WO2023187665A1

WO2023187665A1 - System for testing personal protective equipment of the respiratory tract to assess the effectiveness of protection thereof from biological agents

Info

Publication number: WO2023187665A1
Application number: PCT/IB2023/053111
Authority: WO
Inventors: Andrea Marini
Original assignee: Ares S.R.L.
Priority date: 2022-03-31
Filing date: 2023-03-29
Publication date: 2023-10-05

Abstract

A system (1) is described for testing personal protective equipment (2) for the respiratory tract to assess the effectiveness of its protection against biological agents, the system (1) comprises : a sealed test chamber (4) housing a Sheffield head (5) having an oral-nasal opening (6) onto which one piece of personal protective equipment (2) is applicable to cover it; a generator device (3) for generating an aerosol containing one or more biological agents, preferably viral and/or bacterial ones, the generator device (3) being configured to supply an amount of said aerosol inside the test chamber (4); and a respiration simulation system (8) configured to simulate the human breath, fluidly connected to the Sheffield head (5) and configured to control an aspiration of the aerosol from the test chamber (4) through said oral-nasal opening (6) and through the personal protective equipment (2) applied thereto; the respiration simulation system (8) comprises: a cylinder (12) and a piston (13) engaging the cylinder (12) in a sliding manner; an actuator (14) configured to control the sliding of the piston (13) inside the cylinder (12); and a transmission assembly (15) operationally interposed between the actuator (14) and the piston (13); the transmission assembly (15) comprises a worm screw or a ball screw (16) to transform a rotary motion of the actuator (14) into a reciprocating motion of the piston (13) inside the cylinder (12).

Description

"SYSTEM FOR TESTING PERSONAL PROTECTIVE EQUIPMENT OF THE

RESPIRATORY TRACT TO ASSESS THE EFFECTIVENESS OF PROTECTION THEREOF FROM BIOLOGICAL AGENTS"

Cross-Reference to Related Applications

This Patent Application claims priority from Italian Patent Application No. 102022000006407 filed on March 31, 2022, the entire disclosure of which is incorporated herein by reference.

Technical Field

This invention relates to a system for testing personal protective equipment of the respiratory tract, for example, filtering half-masks, filtering masks, and filters, to evaluate their protective efficacy against biological agents, for example pathogens such as bacteria, fungi, viruses, etc.

State of the Art

It is known to use personal protective equipment (PPE) for the respiratory tract in health environments, in particular that is designed to protect the respiratory tract of the user, positioning the device on the face in order to protect the same against biological agents, such as bacteria, fungi, viruses, etc., which may be in aerosol form coming from breaths of other subjects present in a confined environment and/or possible concentrations in the air of the biological agents mentioned above.

Masks and half-masks are known in particular; these are designed to cover the lower part of the face of a user in order to avoid the dispersion of, or infection via, said biological agents .

Outside health facilities this personal protective equipment is also of growing and current use , in particular to prevent and/or contain the spread of biological agents of an epidemic or pandemic nature and that are highly contagious , for example when one is an epidemic or pandemic and/or in other activities wherein it is necessary to protect the respiratory tract of an operator from these agents .

Known filtering hal f-masks , fi ltering masks , and filters comprise generally multi-layered filtering materials including at least one layer in nonwoven fabric having the right shape to protect the respiratory tract of the user .

To be able to be worn, they are typically equipped with a pair of connections , usually elastic, for example strings or straps , which are fixed to the device .

Systems or assemblies of equipment for testing the degree of protection against biological agents provided by the above-mentioned personal protective equipment of the respiratory tract are known .

In particular, these systems or assemblies of test equipment are designed to reproduce , inside a controlled test environment , the conditions and methods of use of the PPE to be tested, simulating human respiration and reproducing the correct wearing of the PPE itsel f .

To this end, a test system of the type described above typically comprises : a device generating viral and/or bacterial aerosols , i . e . , gases in which a viral and/or bacterial agent is dispersed;

- a sealed test chamber that contains a so-called Shef field head inside ; a respiration simulation system, designed to arti ficially reproduce the human breath ( a human respiratory act ) ;

- a device for taking and analysing samples for determining viral and/or bacterial concentrations on biological targets located operationally downstream of the PPE to be tested, relative to the direction of flow; and

- tubes and/or ducts that fluidically connect the above-mentioned components .

In use , the generator device generates an aerosol containing the pathogen and feeds it inside the test chamber .

The test chamber houses the Shef field head on which the PPE to be tested is applied, generally at and covering an oral-nasal opening that simulates the mouth and/or nose of the user .

The simulation system, which is fluidically connected to the Shef field head by means of tubes/ducts , determines the aspiration of the aerosol contained in the test chamber through the oral-nasal opening in the Shef field head .

Therefore , the aerosol breathed in passes through the PPE to be tested applied to the Shef field head .

In other words , the aerosol is breathed in by the Shef field head via the simulation system .

The sampling and analysis device samples , with a predetermined frequency, samples of aerosol from a position fluidically downstream of the PPE to convey them to one or more biological targets , which are succes sively analysed so as to assess the protection provided by the PPE via the degree of retention of the pathogenic agents on the same . In practice , the smaller the concentration of pathogenic agents on the target , the greater the protection provided by the PPE tested .

CN-U-213600550 illustrates a test system of the type described above . In any case , this invention is not used to test the degree of protection against biological agents , and, thus , does not comprise any generator of viral and/or bacterial aerosols . In contrast , CN-U- 213600550 describes a system for testing the protection against particulates .

According to the set of equipment previously produced, the respiration simulation system is basically defined by, or the simulation of the respiration was obtained via, a pump comprising an actuator, generally an electric motor, a piston that slides inside a cylinder, an intake and delivery valve assembly, and a transmission assembly operationally interposed between the actuator and the piston .

Generally, the transmission assembly comprises a rod-crank system for trans forming the rotary motion of the actuator into the reciprocating motion of the piston .

This configuration enables the variation of the frequency of respiration by controlling the speed of rotation of the actuator, so as to adapt it to the typical human respiratory act.

WO-A-2015082666 describes a respiration simulation system. This system is, in any case, used to calibrate a gas flow meter in the context of determining the 02 and C02 content in the air exhaled by a patient, as well as the flow.

US-A-2007259322 and DE-U-9107222 describe respiration simulation systems of the known type.

The Applicant has observed how the known test systems and equipment previously used are capable of being further improved. The need to test the efficacy of the PPE in the presence of rather irregular respiratory acts in relation to the subject that performs the act itself is, in fact, of growing concern; just think, as far as regards irregularity, of the differences of subjects that will use the PPE, such as, for example, the age, the type of activity (sedentary or not) , the presence of respiratory diseases (serious or moderate) for which there is an irregular respiratory profile, etc.

However, the simulation systems described above make correctly simulating these irregular respiratory profiles very difficult and complicated.

There is, therefore, the need for greater flexibility in varying the simulated respiratory profile.

Object and Summary of the Invention

The purpose of this invention is to produce a system for testing personal protective equipment for the respiratory tract that is highly reliable and inexpensive , and makes it possible to avoid at least some of the drawbacks speci fied above and connected to known systems .

According to the invention, this purpose is achieved with a system as claimed in claim 1 .

Brief Description of the Drawings

To better understand this invention, some preferred, but non-limiting, embodiments of this invention are described below, merely by way of example , and with the aid of the attached figures in which :

- Figure 1 is a diagram of a system for testing PPE produced according to this invention;

- Figure 2 is a perspective view on an enlarged scale of a respiration simulation system of the system in Figure 1 ; and

Figure 3 is a perspective view, with parts removed for clarity, of the respiration simulation system shown in Figure 2 .

Detailed Description

With reference to Figure 1 , the number 1 denotes , as a whole , a system for testing personal protective equipment 2 of the ( or for the ) respiratory tract (hereinafter, the PPE 2 ) to assess the ef ficacy thereof in protecting against biological agents such as bacteria, fungi , and viruses , etc .

In the example illustrated, the PPE 2 to be tested is defined by a filtering hal f-mask or mask or filter, designed to protect the respiratory tract of a user, positioning the PPE 2 on the face in order to protect the same against the above-mentioned biological agents that may be found in aerosol form coming from respiratory acts of other parties present in a confined space and/or from possible concentrations of the above-mentioned biological agents in the air .

For example , the PPE 2 is a surgical hal f-mask, designed to cover the lower part ( in particular the mouth and nose ) of the face of a user in order to avoid the inhalation or dispersion of the biological agents by the mouth and/or by the nose of the user .

The system for testing 1 is designed to reproduce the conditions and methods of use of the PPE 2 to be tested, simulating human respiration and reproducing the correct wearing of the PPE 2 itsel f .

To this end, the testing system 1 comprises :

- a generator device 3 configured to generate an aerosol contaminated with a biological agent , for example an aerosol wherein a viral or bacterial or fungal agent has been dispersed, according to a known method not described in detail ;

- a sealed test chamber 4 fluidically connected to the generator device 3 , so as to receive from the latter the aerosol generated;

- a Shef field head 5 ( known and not described in detail ) housed inside the test chamber 4 and having an oral-nasal opening 6 that simulates the mouth and/or nose of the user, on which opening 6 the PPE 2 to be tested can be applied, to cover the same ; - a sample withdrawal and analysi s device 7 ( of the known type not described in detail ) designed to withdraw aerosol samples at a fluidic position downstream of the PPE 2 to be tested and configured for determining viral and/or bacterial concentrations on the biological targets (not illustrated) located operationally downstream of the PPE 2 to be tested; and

- a respiration simulation system 8 , designed to arti ficially reproduce a human respiratory act .

Conveniently, the system 1 also comprises tubes and ducts to fluidically connect the components described above , schematically illustrated in Figure 1 , together .

Speci fically, the respiration simulation system 8 is fluidically connected to the Shef field head 5 and is configured to control aspiration of the aerosol , generated by the generator device 3 and fed to the test chamber 4 , by the test chamber 4 through the opening 6 and, thus , through the PPE 2 to be tested applied to cover this latter .

In more detail , the Shef field head 5 includes tubes 11 ending in the opening 6 and extending into the rear part of the head . The tubes 11 connect the opening 6 to the respiration simulation system 8 .

The sample withdrawal and analysis device 7 is , conveniently, connected to the tubes 11 so as to withdraw the aerosol that has been filtered by the PPE 2 to be tested, in order to assess the ef f icacy of its protection .

In use , the generator device 3 generates the above- mentioned aerosol and feeds it inside the test 4 chamber . Here, the aerosol enters into contact with the PPE 2 to be tested and is breathed in by the respiration simulation system 8 through the opening 6 and via the tubes 11.

Therefore, the aerosol crosses the PPE 2 to be tested and placed to cover the opening 6.

The Sheffield head 5 enables, in addition, the simulation of the actual wearing of the PPE 2, creating simulating conditions the more similar to reality, including, for example, the effects of leakage of the aerosol at the sides of the PPE 2, i.e., between the PPE 2 and the user's face.

In other words, the aerosol is breathed in by the Sheffield head 5 via the respiration simulation system 8.

The sampling and analysis device 7 samples, with a predetermined frequency, samples of aerosols from the tubes 11 (and, thus, in a position fluidically downstream of the PPE 2) to convey them to one or more biological targets, which are successively analysed so as to assess the protection provided by the PPE 2 via the degree of retention of the pathogenic agents on the same. In practice, the smaller the concentration of pathogenic agents on the target, the greater the protection provided by the PPE 2 tested.

The preferred method for assessing the protection efficacy provided by the PPE 2 will be described below. In particular, the protective efficacy of the PPE 2 is measured using a "challenge" of viral or bacterial aerosol consisting of bacteriophages dispersed in a special test solution. The efficiency is verified via the assessment of the ratio of concentration of the viral or bacterial agent respectively measured in a position upstream of the PPE 2 and in a position downstream of the PPE 2 .

Speci fically, the sampling and analysis device 7 (which defines a sampling system) operates continuously both on the sampling of the aerosol upstream of the PPE 2 and downstream of the PPE 2 , and the value of the flow sampled on both lines is controlled and recorded, preferably via two mass flow meters .

The device 7 comprises , preferably, a pair of bubblers ( known and not illustrated) , placed, respectively, along a line upstream and a line downstream in relation to the PPE 2 , and configured to capture the viral or bacterial agents present in the aerosol sampled, respectively, upstream and downstream of the PPE 2 .

More precisely, the sampling upstream is carried out preferably via a tube (not illustrated) ending in an opening arranged in an area of the head 5 distal to the area covered by the PPE 2 , for example placed near one of the eyes of the head 5 .

As mentioned, the sampling downstream is carried out via tubes 11 and through the opening 6 .

In use , the device 7 compares , in a known way, the viral or bacterial loads detected upstream and downstream . The concentration ratio of the viral or bacterial load will represent the protection ef ficacy of the PPE 2 .

Conveniently, the testing system 1 comprises a tube (not illustrated) selectively connecting the chamber 4 to the external environment via the interposition of a valve element (not illustrated) provided with a special filter . In this way, it is possible to control the pressure of the chamber 4 at a target level , without risks of contamination from the outside environment . It is , in particular, possible to limit , as much as possible , the pressure di f ferential caused by the reduced volume of the chamber 4 compared to the volume of air moved by the respiration simulation system 8 .

As can be seen in detail in Figures 2 and 3 , the respiration simulation system 8 comprises :

- a cylinder 12 and a piston 13 that engages the cylinder 12 in a sliding manner ;

- a rotating actuator 14 configured to control the sliding of the piston 13 inside the cylinder 12 ; and a transmiss ion assembly 15 operationally interposed between the actuator 14 and the piston 13 .

Conveniently, the respiration simulation system 8 also includes a valve assembly 25 arranged in fluid communication with the cylinder 12 and comprising at least one intake valve and a delivery valve , to enable , respectively and selectively, the inlet and outlet of the aerosol from the cylinder 12 .

According to the invention, the transmission assembly 15 comprises a ball screw 16 to trans form a rotary motion of the actuator 14 into a reciprocating motion of the piston 13 inside the cylinder 12 .

In particular, the transmis sion assembly 15 includes : - a screw member 17 extending along a longitudinal axis A and fastened integrally with the piston 13 ; and

- a rotary drive member 18 coupled to the actuator

14 for receiving therefrom the rotary motion and coupled to the screw 17 for transmitting thereto the received motion and determining the trans formation of the received motion into the above-mentioned reciprocating motion along the longitudinal axis A.

In other words , the screw member 17 defines the rod of the piston 13 , and the piston 13 is movable in a sliding manner inside the cylinder 12 along the axis A.

In the example illustrated, the ball screw 16 comprises a ball recirculation nut 18 coupled to the screw member 17 and defining the above-mentioned rotary drive member .

According to an alternative embodiment not illustrated, the transmission assembly 15 comprises a worm screw including the screw member 17 and a rotary drive member defined by a pinion .

As can be seen in Figure 3 , the transmission assembly

15 comprises a first pulley 19 mounted integrally to the actuator 14 , a second pulley 20 mounted integrally to the nut 18 , and a belt 21 that operatively connects the first pulley 19 with the second pulley 20 .

In this way, the rotary motion is transmitted by the actuator 14 to the nut 18 .

The nut 18 is coupled to the screw member 17 so that the screw member 17 engages , movably, the nut 18 itsel f .

According to the configuration illustrated, the nut 18 rotates around the axis A and is axially fixed, compared to the axis A. At the same time , the screw member 17 is rotationally fixed around the axis A and is axially mobile with reciprocating motion along the axis A via the actuator 14 and via the above-mentioned trans formation of the motion, to control the reciprocating motion of the piston 13 inside the cylinder 12 .

More precisely, the actuator 14 transmits the motion to the first pulley 19 and drives the second pulley 20 via the belt 21 . The second pulley 20 drives the nut 18 , which rotates around the axis A.

This rotation causes , in a known way of the ball screws and not described in detail , the movement of the balls contained inside and the movement of the screw member 17 along the axis A. It will be enough to invert the rotation direction of the actuator 14 to invert the forward movement of the screw member 17 and to obtain the above-mentioned reciprocating motion .

According to one aspect of this invention, the actuator 14 comprises , in particular is defined by, an electric multi-pole step motor or an electric multi-pole torque motor, preferably a brushless one .

The Applicant has observed how this type of electric motor enables the achievement of excellent performance in respiration simulation, making it possible to generate ( curved) respiratory profiles variable over time .

Advantageously, the respiration simulation system 8 also comprises an encoder 22 ( of the known type ) operationally coupled to the actuator 14 . In particular, the encoder 22 is fixed to the first pulley 19 .

Thanks to the presence of the encoder 22 , it is possible to obtain a closed-loop control of the system 8 , which is in finer and more precise control of the piston 13 inside the cylinder 12 and, thus , in an increase of precision and flexibility in the control of the simulated respiration .

In addition, the respiration simulation system 8 advantageously comprises a presence sensor or homing sensor 23 configured to detect an axial reference position of the piston 13 compared to the cylinder 12 .

More precisely, the sensor 23 is configured to perform a so-called "homing" of the piston 13 , i . e . , the return of the piston 13 to a coordinate of physical zero of the system .

This makes it possible to additionally improve the closed-loop control of the system, also providing the possibility of defining the " sub-strokes" comprised in the total stroke of the piston 13 , enabling, thus , the simulation of a shorter or fragmented respiratory cycle, or one with a smaller volume of air, without the need to replace the cylinder 12 or other components . Thi s would be impossible with the known simulation systems comprising a rod-crank transmission assembly .

Advantageously, the respiration simulation system 8 comprises an anti-rotation bar 24 mounted integrally with the piston 13 and configured to counteract, in particular to prevent , a rotation of the piston 13 about the longitudinal A.

Specifically, the anti-rotation bar 24 has a first fixed end 24a fixed to the piston 13 and a second free end 24b opposite the first end 24a.

More specifically, the anti-rotation bar 24 extends from one outer surface of the piston 13, opposite an inner surface of the same facing the valve assembly 25, along a direction parallel to the axis A, and slidably engages a sleeve or bushing 26, preferably a recirculating ball one, fixed to a fixed frame T of the system 8.

Advantageously, the sensor 23 is configured to detect the presence of the anti-rotation bar 24 at a predetermined position (Figures 2 and 3) corresponding to said reference position of the piston 13.

More specifically, the sensor 23 is configured to detect the free end 24b of the anti-rotation bar 24 to determine the above-mentioned reference position of the piston 13.

This peculiar configuration makes it possible to detect the reference position of the piston 13 (i.e., the physical zero of the piston 13) without interfering with the piston 13 itself or with the screw member 17, obtaining, at the same time, a simple and reliable system for the homing operation.

Conveniently, the testing system 1 comprises a control unit (for example, an electronic control unit, known and not illustrated) operationally connected with the actuator 14, with the encoder 22, and with the sensor 23, and configured to control the actuator 14 based on the detections made by the encoder 22 and by the sensor 23 .

In particular, the control unit can be programmed so as to control the actuator 14 on the basis of motion profiles pre-set and/or automatically generated on the basis of the above-mentioned detections , in order to reproduce desired respiratory profiles by means of the reciprocating motion of the piston 13 inside the cylinder 12 .

The advantages that can be achieved with the testing system 1 according to the present invention are apparent from an examination of the characteristics thereof .

In particular, thanks to the fact that the transmission assembly 15 includes a ball screw as described above , and thanks to the fact that the actuator 14 is defined by a step motor or torque motor, it is possible to implement irregular respiratory curves or profiles that would be impossible to implement using the known simulation systems , which only enable changing the frequency of respiration and do not enable the variation of the speed of the piston' s movement during the stroke and between the intake and delivery stroke or the variation of the extension of the stroke itsel f .

In particular, the use of a ball screw makes it possible to achieve high precision and, at the same time , a long service life of the components and low noise , since this component is sel f-lubricating and is characterised by plays between the balls and the path for the balls in the order of microns , thus obtaining the motion of the piston 13 with very little friction .

The use of a step or torque motor coupled to an encoder 22 , and preferably to a presence or homing sensor 23 , makes it possible to further increase the control precision, thus allowing the implementation of rather complex respiratory curves . In fact , it is possible to know the position of the piston 13 with an accuracy in the order of millimetres .

It is , for example , possible to vary the speed between the bottom dead centre and the top dead centre and, furthermore , vary the speed between the intake stroke (breathing in) and the delivery stroke (breathing out ) , setting a shorter stroke than the total available , all with great precision and accuracy .

Therefore , thanks to the peculiar respiration simulation system 8 , according to this invention, it is possible to implement irregular respiratory profiles that simulate respiration in the presence of particular respiratory diseases .

This entails greater accuracy of the PPE 2 tests , including in the presence of these respiratory diseases or, in any case , in the presence of a non-nominal respiration of the user of the PPE 2 .

It is clear that the testing system 1 described and illustrated herein can be subj ect to modi fications and variations without however departing from the scope of protection defined by the claims .

Claims

1.- A system (1) for testing personal protective equipment (2) for the respiratory tract to assess the effectiveness of protection thereof from biological agents, the system (1) comprising:

- a sealed test chamber (4) housing a Sheffield head (5) having an oral-nasal opening (6) onto which one said personal protective equipment (2) is applicable to cover it;

- a generator device (3) for generating an aerosol containing one or more biological agents, preferably viral and/or bacterial ones, the generator device (3) being configured to supply an amount of said aerosol inside the test chamber (4) ; and

- a respiration simulation system (8) configured to simulate a human respiratory act, fluidly connected to the Sheffield head (5) and configured to control an aspiration of the aerosol from the test chamber (4) through said opening (6) and through the personal protective equipment (2) applied thereto; wherein the respiration simulation system (8) comprises :

- a cylinder (12) and a piston (13) engaging the cylinder (12) in a sliding manner;

- an actuator (14) configured to control the sliding of the piston (13) inside the cylinder (12) ; and a transmission assembly (15) operationally interposed between the actuator (14) and the piston (13) ; wherein the transmission assembly (15) comprises a worm screw or a ball screw (16) to transform a rotary motion of the actuator (14) into a reciprocating motion of the piston (13) inside the cylinder (12) ;

- wherein the transmission assembly (15) includes a screw member (17) extending along a longitudinal axis (A) and fixed integrally to the piston (13) , and a rotary drive member (18) coupled to the actuator (14) for receiving therefrom the rotary motion and coupled to the screw member (17) for transmitting thereto the received motion and determining the transformation of the received motion in said reciprocating motion along the longitudinal axis (A) .

2.- The system as claimed in claim 1, wherein the transmission assembly (15) comprises a ball screw (16) , wherein the screw member (17) defines a rod of the piston (13) , the piston (13) being movable in a sliding manner inside the cylinder (12) along the longitudinal axis (A) , and wherein the ball screw (16) includes a ball recirculation nut (18) coupled to the screw member (17) and defining said rotary drive member.

3.- The system as claimed in claim 2, wherein the transmission assembly (15) comprises a first pulley (19) mounted integrally to the actuator (14) , a second pulley (20) mounted integrally to the nut (18) and a flexible transmission member (21) operatively connecting the first pulley (19) with the second pulley (20) , the nut (18) being rotatable around the longitudinal axis (A) and being axially fixed with respect to the longitudinal axis (A) , the screw member (17) being rotationally fixed with respect to the longitudinal axis (A) and being axially movable with reciprocating motion along the longitudinal axis (A) by means of said actuator (14) and by means of said motion transformation, for controlling the reciprocating motion of the piston (13) inside the cylinder ( 12 ) .

4.- The system as claimed in any of the preceding claims, wherein the actuator (14) comprises an electric multi-pole step motor or an electric multi-pole torque motor, preferably brushless.

5.- The system as claimed in any of the preceding claims, wherein the respiration simulation system (8) comprises an encoder (22) operatively coupled to the actuator ( 14 ) .

6.- The system as claimed in claim 5, wherein the respiration simulation system (8) comprises a presence sensor (23) configured to detect a reference axial position of the piston (13) relative to the cylinder (12) .

7. The system as claimed in claim 6, wherein the respiration simulation system (8) comprises an antirotation bar (24) mounted integral with the piston (13) and configured to counteract a rotation of the piston (13) about the longitudinal axis (A) ; wherein said presence sensor (23) is configured to detect the presence of the anti-rotation bar (24) at a predetermined position corresponding to said reference position of the piston (13) .

8.- The system as claimed in claim 7, wherein the anti-rotation bar (24) has a fixed end (24a) fixed to the piston (13) and a free end (24b) opposite the fixed end (24a) ; and wherein the presence sensor (23) is configured to detect said free end (24b) to determine said reference position of the piston (13) .

9.- The system as claimed in any one of claims 6 to 8, and comprising a control unit operatively connected with the actuator (14) , with the encoder (22) and with the presence sensor (23) , and configured for controlling the actuator (14) on the basis of the detections made by the encoder (22) and by the presence sensor (23) ; the control unit (17) being programmable so as to control the actuator (14) on the basis of motion profiles pre-set and/or automatically generated on the basis of the detections made by the encoder (22) and by the presence sensor (23) in order to reproduce and/or simulate respiratory profiles by means of the reciprocating motion of the piston (13) inside the cylinder (12) .