the nrcess~ry restriction of the ~llL,~lce to the air inlet 20.
During the ~ dlion of bi-level CPAP L~f ~ -l the exhalation ~
15 ~n,;~Ul~ will be low, in which case the choke plate 54 will be almost seatedL on the mouth of the air inlet 20, which creates a high illlpedallce path for patient expiration.
For this reason, a bleed vent 56 is located in a tube 58 e~/rn~ lg from the fan ch~...h~
12 to the outlet 22. The bleed vent 56 provides a low impedance exhalation path for the patient. As will be al,parellL, the bleed vent 56 also l~lesc.lL~ a leak that will have a minor effect upon the pl~Ul~ of air or breathable gas at the outlet 22 for thetreatment ~l~S~ul~ elienced during single level CPAP or during inspiration in bi-level CPAP treatmPnt. The small plc~s~llle drop inflllrer1 by the bleed vent 56 can easily be compensated by a~propliate adjustment of the choke 50. The ~rt l~tin~ circuitcontrolling the choke S0 may be operab]e under feedba~k control from a sensor sensing 2s pressure at the mask of at the outlet 22, in which case the plC;~iUlt~ drop due to bleed vent 56 will autom~tir~lly be compenc~t~d. The bleed vent 56 should not incur a ~lcs~ule drop in excess of 2 cm H2O otherwise ll~ill;llllllll expiration tre~tmPnt pl~s~ule might be colllplolnised.
CA 02232546 l998-03-l8 W O 97/l0868 PCT/AU96/005~6 Figs. 8 and 9 show a controllable flow genc.ator 48' having an ~ltP~n~tP
arrangement for the bleed vent 56 of Figs. 6 and 7, in that in certain in.ct~nrPc it may not be desirable to have the bleed vent 56 open in any ch.~ -res other than during patient expiration (e.g. bi-level CPAP Lle~ ). As shown, the bleed vent 56 is replaced by a branch 60 from the tube S8, and is in co.. ~ r-~tion wi~ the air outlet 22. The branch 60 is controllably opened and closed by a valve 62 formed by a valve shaft 64 and valve plate 66. The case of Fig. 8 relates to the provision of h~~ Lul~y treatment plcsaule in bi-level CPAP lle~ l, in which case the valve plate 66 closes-off the branch 60 so there is no leak from the outlet 22, and thus the full illS~i 10 output pressure from the flow generator 10 is delivered to the air delivery tube (not shown) and so to the mask (also not shown). The case of Fig. 9 relates to the provision of e~L~hatc)ly trP~tmPnt ~re~ule, whereby the choke plate 54 closes-off the mouth of the air inlet 22, and the branch 60, by ~rtl~ti- n of the valve 62, is opened to the atmosphere to provide an exh~l~tion path. Actuation of the choke 50 and the valve 62 can be s~llcl~ul~ed, and it is preferable that there be a gr~ ting opening of the mouth of the branch 60 in operation of the valve 62, rather than a sudden o~e~ g, to linearise the relationship between ples~uie and valve displ~rPTnPnt The arrangelment of the branch 60 and the valve 62 must be such as to ensure that the ~lei,~ule drop does not exceed the Illill;llllll~ expiration Ll~ S:WI't:, typically 4 cm H20, and most 20 preferably does not exceed 2 cm H2O.
The alla,l~wlle-ll shown in Figs. 10 and 11 show a controllable flow generator 48" that is a variation of the embodiment of Figs. 8 and 9, in that there is a recirculation conduit 68 co~ scl ;"g the branch 60 with the air inlet 20' . Thus air or breathable gas is recirculated during patient expiration, which avoids the necessity to 25 vent to atmosphere, and thus removes a possible noise source. In Fig. 10, the valve plate 66 closes off the exit to the branch 60 during the provision of inspiration treatment pr~:s~ure, with tne valve 62 gradually being raised upwards at the transition to W O 97/10868 PCT/AU~C;~C~6 patient expiration to open the branch 60 to the recirculation conduit 68, as shown in Fig. 11, thus providing the recirculation path during patient expiration.
Figs. 12a and 12b show a yet further embodiment of a controllable flow generator 48 " ' that is similar to the embodiments of Figs. 8 and 9. In place of the choke 50 and valve 62 is a sliding ples~.ulc control plate 70. The ~leS~.ulc control plate 70 has a circular a~c.Lulc 7~ which in colljullclion with the ell~ lce to the air inlet 20 forms a choke valve 74. The a~el~ulc egually could be profiled in a non-regular shape.
The plate 70 also has a profiled slot 76 which in culliull~;lion with the exit to the branch 60 forms an imre-1~nre control valve 78.
The control plate 40 is slidingly operated by an a-;LuaLul (not shown) having connection with the b~cdLllillg ~t~ction and tre~tm~nt l.rcs~.ulc control ~;h.;uiLly. As the plate 70 moves to the left to further restrict the mouth of the inlet 20, the errc~ /e surface area at the exit of the branch 60 open through the slot 76 is c~ dtcly increased, thus providing a lower hll~edallce exhalation path. The converse situation applies when the plate 70 is moved to the right, in that when the circular ~cllul~ 72 is located wholly over the mouth of the inlet 20 colr~s~o~ g to h~.~..dLion llc~
~lC~7~7UlC, the exit of the branch 70 is wholly blocked-off by the control plate 70, as the slot 76 will have past the left-most extent of the exit to the branch 60. The tapered alldngcllltllL for the slot 76 is one of many possible arran~emcllL~ and, in this case, provides a near linear relation between eYh~l~tion impe-i~nre and treatment ~lCS~ùlc.
Fig. 13 shows an alternate arrangement to that of Figs. 12a and 12b wherein the ~lcs~ule control plate 70" is no longer sliding, but rather rotatable, otherwise the principle of operation remains the same.
Fig. 14 shows a yet further embodiment of a controllable flow generator 80 that is somewhat similar to the arrangement shown in Figs. 6 and 7. In this ~ arrangement, the air available to the turbine 18 is controlled by a buLLclny choke valve 81 that acts to restrict the air inlet 22 to the flow of air or breathable gas. Operation of this flow generator is otherwise as described in relation to Figs. 6 and 7. Although not W O 97/10868 PCT/AU~6/'0~58 shown, as with Figs. 6 and 7, a bleed vent can be provided dowl~Ll~,alll of the turbine 18 to provide a low impedance exhalation path.
The actuators that can be used in relation to all of the valve al.,..lg~
previously described can include linear or rotary arrangements of solenoids, brushless motors/a~;luatol~, stepper motors/a~;lua~ols or switched relncf~nre motors/a~:LuaLol~.
One example of an actuator is shown in Fig. 15, which relates generally to the controllable flow gene~alor shown in Fi~gs. 3-5. The baffle plate 44 is not in contact with the turbine blades 24 (or blade housing) hence is non-foldlillg, and is aligned by means of a locating pin 82. The shaft 42' is pivotably connPctp~l with an acLivdLhlg link 84, in turn pivotably mounted from a post 86 st~n~lin~ from the fan chamber 12. The activating link 84 is "L"-shaped, with the downwardly-directed leg having connection with an armature 90 and a helical spring 92. The armature 90 is under the control of a solenoid 94 that has connection at least with the 'ol~Lllillg detection circuit. The spring 92 provides a return force when the solenoid is unpowered. Thus in response to the detection of transitions between i~ aLion and expiration, the solenoid 94 causes the ~rm~tllre 90 to move, in turn moving the activating link 94 and so the baffle plate 44 to control the desired LlcàLlllentpl~ ul~ between patient hl~ ion and e~haLion.
The solenoid 94 also can be connPct~-l to the ~ SSUle control Cil~;uiLly to provide fine control over the desired treatment pressure, particularly and in the regulation of that ~ UiC.
In another form, the solenoid 95 can be connPcte~l only to the bledLllillg detection circuit, and for bi-level CPAP trp~tmpnt~ the hls~ildLillg and e~hdtoly tre~tmPnt l les~ul~s can be mPch~ni~lly selected by means of respective end stops 88,90. For such an alldngelllenL it is not nPce~s~ry to retain the p~s~ule control Cil~;uiLly~ which can lead to a cheaper product to put into the marketplace.
Fig. 16 shows an all~.lla~iv~ arrangement for an actuator for the controllable flow generator shown in Fig. 15. In this case, the baffle plate 44 can be in contact with the turbine blades 24 (or blade housing) so that the shaft 42" may rotate with the CA 02232546 l998-03-l8 W O 97/10868 PCT/AU~G,'~ 5 turbine 18. The upper end of the shaft 42" carries a pL,~llldll~llt or electro-m~gnet 88 that is ~u~ou~ded by a further pe- IIIAIl~lll magnet 90 forrning a m~gn-otic link. In this way, the i"~Lallce of the shaft 42" rotating in concert with the fan 18 can be accommodated, and actuation of the baffle plate 44" is by the vertical movc~llCllL of the shaft 92 conn~-c~d with the outer pe~ or electro-magnet assembly 90.
Fig. 17 shows a l~lcsenL~Li~/e block diagraïn of control of CPAP ~aldLus incorporating controllable flow gellc dlor in accordance with any one of the prece~li~
emboriim~ntc. The turbine 18 is driven at an operational rotational speed by the motor 16 under the control of a motor controller 100 with the rotational speed being held 10 essentially constant at a "set speed" the regulation being provided by a cu",~a~ison bcL~el- the "set speed" signal and a feedb~cl~ signal 102 by a co~.~pdr~tol 104. It is of course possible for the "set speed" signal to vary although Ire~ .S~ulc control is not effected by motor speed control. In that case the "set p~e;,~u~c" signal is independent of the "set speed" signal, and is co~ d with the output of a plCS~ulc tr~n~d~lcer 106 that measures p,es~u,c at the flow generator outlet 22 (via t~be 112) by a cc""~lator 108. The sensed plcS~ull., can alLellldLi~cly be the Ll~aL~lle~L p~s~u,e at the mask. The error signal between the set plts~ulc and the measured plcs~ùlc at the outlet 22 causes the actuator 110 to adjust the position of the control element/choke 40 50. The "set ~ ulc" signal can be constant for single level CPAP or can vary in the instance of bi-level CPAP or autosetting CPAP ~ n~
The output signal from the pressure colll~dldLor 108 will reflect l~ ilalion rate and depth and so also can be used as a signal to trigger transitions between patient h~s~ildlion and expiration. This may lead to a simplification or even rerl-~n~l~n~y of existing bledLllillg detection Cil~;uiLly. It also provides a measure of flow minute volume and like ~ ldlllCtCl~i.
- Figs. 18a 18b l9a and l9b show tWO arrangements in which the efficiency of a flow gellclator is controlled by way of the p~ ..,AIir impedance of the outlet of the flow generator available to the exiting breathable gas. The imre~lAn~e of the flow W O 97/10868 PCT/AU~6~0~586 eld~r is effected in the sense that a change in cross-sectional area or volu~tLlic capacity of the outlet will effect the ability to pressurise a mass of air at a given flow rate and given ~)lCS~iUlC, as will be a~pal~llL to one skilled in the art.
The flow generator 148 shown in Figs. 18a and 18b includes a llulllber of elements common with the embo-limrn~ previously described. A passageway 158 exits from the chamber 12 and comm--nir~tes the exiting gas with a plenum 160 via an entrance lS9. The plenum has an exiting port 162, by which ples~uli~ed bre~th~hle gas can be supplied via a conduit to a patient mask for the ~ dLion of CPAP
Llc~LI~ellL or assisted lci.L~ildlion. The plenum 160 has a further vent 164 in 10 co""".l,~ir~tion with atmosphere. Both the vent 164 and the entrance lS9 to the plenum 160 can be controllably occ~ rci to reduce their open area by a sliding i~ .e~l~nre control plate 166. The control plate 166 inr~ e~ an apeltu.e 168 that, dc~elldillg upon its position, can restrict the respective p~ gP~ in a range from wholly open to fully closed.
In Fig. 18a, the control plate 166 is in a position such that the aperture 168 occludes the control vent 164 yet allows cu,....~ .ir~lion of exiting breathable gas from the passageway 158 to the plenum 160 and so to the exiting port 162. The direction of flow of breathable gas is shown by the line bearing an allowlRad. Fig. 18b shows the situation where the control plate 166 is in a position whereby the entrance 159 is closed, however the impedance control vent 164 is open. This condition accords with the provision of a low impedance path for patient expiration.
Clearly Figs. 18a and 18b show the extreme ranges of operation of the impe-l~nre control plate 166. The aperture 168 is sized so that the entrance 159 to the plenum 160 can be partially open, as can the control vent 164. In this m~nner, the impe~ nre of the outlet 122 is controllable, in turn, controlling the efficiency of the flow generator 148.
Figs. l9a and l9b show a further embodiment of an outlet section 122' as an alternative a~ enl~llL to the outlet sec~ion 122 shown in Figs. 18a and 18b. Again, W O 97/10868 PCT/AU3C'~ t comrnon elements have been in-iic~tecl by use of like reference numerals. The plenum 160' is of circular cross-section. In place of the previous sliding impedance control plate 166 is a rotatable control plate 170. In the position shown in Fig. 19a, the vent 164' is occluded by the control plate 170, ~ that the full flow of gas from the turbine passes from the passageway 158 through the plenum 160' to the exiting opening 162'. This situation represents the m~ximllm Ll.~ .ule.
The situation shown in Fig. 19b is where tne i"l~cdd"ce control plate 170 now fully occludes the entrance 159' to the plenum 160' reS~llting in the ~ il.--- .. output pl~,S~llle, again, providing a low impedance path on patient expiration.
For botn of tne embo-li"~ of Figs. 18a, 18b, 19a and 19b, the arrange",c.lL~.
for controlling the respective ~rnpedance control plates previously applied 166,170 equally apply.
In another embodiment not srecifir~lly shown in the dldwhlg~, the turbine can have adjustable pitch or sized impeller blades that are controllable to effect a change in the turbine, and hence flow g~n~ldLoL efficiency, and in this way have control over output pl~s...ll~. Such Lu~bh~es also rnay have louvre a,.,,..~r,..~ to spoil air flow and adjust efficiency.
In all the valve/choke arrange,l~R~L~ previously described a number of bi-level CPAP hl~pilaLion/expiration transitional sch~m~s can be adopted. A first case, as shown in Fig. 20a an impulsive change b~.w~ell Ll~ plcS~.Ille that is a fast rising plc;SSLlle output, having a rate of rise of approximately 0.5 - 1.0 cm H20 per msec. A
second case, as shown in Fig. 20b is a linear l~illg function, having a gradienttypically between 0.2 - 0.04 cm H2O per msec. The third case, as shown in Fig. 20c is a combination of the first two, as an impulsive step followed by a ramp. The step may be of the order l/2 (Pl - PE)- Finally, Fig. 20d shows a case where the rising ramp has an overpressure ( > Pl) at the commP~ of the hl~ Lol.y phase, and an impulsive change the transition tO the inspi,al()ry phase.
W O 97/10868 -18- PCT/AU96/005~6 Fig. 21 shows a chart of measured outlet ples~ulc versus time for bi-level operation of the embodiment described in Figs. 12 and 12b, for which tne h~ L~lly LledLIllellL p~eia:iUl~; iS about 16 cm H20 and the t~pildtOl~/ trÇ:ltmf~rlt pl~.S~Ule iS about 8 cm H20.
While the embodim~nt~ described have the turbine c~elaLillg at a constant rot~tion~l speed, it is equally possible to combine motor speed control with flow generator efficiency (e.g. control over the air or breathable gas available to the turbine) in the course of control over output pressure.
Disadvantages in motor ~e~ allce associated with the rapid transitions in speed are, for example, noise due to m~gn.otostrictive effects and bearing vibration, and increased thPrm~l dissipation re4uh~ll~llL~. Lower noise will increase patient compliance with the tre~tm~-nt Fig. 1 shows, as a cross-sectional view, a conventional flow gell~,a~ol 10 10 comprising a chamber 12 that is segregated from the casing 14 of the CPAP a~pa-dlus.
The casing 14 houses the control cil~;uiL~y (not shown) associated with the flowg~ lc Lol 10. The flow generator further is culll~-ised by a motor 16 driving anin-lucefl flow centrifugal turbine (impeller) 18, which induces the flow of air or breathable gas by an air inlet 20 to pass the air or breathable gas under ~.es~ult: by an 15 air outlet 22 to the air delivery tube (not shown) and so to the mask (also not shown).
The turbine 18 has radially directed impeller blades 24. The alternate use of axial fans is known also in CPAP appd dLus.
Another form of controllable flow generator involves operation of the driving motor at a COl~.LdllL speed, and venting or bleeding-off excess air from the output side of the turbine. As shown in Fig. 2, the ~urbine 18 is conn~octed to a plenum ch~mher 30 by a supply pipe 32. The plenum chclllbe. has a controllable spill valve 34 operable to indexingly open and close an opening 36 in the chamber wall to allow the venting of air to atrnosphere so as to achieve the desired output p.es~u.e at the air outle~ 38.
Such an arrangement also has disadvantages. Firstly there is excessive noise due to the venting of air when the LleaL~ t pressure is adjusted. This is particularly the case for each expiratory event during bi-level CPAP tre~tmt-nt when the treatment Ule typically is reduced from 16 cm H20 tO 6 cm H20, and thus over one half of the pressure head of the air within the plenum chamber 30 must be vented by the spill ~ ~ - ~
WO 97/10868 PCT/AU~ 86 valve 34. It is also diffl~lllt to m~int:~in precise ~lC~ l P1C~7~ regulation, since small variations of the spill valve position give relatively large variations in tne ples~ul~ at the air outlet 38. This configuration also leads to an il,hclellLly low m~ximllm flow rate which can culllplolllise the efficacy of CPAP Lle~ In particular, the spill valve 34 works by increasing outlet flow from the plenum ch~...'r.e 30, thereby increasing tne pressure drop in the supply pipe 32 and the turbine 18, thus ~llu~illg the p~ UlC in the plenum chamber. The combined p..~ ic i...pc~.r~e of the supply pipe 32 and the turbine 18 limit the m~ximnm achievable flow rate into the plenum chamber 30, and so to the patient, on sllhseqll~nt closure of the spill valve 34.
An example of another prior art arrangement that operates on ~e output ûf tne flow generator can be obtained from Intern~tion~l Publication No. WO 90/14121 (PCT/US90/02800), in the name Puritan-BenneK Corp.
As is noted, the invention also has application to ~palaLuS for the provision of~.csi.~te~1 lci,~i,aLion. Use of the terrn "assisted respiration" is to be understood as elllbrdci lg both ventilators and ~ei~ilarul~. Ventil~tors can broadly be ch~.d~ ed as providing for patient ventilation in a volume cycled mode, and do the worl~ of br~aLllillg for the patient. Re~pild~ùl~, on the other hand, may or may not do the complete work of breathing for a patient, and are characterised by their bi-level operation, with a large tre~trn~t ~ UlC diLr~.ellLial between il~ildLion and expiration and a high ilLsLJilaLol y ~le~ ll pie;,~ult:, which may reach 3040 cm H20 ni.~losure of th~ Tnvention It is an objective of the present invention to overcome or at least ameliorate one or more of the problems associated in the prior art The gist of the invention is to provide control of output pressure by controlling the efficiency of a flow generator or its component turbine Thererol~, tne invention broadly discloses a controllable flow g~ .a~Ol for the supply of breathable gas in the a~l--,i"i.~;l-dLion of CPAP tre~tm~nt or assisted W O 97/10868 PCT/AU~ S8 lc~ildtion, the flow gelle.aLor Cu~ iSillg: a motor coupled to drive a turbine, an inlet for breathable gas in col.ll".ll-ir~lion with the turbine, an outlet for the supply of said breathable gas at a ~lle;~UlC elevated above atmospheric ~lc~ule, and means to control the efficiency of the flow generator and thus the ~l~s~ulc of breathable gas exiting the flow generator.
In this specification the term "efficiency" in relation to a flow gcllel aLor or to the component turbine is to be understood as the ability to ~les~ulise a mass of air at a given flow rate and a given ples~ulc.
In one ~lcÇcl.cd form the control means controls the efficiency of the turbine, 10 and most preferably comprises adjustable pitch turbine blades or turbine louvres. In another ~rercllcd form, the control means controls the breathable gas available to the turbine. Alternatively, it controls the gas available to the inlet. Further, the control means can control the impe~nre of the outlet. The flow ~cn.,~lor can further comprise ~l~s:iurc sensor means for sensing the ~lc~ule of air or breathable gas exiting 15 the flow gel~àlol by the outlet, said sensed ~ ule being provided to said control means, and said control means further operable to compare said sensed ~ ,S:jUlC with a set pressure to m~int~in said exiting ~ u~e substantially the same as said set plC~ ulc by controlling the efficiency of the turbine in accordance with the result of said comparison.
The invention further discloses a controllable flow gel~.aLor for the supply of ;,~ulised breathable gas in the ~(I",;";!~L.alion of CPAP tre~tm.ont or ~csicte,l c~ilaLiom, the flow gellclalol conl~lisillg a motor coupled to drive a turbine, an inlet for breathable gas in cu~ tion with the turbine, an outlet for the supply of said breathable gas at a plcs~ulc elevated above atmospheric pl,s~ulc, and control means for 25 controlling the breathable gas available to the turbine and thus the ~leS~ C of breathable gas at the outlet.
Advantageously, the control means acts to restrict the flow generator inlet.
The restriction can be over a range of inlet opening. The range can be between the W O 97/10868 PCT/~U96/00586 inlet fully open and partly or fully closed. For an operational rotational speed of said turbine, the limits of t'ne range relative to inlet when open and at least partly closed respectively CO1LeS~OIId to tne highest outlet pressure and the lowest outlet ~)~C:i''Ul~ of supplied air or breathable gas.
In a ~ref~llGd form? the control means can comprise means for closing at least a portion of a mout'n of said inlet. Alternatively, said control means can comprise a controllable vane for at least partly restricting said imet.
~lt.orn~tively, the control means acts to adjust the Grre~;livG entry area of the turbine impeller open to the inlet. The adjllctm~nt can be over a range. The range can be between the total effective entry area of the turbine open to the inlet and partial or zero effective entry area of the turbine open to the inlet. For an operational rotational speed of said turbine, the limits of the range relative to said total ~fre~;Live surface area and at last partial crr~.;liv~ entry area respectively correspond to the highest outlet sule and the lowest outlet ples~ulc of supplied air or breathable gas.
In a pl~rGlled form, the control means can comprise a positionally adjustable baffle that can block-off at least a portion of the effective moutn area open to the imet.
In one particular plGrGlled form, the control means acts to cause the l~pe~li..gseq~-.onti~l supply of breathable gas at said outlet at a first higher ~re~.~ulG and a second lower pressure. The flow generator can further comprise pLC;,~ule sensor means for sensing ~l~s~ul~: at said outlet, said sensed ~les~ule provided to said control means1 and said control means further operable to eolll~ale said sensed ~ s~ule with a set pl~s~ule to m~int~in said outlet ~7l~ iule subst~nti~lly the same as said set ~l~,SSUlc by control of the breathable gas available to the turbine in accoldallce wit'n the result of said colllp~lison.
The invention further discloses CP~P tledLIllellL a~aldlus conl~ .ing a patient mask, an air delivery tube conn.octe~l at one end to the mask, a flow generator conn~ctP-I to the otner end of the air delivery tube and collll)lisillg a motor coupled to drive a turbine at an operational rotational speed, an inlet to receive breathable gas, an outlet for the supply of said breathable gas to said air delivery tube at a pl'cS~.ule elevated above atmospheric ~Le;~ r~ and control means for controlling the breathable gas available to the turbine and thus the ~lcs~ule of breathable gas at said outlet.
In one plcfcllcd form the control means acts to restrict the flow gellclaLo imet. Alternatively, the control means acts to adjust the ~frccLivc area of the turbine open to the inlet.
The a~alalus can further comprise a path for patient exh~l~tion from said outlet by-passing the turbine. The exhalation path can vent to atmosphere or recirculate to said imet.
0 Advantageously, the CPAP ap~a,àLus can be for the ,~ L~dLion of bi-level CPAP ll~ nl.l-r~ and the control means is operable between two states ,c~,~ecLi~cly corresponding to a desired patient h~ilàl~lyll~aLlll~llL~leS~ul~, and the reduced desired patient e~i,dLol y treatment ~C~Ul~ .
Advantageously, the CPAP apparatus can be for the a~lminictration of a trP~tmPnt L~ .Ul-, adju~.~il,g in accordance with patient need, whe~cill the control means has a contim-~lly adjusting current set level col,~Jonding to the desired tre~.tmPnt ~les~,urc, and causes the outlet level to be controlled to m,.im,.in the ~)leS~.Ulc at the desired level.
The CPAP apparaLus can further comprise pressure sensor means for sensing ~re~ulc at said outlet or at a point in said air delivery tube or in said mask, said sensed pl~,s~iule provided to said control means, and said control means further operable to e~Jlllpare said sensed ~lc~ule with a curlent set pies~ c to m~int~in the trP~tm~t ~"es~u,e sl~bst~nti~lly co,~LanL at the desired level in accordance with the result of the cc,lllpal iSOll.
In another preferred form, the CPAP tre~rmPnt apparatus can be operable to m~int~in the Lle~ pressure at said mask substantially constant by continuous control of said control means.
WO 97/10868 PCT/AU~5./~ 6 The invention yet further ~ closes a method for control of the F~l~,SSurt: of breathable gas delivered by a flow ~ ene.dL~Jl in the ~r~ l dtion of CPAP L~G~
or ~si~ted lc~pildLion, said method CO~ iSi~g the steps of operating said flowg~llelalol at an operational rotational speed whereby said breathable gas enters the turbine by an inlet of the flow gellel~Lur and exits the turbine at a l,r~s~ule elevated above atmLospheric pressure, and controlling the breathable gas available to thLe turbine and thus the exit plcs~ule.
All the above allallgelllents limit the through-put of breathable gas thLrough thLe flow generator, colll~ar~d with prior art. arrange~ llLs which provide for ~ UlC10 control by spilling excess gas, thLereby resnltin~ in concomitant increase in acoustic emissions and motor power re~uh~lllellL~. Embo~i...f ~ of the invention as defined can provide a controllable flow generator or CPAP a~alalLIs that provides one or more of thLe advantages of lower power, lower acoustic noise, higher m~ximnm air flow and improved ~ S~We control in CCll~dliSOJLl with prior art alldn~elllellL~. In one or more embo~iimpnt~ thLe power supply for thLe flow generator can halve its rating, thus reducing cost, heat dissipation and occupied volume.
It will be understood that all references to "tre~tml-nt pleS~ul'e''inCIULde a continuous pLeS~UlC that can vary with time if desired in accoldallce with L
needs, and therefore is not n.ocess~rily of a constant level.
Rrief rlescriptio~ of the nrawir~
A llUlllbel of emboriimpnt~ of the invention now will be described with reference to the accolllpallyhlg drawings, in which:
Figs. 1 and 2 show exarnples of controllable flow gellel~t~ in the prior art;
Figs. 3-5 show a first embodiment of a controlled flow gene,d~ol in accordance with the present invention;
Figs. 6 and 7 show another embodiment of a controlled flow generator;
Figs. 8 and 9 show a yet further embodiment of a controlled flow gelleldt(JI, W O 97/10868 PCT/AU96,'~ 6 Figs. 10 and 11 show a yet further embodiment of a controlled flow generator;
Figs. 12a and 12b respectively show a cross-sectional and plan view of a further embodiment of a controlled flow generator;
Fig. 13 shows a variation to the controlled flow genela~ur shown in Figs. 12a and 12b;
Fig. 14 shows a yet further embodiment of a controlled flow ~ellel~Lol, Fig. 15 shows an embo-iimPn~ of a controlled flow gel~aLuI inrl~ an gell~e~t for ~ ti~n;
Fig. 16 shows an alternative arrangement for ~rtll~tion of the controlled flow o generator of Fig. 15;
Fig. 17 is a sch~m~tir block diagram of CPAP ~I~/paldLUS in~lllriing any one of the controllable flow generators of the preceding figures;
Figs. 18a and 18b show a cross-sectional view of a further embodiment of a controlled flow ~,e.l~.atol, Figs. 19a and l9b show a sc~ view of a yet further embodiment of a controlled flow g~ aLor, Figs. 20a-20d show examples of ~ e transition functions; and Fig. 21 shows a graph of ~.ei,~ule versus time for the flow ~ el~,~tul of Figs.
12a and 12b.
nescrirtion of Preferred F,mbo~lim~t~ ~n(1 Rtost Mode A llulllber of controllable flow generator arrangell~..ls will be described, and it is to be understood that each and every arrangement can readily be incorporated into the CPAP a~al~Lus m~mlf~ctllred by the present applicant, including the applicant's Sullivan ~ III, Sullivan ~ V, VPAP n' and Autoset su l~chintos.
While the embo-lim~-nt~ to be described refer to CPAP tre~trn~nt, it is to be understood the invention equally is applicable to apparatus for ~si~t~d respiration tre~tm.ont Where a~ u~liale, the same lcr~rel1ce numerals have been used to ;".li~ a component part in common with other embo~1i.,.~.~lx, or with the prior art.
The embodiment shown in Figs. 3 to 5 differs from the prior art all~ngelll~,llL
shown in Fig. 1, in that a control element 40 is located in the air inlet path of the inlet 20 proximate the turbine impeller blades 24, and is comprised of a shaft 42 ending in a baffle plate 44. The control elemPnt 40 is caused to move vertically within a defined range by any convenient actuator (not shown) to change the erf~ ive entry area of the turbine impeller blades 24 open to the inlet 20. Generally, this controls the air or breathable gas available to the turbine 18, and more generally the efficiency of the flow o g~ tor. The baffle plate 44 may have a small clearance b~Lweel1 its ends and the blades 24 (or blade housing) of the turbine 18. Equally, the baffle plate 44 could be in contact with the turbine 18 to rotate together with the turbine 18.
In operation of the flow g~J-~ldlol 10, the motor 16 causes the hlrbine 18 to rotate at a near con~t~nt operational speed concomitant with, or slightly higher than, the m~ximllm required Llc~ 3,es~u,c; to appear at the patient mask. In Pig. 4, the baffle plate 44 is located at its lower-most extent, thereby not l~ ;lhlg the flow of air from the inlet 20 to the turbine impeller blades 24. This l~pl~,selll~ the m~ximllm pressure at the outlet 22, typically 20-30 cm H20 for CPAP tre~tmP~t Fig. S shows the sit~ ti~n where the baffle plate 44 is arranged to be at its top-most extent of the range, whereby ~e air or breathable gas available to the ~urbine impeller blades is almost zero, in that the effective surface area of the blades 24 open to the inlet 20 is pr~rtir~lly zero. Again, Ihe motor 16 is driving the turbine 18 at the same operational rotational speed, in which case a near zero positive ~ S:~Ult; (or at least a very low positive p-~:s~u,c) occurs at the outlet 22. In practice, this a~ gellle would lc~ sell~ a positive plei,~ul~ at the outlet 22 of approximately 0-2 cm H20. A
seal also may be provided at the top of the fan to ensure complete baffling by cooperation of the seal with the baffle plate 44 to avoid leaks around the edge of the baffle plate.
W 0 97/10868 PCT/AU~S~'~OS~'Ç
-10- .
Thus by control of the control element 40, the flow gen~dLul's efficiency can be controlled, and different flow generator outlet (and therefore mask) ~'e~ P~II
S5uleS can be obtained. As will be a~pare~lL, two l)res~.ules can be a~l~u~!liaL~ly selectP~l for implc"l~.lLdLion of bi-level CPAP by control of the baffle element 40. The higher i,~.l,i,ato. y pressure corresponds with a lower position for the control clf -... l.
40, while the lower expiratory ~eS'.~ corresponds with a higher position of the control elern~nt 40.
The ~ctl~ti~ n devices coupled ~o the control element 40 have co~ on with bl~d~ g detection circuitry that detects transitions between patient ilL~ Lion and o expiration, so that control over the movement of the baffle element 40 can be in ~yllcl~ ism with the patient's respi,dlion phases. The present applicant's VPAP
apparatus has such bleaLl~illg ~letPctiQn Ci~;uiLl y.
Importantly, and as noted in Fig. 5, on patient expiration, a low h,~eda"ce e7~h~l~tion path 46 is provided, otnerwise the benefit of a reduced L~ ...ure during expiration may be nPg~tP-l by the patient being required to do excessive work during expiration. The expiration path 46 occurs between the outlet 22 and the inlet 20 by means of t'ne open space around the sides and top of the turbine 18, cledlillg a ready path to atmosL~hele. Without the expiration patn a back l,re..~.u,~ would be formed on patient expiration that would restrict the lowest L~e~l."~"l p,e~..u,e achievable, that being particularly il"polL~l~ to expiration ll~dL,~ L pressure in bi-level CPAP where an expiration ilc~l.llr-l~l ples.~ure of 4 cm H20 is not uncommon. Ideally, the back 7~7Ul~ on expiration should be limited ~o 2 cm H2O through the provision of the e~h~l~tion path 46. A low impedance exh~l~tion path is ~ f~.led not only for bi-level CPAP tre~tmPnt, but also for single level CPAP where, although the ~,es~.u,~ remains col~.L~llL, tnere should not be undue impedance to opposed flow due to patient expiration.
Figs. 6 and 7 show another embodiment of a controllable flow generator 48, in which the supply of air or breat~hable gas to the inlet 20 is controllably restricted (and W O 97/10868 PCT/A~ 86 thus the flow gel~.aLc~r efficiency reduced) by a choke 50 formed by a shaft 52 ending in a choke plate 54. Therefore, by the proxirnity of the plate 54 to the entrance to the air inlet 20~ the air or breathable gas available to the turbine 18 can be controlled. As shown in Fig. 6, the choke plate is remote from the opening to the air inlet 20, hence s there is no ,c~Lli-;Lion of the flow of air or breathable gas into the inlet and to the turbine 18. This represents the situation of the m~ximllm ll~,aLIl~ell~ pl~S~iult: for a given operational rotational speed of the turbine 18. The situation shown in Fig. 7, where the choke plate 54 is seated against the mouth of the air inlet 20 to restrict any flow of air or breathable gas to the inlet, ~ cse~ the lowest possible ~
pressure for the turbine 18 operating a~ or near the same operational rotational speed.
Clearly, ~ pressures intermediate of the limits represented by the arran~llle shown in Figs. 6 and 7 are achieved by vertical lllo~ llL of the choke shaft 52 to provide the nrcess~ry restriction of the ~llL,~lce to the air inlet 20.
During the ~ dlion of bi-level CPAP L~f ~ -l the exhalation ~
15 ~n,;~Ul~ will be low, in which case the choke plate 54 will be almost seatedL on the mouth of the air inlet 20, which creates a high illlpedallce path for patient expiration.
For this reason, a bleed vent 56 is located in a tube 58 e~/rn~ lg from the fan ch~...h~
12 to the outlet 22. The bleed vent 56 provides a low impedance exhalation path for the patient. As will be al,parellL, the bleed vent 56 also l~lesc.lL~ a leak that will have a minor effect upon the pl~Ul~ of air or breathable gas at the outlet 22 for thetreatment ~l~S~ul~ elienced during single level CPAP or during inspiration in bi-level CPAP treatmPnt. The small plc~s~llle drop inflllrer1 by the bleed vent 56 can easily be compensated by a~propliate adjustment of the choke 50. The ~rt l~tin~ circuitcontrolling the choke S0 may be operab]e under feedba~k control from a sensor sensing 2s pressure at the mask of at the outlet 22, in which case the plC;~iUlt~ drop due to bleed vent 56 will autom~tir~lly be compenc~t~d. The bleed vent 56 should not incur a ~lcs~ule drop in excess of 2 cm H2O otherwise ll~ill;llllllll expiration tre~tmPnt pl~s~ule might be colllplolnised.
CA 02232546 l998-03-l8 W O 97/l0868 PCT/AU96/005~6 Figs. 8 and 9 show a controllable flow genc.ator 48' having an ~ltP~n~tP
arrangement for the bleed vent 56 of Figs. 6 and 7, in that in certain in.ct~nrPc it may not be desirable to have the bleed vent 56 open in any ch.~ -res other than during patient expiration (e.g. bi-level CPAP Lle~ ). As shown, the bleed vent 56 is replaced by a branch 60 from the tube S8, and is in co.. ~ r-~tion wi~ the air outlet 22. The branch 60 is controllably opened and closed by a valve 62 formed by a valve shaft 64 and valve plate 66. The case of Fig. 8 relates to the provision of h~~ Lul~y treatment plcsaule in bi-level CPAP lle~ l, in which case the valve plate 66 closes-off the branch 60 so there is no leak from the outlet 22, and thus the full illS~i 10 output pressure from the flow generator 10 is delivered to the air delivery tube (not shown) and so to the mask (also not shown). The case of Fig. 9 relates to the provision of e~L~hatc)ly trP~tmPnt ~re~ule, whereby the choke plate 54 closes-off the mouth of the air inlet 22, and the branch 60, by ~rtl~ti- n of the valve 62, is opened to the atmosphere to provide an exh~l~tion path. Actuation of the choke 50 and the valve 62 can be s~llcl~ul~ed, and it is preferable that there be a gr~ ting opening of the mouth of the branch 60 in operation of the valve 62, rather than a sudden o~e~ g, to linearise the relationship between ples~uie and valve displ~rPTnPnt The arrangelment of the branch 60 and the valve 62 must be such as to ensure that the ~lei,~ule drop does not exceed the Illill;llllll~ expiration Ll~ S:WI't:, typically 4 cm H20, and most 20 preferably does not exceed 2 cm H2O.
The alla,l~wlle-ll shown in Figs. 10 and 11 show a controllable flow generator 48" that is a variation of the embodiment of Figs. 8 and 9, in that there is a recirculation conduit 68 co~ scl ;"g the branch 60 with the air inlet 20' . Thus air or breathable gas is recirculated during patient expiration, which avoids the necessity to 25 vent to atmosphere, and thus removes a possible noise source. In Fig. 10, the valve plate 66 closes off the exit to the branch 60 during the provision of inspiration treatment pr~:s~ure, with tne valve 62 gradually being raised upwards at the transition to W O 97/10868 PCT/AU~C;~C~6 patient expiration to open the branch 60 to the recirculation conduit 68, as shown in Fig. 11, thus providing the recirculation path during patient expiration.
Figs. 12a and 12b show a yet further embodiment of a controllable flow generator 48 " ' that is similar to the embodiments of Figs. 8 and 9. In place of the choke 50 and valve 62 is a sliding ples~.ulc control plate 70. The ~leS~.ulc control plate 70 has a circular a~c.Lulc 7~ which in colljullclion with the ell~ lce to the air inlet 20 forms a choke valve 74. The a~el~ulc egually could be profiled in a non-regular shape.
The plate 70 also has a profiled slot 76 which in culliull~;lion with the exit to the branch 60 forms an imre-1~nre control valve 78.
The control plate 40 is slidingly operated by an a-;LuaLul (not shown) having connection with the b~cdLllillg ~t~ction and tre~tm~nt l.rcs~.ulc control ~;h.;uiLly. As the plate 70 moves to the left to further restrict the mouth of the inlet 20, the errc~ /e surface area at the exit of the branch 60 open through the slot 76 is c~ dtcly increased, thus providing a lower hll~edallce exhalation path. The converse situation applies when the plate 70 is moved to the right, in that when the circular ~cllul~ 72 is located wholly over the mouth of the inlet 20 colr~s~o~ g to h~.~..dLion llc~
~lC~7~7UlC, the exit of the branch 70 is wholly blocked-off by the control plate 70, as the slot 76 will have past the left-most extent of the exit to the branch 60. The tapered alldngcllltllL for the slot 76 is one of many possible arran~emcllL~ and, in this case, provides a near linear relation between eYh~l~tion impe-i~nre and treatment ~lCS~ùlc.
Fig. 13 shows an alternate arrangement to that of Figs. 12a and 12b wherein the ~lcs~ule control plate 70" is no longer sliding, but rather rotatable, otherwise the principle of operation remains the same.
Fig. 14 shows a yet further embodiment of a controllable flow generator 80 that is somewhat similar to the arrangement shown in Figs. 6 and 7. In this ~ arrangement, the air available to the turbine 18 is controlled by a buLLclny choke valve 81 that acts to restrict the air inlet 22 to the flow of air or breathable gas. Operation of this flow generator is otherwise as described in relation to Figs. 6 and 7. Although not W O 97/10868 PCT/AU~6/'0~58 shown, as with Figs. 6 and 7, a bleed vent can be provided dowl~Ll~,alll of the turbine 18 to provide a low impedance exhalation path.
The actuators that can be used in relation to all of the valve al.,..lg~
previously described can include linear or rotary arrangements of solenoids, brushless motors/a~;luatol~, stepper motors/a~;lua~ols or switched relncf~nre motors/a~:LuaLol~.
One example of an actuator is shown in Fig. 15, which relates generally to the controllable flow gene~alor shown in Fi~gs. 3-5. The baffle plate 44 is not in contact with the turbine blades 24 (or blade housing) hence is non-foldlillg, and is aligned by means of a locating pin 82. The shaft 42' is pivotably connPctp~l with an acLivdLhlg link 84, in turn pivotably mounted from a post 86 st~n~lin~ from the fan chamber 12. The activating link 84 is "L"-shaped, with the downwardly-directed leg having connection with an armature 90 and a helical spring 92. The armature 90 is under the control of a solenoid 94 that has connection at least with the 'ol~Lllillg detection circuit. The spring 92 provides a return force when the solenoid is unpowered. Thus in response to the detection of transitions between i~ aLion and expiration, the solenoid 94 causes the ~rm~tllre 90 to move, in turn moving the activating link 94 and so the baffle plate 44 to control the desired LlcàLlllentpl~ ul~ between patient hl~ ion and e~haLion.
The solenoid 94 also can be connPct~-l to the ~ SSUle control Cil~;uiLly to provide fine control over the desired treatment pressure, particularly and in the regulation of that ~ UiC.
In another form, the solenoid 95 can be connPcte~l only to the bledLllillg detection circuit, and for bi-level CPAP trp~tmpnt~ the hls~ildLillg and e~hdtoly tre~tmPnt l les~ul~s can be mPch~ni~lly selected by means of respective end stops 88,90. For such an alldngelllenL it is not nPce~s~ry to retain the p~s~ule control Cil~;uiLly~ which can lead to a cheaper product to put into the marketplace.
Fig. 16 shows an all~.lla~iv~ arrangement for an actuator for the controllable flow generator shown in Fig. 15. In this case, the baffle plate 44 can be in contact with the turbine blades 24 (or blade housing) so that the shaft 42" may rotate with the CA 02232546 l998-03-l8 W O 97/10868 PCT/AU~G,'~ 5 turbine 18. The upper end of the shaft 42" carries a pL,~llldll~llt or electro-m~gnet 88 that is ~u~ou~ded by a further pe- IIIAIl~lll magnet 90 forrning a m~gn-otic link. In this way, the i"~Lallce of the shaft 42" rotating in concert with the fan 18 can be accommodated, and actuation of the baffle plate 44" is by the vertical movc~llCllL of the shaft 92 conn~-c~d with the outer pe~ or electro-magnet assembly 90.
Fig. 17 shows a l~lcsenL~Li~/e block diagraïn of control of CPAP ~aldLus incorporating controllable flow gellc dlor in accordance with any one of the prece~li~
emboriim~ntc. The turbine 18 is driven at an operational rotational speed by the motor 16 under the control of a motor controller 100 with the rotational speed being held 10 essentially constant at a "set speed" the regulation being provided by a cu",~a~ison bcL~el- the "set speed" signal and a feedb~cl~ signal 102 by a co~.~pdr~tol 104. It is of course possible for the "set speed" signal to vary although Ire~ .S~ulc control is not effected by motor speed control. In that case the "set p~e;,~u~c" signal is independent of the "set speed" signal, and is co~ d with the output of a plCS~ulc tr~n~d~lcer 106 that measures p,es~u,c at the flow generator outlet 22 (via t~be 112) by a cc""~lator 108. The sensed plcS~ull., can alLellldLi~cly be the Ll~aL~lle~L p~s~u,e at the mask. The error signal between the set plts~ulc and the measured plcs~ùlc at the outlet 22 causes the actuator 110 to adjust the position of the control element/choke 40 50. The "set ~ ulc" signal can be constant for single level CPAP or can vary in the instance of bi-level CPAP or autosetting CPAP ~ n~
The output signal from the pressure colll~dldLor 108 will reflect l~ ilalion rate and depth and so also can be used as a signal to trigger transitions between patient h~s~ildlion and expiration. This may lead to a simplification or even rerl-~n~l~n~y of existing bledLllillg detection Cil~;uiLly. It also provides a measure of flow minute volume and like ~ ldlllCtCl~i.
- Figs. 18a 18b l9a and l9b show tWO arrangements in which the efficiency of a flow gellclator is controlled by way of the p~ ..,AIir impedance of the outlet of the flow generator available to the exiting breathable gas. The imre~lAn~e of the flow W O 97/10868 PCT/AU~6~0~586 eld~r is effected in the sense that a change in cross-sectional area or volu~tLlic capacity of the outlet will effect the ability to pressurise a mass of air at a given flow rate and given ~)lCS~iUlC, as will be a~pal~llL to one skilled in the art.
The flow generator 148 shown in Figs. 18a and 18b includes a llulllber of elements common with the embo-limrn~ previously described. A passageway 158 exits from the chamber 12 and comm--nir~tes the exiting gas with a plenum 160 via an entrance lS9. The plenum has an exiting port 162, by which ples~uli~ed bre~th~hle gas can be supplied via a conduit to a patient mask for the ~ dLion of CPAP
Llc~LI~ellL or assisted lci.L~ildlion. The plenum 160 has a further vent 164 in 10 co""".l,~ir~tion with atmosphere. Both the vent 164 and the entrance lS9 to the plenum 160 can be controllably occ~ rci to reduce their open area by a sliding i~ .e~l~nre control plate 166. The control plate 166 inr~ e~ an apeltu.e 168 that, dc~elldillg upon its position, can restrict the respective p~ gP~ in a range from wholly open to fully closed.
In Fig. 18a, the control plate 166 is in a position such that the aperture 168 occludes the control vent 164 yet allows cu,....~ .ir~lion of exiting breathable gas from the passageway 158 to the plenum 160 and so to the exiting port 162. The direction of flow of breathable gas is shown by the line bearing an allowlRad. Fig. 18b shows the situation where the control plate 166 is in a position whereby the entrance 159 is closed, however the impedance control vent 164 is open. This condition accords with the provision of a low impedance path for patient expiration.
Clearly Figs. 18a and 18b show the extreme ranges of operation of the impe-l~nre control plate 166. The aperture 168 is sized so that the entrance 159 to the plenum 160 can be partially open, as can the control vent 164. In this m~nner, the impe~ nre of the outlet 122 is controllable, in turn, controlling the efficiency of the flow generator 148.
Figs. l9a and l9b show a further embodiment of an outlet section 122' as an alternative a~ enl~llL to the outlet sec~ion 122 shown in Figs. 18a and 18b. Again, W O 97/10868 PCT/AU3C'~ t comrnon elements have been in-iic~tecl by use of like reference numerals. The plenum 160' is of circular cross-section. In place of the previous sliding impedance control plate 166 is a rotatable control plate 170. In the position shown in Fig. 19a, the vent 164' is occluded by the control plate 170, ~ that the full flow of gas from the turbine passes from the passageway 158 through the plenum 160' to the exiting opening 162'. This situation represents the m~ximllm Ll.~ .ule.
The situation shown in Fig. 19b is where tne i"l~cdd"ce control plate 170 now fully occludes the entrance 159' to the plenum 160' reS~llting in the ~ il.--- .. output pl~,S~llle, again, providing a low impedance path on patient expiration.
For botn of tne embo-li"~ of Figs. 18a, 18b, 19a and 19b, the arrange",c.lL~.
for controlling the respective ~rnpedance control plates previously applied 166,170 equally apply.
In another embodiment not srecifir~lly shown in the dldwhlg~, the turbine can have adjustable pitch or sized impeller blades that are controllable to effect a change in the turbine, and hence flow g~n~ldLoL efficiency, and in this way have control over output pl~s...ll~. Such Lu~bh~es also rnay have louvre a,.,,..~r,..~ to spoil air flow and adjust efficiency.
In all the valve/choke arrange,l~R~L~ previously described a number of bi-level CPAP hl~pilaLion/expiration transitional sch~m~s can be adopted. A first case, as shown in Fig. 20a an impulsive change b~.w~ell Ll~ plcS~.Ille that is a fast rising plc;SSLlle output, having a rate of rise of approximately 0.5 - 1.0 cm H20 per msec. A
second case, as shown in Fig. 20b is a linear l~illg function, having a gradienttypically between 0.2 - 0.04 cm H2O per msec. The third case, as shown in Fig. 20c is a combination of the first two, as an impulsive step followed by a ramp. The step may be of the order l/2 (Pl - PE)- Finally, Fig. 20d shows a case where the rising ramp has an overpressure ( > Pl) at the commP~ of the hl~ Lol.y phase, and an impulsive change the transition tO the inspi,al()ry phase.
W O 97/10868 -18- PCT/AU96/005~6 Fig. 21 shows a chart of measured outlet ples~ulc versus time for bi-level operation of the embodiment described in Figs. 12 and 12b, for which tne h~ L~lly LledLIllellL p~eia:iUl~; iS about 16 cm H20 and the t~pildtOl~/ trÇ:ltmf~rlt pl~.S~Ule iS about 8 cm H20.
While the embodim~nt~ described have the turbine c~elaLillg at a constant rot~tion~l speed, it is equally possible to combine motor speed control with flow generator efficiency (e.g. control over the air or breathable gas available to the turbine) in the course of control over output pressure.
Claims (34)
1. A controllable flow generator for the supply of breathable gas in the administration of CPAP treatment or assisted respiration, the flow generator comprising: a motor coupled to drive a turbine, an inlet for breathable gas in communication with the turbine, an outlet for the supply of said breathable gas at a pressure elevated above atmospheric pressure, and means to control the efficiency of the flow generator and thus the pressure of breathable gas exiting the flow generator.
2. A controllable flow generator as claimed in claim 1, wherein said control means controls the efficiency of the turbine and thus the pressure of air or breathable gas exiting the flow generator by the outlet.
3. A controllable flow generator as claimed in claim 2, wherein the controlling means comprises adjustable pitch turbine impeller blades or turbine louvres.
4. A controllable flow generator as claimed in claim 1, wherein said control means controls the breathable gas available to the turbine.
5. A controllable flow generator as claimed in claim 1, wherein said control means controls the breathable gas available to the inlet.
6. A controllable flow generator as claimed in claim 1, wherein said control means controls the impedance of the outlet available to said exiting breathable gas.
7. A controllable flow generator as claimed in any one of the preceding claims, further comprising pressure sensor means for sensing the pressure of air or breathable gas exiting the flow generator by the outlet, said sensed pressure being provided to said control means, and said control means further operable to compare said sensed pressure with a set pressure to maintain said exiting pressure substantially the same as said set pressure by controlling the efficiency of the turbine in accordance with the result of said comparison.
8. A controllable flow generator for the supply of pressurised breathable gas in the administration of CPAP treatment assisted respiration, the flow generator comprising a motor coupled to drive a turbine, an inlet for breathable gas in communication with the turbine, an outlet for the supply of said breathable gas at a pressure elevated above atmospheric pressure, and control means for controlling the breathable gas available to the turbine and thus the pressure of breathable gas at the outlet.
9. A controllable flow generator as claimed in claim 8, wherein the control means acts to restrict the flow generator inlet.
10. A controllable flow generator as claimed in claim 9, wherein the restriction is over a range of inlet opening.
11. A controllable flow as claimed in claim 10, wherein the range is between the inlet fully open and partly or fully closed, which, for an operational rotational speed of said turbine, correspond respectively to the highest outlet pressure and the lowest outlet pressure of supplied air or breathable gas.
12. A controllable flow generator as claimed in any one of claims 8 to 11, wherein the control means comprises means for closing at least a portion of a mouth of said inlet.
13. A controllable flow generator as claimed in claim 12, wherein said control means is a sliding member having an aperture therethrough, the sliding member operable in a range of motion to align said aperture with said mouth and to mis-align said aperture with said mouth to close at least a portion of said mouth.
14. A controllable flow generator as claimed in claim 12, wherein said control means is a controllable baffle that moves in a direction orthogonal to said mouth to restrict said mouth.
15. A controllable flow generator as claimed in any one of claims 8 to 11, wherein said control means comprises a controllable vane for at least partly restricting said inlet.
16. A controllable flow generator as claimed in claim 8, wherein the control means acts to adjust the effective entry area of the turbine impeller open to the inlet.
17. A controllable flow generator as claimed in claim 16, wherein the adjustment is over a range of impeller effective surface area.
18. A controllable flow generator as claimed in claim 17, wherein the range is between the total effective entry area of the turbine impeller open to the inlet and partial or zero effective entry area of the turbine impeller open to the inlet, which, for an operational rotational speed of said turbine, correspond respectively to the highest outlet pressure and the lowest outlet pressure of supplied air or breathable gas.
19. A controllable flow generator as claimed in any one of claims 15 to 18, wherein the control means comprises a positionally adjustable baffle that can block-off at least a portion of the effective mouth area open to the inlet.
20. A controllable flow generator as claimed in any one of claims 8 to 19, wherein the control means acts to cause the repeating sequential supply of breathable gas at said outlet at a first higher pressure and a second lower pressure.
21. A controllable flow generator as claimed in any one of claims 8 to 20, further comprising pressure sensor means for sensing pressure at said outlet, said sensed pressure provided to said control means, and said control means further operable to compare said sensed pressure with a set pressure to maintain said outlet pressure substantially the same as said set pressure by control of the breathable gas available to the turbine in accordance with the result of said comparison.
22. CPAP treatment apparatus comprising: a patient mask, an air delivery tube connected at one end to the mask, a flow generator connected to the other end of the air delivery tube and comprising a motor coupled to drive a turbine at an operational rotational speed, an inlet to receive breathable gas, an outlet for the supply of said breathable gas to said air delivery tube at a pressure elevated above atmospheric pressure in accordance with a desired treatment pressure at the mask, and control means for controlling the breathable gas available to the turbine and thus the pressure of breathable gas at said outlet and in turn the treatment pressure.
23. CPAP treatment apparatus as claimed in claim 22, wherein said control means acts to restrict the flow generator inlet.
24. CPAP treatment apparatus as claimed in claim 22, wherein the control means acts to adjust the effective entry area of the turbine open to the inlet.
25. CPAP treatment apparatus as claimed in any one of claims 22 to 24, further comprising a path for patient exhalation from said outlet by-passing the turbine.
26. CPAP treatment apparatus as claimed in claim 25, wherein said exhalation path vents to atmosphere.
27. CPAP treatment apparatus as claimed in claim 25, wherein said exhalation path recirculates from said outlet to said inlet.
28. CPAP treatment apparatus as claimed in either one of claims 26 or 27, wherein said exhalation path is controllably restricted by valve means, and wherein said control means is operable to not restrict the exhalation path in opposition to a reduction of air or breathable gas to said inlet, and vice versa.
29. CPAP treatment apparatus as claimed in any one of the claims 22 to 28 for the administration of bi-level CPAP treatment, wherein the control means causes the apparatus to be operable between two states respectively corresponding to a desired patient inspiratory treatment pressure and the reduced desired patient expiratory treatment pressure.
30. CPAP treatment apparatus as claimed in any one of claims 20 to 26 for the administration of a treatment pressure adjusting in accordance with patient need, wherein the control means has a continually adjusting current set level corresponding to the desired treatment pressure, and causes the outlet level to be controlled to maintain the pressure at the desired level.
31. CPAP treatment apparatus as claimed in any one of claims 22 to 30, further comprising pressure sensor means for sensing pressure at said outlet or at a point in said air delivery tube or in said mask, said sensed pressure provided to said control means, and said control means further operable to compare said sensed pressure with a current set pressure to maintain the treatment pressure substantially constant at the desired level in accordance with the result of the comparison.
32. A method for control of the pressure of breathable gas delivered by a flow generator in the administration of CPAP treatment or assisted respiration, said method comprising the steps of operating a turbine of said flow generator at an operational rotational speed whereby said air or breathable gas enters the turbine and exits the turbine at a pressure elevated above atmospheric pressure, and controlling the efficiency of the flow generator and thus the exit pressure.
33. A method for control of the pressure of breathable gas delivered by a flow generator in the administration of CPAP treatment or assisted respiration, said method comprising the steps of operating a turbine of said flow generator at an operational rotational speed whereby said breathable gas enters the turbine by an inlet of the flow generator and exits the turbine at a pressure elevated above atmospheric pressure, and controlling the breathable gas available to the turbine and thus the exit pressure.
34. A controllable flow generator as claimed in claim 6. wherein said control means comprises a member controllable to vary the area open to exiting breathable gas passing to an exiting port and to vary the open area of a control vent in communication with said exiting port.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AUPN5498A AUPN549895A0 (en) | 1995-09-18 | 1995-09-18 | Apparatus and methods for the control of pressure in cpap treatment or assisted respiration |
| AUPN5498 | 1995-09-18 | ||
| AUPN7359 | 1995-12-28 | ||
| AUPN7359A AUPN735995A0 (en) | 1995-12-28 | 1995-12-28 | The control of pressure in CPAP treatment or assisted respiration |
| AUPN9761A AUPN976196A0 (en) | 1996-05-09 | 1996-05-09 | Pressure control in cpap treatment or assisted respiration |
| AUPN9761 | 1996-05-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2232546A1 true CA2232546A1 (en) | 1997-03-27 |
Family
ID=27157886
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2232546 Abandoned CA2232546A1 (en) | 1995-09-18 | 1996-09-18 | Pressure control in cpap treatment or assisted respiration |
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| US (2) | US6182657B1 (en) |
| EP (1) | EP0862474A4 (en) |
| JP (1) | JP3845736B2 (en) |
| CA (1) | CA2232546A1 (en) |
| WO (1) | WO1997010868A1 (en) |
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-
1996
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- 1996-09-18 CA CA 2232546 patent/CA2232546A1/en not_active Abandoned
- 1996-09-18 US US08/894,305 patent/US6182657B1/en not_active Expired - Lifetime
- 1996-09-18 WO PCT/AU1996/000586 patent/WO1997010868A1/en not_active Application Discontinuation
- 1996-09-18 EP EP96929975A patent/EP0862474A4/en not_active Withdrawn
-
2000
- 2000-08-22 US US09/642,824 patent/US6526974B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US6526974B1 (en) | 2003-03-04 |
| JPH11514259A (en) | 1999-12-07 |
| WO1997010868A1 (en) | 1997-03-27 |
| EP0862474A4 (en) | 2000-05-03 |
| EP0862474A1 (en) | 1998-09-09 |
| JP3845736B2 (en) | 2006-11-15 |
| US6182657B1 (en) | 2001-02-06 |
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|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |