FI84693C - KAENSELORGAN SOM LAEMPAR SIG FOER ANDNINGSKONTROLL. - Google Patents

Description

1 84693

A sensor suitable for breathing monitoring

The invention relates to a sensor 5 suitable for monitoring a patient's airways or respiratory tract. The invention also relates to the use of a material which has proven to be particularly useful in detecting a respiratory gas flow.

In general, methods of monitoring a patient's respiration 10 are based on chest movement or changes in lung volume during respiration. Pressure sensors attached to the skin detect chest movement. A piezoelectric membrane, which also detects chest movement, has been used to monitor breathing.

15 Impedance sensors, on the other hand, measure changes in tidal volume. However, measurements made with these principles are very artifact sensitive, as all muscle movements are reflected in the measurement results, making it difficult to interpret the results.

In addition, these methods must be considered unreliable because they monitor the patient's respiratory movements, which may continue even if airflow to the lungs is blocked, for example due to mucus accumulated in the airways. Only at the stage when the breathing movements have stopped and the patient's oxygen supply has been blocked for some time will these methods provide information about the serious situation. This problem must therefore be considered very significant.

In principle, there is a more reliable measurement method based on monitoring the air flow with a nose thermistor. The operation of the thermistor is based on a change in the value of 35 resistors as a result of a temperature change of 2,84693. The disadvantage of such a thermistor is its awkward structure. In addition, the problem of cheap thermistors is limited sensitivity. Moisture causes problems in the measurement. If the mucus 5 separating from the patient's airways gets on the terraistor for one reason or another, this will lead to a measurement error. Skin contact with the thermistor also results in a measurement error. The location of the thermistor in front of the airway is very critical. It must therefore be in exactly the right place for the respiratory signal to be detected. For this reason, installing a thermistor requires a lot of work.

The object of the present invention is to eliminate the above-mentioned problems. The object is to provide a sensor which is simple in construction and inexpensive.

It is a further object to provide a sensor which reliably obtains a breathing signal directly from the breathing air flow.

The characteristic features of the device according to the invention are set out in the claims.

The invention is based on the use of a pyroelectric phenomenon in the monitoring of a patient's breathing. As the patient breathes through the mouth or nose, the temperature change caused by the reciprocating breathing air flow can be detected as electrical polarization in the pyroelectric materials. The voltage signal caused by the polarization is applied to the monitoring instrument.

30

A material with pyroelectric properties is particularly advantageous for detecting airflow through the airways, for example compared to a thermistor. The pyroelectric material is not sensitive to moisture or skin contact unlike a thermistor.

3,84693

Liquid secretion from the airways that comes into contact with the electrically insulated pyroelectric material renders this material inactive only at the point of contact. Since the surface area of the 5 pyroelectric material is relatively large, this fact has no significant effect on the measurement itself. The effect of skin contact is the same as moisture, ie minor.

10 The surface area of a sensor made of pyroelectric material is made large, so that the placement of the sensor in front of the airways is not very precise, unlike in the case of a thermistor.

15 Pyroelectric properties have often been considered to be disadvantages of piezoelectric materials with mechanical-electrical and electromechanical properties. The mechanical-electrical properties of the piezoelectric membrane have been exploited in the observation of the thoracic respiratory ligaments 20. However, in addition to artifact sensitivity, a problem with the exploitation of mechanical-electrical properties has been that the patient's breathing movements may continue even if airflow to the lungs is obstructed.

25 Pyroelectric materials, thus often the same as piezoelectric materials, are known. Such a material is, for example, polyvinylidene fluoride. Ceramic materials are also known.

The invention will now be described in more detail with reference to the accompanying patent drawings, in which Fig. 1 shows a front view of a sensor according to the invention, Fig. 2 shows a sensor according to Fig. 1 in section 35 AA, Fig. 4 84693 Fig. 3 shows a sensor according to Fig. 1 in section BB, Fig. 4 shows Fig. 1 a sensor attached below the patient's nose when viewed 5 directly toward the patient's face.

Figure 1 shows a sensor 1 according to the invention seen from the front. A pair cable 2 leads from the sensor to a measuring instrument which is not shown in the figure. The sensor 10 is preferably shaped so that it extends from the front of both nostrils to the mouth. In this case, a respiratory signal is certainly obtained, even if one of the airways becomes blocked.

Fig. 2, which shows a cross-section of the sensor along the line A-A in Fig. 1, shows a body 3 made of a material having pyroelectric properties. This body is preferably in a film-like form. The surface of this piece has electrodes 4.

20 The electrodes can be, for example, a metal film, a carbon film or, for example, a conductive paint layer. The breathing air flow detecting surface of the element formed by the body 3 and the electrodes 4 is coated with an electrically insulating layer 5 which separates the 25 galvanically conductive surface films from the patient. This layer should preferably be as thin as possible so that the change in temperature caused by respiration is detected with sufficient clarity. For this reason, the thermal conductivity of the layer should preferably also be as good as possible. For example, the electrically insulating layer could be polyethylene.

On the surface of the film-like body 3 made of pyroelectric material, such as skin 35, a heat-insulating layer 84693 6 is required, otherwise heat is transferred from the patient's breathing air through the thin film-like body 3 directly to the skin or vice versa, substantially reducing measurement sensitivity. The heat insulating layer 5 is preferably foam. At the same time, the foam supports the structure of the sensor. The air layer is also a suitable thermal insulator.

The conductor ends 7 of the pair cable 2 are directly attached to the body 3 made of pyroelectric material 10 using, for example, a crimp connection or a conductive paint or glue.

Fig. 3, in turn, shows the sensor section along the line B-B in Fig. 1. In this preferred embodiment, the part facing the mouth of the sensor is formed simply by turning a film-like body 3 made of a material 3 having pyroelectric properties over the lower edge of the sensor below. The portion of the sensor in front of the nose is also slightly bent. In the latter case, of course, it is not necessary to extend the folded portion as far to the opposite side of the sensor as in front of the mouth.

In Figure 4, the sensor 1 is fastened under the patient's nose with tape 8. As can be seen from the figure, the same sensor can detect both nasal and oral respiration.

The invention is in no way limited to the embodiments described above, but various details of the invention may be modified within the scope of the claims.

It is self-evident that the shape of the sensor can be changed. The sensor could also consist of, for example, 6,84693 separate elements in front of one or more airways. The sensor could also be shaped so as to form a kind of covering mask, e.g. in front of the nostrils or both the nostrils and the mouth.

Claims (14)

A sensing means for controlling a patient's breathing through a respiratory pathway or paths, characterized in that the sensing means consists of one or more elements, which are constituted by a body (3) having a pyroelectric property and electrodes known per se (4). , and a heat-insulating layer (6) which is at least partially located between the patient's tissue and said element, and an element of electrically insulating layer (5). 2. Sensing means according to claim 1, characterized in that the element constituted by the body (3) and the electrodes (4) is further protected against the heat-insulating layer (6) by a separate electrically insulating layer (5). 3. Sensing means according to claim 1, characterized in that the heat-insulating layer (6) which protects the element comprising the body (3) and the electrodes (4) acts as a thermal and electrical insulation. 4. Sensing means according to any of the preceding claims, characterized in that the heat-insulating layer (6) is of foamed plastic. Sensor according to any of claims 1-3, characterized in that the heat-insulating layer (6) is air. 6. Sensing means according to any of the preceding claims, characterized in that the electrically insulating layer (5) is of polymer-based material. 7. Sensing means according to claim 6, characterized in that the electrically insulating polymer-based material is polyethylene. : 8. Sensor according to any of the preceding claims, characterized in that the body (3) with pyroelectric properties is of polyvinylidene fluoride. Sensing means according to any of the preceding claims, characterized in that the body (3) is tab-shaped. 10 84693 10. Sensing means according to claim 9, characterized in that the tab extends from the front of the nostrils in front of the mouth. 11. Use of materials with pyroelectric properties to detect gas flow through a patient's respiratory tract or respiratory tract. Use according to claim 11, characterized in that the material having pyroelectric properties is polymer-based. Use according to patent claim 12, characterized in that the polymer-based material is polyvinylidene fluoride. Use according to claim 11, characterized in that the pyroelectric material is ceramic material.