WO2020008380A1

WO2020008380A1 - Method for carrying out oxymetric tests and medical apparatus with an improved oxymetric device with a reflective sensor

Info

Publication number: WO2020008380A1
Application number: PCT/IB2019/055666
Authority: WO
Inventors: Paolo Boschetti Sacco
Original assignee: Mir Srl - Medical International Research
Priority date: 2018-07-05
Filing date: 2019-07-03
Publication date: 2020-01-09
Also published as: IT201800006942A1

Abstract

A portable medical apparatus (2) comprises an oxymetric device (1) with a reflective sensor (5) which can detect the percentage of oxygen in the blood of a user and his heart rate by means of the positioning of a finger on the sensor (5), said oxymetric sensor (5) being associated with a body (2A) of the medical apparatus (2), the latter being provided with detection means (24) which can detect the force exerted by the user at the reflective sensor (5), said body (2A) of the medical apparatus being provided with indicator means (36, 37, 38, 39) which can indicate whether this force can make it possible to carry out an oxymetric measurement without incorrect results. The method for carrying out oxymetric tests with said apparatus is also claimed.

Description

METHOD FOR CARRYING OUT OXYMETRIC TESTS AND MEDICAL

APPARATUS WITH AN IMPROVED OXYMETRIC DEVICE WITH A REFLECTIVE SENSOR

The subject of the present invention is a method for carrying out oxymetric tests and a portable medical apparatus comprising an oxymetric device with a reflective sensor according to the preamble of the corresponding independent claims.

As is known, an oxymetric device, or more simply an oxymeter, is a medical instrument which determines the percentage of oxygen in the blood and the heart rate of a user. In particular, it measures the "oxygen saturation" (Sp0₂) which indicates the percentage of haemoglobin associated with the oxygen present in the arterial blood. For example, when all the haemoglobin molecules are associated with oxygen, it means that the Sp0₂ is equal to 100% .

Typically, in order to calculate the oxygen saturation, the oxymeter uses the emission of two different sources of signal, respectively with frequencies in the field of the red and infrared, applied at the site at which the measurement is being carried out: for example a finger, the wrist, the earlobe, or other parts of the body which are supplied with blood.

A detector can measure the absorption of each of the two signals by the haemoglobin: in fact, in practice, a part of the signals emitted is absorbed by the haemoglobin present at the site where the measurement is being carried out, whereas another, non—absorbed part, reaches the detector .

The quantity of red and infrared signals absorbed is proportional to the concentration of haemoglobin, such that, when the quantity of signals emitted is known, by measuring the quantity of signals which reach the detector, the oxymeter calculates the value of SpCq .

However, it is also known that, in the presence of a force exerted at the site where the measurement is being carried out (for example a finger), the relative compression on the veins and on the arteries can affect the flow of blood, and ultimately can alter the measurement of the oxymetric parameters, thus generating possible incorrect results in this measurement.

The risk of alteration of this type is reduced in the case of oxymeters of the "transmission" type using two emitters for the red and infrared signals, facing towards the receiver, and disposed inside a specific sensor, which in general is constituted by a rigid cap, or is made of flexible rubber similar to a thimble, or is constituted by a spring gripper to be applied to the finger, to the earlobe, etc. By regulating the compression exerted by the rigid cap or by the spring gripper, it is possible to prevent the alteration of the vascularisation of the blood. This possible alteration is further controlled by using caps or spring grippers of a size suitable for the dimensions of the finger (or the earlobe) on which the SpCy is to be measured.

However, this involves having available caps or spring grippers with different dimensions (small, medium and large, to be used respectively on young children, adolescents and adults), with a consequent increase in the number of devices which can be used.

It is also known to use oxymeters which operate with "reflective" photometric technology; in this case, it is possible to carry out oxymetric measurements simply by touching the sensor, without any other particular manoeuvre, and without a specific sensor applied. However in this case also, the problem is known of the possible compression of the veins and arteries, which problem requires a different solution compared with what happens with the transmission oxymeters. In fact, the simple gesture of putting a finger on a reflective sensor placed on a face of the oxymeter, or also of grasping the oxymeter with the hand, resting the thumb on the reflective sensor, does not guarantee the level of compression necessary for correct measurement of the percentage of oxygen in the blood and of the heart rate of a user. In fact, this level of compression could be excessive or insufficient, to the extent that the touch sensor is not able to measure the data required correctly.

In particular, the force with which the finger is pressed on the surface at the effective area of the sensor itself varies from one person to another, and is not necessarily repetitive between one measurement and another of the same person.

In addition, it is considered that, in order to operate correctly, the reflective photometric touch sensors require good "reflection" of the signals generated respectively by the two, red and infrared emitters, such that the signals can be acquired adequately by the detection system placed in the vicinity of the two emitters. Thus, if, during the measurement of the oxygen in the blood and of the heart rate, compression on the veins and the arteries takes place, this can affect the flow of blood, and, in the case of reflective photometric touch sensors, it can alter the "reflection" of the red and infrared signals, which is precisely the principle on which the operation of sensors of this type is based. Therefore, in the final analysis, this compression can compromise the measurement of the oxymetric parameters, or of the datum required.

This poses a problem of reliability of the measurement of the values of SpCt and heart rate, especially in cases of self-measurement , when an inexpert patient, not being observed by medical staff, cannot autonomously correct the possible incorrect results in the measurements, derived for example from alteration of the vascularisation because of excessive compression of the blood vessels.

In addition, taking into consideration the fact that a user needs to carry out brief measurements (of 30 seconds for example) several times during the day, if there is no direct control system, the probability increases of measurements which are unreliable, or have a low level of repeatability .

US2018/0177413 relates to an apparatus for measurement of arterial pressure of the contact type, which is distinguished from the known devices for measurement of the pressure having a sleeve to be placed around an arm of a patient/user .

This apparatus comprises a touch sensor which can generate a contact signal of a measurement area when the user puts his own finger on this area; the apparatus also comprises a plethismogram (PPG) sensor or plethismograph and a force centre. All of these sensors are associated with a single body on which there can be positioned the finger of a patient who is carrying out the measurement of his own pressure by means of the set of data generated by said sensors and received by a controller. The controller can be a device with the capacity to evaluate data received, such as a microprocessor, and calculates the pressure of the user on the basis of the signal of the touch sensor and of the force sensor, as well as on the basis of the change of PPG signal according to the contact pressure calculated.

The apparatus according to the US text also comprises a display and a communication unit. The display can display the contact pressure, in order to guide the user in applying a contact pressure in a predetermined manner on the touch sensor. This display also displays the variation of the contact pressure, as well as other, additional information such as alarms or warnings, according to the information on the pressure to be supplied to the user.

It should be noted that the controller can analyse the change of the PPG signal according to the contact pressure detected, and thus estimate the blood pressure of the patient/user .

Finally, the communication unit comprises a transmitter and receiver, and can access a communication network under the control of the controller. This can take place by means of BLE technology. When the pressure is detected, by means of this communication unit the controller can supply the information by means of an external device such as a smartphone .

Thus, the apparatus according to US 2018/0177413 is an apparatus specifically produced to measure the blood pressure of a patient/user using a PPG signal, which is optionally corrected on the basis of the detection of a signal of pressure exerted by this patient/user on a contact area of the apparatus. However, the PPG signal is not displayed and shown to the user, and nor is this possibility indicated in the prior art. This is not the subject of patenting of the US invention. Nor is anything said in the US text concerning the form of the area on which the patient/user places his finger in order to carry out the pressure measurement, and all that is described is the position of the touch sensor in the apparatus, its form of implementation (by means of a capacitive sensor), and its use.

US 2009/086452 on the other hand describes a pulse oxymeter with a pressure sensor. The new solution concerns a sensor with a case on which a user can place a finger to carry out an oxymetry test, said case being of the portable type which fits in the palm of a hand.

This case comprises a sensor to carry out the oxymetric measurement, optionally a keypad, and a display which can allow a user to read the parameters measured by the pulse oxymeter. There is also a pressure sensor which has a threshold value beyond which the oxymetric measurement is not possible. All of these components are connected by means of a printed circuit.

The document in question discloses that, if, during the oxymetric measurement, a pressure which is excessive or greater than a threshold value is exerted on the pulse oxymeter, which can give rise to an error in the measurement, the pulse oxymeter indicates by means of the display that excessive pressure is being applied, or it asks the user to apply less pressure. If the user does not reduce the pressure, the measurement can be stopped. Thus, the oxymeter can be configured to carry out measurements only when a suitable pressure is applied to it.

The sensitivity of the pressure sensor can be regulated .

The objective of the present invention is to provide a method and a portable medical apparatus provided with an oxymetric device with a reflective oxymetric sensor, which is improved in comparison with the solutions known in the prior art .

In particular, an objective of the invention is to provide a medical apparatus which permits safe use by any user, whether this is an adult or a child, carrying out an oxymetric test.

Another objective is to provide a medical apparatus wherein the user who is carrying out the oxymetric test is substantially guided in positioning and maintaining his own finger above the oxymetric sensor.

Another objective of the invention is to provide such a medical apparatus of the aforementioned type which has the possibility of obtaining correct oxymetric measurements, which are not affected by the force exerted by a user on the oxymetric sensor, which force can give rise to possible incorrect results (i.e. incorrect data) in the measurement of the oxymetric parameters (i.e. the percentage of oxygen in the blood and heart rate), caused by the alteration of the vascularisation of the site (for example a finger) on which the measurement is being carried out.

Another objective is to provide a method for carrying out oxymetric tests with a medical apparatus of the aforementioned type with an oxymetric device, having a reflective oxymetric sensor which is simple to produce and has a limited cost.

Another objective is to provide a medical apparatus of the aforementioned type which incorporates inseparably an oxymetric device and a spirometric device, and which makes it possible to carry out alternatively or jointly a spirometric analysis and an oxymetric analysis, the latter not being subject to incorrect results or errors caused by incorrect positioning of the finger of the user on the reflective oxymetric sensor, or by excessive force applied by the user on said sensor.

These objectives and others which will become apparent to persons skilled in the art are achieved by a method for carrying out oxymetric tests and by a medical apparatus according to the appended claims.

For better understanding of the present invention, by way of non-limiting example, the following drawings are appended, in which:

figure 1 shows a view in longitudinal cross-section of a medical apparatus with an oxymetric device according to the invention;

figure 2 shows a view similar to that in figure 1, but during the use of the oxymetric device according to the invention;

figure 3 shows a view in perspective of the device in figure 1 during use; and

figure 4 shows an enlarged view of the detail indicated as A in figure 3.

Said figures show a medical apparatus provided with a body 2A with which there is associated an oxymetric device with a reflective oxymetric sensor. This device, indicated generally as 1, is associated with the medical apparatus 2, which makes it possible, by means of a spirometric device which in itself is known, also to check the state of health of a user or patient affected by a respiratory disease.

The apparatus 2 of a portable type is provided with a flow measurer 3, which can make it possible to carry out a spirometric measurement (spirometric device), and also comprises a reflective photometric oxymetric touch sensor 5 which can make it possible to carry out an oxymetric measurement of the saturation of oxygen in the blood and of the heart rate. The data obtained from both these spirometric and oxymetric measurements, which can be carried out alternately with one another as well as jointly, are then used to define the state of health of the patient, and to determine any exacerbation of the disease. This measurer 3 and oxymetric sensor 5 are associated inseparably with the body 2A, such as to be able to be always available to the user, without separable and replaceable parts, as described for example in EP2603132.

The flow measurer 3 comprises a known system for detection of the respiratory flow 6, and a corresponding element 7 which is sensitive to the respiratory flow (in practice a turbine element which rotates around its own axis A when supplied with a flow of air emitted by the user) . This element 7 is associated with the body 2A of the medical apparatus 2.

The element which is sensitive to the respiratory flow 7 can be associated with a removable tubular body 9 (figure 3) which can act as a nozzle for the patient.

The oxymetric device 1 on the other hand is defined by a known reflective photometric oxymetric touch sensor 5. This sensor is accommodated at an appropriate recessed seat 10 provided in a face 11 of the body 2A of the medical apparatus 2; this seat has an elongate, substantially elliptical form, and has a wall 12 which connects an inner or bottom part 13 of this seat (where it faces the sensor 5) to the wall or face 11 of said body 2A.

Advantageously, the morphology of the seat 10 is such as to adapt to the anatomy of a finger of a patient and to permit the use of the device 1 by any type of patient, whether this is an adult or a child.

Thanks to the form of the seat 10, the user o patient is guided in placing his own finger correctly within the seat 10, until the wall 13 is reached and thus the sensor 5.

By positioning a finger in this way at the upper part of the touch sensor 5 (which defines the effective area thereof for the oxymetric measurement), the patient can obtain the detection of signals associated with the oxymetry. As stated, this detection can or need not be simultaneous with the spirometric test carried out by means of the unit 3, thus reducing the test times.

The reflective sensor 5 requires a simple touch in order to measure the SpCt (the main parameter for the oxymetry) , and can also make possible the detection of the heartbeat. It is therefore possible to carry out oxymetry measurements simply by touching the sensor, without any other particular manoeuvre.

Inside the body 2A there is a printed circuit 20 (bearing the sensor 5) which circuit is provided with a control unit 21 which can receive the oxymetric and spirometric data detected, and can be connected to a portable device (such as a smartphone or tablet), or to an Internet network present in the environment in which the medical apparatus 2 is located, by means of known remote connection means such as a BLE (Bluetooth Low Energy) chip. In this last case, the connection takes place by means of a network node, a gateway, a smartphone, a smartwatch, a tablet, or a desktop computer as a point of access to the network .

The unit 21 comprises a built-in microcontroller which controls simultaneously all the components of the oxymetric device 1 and the spirometric device, and, by means of the sensor 5 and the element 7, receives the oxymetry and spirometry parameters of a patient.

In the vicinity of the reflective sensor 5 (for example below it), inside the body 2A, there are present force detection means 24 which can detect the effects of the force exerted by the finger of the user at the sensor 5.

It should be noted that the terms "at the sensor 5" indicate that the effect of the force (i.e. the datum or value of this force) is detected after the positioning of the finger of the user directly on the sensor 5 (i.e. on the upper part which defines the effective area thereof), or on the part 13 of the seat in which this sensor is placed. In both cases, generally, the area of support of the finger of the user will be considered to define the effective area of the sensor 5, and will be considered as such in the present document.

The force detection means comprise a transducer, which converts the effects of the force exerted by the user into an electrical signal which reaches the control unit 21.

During the measurement, the patient rests his finger in the seat 10 at the reflective sensor 5 (figure 2), guided in this positioning by the form of this seat. The force exerted is transferred to the transducer 24 below, such that the electrical signal generated by the latter is transferred to the control unit 21 incorporated in the oxymeter .

This unit thus detects both the datum measured by the oxymetric sensor 5, and that relating to the effects of the force exerted by the user on the free surface of the sensor

5, i.e. on the base part 13 where this sensor is present (which, it will be remembered, defines the effective area of the sensor) . Before determining the oxymetric datum or parameter ( SpCy and the heart rate), the control unit 21 determines whether the force exerted at the sensor (i.e. for example on the part 13 of the seat 10) is within a predefined interval (for example from 1 to 2 Newtons equivalent to 0.1 - 0.2 kg of force) . This interval is determined taking into consideration the fact that, experimentally, it has been found that for values lower than those preselected, the sensor 5 is not able to provide an oxymetric datum, and for greater values, this datum detected is an incorrect result because of the alteration of the vascularisation of the site (finger) on which the measurement is being carried out.

If the value of the effect of the force detected is within the preselected interval, the control unit 21 detects the oxymetric datum.

As shown in figures 3 and 4, the device operates interactively in combination with an app of the control unit 21 which can be loaded onto a smartphone, a smartwatch, a tablet, a computer or the like, which receives the data relating to the oxymetry of the patient from the control unit 21, and matches these data to those supplied by the (integrated) transducer 24 disposed in the vicinity of the reflective photometric touch sensor 5.

The datum obtained can be displayed for example by means of a screen 30 shown in figure 4. The screen represented in this figure includes, as well as the value of the oxymetric parameters (data 31 and 32) an appropriate area 33 which shows the level of force exerted on the effective area of the touch sensor, measured by means of the appropriate transducer and the relevant interval of acceptability. In the manner of a dynamometer, the interval can easily be represented graphically (i.e. in an analogue mode) by a graduated indicator 36, which, in accordance with the expected values of the force exerted, covers the minimum-maximum scale of values.

For example, by means of the coloured elements 37, 38 and 39, information of the type "press harder" or "press less hard" or "good, continue like this" is given. This serves the purpose of guaranteeing the reliability of the measurement, avoiding the problems compression of the veins and arteries, and thus eliminating the cause of possible incorrect results in the measurement of the oxymetric parameters . Each patient will be able to verify the correct use of the oxymeter 1 in a simple, integrated and interactive manner, and, by means of the immediate display provided by the aforementioned app, when necessary he will be able to correct the force exerted such that it returns to within the interval of acceptability.

The device does not require any adaptation to the physical characteristics of the patient, and can be used equally well by young children, adolescents and adults, which makes it suitable for use even in the absence of medical staff, and it is therefore ideal in cases of self measurement and autonomous control of health.

In addition to the graphic display illustrated in the diagram in figure 4, or another equivalent, the value of the effect of the force exerted measured by the appropriate transducer can also be displayed directly in numerical or digital form on a corresponding scale, for example with a value expressed in N (Newtons) or in kgf (kilograms of force), or in kgw (kilograms of weight) .

A possible variant (not shown in the drawings) which persons skilled in the art can easily implement in order to replace the sensor for measurement of the intensity of the force exerted by the user on the effective area of the reflective sensor, consists of measurement of the intensity of the effect derived from the force itself. Since the main effects of said force include the variation of pressure and dimensional deformation, these physical values can easily be measured respectively with a pressure transducer and with a strain gauge, or with equivalent transducers.

Claims

1. Method for carrying out an oxymetric test by means of the use of a medical apparatus with an oxymetric device provided with a reflective oxymetric sensor (5) connected to a control unit (21) which receives the oxymetry data or parameters of a user or patient, said device (1) having an effective area of measurement of said reflective oxymetric sensor (5), said method comprising:

a) positioning of a part of the body of the user, usually a finger, on said effective area of measurement of said reflective oxymetric sensor (5);

b) activation of said sensor (5);

c) generation by said reflective oxymetric sensor (5) of electrical signals corresponding to the oxymetric parameters detected, and transmission of these electrical signals to a control unit (21),

characterised in that it comprises:

d) measurement of a datum or value derived from the effect of a force exerted by the user on the effective area of measurement of said sensor (5) during the measurement of the oxymetric parameters;

e) comparison of the force data measured with an interval of predefined reference values;

f) determination by the control unit (21) of the oxymetric parameters detected by said sensor (5) only if the force datum measured is within the interval of predefined reference values.

2. Method according to claim 1, characterised in that said effective area of measurement where the force exerted by the user is detected is alternatively a free surface of the reflective oxymetric sensor or a part (13) of the reflective oxymetric device (5) and wherein the user positions his finger for the measurement of the oxymetric parameters .

3. Method according to claim 1, characterised in that the datum of force exerted on the effective area of measurement of said reflective oxymetric sensor (5) is indicated to the user.

4. Method according to claim 3, characterised in that the indication of the datum of force exerted is alternatively provided on the oxymetric device or on a remote device.

5. Method according to claim 4, characterised in that the remote device is a smartphone, a smartwatch, a tablet or a personal computer.

6. Method according to claim 4, characterised in that the remote device displays on a screen (30) the oxymetric parameters detected, and the effect of the force exerted by the user on the effective area of measurement of the reflective oxymetric sensor, said force being indicated in analogue and/or digital mode.

7. Portable medical apparatus comprising an oxymetric device with a reflective oxymetric sensor (5) which can detect oxymetric data or parameters of a user, said device (1) having an effective area of measurement of said sensor (5), the reflective oxymetric sensor (5) being associated with a body (2A) of said medical apparatus, and cooperating with a control unit (21) which can receive electrical signals from said sensor (5) after the user has positioned a part of his body, usually a finger, above the effective area of measurement of the reflective oxymetric sensor, said electrical signals being generated according to the oxymetric data or parameters detected, said apparatus (1) being characterised in that it comprises means for detection (24) which are placed at the effective area of measurement of the reflective oxymetric sensor (5) and are connected to said control unit (21), said means for detection (24) being able to detect the value of the effect of the force exerted on this effective area of measurement of said reflective oxymetric sensor (5), such as to provide said control unit (21) with a corresponding force datum, said control unit (21) comparing this force datum with a predetermined interval of parameters, and determining the oxymetric data or parameters if this force datum is within this interval.

8. Medical apparatus according to claim 7, characterised in that it comprises display means (30) which are alternatively remote or associated with said oxymetric device (1), and can display the oxymetric data or parameters and the force datum detected.

9. Medical apparatus according to claim 8, characterised in that said remote display means (30) are a screen of a smartphone, a smartwatch, a tablet or a personal computer.

10. Medical apparatus according to claim 7, characterised in that the means for detection of the force datum are a load cell or a pressure transducer or a strain gauge or an equivalent transducer placed in the body (2A) of the oxymetric device (1) .

11. Medical apparatus according to claim 1, characterised in that it comprises a flow measurer (3) which is associated with the body (4) of this medical apparatus (2), and can make it possible to carry out spirometric measurements, the data obtained from this flow measurer and from an element (7) sensitive to the respiratory flow associated with said body (2A) and the data obtained from the reflective oxymetric sensor (5) indicating the state of health of the user.

12. Medical apparatus according to claim 7 characterised in that said body (2A) has a recessed seat (10) on one of its faces (11) inside which the reflective sensor (5) is present, and below which, in said body (2A) there are present the aforementioned detection means (24), this recessed seat (10) having an elongate form such as to adapt to the anatomy of the finger of any patient, and guide its positioning on the effective area of measurement of said sensor (5) .

13. Medical apparatus according to claim 7, characterised in that said seat (10) has an elongate form, and has a wall (12) which connects an inner or base part (13) of said seat (10) to the face (11) of the body (2A) of said medical apparatus (1), the effective area of measurement of said sensor (5) and the detection means (24) being placed at this base part (3) .