DEVICE AND METHOD FOR CHARACTERIZING PARTICLES OF EXHALED AIR

Abstract

A device for characterizing particles of exhaled air. The device comprises an inlet line directed towards an outer environment with a filter for filtering particles. The inlet line is fluidly connected to a breathing line which comprises an interface through which air is breathable. A measurement line is fluidly connected to the breathing line and is fluidly connected to a particle measurement device for determining a parameter corresponding to the particles of the exhaled air. An inventive method comprises the following steps: Directing ex- haled air to a particle measurement device and determining a parameter corresponding to the particles of exhaled air, the parameter being at least one of the following parameters: Particle number, particle concentration (density), particle diameter, particle mass, particle size distribution, particle mass distribution, particle mass concentration, particle number concentration.

Claims

1. A device for characterizing particles of exhaled air, the device comprising: an inlet line directed towards an external environment, the inlet line comprising a filter for filtering particles, the inlet line being fluidly connected to a breathing line that comprises an interface through which air is breathable; and a measurement line that is fluidly connected to the breathing line and that is fluidly connected to a particle measurement device to determine a parameter corresponding to the particles of the exhaled air.

2. The device according to claim 1, wherein the breathing line is arranged substantially parallel to the inlet line or arranged coaxially to the inlet line.

3. The device according to claim 1, wherein the interface is fluidly sealable to block air flow through the interface.

4. The device according to claim 1, wherein the particle measurement device comprises an air flow generator configured to create an air flow with a preset flow rate, and wherein a flow rate is in a range from 0.1 I/min to 101 I/min, from 0.1 I/min to 20 I/min, or in the range from 1 I/min to 10 I/min.

5. The device according to claim 1, wherein the measurement line and/or the particle measurement device comprise a heater configured to keep the temperature at a preset value.

6. The device according to claim 1, wherein the measurement line or an inner wall of the measurement line and/or the particle measurement device comprise at least one antistatic and/or electrically conductive component.

7. The device according to claim 1, wherein the measurement line and/or the particle measurement device comprise at least one check valve.

8. The device according to claim 1, wherein a diameter of the measurement line is smaller than a diameter of the inlet line and/or a diameter of the breathing line.

9. The device according to claim 1, wherein the particle measurement device determines at least one of the following parameters of the particles of the exhaled air: particle number, particle concentration, particle diameter, particle mass, particle size distribution, particle mass distribution, particle mass concentration, and/or particle number concentration.

10. The device according to claim 9, wherein the particle measurement device determines a particle concentration in a range from 0 to 10.sup.7 particles per liter air, in a range from 0.01 to 10.sup.7 particles per liter air, in a range from 0.01 to 5*10.sup.6 particles per liter air, or in a range from 0.01 to 10.sup.6 particles per liter air.

11. The device according to claim 9, wherein the particle measurement device determines particle diameters in a range from 0.1 .Math.m to 5 .Math.m, in a range from 0.1 .Math.m to 1 .Math.m, in a range from 0.2 .Math.m to 5 .Math.m, in a range from 0.3 .Math.m to 5 .Math.m, or in a range from 0.5 .Math.m to 5 .Math.m.

12. The device according to claim 1, wherein the particle measurement device is an optical particle measurement device which comprises at least one light source, wherein the light source is adapted to emit polychromatic light and/or light with at least one wavelength in a range from 380 nm to 490 nm.

13. The device according to claim 12, wherein the particle measurement device comprises an aerosol spectrometer, wherein particles of exhaled air are arranged inside a measuring cell of the aerosol spectrometer to illuminate the particles by a light beam, wherein scattering light of the particles is received by a sensor and scattering light signals of the particles are registered by intensity spectroscopically such that a size distribution of the scattering light signals is determined to represent a particle size distribution.

14. The device according to claim 13, wherein a direction of movement of the particles inside the measuring cell, a direction of the light beam inside the measuring cell and a direction of the scattering light are arranged substantially perpendicular to one another, respectively.

15. The device according to claim 1, wherein the particle measurement device comprises between 1 and 256 channels, between 4 and 256 channels, or at least 4 to 256 spectral channels which are adapted to detect light.

16. A method for characterizing particles of exhaled air, the method comprising: directing exhaled air to a device for characterizing particles of exhaled air; and determining a parameter corresponding to the particles of exhaled air, the parameter being at least one of the following parameters: particle number; particle concentration; particle diameter; particle mass; particle size distribution; particle mass distribution; particle mass concentration; and/or particle number concentration.

17. The method according to claim 16, wherein the method is executed by a device for characterizing particles of exhaled air, the device comprising: an inlet line directed towards an external environment, the inlet line comprising a filter for filtering particles, the inlet line being fluidly connected to a breathing line that comprises an interface through which air is breathable; and a measurement line that is fluidly connected to the breathing line and that is fluidly connected to a particle measurement device to determine a parameter corresponding to the particles of the exhaled air.

18. The method according to claim 16, wherein the exhaled air is directed towards the device at a preset flow rate which is in a range from 0.1 I/min to 101 I/min, in a range from 0.1 I/min to 20 I/min, or in a range from 1 to 10 I/min.

19. The method according to claim 16, wherein the parameter is determined for a preset time interval after which a decision parameter is determined.

20. The method according to claim 19, wherein the decision parameter is compared to a preset value and, depending on the outcome of the comparison, a signal is output.

21. The method according to claim 16, wherein a cleaning phase is executed before the determining of the parameter, wherein the cleaning phase comprises: determining the parameter corresponding to the particles of exhaled air for a preset time interval; determining a change parameter based on the parameter; and outputting a signal if the change parameter fulfills a preset comparison.

22. The method according to claim 16, wherein a sealing checking phase is executed before the determining of the parameter or before a cleaning phase, and wherein the sealing checking phase comprises: blocking the flow of exhaled air to the device; directing filtered air of the external environment to the device; determining the parameter for a preset time interval; determining a parameter based on the parameter; and outputting a signal if the parameter fulfills a preset condition.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0035] FIG. 1 is an example of the inventive device in a schematic view,

[0036] FIG. 2 is a detailed view of a particle measurement device of the example according to FIG. 1,

[0037] FIG. 3 is a flow chart of an example of the inventive method,

[0038] FIG. 4 is a flow chart of a sealing checking phase of the inventive method,

[0039] FIG. 5 is an exemplary result of the sealing checking phase according to FIG. 4,

[0040] FIG. 6 is an exemplary result of a cleaning phase of the inventive method,

[0041] FIG. 7 is a flow chart of the cleaning phase according to FIG. 6,

[0042] FIG. 8 is an exemplary result of a measurement phase of the inventive method,

[0043] FIG. 9 is a flow chart of the measurement phase according to FIG. 8,

[0044] FIG. 10 is an exemplary result of a particle concentration determination of exhaled air by a healthy user,

[0045] FIG. 11 is an exemplary result of a particle concentration determination of exhaled air by a high emitting user,

[0046] FIG. 12 is an exemplary result of a particle size distribution determination of exhaled air by a healthy user,

[0047] FIG. 13 is an exemplary result of a particle size distribution determination of exhaled air by a high emitting user, and

[0048] FIG. 14 is the inventive device according to an example in a schematic view.

DETAILED DESCRIPTION

[0049] FIG. 1 shows an inventive device 10 for calculating the particle concentration c.sub.n of exhaled air as a parameter p for characterizing the particles of exhaled air according to a first embodiment in a schematic view. The device 10 comprises an inlet line 11 which is directed to an external environment 12, usually a room in which a user is located. The inlet line 11 is fluidly connected to the external environment 12.

[0050] The inlet line 11 comprises a filter 13 which in this embodiment is realized as a depth filter 14 having a porous filtration medium for retaining particles throughout the medium. In this example, the porous medium comprises mats of randomly arranged glass fibers which are not shown in FIG. 1. This type of filters 14 is also known as HEPA filter which filters out at least 99.97% of particles of the air passing through the filter 14. In this embodiment, the depth filter 14 is form-fittingly connected to the inlet line 11 by being screwed to the inlet line 11. The depth filter 14 is replaceable.

[0051] The inlet line 11 is fluidly connected to a breathing line 15 which is arranged parallel, especially coaxial to the inlet line 11. The breathing line 15 comprises an interface 16 which is connected to the end face 17 of the breathing line 15 which is directed away from the inlet line 11. The interface 16 in this embodiment is a facemask 18 covering the mouth and nose of a user. Alternatively, a closeable mouthpiece can be used as an interface 16, wherein the nose of the user is sealed by a nasal clamp (not shown). The facemask 18 is replaceable, disposable after being used and disinfectable. By means of a valve 19 inside the facemask 18, the facemask 18 is closeable, especially sealable, in order to prevent air flow between the breathing line 15 and the facemask 18. The diameter of the breathing line 15 is smaller than the diameter of the inlet line 11.

[0052] A measurement line 20 is arranged between the inlet line 11 and the breathing line 15 and perpendicular to both of said lines 11, 15. The diameter of the measurement line 20 is smaller than the diameters of both the inlet line 11 and the breathing line 15. The inlet line 11, the breathing line 15 and the measurement line 20 are integrally formed as a T-shaped component 21 wherein the inlet line 11, the breathing line 15 and the measurement line 20 are designed as pipe sockets of the component 21.

[0053] The measurement line 20 comprises a heater 24 for keeping the measurement line 20, particularly its inner wall 25, at a preset temperature T of 60° C. The measurement line 20 is made of metal and/or an (electrically) conductive polymer tubing both of which have antistatic properties. The measurement line 20 further comprises a check valve 26 which prevents a return flow of air. The inlet line 11, the breathing line 15 and the measurement line 20 sectionally comprise a measurement chamber 27 with a volume of 25 ml, wherein the measurement chamber 27 is fluidly connected to the depth filter 14 and the facemask 18.

[0054] At its end face 28 facing away from the measurement chamber 27, the measurement line 20 is removably connected to a particle measurement device 29 which is capable of characterizing particles 35 of exhaled air. In this embodiment, the particle measurement device 29 is an aerosol spectrometer 30 with part of its design being schematically shown in FIG. 2. The aerosol spectrometer 30 comprises an air flow generator 22, here a fan 23 and/or a pump 33, for generating a defined air flow in the measurement line 20 with a flow rate q.sub.fl of a preset value in the range from 0.1 I/min to 101 I/min by which the particles 35 of the exhaled air are directed towards an opening 31 of the aerosol spectrometer 30. Moreover, the aerosol spectrometer comprises a heater 33, as well.

[0055] A flow tube 34 of the aerosol spectrometer 30 carrying the particles 35 is shown in FIG. 2 as being arranged perpendicular to the drawing area. The particles 35 in the flow tube 34 are illuminated by a collimated light beam 36 of polychromatic light emitted by a light source 37, here an LED, and a lens 38 with wavelength in the range from 390 nm to 490 nm. By scattering processes, the particles 35 emit scattering light 39 which is perpendicular to both the direction of flight of the particles 35 and the direction of the light beam 36 coming from the LED 37. The scattering light 39 hits a converging lens 40 which focuses the scattering light 39 on an optoeletric sensor 41, comprising here a photomultiplier and a photometer (not shown), which converts the intensity of the scattering light 39 to electric signals. Based on the electric signals, an electronic processing unit 42 determines a particle size distribution c.sub.n(d.sub.p) as a function of the particles’ diameters d.sub.p in order to characterize the particles 35 of the exhaled air. The electronic processing unit also comprises a control module which is electronically connected to the valve 16, the check valve 26, the heater 24, 33, the air flow generator 22, 32 and is capable of executing an inventive procedure which is described below.

[0056] The spatial overlap of the light beam 36, the registered scattering light 39 and the registered part of the particles 35 in the flow tube 34 defines a virtual spatial measuring cell 43 in which the particle size distribution c.sub.n(d.sub.p) is determined. In the course of the measurement, the light intensity of the scattering light 39 and therefore the hereby determined electrical signal strength is a measure of the size of the particles which is attributed a particle diameter d.sub.p. The determined particle size distribution c.sub.n(d.sub.p) is a function of the particle diameter: c.sub.n = f(d.sub.p). The particle size distribution c.sub.n(d.sub.p) is determined for discrete particle diameters d.sub.p as measuring points wherein usually 256 measuring channels are used. To improve the measurement quality, the particle size distribution c.sub.n(d.sub.p) are interpolated, preferably by means of cubic splines. The particle concentration c.sub.n is the sum of the particle size distribution c.sub.n(d.sub.p) over every particle diameter d.sub.p.

[0057] In an embodiment of the inventive method outlined in the flow chart according to FIG. 3, the procedure comprises three phases, a sealing checking phase A with regard to the correct sealing of the device 10, a cleaning phase B and a determining phase C. In this embodiment, the particle concentration c.sub.n, also known as the particle density, will be determined. The method is described in detail as follows:

[0058] The object of the sealing checking phase A is to ensure that the device 10 is correctly sealed and no unfiltered air of the external environment 12 enters the device 10. This phase also removes any residual airborne particles within the device (including facemask, inlet line, breathing line and measurement line). The sealing checking phase A is outlined in the flow chart according to FIG. 4 and begins with a step A1 of opening the valve 19 of the facemask 18, starting of the measurement and determining the particle concentration c.sub.n inside the device 10. Unfiltered air can enter the facemask 18 so the particle concentration c.sub.n is comparatively high. FIG. 5 shows the development of the determined particle concentration c.sub.n over time t during the course of the sealing checking phase A. In a first area 44, the particle concentration c.sub.n is about 80.000 particles per liter air or 80.000/l. The facemask 18 is then closed A2 which results in that now only filtered air can enter the device 10 (via the depth filter) and is thus measured. As this kind of air contains only a small amount of particles 35, the particle concentration c.sub.n decreases continuously until it reaches a smaller level which is shown in a second area 45 in FIG. 5. The particle concentration c.sub.n decreases from about 80.000 particles per liter air to a value of almost 0 over the course of about 10 seconds. The average value of the particle concentration c.sub.n is measured over a preset time interval Δt.sub.1, in this case 12 seconds. If the average value of the particle concentration c.sub.n is below a preset threshold value c.sub.n;t of less than 1 particle per liter air, preferably 0 particles per liter air (step A3), a signal is output A4 indicating that the device 10 is correctly sealed and can be used for further measurements. If the particle concentration c.sub.n remains at a higher level than the threshold value c.sub.n;t, the sealing of the device is assumed to be damaged and a corresponding warning signal is output A5 by an output device for example a display and/or a speaker.

[0059] After having verified that the device 10 is properly sealed, the method continues with the cleaning phase B in which the facemask 18 is opened and through which the user breathes. By means of the facemask 18, the exhaled air completely enters the measurement chamber 27 through the measurement line 20 and is subsequently directed towards the aerosol spectrometer 30 where the particle concentration c.sub.n of the exhaled air is continually measured. As the lungs of the user at first still contain particles from the external environment 12, the device 10 at first registers a still high level of particle concentration c.sub.n which is shown in a first area 46 of the measurement according to FIG. 6 where the development of the particle density c.sub.n is shown over time t. It should be noted that the values for the particle concentration c.sub.n are illustrated on a logarithmic scale so that the value for the particle concentration c.sub.n in the first area 46 is at its maximum of about 40.000 particles per liter air.

[0060] During the course of continued breathing, the user only inhales filtered air through the depth filter 14 and exhales air which is directed B1 into the measurement line 20 so the particle concentration c.sub.n continually decreases which can be seen in a second area 47 in FIG. 6. This trend continues until the particle concentration c.sub.n reaches an approximately constant level as shown in a third area 48 of FIG. 6 which corresponds to a state of equilibrium in which the registered particles 35 can be assumed to come only from inside the user’s lungs and air ways, generally the respiratory tract. The value of the particle concentration c.sub.n in the third area 48 of FIG. 6 is below 1.000 particles per liter air. A change parameter Δc.sub.n is calculated B2 (for example the variance) and, in a comparison B3, compared to a preset value Δc.sub.n;th. If the particle concentration c.sub.n does not change more than the preset value Δc.sub.n over a preset time interval Δt.sub.2, here about a minute, the measurement phase C begins and a corresponding signal is output B4. If not, a corresponding warning signal is output B5 indicating that a state of equilibrium has not (yet) been reached. The cleaning phase B illustrated in the flow chart according to FIG. 7.

[0061] The device 10, more exactly the control module, afterwards executes the measurement phase C in which the particle concentration c.sub.n is determined C1 over a preset time interval Δt.sub.3, here about two minutes, after which an average value ĉ.sub.n for the particle concentration c.sub.n as a decision parameter p.sub.dec for characterizing the exhaled air is calculated C2. FIG. 8 shows an exemplary measurement, in which the average value ĉ.sub.n for the particle concentration c.sub.n is calculated to 424 particles per liter air. This determined decision parameter p.sub.dec is then compared C3 to a preset value p.sub.h which is an average value for the particle concentration c.sub.n of a healthy user. If the decision parameter p.sub.dec of the user is higher than the preset value p.sub.h, the system assumes he user to be a high emitter, also known as “superspreader” (emitting more-than-average amount of particles per liter air) which in some cases indicates a potentially heightened risk of infection and and outputs C5 a corresponding warning signal via the output. If not, the user is considered healthy and a corresponding signal is output C4. FIG. 9 illustrates the measurement phase C by a flow chart.

[0062] FIG. 10 shows the determining of the particle concentration c.sub.n for a healthy user with an average value ĉ.sub.n for the particle concentration c.sub.n calculated to 416 particles per liter air which roughly corresponds to the measurement according to FIG. 8. In contrast, FIG. 11 shows the determined particle concentration c.sub.n for a high emitting user who might be infectious. It can be noticed that the particle concentration c.sub.n does not decrease during the time of measurement which suggests that the amount of particles from the user’s lungs is at least as high as particle concentration c.sub.n of the external environment 12. Correspondingly, the average value ĉ.sub.n for the particle concentration c.sub.n was calculated to 66.490 particles per liter air which is significantly higher than the corresponding value for the healthy person according to FIG. 10. Accordingly, the device 10 outputs C5 out a warning signal indicating that the user might be a high emitting user and/or at least potentially infectious. The exhaled concentration depends on the breathing manoeuver of the user, e.g. forced breathing, tidal breathing. Preferably, tidal breathing is measured.

[0063] In another example of the inventive method, the particle size distribution c.sub.n(d.sub.p) of the exhaled air is additionally determined. FIG. 12 shows the particle size distribution c.sub.n(d.sub.p) of a healthy person with both axes being logarithmically displayed. The particle size distribution c.sub.n(d.sub.p) is registered by 256 measurement channels of the aerosol spectrometer 30 with each channel representing an interval of particle sizes, here particle diameters d.sub.p. In this embodiment, the intervals of particle diameters d.sub.p are logarithmically arranged as can be seen from the x axis in FIG. 12. The y axis corresponds to the particle concentration c.sub.n(d.sub.p) for the respective particle diameter d.sub.p. FIG. 11 shows a global peak 49 of the particle concentration c.sub.n(d.sub.p) for a particle diameter d.sub.p of about 0.2 .Math.m with the peak 49 having a value of about 200 particles per liter air. For particle diameters d.sub.p greater than 1 .Math.m, no particles are registered. The total particle concentration c.sub.n can be calculated from the particle size distribution c.sub.n(d.sub.p) by integration over the full range of particle diameters d.sub.p.

[0064] FIG. 13 shows a particle size distribution c.sub.n(d.sub.p) for a high emitting and/or at least potentially infectious user. The global peak 50 is located at a particle diameter d.sub.p of about 0.2 .Math.m which was also the case for a healthy user. However, the corresponding particle concentration c.sub.n(d.sub.p) for the high emitting and/or at least potentially infectious user is about 30.000 particles per liter air which is significantly higher than the corresponding value of about 200 particles per liter air for a healthy user. Comparing particle concentration values c.sub.n(d.sub.p) for specific particle diameters d.sub.p can be a way of discerning between healthy and high emitting users, especially for particle diameters d.sub.p in the range from 0.1 .Math.m to 1 .Math.m. The measurement for the high emitting user also shows that particles with diameters d.sub.p greater than 1 .Math.m are registered with the highest particle diameter d.sub.p being about 2 .Math.m to 3 .Math.m for which about 11 particles per liter are registered. This was not the case for a healthy user so also the amount of particles c.sub.n(d.sub.p) for particle diameters d.sub.p greater than a preset value can be used to discern a healthy user from a high emitting user.

[0065] Looking at FIGS. 12 and 13, the overall particle concentration c.sub.n is therefore not the only decision parameter p.sub.dec on the basis of which a healthy user can be distinguished from a high emitting user. Additional parameters p.sub.dec for this means could also be: (Scaled) average particle diameter, shape of particle size distribution, minimum particle diameter, maximum particle diameter, local peaks and/or global peaks. The Inventive method is executed in the form of a computer program which is run on the control module and which is saved on a computer readable medium.

[0066] FIG. 14 shows a second embodiment of the inventive device 10 in a schematic view. The inlet line 11, the breathing line 15 and the measurement line 20 are formed integrally as pipe sockets of a single T-shaped component 21 which also comprises the measuring chamber 27. The diameter of the inlet line 11 is equal to the diameter of the breathing line 15, wherein the diameter of the measurement line 20 is smaller than the two former diameters.

[0067] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.