WO2004049940A1

WO2004049940A1 - Portable peak flow meter

Info

Publication number: WO2004049940A1
Application number: PCT/ES2002/000578
Authority: WO
Inventors: Antonio Bote Bote; Justo Crespo Tejero
Original assignee: Servicio De Instrumentacion Hospitalaria, S.L.
Priority date: 2001-10-22
Filing date: 2002-12-04
Publication date: 2004-06-17

Abstract

The invention relates to a portable peak flow meter. The invention consists of a sensor (2) which is positioned in the necking (5) of a suction pipe (1), said sensor comprising a Pitot tube (3) and a Venturi tube (4), and which can measure the peak expiratory flow (PEF) in accordance with international recommendations. The result of the measurements are displayed on an alphanumeric screen (8) together with instructions suitable for the user. The invention also comprises a memory element (7) in which the aforementioned results are stored, a microprocessor (6) which processes said results and data transmission means (9).

Description

PICO PORTABLE SPIROMETER

Object of the invention

The present invention relates to a portable peak or peak spirometer

Flow Meter, designed to measure the maximum expired flow, also known by its initials in English PEF (Peak espiratory Flow), based on the combination of a Pitot tube and a Venturi tube, whose pressure difference is collected and analyzed by a microprocessor that shows it on a display.

This invention has application in the field of medicine.

Background of the invention

Spirometry is the measurement of air flows during breathing. These measures are essential for the diagnosis and control of various diseases of the respiratory system, such as asthma, emphysema and COPD (Chronic Pulmonary Obstructive Disease). In a complete spirometry, various parameters are measured such as the total expired volume, the total volume in the first second, and others. One of the most important parameters measured in a spirometry is the aforementioned PEF, or maximum exhaled flow. It consists of the maximum speed at which the air is expelled from the lungs during a forced exhalation. It is usually measured in liters per second or liters per minute. This maximum value is usually reached a few tens of milliseconds after expiration (from 40ms to 200ms), and is maintained for a few milliseconds.

For example, the effects of different medicines used to treat patients with the aforementioned problems can be better analyzed by controlling the volume and the expired air flow regime at regular intervals, before and after the administration of a medication. In general, spirometers carry out their measurement by one of two types below. One of the types collects the exhaled volume of the subject in bellows or in another container, whose displacement corresponds to the volume of exhaled air. These devices are great by nature to allow you to pick up one _. Enough air volume, so you can't easily make laptops. A second type measures the air flow rate through a flow measurement device. The exhaled volume is derived by integrating the airflow regime over some period of time.

As can be deduced from the foregoing, mechanical equipment with propellers, springs, weights or other mobile mechanical elements is usually used to measure the PEF. These moving parts have to be very light to be able to move quickly and accurately measure the exact value, and at the same time robust to withstand the force of exhalation without deforming, which implies that they are of high manufacturing cost, and of delicate maintenance. On the other hand, the measurement results of these devices cannot be stored or transmitted unless it is manually. Finally, cleaning and disinfection is complicated, if not impossible, involving new adjustments and calibrations; One of these examples is shown in US-A-3797479, or that described in US-A-4598700.

Description of the invention

In order to avoid or alleviate all these problems, the portable spiometer, object of the present invention, is based on the measurement of the pressure difference between a Venturi tube (negative pressure or depression) and a Pitot tube ( positive pressure) placed in the center of a narrowing of the tube where the user exhales. This double arrangement generates a pressure difference greater than that of any of the elements separately.

It is known that the Pitot tube is an application of fluid dynamics used to measure velocities, obtaining a pressure at its outlet, called stagnation pressure, proportional to the square of the velocity and the density of the fluid. On the other hand, the Venturi tube is another application of fluid dynamics with which a depression is created when a fluid passes, also proportional to the square of the velocity and the density of the fluid. This pressure difference is injected into a differential pressure sensor., .- which generates a voltage!, Which feeds an analog / digital converter, and a microprocessor, which applies the correct corrections to ensure accuracy and linearity required. The value of the measure is presented on an alphanumeric screen, stored and transmitted by electronic procedures. This screen also presents messages to the user for easy handling.

Therefore, what is achieved with the present invention is a spirometer of reduced volume and cost, since the electronics it carries are very common. The possibility of this significant reduction in volume and cost implies, on the one hand, the mobility of these means and materials, that is, the user himself can have one in his usual place for a certain control, and on the other hand, it is more Easy application to a greater number of cases, being also easier to reach the end user.

Description of the drawings

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, a series of figures are attached as an integral part thereof, illustrative and not limiting, the following has been represented:

Figure 1.- Schematic sectional view of an application tube to the spirometer object of the present invention.

Figure 2.- Block diagram of the spirometer.

Preferred Embodiment of the Invention

As can be seen in the attached figures, the tube (1) is distinguished in the first place where the patient is exhaling; in its final part there is a narrowing (5) where a sensor head (2) has been placed with the two pressure taps: the one corresponding to the Pitot tube (3) in the direction of the flow, and that corresponding to the depression caused in the Venturi tube (4), in the sense.perpe.ndjcu.lar to the flow ..

Two ways of assembling the pieces have been considered:

* The sensor head (2) integral with the spirometer body, the tube (1) being removable. The tube is simple and cheap to make, it can be discarded at a low cost or be disinfected. The sensing head (2) can be cleaned externally without the risk of clogging the holes due to their small size and because they are sealed at its other end.

* The sensor head (2) is integral with the tube (1), where the holes communicate with the sensor through two holes provided with joints and membranes. With this arrangement all parts that may be contaminated by a patient can be completely discarded or disinfected.

In both cases, the tube (1) is fixed to the body of the spirometer thanks to a groove that carries on one side of the same diameter as the tube.

The measurements of the tube (1) and the sensor head (2) are adequate to obtain a sufficient pressure difference to comply with international recommendations on this type of equipment, and so that the pressure loss in the apparatus is as low as possible. Another of the innovations present in this device is the transmission of the measurements made and stored, through various electronic procedures. In this way, the doctor can receive the information quickly, and act accordingly.

Its application and operation is very simple, for this, once the tube (1) is attached to the spirometer, the patient in his exhalation generates a fluid flow at a certain speed and force. When this flow passes through the opening of the Pitot tube (3), a pressure is generated that is measured by it; at the same time this flow also causes strangulation (5), a speed increase and a depression in the Venturi tube (4), which also picks up. the measure of _. This _^ negative pressure.

Both measures taken, the positive pressure of Pitot and the negative pressure of Venturi, are captured by the differential pressure sensor (2), which through a transducer generates a voltage proportional to this pressure difference. The signal is converted from analog to digital in a converter and from here it passes to a microprocessor (6), which applies the appropriate corrections, according to a specific program and parameters, which guarantees the required accuracy and linearity.

These values are stored in a memory (7) and displayed by means of a display (8) or alphanumeric display to the user. So, thanks to a small keyboard (9), this stored data can be requested and displayed on the screen (8), being able to create historical, graphical, average, etc., depending on the program inserted in the microprocessor (6). Likewise, this data and applications can be exported by an RS-232 data transmission module (9).

In order to be easily transported by the user, the device is highly portable, thanks to the possibility of the materials and technology used, of a size and weight similar to that of a tobacco package, and powered by standard batteries ( 10), easily obtainable in commerce.

Once the nature of the present invention has been sufficiently described, as well as a way of putting it into practice, we only have to add that as a whole and its component parts it is possible to introduce changes in form, materials and arrangement, as long as these Alterations do not substantially vary the characteristics of the invention claimed below:

Claims

1- Portable peak spirometer, to measure the maximum expired flow, also known by its initials in English PEF Peak Flow Meter, characterized in that a combination of Venturi and Pitot tubes placed in the tube is used as the measuring principle ( 1) that is where the patient exhales; in its final part there is a narrowing (5) where a sensor head (2) has been placed with the two pressure taps: the one corresponding to the Pitot tube (3) in the direction of the flow, and the one corresponding to the depression caused in the Venturi tube (4), in the direction perpendicular to the flow; This pressure difference is measured by the electronic pressure sensor (2) and processed by a microprocessor (6) which has a data storage memory taken (7) and a transmission module of this RS-232 data, all the device powered by a battery (10), the two sensor tubes (3 and 4) being one behind the other in the direction of the exhaled air flow in the narrowing of the tube (1) since here the air velocity is increased, causing a small pressure drop.

2.- Portable peak spirometer, according to claim one, characterized in that it carries a transducer that generates a voltage, or electrical signal, proportional to the differences in the pressures measured by the respective tubes (3 and 4) and captured by the sensor. differential pressure (2).

3.- Portable peak spirometer, according to the preceding claim, characterized in that it is equipped with a digital analog converter that converts the electrical signal generated by the analog to digital transducer by passing to a microprocessor (6), which applies the appropriate corrections, of according to a specific program and parameters, which guarantees the precision and linearity required.

4.- Portable peak spirometer, according to the preceding claim, characterized in that it has a keyboard (9) for use by the user as well as an alphanumeric display or screen (8) where the data obtained from the measurement are displayed as those stored in the memory (7).

5. Espirómetro_ portable de_ peak according to claim _^ characterized in that the tube (1) is removable by simple pressure, while the sensor head (2) is integral with the body of the apparatus.

6. Portable peak spirometer according to claim one, characterized in that the tube (1) is integral with the sensor head (2), the assembly being removable by simple pressure from the body of the apparatus, where the pressures taken by the tubes (3, 4) they are communicated to the sensor (2) through holes provided with joints and membranes, which completely isolate the sensor from the tube through which the user makes the expiration.

7.- Portable peak spirometer according to previous claims, characterized in that the tube (1) is attached to the body of the apparatus in a groove thereof, of the same diameter of this tube (1).