GB2356457A

GB2356457A - Device for measuring airflow in a nostril

Info

Publication number: GB2356457A
Application number: GB9922439A
Authority: GB
Inventors: Gary Rogers; Mark Shopland
Original assignee: MELDET Ltd
Current assignee: MELDET Ltd
Priority date: 1999-09-23
Filing date: 1999-09-23
Publication date: 2001-05-23
Also published as: GB9922439D0

Abstract

A device for measuring nasal flow which has a nozzle 1 for insertion into a nostril, the nozzle having a Venturi sensor 2 with ports 2A, 2A, communicating with the passages 3A, 3B emergent from the nozzle and through which air pressure measurements are made and signals are generated proportional to the pressures for supply to electric processing circuitry. The signals may be used to generate a display which may be graphical, or use an LCD, or be in the form of a spreadsheet.

Description

2356457 Device for Measuring Nasal Air Flow Rates This invention relates

to a device for measuring nasal air flow rates, especially but not exclusively when a patient sniffs or exhales forcibly through the nose.

According to the invention there is provided a device for measuring nasal air flow rates comprising a nozzle dimensioned for insertion into a nostril, a sensor for measuring air flow through the nozzle, and means emergent from the nozzle for transmitting measured air flow rates to an indicating or recording device.

The nozzle will preferably carry externally a stop for limiting insertion of the nozzle into the nostril.

The nozzle may also incorporate a bacterial filter.

A preferred sensor is a Venturi-shaped passage incorporated in the nozzle.

However, the rate of cooling of a heated wire or the speed of rotation of a small fan incorporated in the nozzle could be used for measurement purposes, either alternatively or additionally to sensing air flow by means of a Venturi.

Air flows are preferably sensed at positions of minimum air flow speed and of maximum air flow speed within the nozzle.

A preferred Venturi has two longitudinally spaced air exit ports through which pressures at the ports are extracted through small air tubes emergent from the nozzle. These pressures are thereby transmitted to transducers, such as strain gauges or piezo-resistive devices, converting the pressures into electrical signals. Preferably the signal difference is taken as a measure of the air flow rate in the Venturi.

It is especially useful to know the nasal air flow rate of a subject when sniffing, because there is an increasing interest in delivering drugs to patients via the nasal membranes, from which the drugs are absorbed directly into the blood stream.

The nasal air flow rate when a drug is sniffed into the nozzle is a factor important to drug take-up efficiency when the drug is administered by sniffing.

For optimum sensitivity, the flow rate sensor is designed for peak efficiency and accuracy at an air flow rate of 10 to 200 litres/minute. In contrast, in a conventional spirometer, the air flow sensor is designed for peak efficiency and accuracy at an air flow rate of the order of 600 to 700 litres/minute.

However, it is possible to design the nozzle to be double ended, with a mouthpiece opposite the end for nasal insertion, and with two air flow sensors of differing appropriate sensitivities incorporated, together with means for switching between them.

For measuring nasal air flow rates, the air flow at the sensor may be sampled of the order of 200 to 300 times in about 8 to 10 seconds, the readings being displayed graphically or on an LCD display or being plotted for display, on a spreadsheet for example.

Measurements to be derived from the readings are typically the length of sniff, the maximum nasal air flow, and the nasal air flow per second.

Readings can be taken during sniffing and forced exhalation through the nose, and also during normal breathing through the nose.

It is also possible to incorporate in the nozzle a spring loaded diaphragm coupled to an indicator element, whereby to measure the peak sniffing pressure developed within the nozzle.

The device in accordance with the invention is now further described with reference to the accompanying drawings, in which:- Figure 1 shows a nozzle; and Figure 2 is a block circuit diagram.

Referring first to Figure 1, a nozzle for insertion into a nostril comprises a tube 1 having an external stop IA for determining the extent of insertion, rounded end IB first. Internally, the tube I is formed with a Venturi section 2 having associated ports 2A, 2B. The ports 2A, 2B open into passages 3A, 3B which extend back through a thickened section of the wall of the tube 1 to the trailing end IC thereof. The ports 2A, 2B are longitudinally spaced apart between points of minimum air flow rate, i.e. minimum air pressure, and maximum air flow rate, i.e. maximum pressure, at the Venturi section 2. From the ends of the passages 3A, 3B, tubing 4A, 4B connects to processing equipment shown in Figure 2. A bacterial filter 1D may be incorporated in the nozzle.

When a subject sniffs in air through the nozzle, a pressure difference, typically rising to and then falling from a peak, is created between the ports 2A, 2B in the tube 1.

Referring to Figure 2, tubing 4A, 4B leads to an electronic pressure sensitive device 5 acting as a differential pressure transducer. The signal representing pressure difference from the device 5 is outputted to an analog to digital converter 7. From here serial digital data is routed to an embedded processor 8, which samples the data signal, say 256 times per 9 seconds, which exceeds the typical duration of a sniff. The sampled output from this processor is thereon relayed to a p.c. 9 for display purposes or to a data logger 10 for storage, either to be later reviewed by a p.c. 11 or outputted to a display such as an LCD display 12.

Data from the data logger can alternatively be interpreted by a processor 13 which will store clinical algorithms and graphic display programs by which the data can be interpreted and feedback given to the patient. These stored programs and algorithms can also be held on the p.c. 9.

Claims

1. A device for measuring nasal airflow rates comprising a nozzle dimensioned for insertion into a nostril, a sensor for measuring airflow through the nozzle, and means emergent from the nozzle for transmitting measured airflow rates to an indicating or recording device.

2. A device according to claim 1, wherein the nozzle carries externally a stop for limiting insertion of the nozzle into the nostril.

3. A device according to claim 1 or claim 2, wherein the nozzle incorporates a bacterial filter.

4. A device according to any of claims 1 to 3, wherein the sensor is a Venturi-shaped passage incorporated in the nozzle.

5. A device according to any of claims 1 to 4, wherein the rate of cooling of a heated wire or the speed of rotation of a small fan incorporated in the nozzle is used for measuring airflow.

6. A device according to any of claims 1 to 5, wherein airflows are sensed at positions of minimum airflow speed and of maximum airflow speed within the nozzle.

7. A device according to claim 4, wherein the Venturi passage has two longitudinally spaced air exit ports through which pressures at the ports are extracted through small air tubes emergent from the nozzle.

8. A device according to claim 7, wherein said pressures are transmitted to transducers, such as strain gauges or piezo-resistive devices, converting the pressures into electrical signals.

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9. A device according to claim 8, wherein the signal difference is taken as a measure of the airflow rate in the Venturi passage.

10. A device according to any of claims 1 to 9, when used to measure drug take-up efficiency when the drug is administered by sniffing.

11. A device according to any of claims 1 to 10, wherein the flow rate sensor is designed for peak efficiency and accuracy at an airflow rate of 10 to 200 litres/minute.

12. A device according to any of claims 1 to 11, wherein the nozzle is double ended, with a mouthpiece opposite the end for nasal insertion, and with two airflow sensors of differing appropriate sensitivities incorporated, together with means for switching between them.

13. A device according to any of claims I to 12, wherein for measuring nasal airflow rates, the airflow at the sensor is sampled at a rate of the order of 200 to 300 times in about 8 to 10 seconds and the readings being displayed or stored for presentation.

14. A device as claimed in claim 13 wherein the display or presentation is graphical or by way of an LCD or spreadsheet.

15. A device according to claims 13 or 14 wherein measurements derived ftom readings include the length of sniff, the maximum nasal airflow, and the nasal airflow per second.

16. A device according to claims 13, 14 or 15 wherein readings are taken during sniffing and forced exhalation through the nose, and also during normal breathing through the nose.

17. A device according to any of claims I to 16, wherein there is incorporated in the nozzle a spring-loaded diaphragm coupled to an indicator element, whereby to measure the peak sniffing pressure developed within the nozzle.

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18. A device for measuring nasal airflow substantially as herein described with reference to the accompanying drawings.