GB2372704A

GB2372704A - A device for determining respiratory flow rate

Info

Publication number: GB2372704A
Application number: GB0100308A
Authority: GB
Inventors: David William Spencer; Jonathan Robert Nicholas Bell
Original assignee: Clement Clarke International Ltd
Current assignee: Clement Clarke International Ltd
Priority date: 2001-01-05
Filing date: 2001-01-05
Publication date: 2002-09-04
Anticipated expiration: 2021-01-05
Also published as: GB2372704B; GB0100308D0

Abstract

A device (e.g. spirometers) for determining respiratory flow rate comprises two means 4, and 5 of generating an audible signal upon excitation by air flow through the device, a combination of the signals or absence of one or more of the signals indicate that air flow is respectively below, within or above an optimal range of rates of such flow. A first audible signal means may be activated at and above a first flow rate and a second audible signal means is activated at and above a second flow rate, higher than the first. The audible signal means may be provided by whistles or reeds 4 and 5, wherein the respective signals generated are different from each other by being at different pitch. A self-contained disposable tube 1 may be provided wit the signal generators 4 and 5, being mounted inside, and the tube 1 may be made from cardboard. Air flow resistence means may be incorporated so as to simulate the air flow resistence of a given meter or inhaler. An inhalation (figs 5 and 6) or exhalation meter or inhaler incorporating the device may be provided, the device may be mounted within a mouthpiece.

Description

RESPIRATORY FLOW RATE DETERMINATION

This invention relates to respiratory flow rate determination and has the object of providing an audible signal to indicate that such a flow rate is within desired limits.

Sound signals have been used before in connection with respiration, in the medical or pharmaceutical context. For example, De Bono in the British Medical Journal 1965, 2, pages 1040-1041 and in the Lancet, November 30,1963, pages 1146-1147 discloses that a tube fitted with a whistle and a variable leak hole could be used to establish a patient's exhalatory flow rate. The patient blew through the device with the size of the leak hole being progressively increased until the whistle signal no longer operated. The condition of the leak hole at that stage provided a measure of flow rate.

Audible signals have also been used in connection with inhaled medication. For example a Turbohaler" Training Whistle activates a sound signal above a certain inhalation flow rate if the patient is breathing too fast for medication inhalation to be optimally effective.

The present invention is in contrast not concerned with metering flow rates directly. Rather, it is concerned to establish that an inhalatory or exhalatory flow meter or a medication inhaler will be or is being used within a prescribed range of flow rates, representing an optimal range for the accurate operation of that flow meter or inhaler.

The device incorporated in the invention can be used as a "stand alone" trainer so as to accustom a patient to inhale or exhale at an optimal rate when subsequently using a flow meter or inhaler, or can be incorporated into a flow meter or inhaler itself,

perhaps detachably so, to indicate to the patient or to the medical attendant that the flow rate meter or inhaler is being used optimally.

According to the invention we provide a device for the passage of respiratory air and which has two means of generating an audible signal upon excitation by air flow through the device, a combination of the signals from the respective devices or absence of one or more thereof indicating that air flow is respectively below, within, or above an optimal range of rates of such flow. In an embodiment, for example, a first such means is activated at and above a first flow rate and the second such means is activated at and above a second flow rate higher than the first. The patient is instructed to inhale or exhale at such a rate that only one signal is heard, this representing a flow rate within a predetermined desirable range of such rates.

The means for generating the audible signals may be whistles and/or reeds and the respective signals generated will be different from each other as for example being at different pitch or being different in character due to one for example being generated by a whistle and the other by a reed.

In one embodiment the device is a self-contained simple tube as for example a disposable tube of cardboard with the signal generators being mounted in it in such a way as to be activated by air flow in the tube. The tube can be used as a training device for patients who are to use inhalation or exhalation meters or inhalers, or could be an "add-on" to a conventional inhalation or exhalation meter or inhaler, or such a meter or inhaler may be modified by the incorporation of the audible signal generators in an air flow passage thereof as for example in its mouthpiece, as an integral part thereof or as a removable insert.

In the stand-alone device air flow resistance means may also be incorporated so as to simulate the air flow resistance of the meter or inhaler intended for use by that particular patient, and the signal generating means may be selected to respectively operate at flow rates of ranges optimal for respectively intended meters or inhalers.

Particular embodiments of the invention are described with reference to the accompanying drawings wherein: Figure 1 is an end view and Figure 2 is a diametrical section through a first embodiment of stand-alone device; Figure 3 is an end view and Figure 4 is a diametrical section through a second embodiment of stand-alone device; Figure 5 is a sketch diametrical section through an inhalation meter with a device attached; and Figure 6 shows an inhalation meter with an integral device.

All of the embodiments discussed here relate to inhalers, but it is clear that with appropriate kinematic inversion the invention is applicable to exhalation meters also.

Looking first at Figure 1, a device intended for use in training a patient is a tube 1 with a barrier end wall 2 having a restricted orifice 3.

Two reeds 4 and 5, such as mouth-organ reeds, are mounted in an aperture in the tube wall in a housing 7 so as to be subjected to air flow through that tube in the direction of the arrow 6 as a result of pressure reduction behind the restricted orifice 3. The reeds 4 and 5 being of different mass and/or different length emit different tones when activated by the air flow, but they are activated at different air flow rates. In the present embodiment reed 4 will start to vibrate at

a lower air flow rate than will reed 5. By selecting the mass and/or length of the reeds minima and maxima of ranges appropriate to various respiratory flow rate meters may be signalled. The patient learns that if a first tone is sounding a first and lower end optimal rate has been achieved while if the second starts sounding the upper end of that optimal range is being exceeded. Likewise, the resistance exerted to air flow passage through the tube can be set to simulate that of known meters which the patient will be using.

A second embodiment of trainer is seen in Figures 3 and 4 where tube 10 has a partial wall 11 across its cross-section providing a restricted gap 12 to generate resistance to air flow in the direction of the arrow 6.

Reeds 4 and 5 are mounted to be activated by that air flow as before but this time being mounted transversely to the direction of flow of the air in the wall 11.

In use the patient puts the end of the tube which is to the right in Figure 2 and the left in Figure 4 to his lips and inhales in such a way as to generate the desired tone. In simulating an exhalation meter he would place his lips to the right-hand end of the tube in Figure 2 or left in Figure 4 and exhale.

In variants, one end of the tube could be blocked with air passage being permitted only through the aperture in the cylindrical wall of the tube and this air passage could serve as the resistance-generating means: the signal generators could be mounted freely within the tube, with no aperture in the cylindrical wall and resistance being provided, if desired, by a partial cross wall or end wall as in the above embodiments.

It is clear that the devices as shown in Figures 1-4 but modified by the removal of any substantial resistance to air may be used as an add-on mouthpiece 20 to an inspiratory flow meter diagrammatically

indicated at 21 in Figure 5 with air entering the meter conventionally at its far end as indicated by arrows 22.

Alternatively as indicated in Figure 6 the reeds 4,5 may be incorporated either integrally or as a removable insert within the mouthpiece end of a meter 23.

Claims

CLAIMS :

1. A device for the passage of respiratory air and which has two means of generating an audible signal upon excitation by air flow through the device, a combination of the signals from the respective devices or absence of one or more thereof indicating that air flow is respectively below, within, or above an optimal range of rates of such flow.

2. A device according to claim 1 wherein a first audible signal means is activated at and above a first flow rate and the second audible signal means is activated at and above a second flow rate higher than the first.

3. A device according to claim 1 or claim 2 wherein the audible signal means are whistles and/or reeds.

4. A device according to any one of the preceding claims wherein the respective signals generated are different from each other by being at different pitch.

5. A device according to any one of the preceding claims wherein the respective signals are different in character due to one being generated by a whistle and another by a reed.

6. A device according to any one of the preceding claims which is a self-contained disposable tube of cardboard with the signal generators being mounted in it

in such a way as to be activated by air flow in the tube.

7. A device according to any one of the preceding claims wherein air flow resistance means are also incorporated so as to simulate the air flow resistance of a given meter or inhaler.

8. A device for the passage of respiratory air substantially as herein described with reference to and as illustrated in the accompanying drawings.

9. An inhalation or exhalation meter or inhaler incorporating a device according to any one of the preceding claims in an air flow passage thereof as an integral part thereof or as a removable insert.

10. A meter or inhaler according to claim 9 wherein the device is in the mouthpiece thereof.