WO1997030632A1

WO1997030632A1 - Peak-flow monitor

Info

Publication number: WO1997030632A1
Application number: PCT/GB1997/000488
Authority: WO
Inventors: Philipp Friedrich Wilhelm Wagner; Anthony Edward Bunn
Original assignee: Farmarc Nederland B.V.; Dyer, Alison, Margaret
Priority date: 1996-02-26
Filing date: 1997-02-20
Publication date: 1997-08-28
Also published as: AU1885797A

Abstract

A peak-flow monitor (10.1) comprises a body or tube (12) having an expiratory air inlet (18) and defining a flow path (14) for the expiratory air. A whistle (16) of the beating reed type is arranged in the flow path (14). The monitor (10.1) includes an annular wall (20) in which are located a plurality of removable pieces (24). In use any one or more of the removable pieces (24) may be removed to form a leak opening of a predetermined and variable size, depending on the size and number of the removable pieces (24) removed, through which part of the expiratory air can blow to bypass the whistle (16). The peak-flow monitor (10.1) is particularly useful in the treatment of asthma.

Description

PEAK FLOW MONITOR

BACKGROUND OF THE INVENTION

This invention relates to a peak- flow monitor.

A peak-flow monitor is a device that is used in medical applications to deteπnine whether the peak expiratory air flow of a subject falls above or below a certain threshold, and is particularly useful in the treatment of asthma.

Asthma is a disease which is known to reduce peak expiratory air flow during a forced expiratory manoeuvre from total lung capacity to residual volume. The broncho-constriction caused by asthma can be well controlled and reversed using a variety of broncho-dilator inhalants. Efficacy of treatment can therefore be evaluated by measuring peak expiratory flow rates. The cost of conventional flow meters to measure peak expiratory flow, however, prohibits their extensive home use, particularly in developing countries.

UK Patent No 1 ,018,387 to De Bono discloses a device for testing lung function comprising a whistle having a mouthpiece and a leak opening arranged to allow a proportion of the air flow at the mouth to pass through the mouthpiece without passing through the whistle, and having provision for adjustment of the leak opening so that a measured total air flow-rate within the capacity of human lungs is required to cause the whistle to sound. The whistle has a tubular body with the leak opening in its tubular wall, the mouthpiece being an open tube having telescopic engagement with the tubular body so that it occludes the leak opening to an extent which can be adjusted by sliding movement of the mouthpiece relative to the body to vary the air- flow rate required to sound the whistle.

US Patent No 4,421,120 to Biotrine Corporation discloses a peak respiratory flow monitor which comprises an enclosure having a front end serving as an air input port, a series of openings through the wall of the enclosure, an input flow axis passing through the centre of the input port in the direction of air flow at the air input port, a sliding tube slidable over the enclosure for covering a desired number of the openings, and a whistle which generates a signal when the air flow there; jugh reaches a threshold, the whistle including a reed and means for causing displacement of air flow from the input flow axis prior to flowing along the reed.

US Patent No 5,357,975 to Isoraw S.A. discloses a device for measuring the flow-volume of pulmonary air which is comprised of a connection conduit comprising a mouthpiece at one end of its extremities, a sound generator as well as a digital time measuring unit. A tapping exhaust orifice allows to tap a portion of the expired air. The orifice has an opening which is adjustable by simply turning a cuff screwed on the outside of the conduit. When the patient expires in the apparatus, only a well defined fraction of the air flow is directed towards the sound generator, the remainder being eliminated in the atmosphere through the tapping exhaust. The air flow which remains is directed through the sound generator wherein a well defined note is produced.

South African Patent No 96/4173 to Harwill Industries (Proprietary) Limited discloses a flow monitoring device comprising a signal generator that is adapted to generate a signal in dependence on the achievement of a predetermined volume flow rate of fluid across the signal generator, the signal generator being located in a fluid flow passage extending between an inlet and a vent outlet formed in a body, the size of the vent outlet being variable to vary the fluid flow resistance characteristics of the passage and the variation of the vent outlet being settable at a predetermined variation of the vent outlet size. The signal generator is preferably a reed type whistle. The body is preferably comprised of two body shells that are interengagable to define the body, the outlet being formed in one body shell and the other body shell being provided with an occluder for the outlet, the shells being movable relatively to one another for the occluder to occlude the outlet to a greater or lesser extent, depending on d e relative positions of the shells thereby to vary the size of the vent outlet. The shells may be at least partially lockable to one another to set the vent outlet at a predetermined variation of the vent outlet size. In addition to these patents which disclose peak-flow monitors incorporating a whistle to provide an audible signal, there are a number of other mechanical devices for measuring the peak-flow rate of a single forced expiration. The devices disclosed in US Patents Nos 3862628, 3871364, 3822699, 5565630, 4768520 and 3848585, as well as in WO 96/20642 and EP 653187, all utilize the displacement of a piston under controlled circumstances as the method for indicating pulmonary function. Another mechanical device which does not utilize a whistle is disclosed in US Patent No 4638812.

Although all these peak-flow monitors are satisfactory to perform the function required, they are generally of relatively complex construction. There is thus a need for a peak-flow monitor with a simple construction.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a peak-flow monitor which comprises a body having an expiratory air inlet and defining a flow path for the expiratory air, a whistle arranged in the flow path, and one or more removable pieces in the body, wherein in use any one or more of the removable pieces may be removed to form a leak opening of a predetermined and variable size, depending on the size and/or number of the removable pieces removed, through which part of the expiratory air can flow to bypass the whistle.

The removable pieces are preferably integrally formed with the body.

The peak-flow monitor preferably includes a plurality of removable pieces and the pieces may be of one size or of at least two sizes. This allows for greater variation of the size of the leak opening which may be formed.

The body of the peak flow monitor may comprise a tube and a transverse wall extending across the tube, with the removable pieces being located in the transverse wall. In this case, the whistle may also be mounted in the transverse wall.

Preferably, the whistle is mounted centrally in the transverse wall and the removable pieces are arranged around the whistle.

In another embodiment, the body of the peak-flow monitor may comprise a tube with the removable pieces being located in a side wall of the tube.

In this case, the body may include a transverse wall extending across the tube with the whistle mounted in the transverse wall.

The whistle is preferably a beating reed whistle.

Each removable piece may be a breakaway piece that is defined by one or more slits or by one or more lines of weakness in the body. In this case, in use, the removable pieces may simply be broken out to form the leak opening.

Alternatively, each removable piece may be a hollow promberance which may be cut or broken off to form a leak opening.

In another alternative, the body of the peak-flow monitor may be formed with one or more apertures which apertures are closed by removable pieces which, in use, may be pushed out to form the leak opening.

It is to be noted that, in use, no removable pieces need be removed for the monitor to function.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a longimdinal sectional view of a first peak-flow momtor of the invention; Figure 2 is a detail of the distal end of the peak-flow monitor of Figure

1 ; Figure 3 is an end view of the peak-flow monitor of Figures 1 and 2, in the direction of arrow (III) in Figure 2; Figure 4 is a longimdinal sectional view of a second peak-flow momtor of the invention; Figure 5 is a longimdinal sectional view of a third peak-flow monitor of the invention; Figure 6 is a longimdinal sectional view of a fourth peak-flow monitor of the invention; Figure 7 is a detail of the distal end of the peak-flow monitor of Figure

6; Figure 8 is a longimdinal sectional view of a fifth peak-flow monitor of the invention; and Figure 9 is an end view of the peak-flow momtor of Figure 8 in the direction of arrow (IX) in Figure 8. DESCRD7TION OF EMBODIMENTS

Referring first to Figures 1 to 3, reference numeral 10.1 generally indicates a peak-flow monitor or whistle which comprises a tube 12 forming a flow path 14, there being a whistle 16 of the beating reed type in the flow path 14, towards the distal end of the tube 12. The end of the tube 12 is plain and forms a mouthpiece 18. The arrow indicates the direction of flow of expiratory air through the monitor 10.1 during use.

Between the whistle 16 and the tube 12 there is an annular wall 20 which, when intact, essentially closes that part of the flow path which is between the whistle 16 and the side wall of the tube 12. The annular wall 20 includes a pattern of narrow slits 22 which define a number of break-away or removable pieces 24. Each break-away piece 24 is connected to the tube 12 and to the whistle 16 by means of breakable bridges 26. In use any one or more of the break-away pieces 24 may be broken away from the remainder of the annular wall 20, leaving a leak opening 28 in the annular wall 20 through which expiratory air flowing through the tube 12 can leak to bypass the whistle 16. If all the break-away pieces 24 are removed, connecting pieces 30 in the annular wall 20 remain to keep the whistle 16 connected to the tube 12.

By selecting the number of break-away pieces 24 that are removed, the total flow rate of expiratory air through the tube 12 at which the whistle 16 commences to whistle can be adjusted. Thus, for example, in the case of a subject from whom a low flow rate is required for the whistle 16 to come into operation, all the break-away pieces 24 can be left in place. On the other hand, where a high flow rate is required for the whistle 16 to come into operation, all the break-away pieces 24 can be removed. A number of different flow rates between the low and high values can be selected by selecting the number of break-away pieces 24 that are removed. The number of break-away pieces 24 that are removed is related to the subject's nomogram peak-flow value. A nomogram is a table or formula which predicts a normal value for peak-flow for a subject based on the subject's details, such as sex, age and height. In this way the whistle 16 can be set to sound at a certain flow rate that is individually adjusted for a specific subject. If the subject is unable to sound the whistle 16 even after broncho- dilator therapy, then appropriate action should be taken as advised by the doctor or clinic in charge of the subject.

It is to be noted that the entire monitor 10.1 can be made as a one-piece injection moulding from a suitable plastics material. Examples of suitable plastics materials are ABS and polystyrene.

Figure 4 illustrates a peak-flow monitor whistle 10.2 whose construction is similar to that of the peak-flow momtor 10.1, the same reference numerals being used to indicate the same or similar pans. The construction of the momtor 10.2 differs from that of the monitor 10.1 in that the annular wall 20 is flat and in a plane that is normal to the longimdinal axis of the momtor 10.1 , whereas the annular wall 20 of the momtor 10.1 is of frusto¬ conical configuration.

Figure 5 illustrates a peak-flow momtor or whistle 10.3 whose construction is similar to that of the peak-flow monitor 10.2, the same reference numerals being used to indicate the same or similar parts. The construction of the monitor 10.3 differs from that of the momtor 10.2 in that the annular wall 20 is set back from the distal end of the tube 12. This can be advantageous in that it makes it more difficult for the subject accidentally or deliberately to close any of the leak openings 28 formed by removal of the break-away pieces 24.

Figures 6 and 7 illustrate a peak- flow monitor whistle 10.4 whose construction is similar to that of the peak-flow monitor 10.2, the same reference numerals being used to indicate the same or similar pans. The construction of the monitor 10.4 differs from that of the momtor 10.2 in that, instead of the break-away pieces 24 being in an annular end wall 20 between the whistle 16 and the mbe 12, the break-away pieces 24 are in a side wall of the mbe 12. Between adjacent break-away pieces 24, the mbe 12 is provided with radially extending fins 32 which make it difficult for the leak openings 28 formed by removal of the break-away pieces 24 accidentally or deliberately to be closed by a user.

Figures 8 and 9 illustrate a peak-flow momtor or whistle 10.5 whose construction is similar to that of the peak-flow whistle 10.2, the same reference numerals being used to indicate the same or similar parts. The construction of the momtor 10.5 differs from that of the monitor 10.2 in that, instead of the annular wall 20 being provided with break-away pieces 24, it is provided with a number of hollow, tubular protuberances or nipples 34 whose ends are closed. The plastics material from which the momtor 10.5 is made is relatively soft as compared with that from which the monitors 10.1 to 10.4 are made, which may be relatively brittle. In the momtor 10.5 one or more leak openings can be formed by snipping or cutting off one or more of the nipples 34. As illustrated in Figure 9, the various nipples 34 are of different diameter. This increases the selection of total leak opening cross-section that is available, due to the different permutations of larger and smaller nipples that may be removed. The peak-flow monitor of the invention has the advantage that it is a very simple design and thus is easy and economic to manufacmre, and is easy to use.

Claims

A peak-flow monitor comprises a body having an expiratory air inlet and defining a flow path for the expiratory air, a whistle arranged in the flow path, and one or more removable pieces in the body, wherein in use any one or more of the removable pieces may be removed to form a leak opening of a predetermined and variable size depending on the size and/or number of the removable pieces removed, through which part of the expiratory air can flow to bypass the whistle.

A peak-flow monitor according to claim 1 wherein the removable pieces are integrally formed with the body.

A peak-flow monitor according to claim 1 or claim 2 which includes a plurality of removable pieces.

A peak-flow monitor according to claim 3 wherein the removable pieces are of at least two sizes.

A peak-flow monitor according to any one of claims 1 to 4 wherein the body comprises a mbe and a transverse wall extending across the mbe with the removable pieces in the transverse wall.

A peak-flow monitor according to claim 5 wherein the whistle is mounted in the transverse wall.

A peak-flow monitor according to claim 6 wherein the whistle is mounted centrally in the transverse wall and the removable pieces are arranged around the whistle.

A peak-flow monitor according to any one of claims 1 to 4 wherein the body comprises a mbe with the removable pieces in a side wall of the mbe.

A peak-flow monitor according to claim 8 wherein the body includes a transverse wall extending across the mbe with the whistle mounted in the transverse wall.

A peak-flow monitor according to any one of claims 1 to 9 wherein the whistle is a beating reed whistle.

A peak-flow monitor according to any one of claims 1 to 10 wherein each removable piece is a breakaway piece that is defined by one or more slits or by one or more lines of weakness in the body.

A peak-flow monitor according to any one of claims 1 to 10 wherein each removable piece is a hollow promberance which may be cut or broken off to form a leak opening.