WO2016178141A1

WO2016178141A1 - Apparatus for non-invesive pulmonary ventilation and calculation method of at least one breathing signal

Info

Publication number: WO2016178141A1
Application number: PCT/IB2016/052508
Authority: WO
Inventors: Lorenzo CORTELAZZI
Original assignee: Cortelazzi Lorenzo
Priority date: 2015-05-04
Filing date: 2016-05-03
Publication date: 2016-11-10

Abstract

An apparatus (10) for a pulmonary noninvasive ventilation is described, wherein the apparatus (10) includes a ventilation circuit (CV), a nasal-cannula circuit (CNC) and a flow generator (GRF). The apparatus (10) further includes an orofacial mask (MORI) provided with one or more passages or recesses for receiving one or more conduits of the nasal cannula circuit (CNC) and configured to create a sealed chamber when associated to the face of a user; a first measurement device (PNT_1) connected in series to the ventilation circuit (CV) between the ventilation circuit itself (CV) and the flow generator (GRF) for measuring an monitoring a first signal or ventilation value (Fven); a second measurement device (PNT_3) associated to the orofacial mask (MORI); wherein the second measurement device is apt to measure a second signal or value representative of a flow loss (Floss) which occurs in the sealed chamber of the orofacial mask; a calculator apt to calculate and/or quantify at least an actual ventilation value corresponding to, or based upon, a difference between the signal or ventilation value (Fven) and the signal or value of flow loss (Floss).

Description

APPARATUS FOR NON-INVESIVE PULMONARY VENTILATION AND CALCULATION METHOD OF AT LEAST ONE BREATHING SIGNAL

DESCRIPTION

The present illustration relates in general to the field of the pulmonary noninvasive ventilation, hereinafter called for convenience in abbreviated form NIV. The NIV modes or techniques are all those whereby the interaction between the respiratory apparatus of the patient and the ventilation circuit fed by the ventilation system does not provide the in sito insertion of the endotracheal tube.

Hereinafter in the description each technical term designated for the first time is followed by an acronym placed between brackets. It is to be meant that hereinafter the acronym replaces the technical term by convenience in abbreviated form.

In case the patient has spontaneous respiratory activity, even if with reduced effectiveness with respect to the physiological case, the respiratory assistance takes place, mostly, by means of using different interfaces, such as the helmet, the facial mask (FM), and the nasal cannulae or nasocannulae (NC).

The NIV respiratory assistance in the various modes thereof: "High Flow Nasal Cannula" (HFNC), "Nasal Continuous Positive Airways Pressure" (NCPAP), "Nasal Bilevel PAP" (NBiPAP), "Nasal Intermittent Positive Pressure Ventilation" (NIPPV), "Nasal Synchronized Intermittent Positive Pressure Ventilation" (NSIPPV) e "Nasal Synchronized Intermittent Mandatory Ventilation" (NSIMV), nowadays allows assisting most patients with acute or chronic respiratory insufficiency and then avoiding the invasive mechanical ventilation. By administering to the patient an air flow through the above-mentioned interfaces, which involves the application of a positive pressure, on one or two levels, at the nasal nostrils or the mouth, it is possible restoring the physiological level of the transpulmonary pressure allowing to obtain an adequate inhaled volume during each breath (tidal volume) or in the time range equal to a minute (minute volume).

Currently there are on the market several conventional apparatuses used for the NIV respiratory assistance by means of NC, but, from the engineering point of view, all can be traced back to the following 2 different fundamental configurations:

1) flow control apparatuses (ACF));

2) pressure control apparatuses (ACP).

The scheme of a conventional ACF is shown in Figure 1 , wherein it is easy to distinguish the following 3 devices, obviously apart from the patient:

1) flow generator and regulator (GRF);

2) ventilation circuit (CV);

3) NC circuit (CNC).

The GRF is capable of supplying to the CV, thereto it is connected in series, the selected value of the air oxygen-enriched, heated and humidified according to the clinical requirements. The flow supplied by the GRF is designated as ventilation flow (Fven). The CV, constituted by a corrugated cylindrical tube (branch), connects the GRF output to the CNC input, the output thereof is ending with the NC. As it is highlighted in Figure 1 , the CNC can assume the 2 following different types:

1) CNC constituted by a single corrugated tube with medium-big size for large flows, to be used in case of adult patient (CNC_line);

2) CNC constituted by a small corrugated tube shaped like a ring with small size for reduced flows, to be used in case of paediatric patient (CNC_ring).

The conventional ACFs are used in the mode or technique for NIV respiratory assistance designated HFNC ("High Flow Nasal Cannula") wherein, apart from the oxygen percentage included in the air mixture supplied to the patient (%02), the only parameter which is set manually by varying an inner resistance to the GRF, is Fven. However, it is not possible to measure and thus to monitor the real Fven value unless through a ball flowmeter ("asameter") the measured values thereof are affected by an uncertainty (error) often unacceptable for the subject application. Furthermore, the above-mentioned uncertainty does not allow to detect and monitor the oscillations subjected by Fven around the equilibrium value thereof set due to the spontaneous respiratory activity of the patient (disadvantage^).

From the functional point of view, such drawback, associated to the uncertainty of the Fven measured value, constitutes the main disadvantage of conventional ACFs, but it is not the only one. In fact, in order to optimize the clinical use of ACFs in the HFNC mode, it is necessary to estimate with accuracy and precision both the parameters linked to the respiratory mechanics in the patient, thereamong the most important ones are the thoracic and pulmonary compliance and the thoracic and pulmonary resistances, and the various components of the effort and the respiratory work performed by the patient. In order not to loose the advantages guaranteed by ventilation, such estimation or measurement has to be performed "online" and that is contemporarily to the ventilation itself. In absence of such monitoring, any NIV respiratory assistance apparatus or system is not capable of providing on itself such information and then the clinician has not the possibility of modifying the parameters to be set of the NIV respiratory assistance system based upon the patient's requirements but only based upon clinical or hemogasanalytical data, which often are late. The optimization of the ventilator parameters to be set, then, has important involvements in managing the patient with respiratory insufficiency such as improving the patient conditions and avoiding that NIV fails and one has to have recourse to the mechanical ventilation. Any system for monitoring the respiratory mechanics in the patient (SMMRP) currently on the (conventional) market cannot be used in combination with the conventional ACFs in the HFNC mode, as it would provide unreliable results or results affected by unacceptable errors due to the fact that it is not able to measure and monitor the progress in time (signal) of the respiratory flow (Fres) of the patient. This constitutes a relevant drawback (disadvantage_2), as the fact of having available the Fres signal is fundamental as therein most useful information is contained, and by processing them it is possible calculating all parameters of the respiratory mechanics in the patient, including those associated to the effort and to the respiratory work performed by the same. Any conventional SMMRP combined with the conventional ACFs in the HFNC mode is not capable of measuring the Fres signal due to the flow losses occurring between the CNC and the distal airways of the patient, mainly through the mouth and the nasal cavities. Due to such losses, the Fres signal does not coincides with the Fven signal (the only one which can be measured and monitored by the conventional SMMRP systems), but it results to be equal to the difference between the Fven signal and the total flow signal associated to the losses themselves (Floss), according to the following expression:

Fres = Fven - Floss (1)

The problem is difficult to be solved due to the fact that the extent of such losses and then, the Floss signal, in absence of a specific application innovation, cannot be in any way estimated nor either controlled, as it varies considerably, both between patient and patient and between different breaths performed by the same patient.

All techniques proposed up to now to solve the above-mentioned problem which would allow to overcome disadvantage_2, are based upon the fact of monitoring the signal of some physical quantities correlated to the signal related to the variation in the pulmonary volume designated as tidal volume (VC). The technique most widespread in the clinical field is the so-called respiratory Impedance or Inductance Plethysmography (RIP), measuring the variation in impedance or electric inductance of the thorax and abdomen induced by the expansion and retraction of the same during breathing, by means of using two metal bands adhering to the patient body. Other techniques are under study, currently used exclusively in the experimental field, which through the use of remote electromagnetic sensors (remote sensing) are potentially capable of monitoring the VC signal. Once determined the VC signal, the Fres signal is obtained by deriving the VC signal itself with respect to time. Both RIP and the other above-mentioned techniques do not provide sufficiently reliable performances, in the sense that the error associated to the measurement is not acceptable. Besides, they are quite expensive, particularly those associated to the remote sensing.

A third drawback (disadvantage_3) is linked to the impossibility of verifying "online", that is contemporarily to the ventilation, if the set Fven value allows obtaining the primary purpose of the HFNC mode. Such impossibility is the consequence of disadvantage_2 and in particular, in absence of a specific application innovation, of the absence of the Floss signal, by analysing the information included inside thereof it is possible to verify "online" if the conditions associated to the primary purpose of the HFNC mode have been reached.

Similarly, the scheme of a conventional ACP is shown in Figure 5, wherein it is easy to distinguish the following 3 devices apart from, obviously, the patient:

1) flow generator and regulator (GRF);

2) ventilation circuit (CV);

3) NC circuit (CNC).

Differently from ACFs, in ACPs the CV is constituted by 2 corrugated cylindrical tubes (branches) having a terminal in common (intersection) and the other one differentiated. The first branch of CV (CV_1) connects the GRF output tot the CNC input (intersection), the output thereof is terminated with NC. As in case of ACF (see Figure 1), even in ACPs, CNC can assume the following 2 different types:

The second branch of CV (CV_2) connects the intersection to the input of the first one of the following 2 devices in series therebetween:

1) pneumatic valve for opening/closing the CV_2 (Ron/off);

2) pneumatic valve allowing to vary and adjust the fluidodynamic resistance of CV_2 (Rext).

The Ron/off output is connected to the Rext input, the output thereof is connected to the outer environment.

With the just described configuration, shown in Figure 5, an ACP is capable of applying the selected pressure at the level of the intersection by adjusting the Rext value depending upon the flow crossing CV_2 designated outer flow (Fext). The pressure at the level of the intersection (Pcv), in fact, by definition, is equal to the product between Fext and Rext. In each time instant, thus as it can be seen by observing Figure 5, the flow supplied by GRF to CNC designated flow to the nasocannulae (Fnc) results to be equal to the difference between Fven and Fext, according to the following expression:

Fnc = Fven - Fext (6)

The conventional ACP are used in the following modes or techniques for NIV respiratory assistance:

1) NCPAP ("Nasal Continuous Positive Airways Pressure");

2) NBiPAP ("Nasal Bilevel Positive Airways Pressure");

3) NIPPV ("Nasal Intermittent Positive Pressure Ventilation");

4) NSIPPV ("Nasal Synchronized Intermittent Positive Pressure Ventilation");

5) NSIMV ("Nasal Synchronized Intermittent Mandatory Ventilation").

In the conventional ACPs the Ron/off remains always open in the NCPAP and NBiPAP, whereas it is cyclically opened and closed with frequency set in the NIPPV or in synchrony with the spontaneous respiratory activity of the patient in the NSIPPV and NSIMV.

Apart from the oxygen percentage included in the air mixture supplied to the patient (%02), the parameters to be set in each one of the above-mentioned modes or techniques will be described hereinafter.

In the NCPAP, during which all breaths are spontaneous, the only parameter which is set by varying both the resistance inside GRF (Rg) and Rext, is the Pcv equilibrium value designated CPAP. NBiPAP differentiates from NCPAP only for the fact that the Pcv equilibrium value varies cyclically between 2 different set values.

NIPPV is a mode or technique during which ACPs apply positive pressure waves to the CV level with set (controlled breaths) features and periodicity (frequency) alternating with the spontaneous breaths performed by the patient. These latter are assisted as in NCPAP. In the conventional ACPs, the pressure waves are generated by closing cyclically the Ron/off (Fext=0) during each inspiration so that the GRF is directly connected to the CNC through CV_1 and by opening the same Ron/off during each expiration so that the CNC is directly connected to outside by means of CV_2.

NSIPPV and NSIMV are modes or techniques during which ACPs, by detecting a triggering signal apply positive pressure waves at the level of CV (controlled breaths) in synchrony with the attempts of spontaneous breaths performed by the patient. In the conventional ACPs such pressure waves are generated as already described about the NIPPV mode. The parameters characterizing the above- mentioned pressure waves are set with the purpose of compensating the reduction in the breathing capability of the patient. In most cases, the triggering signal is represented by a variation experienced by a ventilatory quantity. One speaks about pressure or flow trigger in case the above-mentioned variation is associated to Pcv or to Fnc. At the beginning of the attempt of spontaneous breathing performed by the patient, Pcv decreases and Fnc increases with respect to the related values taken up during apnea. Fnc increases consequently to the Pes decrease which occurs at the beginning of the spontaneous inspiration whereas Pcv decreases as, by increasing Fnc, Fven and Rext being equal, Fext decreases. The most widespread triggering signal is the flow trigger which, in the conventional ACPs, is detected by inserting in series to CNC a PNT with the purpose of monitoring the Fnc signal. Such design solution involves 2 relevant functional drawbacks. The first drawback consists in that the detection of the beginning of attempt of spontaneous inspiration is not carried out on the signal most effective to the purpose (Fres), on the contrary on the Fnc signal. From what said previously about the HFNC mode, in fact, and by observing Figure 6, it results evident that Fnc does not coincide with Fres, the latter resulting to be equal to the difference between Fnc and Floss, according to the following expression:

Fres = Fnc - Floss (7)

Such drawback limits in relevant way the functional performances of the NSIPPV and NSIMV modes (disadvantage_4). The second drawback consists in that the insertion of a PNT involves inevitably both an increase in the fluidodynamical resistance which the patient has to contrast to inspire, with associated increase in the effort and the respiratory work and a more cumbersome and heavy CNC (disadvantage_5).

Exactly as already described in detail about the ACFs used in the HFNC mode, in order to optimize the clinical use of ACPs in the NCPAP, NBiPAP, NIPPV, NSIPPV and NSIMV modes, it is necessary to estimate with accuracy and precision both the parameters linked to the respiratory mechanics in the patient, thereamong the most important are the thoracic and pulmonary compliance and the thoracic and pulmonary resistances, and the various components of the effort and of the respiratory work performed by the patient. In order not to loose the advantages guaranteed by ventilation, such estimation or measurement must be performed "online" and that is simultaneously to the ventilation itself. In absence of such monitoring, any NIV apparatus or respiratory assistance system is not capable of providing such information on itself and then the clinical has not the possibility of modifying the parameters to be set of the NIV respiratory assistance system based upon the patient's requirements, but only based upon clinical or hemogasanalytical data, which often are late. The optimization of the ventilator parameters to be set, then, important involvements in managing the patient with respiratory insufficiency such as improving the patient conditions and avoiding that NIV fails and one has to have recourse to the mechanical ventilation. Any system for monitoring the respiratory mechanics in the patient (SMMRP) currently on the (conventional) market cannot be used in combination with conventional ACPs in the NCPAP, NBiPAP, NIPPV, NSI PPV and NSIMV modes, as it would provide unreliable results or results affected by unacceptable errors due to the fact that it is not able to measure and monitor the progress in time (signal) of the respiratory flow (Fres) of the patient. This constitutes a relevant drawback (disadvantage_6 the dual of the disadvantage_2 for ACFs), as the fact of having available the Fres signal is fundamental as therein most useful information is contained, and by processing them it is possible calculating all parameters of the respiratory mechanics in the patient, including those associated to the effort and to the respiratory work performed by the same. Any conventional SMMRP combined with the conventional ACPs in the NCPAP, NBiPAP, NIPPV, NSIPPV and NSIMV modes is not capable of measuring the Fres signal due to the flow losses occurring between CNC and the distal airways of the patient, mainly through the mouth and the nasal cavities. Due to such losses, as it appears evident by observing Figure 6, the Fres signal does not coincide with the Fven signal nor with the Fnc one (the only ones which can be measured and monitored by the conventional SMMRP systems), but, as it derives from (6) and (7) it results to be equal to the difference between the Fnc signal (in turn equal to the difference between the Fven signal and the Fext signal) and the total flow signal associated to the losses themselves (Floss), according to the following expression:

Fres = Fnc - Floss = (Fven - Fext) - Floss (8)

The problem is difficult to be solved due to the fact that the extent of such losses and then, the Floss signal, in absence of a specific application innovation, cannot be in any way estimated nor even controlled, by varying considerably, both between patient and patient and between different breaths performed by the same patient.

All techniques proposed up to now to solve the above-mentioned problem, which would allow overcoming disadvantage_6, are based upon monitoring the signal of some physical quantities correlated to the signal related to the variation in the pulmonary volume designated tidal volume (VC). The most widespread technique in clinical field is the so-called respiratory Impedance or Inductance Plethysmography (RIP), which measures the variation in the electric impedance or inductance of the thorax or abdomen induced by the expansion and the retraction of the same during breathing, by using two metal bands adhering to the patient body. Other techniques are under study, currently used exclusively in experimental field, which through the use of remote electromagnetic sensors (remote sensing) are potentially capable of monitoring the VC signal. Once determined the VC signal, the Fres signal is obtained by deriving the VC signal itself with respect to time. Both RIP and the other above-mentioned techniques do not provide sufficiently reliable performances, in the sense that the error associated to the measurement is not acceptable. Besides, they are quite expensive, particularly those associated to the remote sensing.

A technical problem underlying the present illustration is in the fact of making available an apparatus which could allow overcoming the 3 above-mentioned disadvantages of a ACF system by using a new apparatus according to the present illustration which can be integrated with all conventional apparatuses used in the NIV respiratory assistance by means of NC and in particular, with the conventional ACFs used in the HFNC mode.

This it obtained by providing an apparatus and a method according to the independent claims. Secondary features of the subject of the present illustration are defined in the corresponding depending claims.

The apparatus according to the present illustration allows measuring and monitoring "online" the respiratory mechanics in the patient with respiratory insufficiency subjected to NIV respiratory assistance in the HFNC mode.

Differently from other SMMRPs on the market, in fact, the apparatus according to the present illustration, is capable of performing the detections contemporarily to the NIV assistance in the HFNC mode, by allowing not to lose the advantages of the same during measurements and to verify instantaneously if the set Fven value determines the physiopathological conditions required for the HFNC mode (see Procedure for the optimum control of the HFNC mode by means of the apparatus according to the present illustration ).

More specifically, the apparatus according to the present illustration allows measuring, monitoring and storing the Fres signal and in synchronous mode with respect thereto, the signals related to the pressures at airways (Paw), pharyngeal (Pfa), oesophageal (Pes), gastric (Pga), internal to the respiratory orofacial mask (Pma) or sometimes even called facial mask integrated with CNC sealingly on the face (MORI).

In this way, it is possible calculating online and offline the main parameters of the respiratory mechanics in the patient (see subsequent TABLE) and guaranteeing the optimum control of the HFNC mode. The apparatus according to the present illustration is compatible to the production of a portable apparatus which can be used directly at the sick person's bed, thus by offering the guarantee of optimizing the respiratory assistance parameters instantaneously without having to wait for the offline data processing (see Procedure for the "online" monitoring of the respiratory mechanics in the patient in the HFNC mode and Procedure for the optimum control of the HFNC mode by means of the apparatus according to the present illustration).

The monitoring of the signals related to the pressure is performed by connecting, by means of a small tube, a sensible element of a differential pressure transducer (TPD) with the customized involved section. The monitoring of the signals related to the flow is performed by connecting, by means of 2 small pneumatic tubes, the 2 terminals of a pneumotachograph (PNT), connected in series to the duct inside thereof the flow to be measured flows, with the 2 sensible elements of a TPD. A PNT, in fact, is a device capable of generating between the 2 terminals thereof a difference in pressure proportional to the flow crossing it. In particular, according to the present illustration and to overcome the above- mentioned technical problem, the apparatus according to the present illustration includes a respiratory orofacial mask integrated with CNC and configured to be sealingly placed onto a user's face. The mask is provided with TPD and PNT.

In an embodiment of the present illustration, the mask is apt to be connected to a measurement and acquisition apparatus (AMA) interfaced with CV, CNC and with MORI (see Element H);

In an embodiment of the present illustration, the apparatus is configured to process data according to a dedicated software principle (SW), developed in MATLAB environment, residing in a portable computer (LAP) interfaced with AMA (see Element I).

Similarly, in relation to a ACP system, the above-mentioned technical problem, and in particular the above-mentioned three disadvantages of a known ACP system are solved and overcome by using a new apparatus according to the present illustration which can be integrated with all conventional apparatuses used in the NIV respiratory assistance by means of NC and in particular, with the conventional ACPs used in the NCPAP, NBiPAP, NIPPV, NSIPPV and NSIMV modes. More in particular, the apparatus according to the present illustration allows measuring and "online" monitoring the respiratory mechanics in the patient with respiratory insufficiency subjected to NIV respiratory assistance in the NCPAP, NBiPAP, NIPPV, NSIPPV and NSIMV modes.

Differently from other SMMRPs on the market, in fact, the apparatus according to the present illustration is capable of performing the detections contemporarily to the NIV assistance in the NCPAP, NBiPAP, NIPPV, NSIPPV and NSIMV modes, by allowing not to lose the advantages of the same during the measurements.

More specifically, the apparatus according to the present illustration allows measuring, monitoring and storing the Fres signal and in asynchronous mode with respect thereto, the signals related to the pressures at the airways (Paw), pharyngeal (Pfa), oesophageal (Pes), gastric (Pga), internal to the respiratory orofacial mask integrated with CNC sealingly on the face (MORI) (Pma). In this way, it is possible calculating online and offline the main parameters of the respiratory mechanics in the patient (see subsequent TABLE) in the NCPAP, NBiPAP, NIPPV, NSIPPV and NSIMV modes. The apparatus can be compatible with the production of a portable apparatus which can be used directly at the sick person's bed, thus by offering the guarantee to optimize the respiratory assistance parameters instantaneously without having to wait for the offline data processing (see procedure for the "online" monitoring of the respiratory mechanics in the patient in the NCPAP, NBiPAP, NIPPV, NSIPPV and NSIMV modes).

The monitoring of the signals related to the pressure can be performed by connecting, by means of a small tube, a sensible element of a differential pressure transducer (TPD) with the customized involved section. The monitoring of the signals related to the flow is performed by connecting, by means of 2 small pneumatic tubes, the 2 terminals of a pneumotachograph (PNT), connected in series with the duct inside thereof the flow to be measured flows, with the 2 sensible elements of a TPD. A PNT, in fact, is a device capable of generating between the 2 terminals thereof a difference in pressure proportional to the flow crossing it.

As shown in Figure 2, the apparatus according to an embodiment according to the present illustration is constituted by the following functional components:

1) respiratory orofacial mask integrated with CNC sealingly on the face (MORI) (see Element F);

2) measurement and acquisition apparatus (AMA) interfaced with CV, CNC and MORI (see Element H);

3) dedicated software (SW), developed in MATLAB environment, residing in a portable computer (LAP) interfaced with AMA (see Element I).

Additional advantages, features and use modes of the subject of the present illustration will result evident from the following detailed description of some preferred embodiments, shown by way of example and for limitative purposes.

It is however evident that each embodiment of the subject of the present illustration can have one or more advantages enlisted above; in any case it is not however requested that each embodiment has simultaneously all enlisted advantages.

The figures of the enclosed drawings will be referred to, wherein:

- figure 1 shows a scheme of a conventional ACF;

- figure 2 shows an apparatus including a mask according to an embodiment of the present illustration;

- figure 3 shows an additional apparatus including a mask according to an embodiment of the present illustration; - figure 4 shows schematically an operating principle of an apparatus according to an embodiment of the present illustration;

- figure 5 shows a scheme of a conventional ACP;

- figure 6 further shows schematically an operating principle of an apparatus according to an embodiment of the present illustration;

- figure 7 shows a side view di a mask according to an embodiment of the present illustration under worn condition;

- figure 8 shows a front view of the mask of figure 7;

- figure 9 shows a view of a mask according to an additional embodiment of the present illustration under worn condition;

- figure 10 shows a view of a detail in enlarged form of the detail X of figure 9;

- figure 1 1 shows a view from the top in schematic form of a mask according to the embodiment of figure 9;

- figures 12 and 13 show further views of a stop body for the mask of figure 9. By firstly referring to figure 3, an apparatus 10 according to an embodiment of the present illustration is shown.

According to the present illustration, an apparatus 10 provided with an orofacial mask is made available, suitable to be sealingly placed onto a user's face even in presence of NC.

More in particular an apparatus 10 is made available equipped with an orofacial mask apt to be sealingly placed on the face of a user even in presence of NC.

More in particular the apparatus includes a ventilation circuit (CV), a nasal cannula circuit and a flow generator (GRF),

- an orofacial mask (MORI) equipped with one or more passages for receiving one or more conduits of the nasal cannula circuit CNC and configured to create a sealed chamber when associated to the face of a user

- a first measurement device (PNT_1) connected in series to the ventilation circuit (CV) between the ventilation circuit itself (CV) and the flow generator (GRF) for measuring and monitoring a first signal or ventilation value (Fven);

- a second measurement device (PNT_3) associated to the orofacial mask (MORI); wherein the second measurement device is apt to measure a second signal or value representative a total flow loss which occurs inside the chamber of the orofacial mask(Floss);

- a calculator apt to calculate and/or quantify an actual ventilation value corresponding to, or based upon, the difference between the signal or ventilation value (Fven) and the signal or flow loss (Floss) value.

In other words, the apparatus 10 provides the insertion (integration) of a first measurement device (PNT_1) between GRF and CV which allows the precise and accurate measurement and the monitoring of the Fven signal. PNT_1 is connected to the corresponding TPD (TPD_1) thereof belonging to AMA. Such insertion allows overcoming the first shown drawback.

It is to be noted that the use of MORI and of the same PNT_1 (disadvantage^) together with a second measurement device (PNT_3) inserted directly in the main opening of MORI allow overcoming the above-mentioned disadvantage_2 and disadvantage_3. PNT_3 allows measuring and monitoring the Floss signal. PNT_3 is connected to the corresponding TPD (TPD_3) thereof belonging to AMA.

It is to be noted then that the apparatus according to the present illustration provides the use both of a facial mask (allowing to implement a sealing chamber for measuring Floss) and a nasal-cannula circuit.

In a preferred embodiment of the present illustration, as it is shown in Figure 3, the apparatus according to the present illustration is characterized by the following structure:

Element A : PNT_1 connected in series to CV between CV itself and GRF for measuring and monitoring the Fven signal. PNT_1 is connected to TPD_1 belonging to AMA;

Element B : (not present in case of ACF for the HFNC mode);

Element C : small connection tube between MORI and TPD_4, belonging to AMA, for measuring Pma;

Element D : oesophageal/gastric catheter with balloon, for measuring Pes and Pga, connected through two small connection tubes to corresponding TPD_6 and TPD_5;

Element E : pharyngeal catheter with multiple terminal holes, for measuring Pfa, connected through a small connection tube to TPD_ 7;

Element F : MORI on the main opening thereof PNT_3 (Element G) is inserted. It is equipped with several outputs with pneumatic sealing for the oesophageal/gastric (Element _D) and pharyngeal (Element _E) catheters, for the connector thereon the small tube for measuring Pma (Element C) is inserted and for CNCJine and CNC_ring. MORI is further equipped with systems for fastening to the patient's head which guarantee a complete adhesion of the same to the patient face and prevent the flow loss from the edges of the mask;

Element G : PNT_3 inserted directly in the main opening of MORI, for measuring and monitoring the flow directed from the MORI itself towards outside or loss flow (Floss). PNT_3 is connected to TPD_3 belonging to AMA;

Element H : AMA constituted by 7 TPD and by an apparatus for monitoring, filtering, sampling, converting and storing in synchronous way (AMS) 7 signals outgoing from TDP. The conversion is necessary so that the measuring unit associated to the values of the respective quantity is transformed by a potential difference (volt) to the one congruous for the pressure (cmH₂0) or for the flow (litres/minute or millilitres/second). Each one of the 7 TPD is connected, by means of a double or single small pneumatic tube, to the following devices or critical points already described previously:

1) PNT_1 , for measuring Fven (TPD_1);

2) PNT_2, for measuring Fext (TPD_2) (deactivated in case of ACF for the HFNC mode); 3) PNT_3, for measuring Floss (TPD_3);

4) connector outgoing from MORI, for measuring Pma (TPD_4);

5) oesophageal/gastric small probe, for measuring Pga (TPD_5);

6) oesophageal/gastric small probe, for measuring Pes (TPD_6);

7) pharyngeal small probe, for measuring Pfa (TPD_7). Element I : control and processing unit (LAP) connected to a display (MONITOR). In the LAP, interfaced with AMS, there are both SW for managing acquisition by means of AMS and the software for the analysis and "on-line" and "off-line" processing of the signals available from AMS developed in MATLAB environment. By considering the importance that Element F (MORI) assumes for the performances of the apparatus according to the present illustration, the geometrical and functional aspects thereof will be examined deeper hereinafter.

As it appear evident by observing Figure 3, MORI can be constituted by a facial mask with pneumatic seal, shown in section thereon 3 openings at as many outputs are performed. In the main opening (AP_1) the PNT_3 dedicated to the Floss monitoring is inserted. A second opening (AP_2) is necessary to make that the small tube connecting the oesophageal/gastric small probe to AMA could cross the MORI, by allowing to measure Pfa. Similarly, a third opening (AP_3) is necessary to make that the 2 small tubes connecting the pharyngeal small probe to AMA could cross the MORI, by allowing to measure Pes and Pga. Both AP_2 and AP_3 are equipped with a mechanism allowing to activate the perfect pneumatic sealing at the same and to deactivate the same, with the purpose of making to flow depending upon the patient's needs and the procedure described hereinafter. Such mechanism consists in a hollow conical stiff connector surrounding the small tubes connected to the respective small probes and which can be inserted by interlocking into the AP_2 and AP_3 themselves. In order to deactivate such mechanism it is sufficient extracting the above-mentioned connector from AP_2 and AP_3.

In Figure 3 the presence of an air bearing and 2 hooks for as many elastic belts is highlighted, both applied to the MORI. The bearing, extending along whole edge in contact with the patient, is equipped with an outer side tongue (adhesive tape- bandage) perfectly adhering to the facial profile even in presence of CNCJine or CNC_ring (see also Figure 9 and Figure 10). The belts, the length thereof can be adjusted depending upon the patient size, are hooked to the MORI in 2 different points, an upper and a lower one, so as to keep stable the position of MORI itself with respect to the patient head. The bearing and the belts guarantee a perfect pneumatic sealing (absence of flow losses through the side edge of the MORI under any operating condition), without worsening comfort for the patient.

The correct procedure for applying the MORI provides the following sequential procedures:

1) deactivating the pneumatic sealing mechanism on AP_2 and AP_3;

2) sliding of the 2 small tubes connected to the small probes for measuring Pfa, Pes and Pga so as to remove MORI from the patient airways and to allow the manoeuvrability required to perform points 3 and 4; 3) inserting the oesophageal/gastric small probe required for measuring Pes and Pga through the nasal nostrils or the oral cavity;

4) inserting the pharyngeal small probe required for measuring Pfa through the nasal nostrils or the oral cavity;

5) inserting NC in situ required for supplying the flow to the patient;

6) sliding the MORI as far as positioning it in contact with the facial surface of the patient;

7) adhering with perfect pneumatic sealing the MORI to the facial surface of the patient according to what just described about the functions associated to the bearing equipped with outer side tongue and to the 2 belts;

8) activating the pneumatic sealing mechanism on AP_2 and AP_3.

It is important specifying that the MORI application according to the 8 just described procedures, being necessary for carrying out the Procedure for the "online" monitoring of the respiratory mechanics in the patient in the HFNC mode and for the Procedure for the optimum Control of the HFNC mode, both described hereinafter, is finalized to optimize the diagnostic and functional performances of the apparatus according to the present illustration. In case such performances are not requested continuously, but only periodically during brief time intervals, the MORI application is reserved only to such time intervals. In this case, outside such "diagnostic" and "functional" time intervals, it will be sufficient to perform the first 5 procedures only of the just-described procedure.

- Procedure for the "online" monitoring of the respiratory mechanics in the patient in the HFNC mode

MORI represents the specific applicative innovation required to solve the problem of measuring and monitoring the Floss signal. By applying MORI and that is, a sealing orofacial mask on the patient face surrounding nose and mouth, it is possible detecting, measuring and monitoring the flow losses and that is, the Floss signal both during inspiration and expiration. In this way, the Fres signal results to be equal to the difference between the Fven signal coming from GRF and the total loss flow (Floss), in perfect agreement with (1).

Still more in particular, in relation to the orofacial mask (MORI) it is noted that, as said, it is configured for creating a pneumatic sealing with the patient face, notwithstanding the presence of conduits of the nasal cannula circuit CNC. In order to implement the pneumatic sealing a lot of technical solutions within the comprehension of the person skilled in the art can be provided.

In particular MORI can include a soft plastic body shaped like a hollow or shell or cap, and provided on an edge 100 intended to be placed on the face of a patient by means of an adhesive tape of known type and adequate to fasten MORI sealingly.

The selection of MORI plastic material is made so as to allow a maximum adaptability and adherence of the edge 100 onto the user face.

In an embodiment such as the one of figure 7 and figure 8, in order to allow the passage of the conduits feeding the nasal cannulae (NC), MORI is equipped with an opening in the lower area wherein the conduits of the nasal-cannula circuit (CNC) insert sealingly. In order to guarantee the sealing, a stopper 102 or cover can be provided wherein the conduits are inserted by sliding until maximum adhesion.

A similar stopper 102 can be provided for the small tubes for monitoring the gastric, oesophageal and pharyngeal pressure.

In particular, the stopper 102 is a rubber disc equipped with holes, in case with conical section, with decreasing diameter as one goes towards the inside of the facial mask. The conduits of the nasal cannula circuit and/or the small tubes are inserted into the holes as far as obtaining maximum adhesion. The stopper is then inserted by pressure, with respective maximum adhesion in the hole obtained in the mask.

It is to be meant that such technical solutions to allow implementing a watertight or pneumatic sealed mask are all within the comprehension of the person skilled in the art.

For example, in an alternative embodiment, like the one of figure 9 and 10, the use of a stop body 1 10 is provided shaped like a block or parallelepiped or any other adequate form, which is placed adjacent to the mask at respective recesses intended to accommodate the conduits of the nasal cannula circuit (CNC).

The stop body is a body with a central hole interposed between two half-portions connected by the central hinge (see figures 9-13). The stop body 1 10 is opened to allow positioning the conduits of the nasal cannula circuit CNC, and then re-closed and fastened, for example by means of adhesive tape or similar adhesive application. Glue can be provided on one side of the stop body 1 10 intended to be adhered to the edge of the MORI mask and on one side destined to be placed in contact with the skin of a user.

It is to be noted that it is advisable that the opening side of the stop body 1 10 is opposite with respect to the side directed towards the patient, to avoid a surface continuity with the recesses for the conduits of the nasal cannula circuit (CNC).

It is also to be noted that the use of a stop body 1 10 as the one described is of practical use for a user who has to wear the MORI, in fact it is sufficient for the operator to open the stop body and make to slide therein the conduits of the nasal cannula circuit (CNC) as far as the stop body adheres against the user face and the mask.

A) "Timing" identification

By measuring, monitoring and storing in synchronous way the Fven signal and the Floss signal and by applying continuously (1), it is possible having available "online" and "off-line" the Fres signal and by integration with respect to time, even the VC signal. In particular, "timing" and that is, the start and end of the inspiration phase, being defined as the 2 consecutive time instants thereat Fres assumes the null value, from (1), are perfectly determined from the following equality:

Fven = Floss (2)

From (2) it results evident that the start and end of the inspiration phase result to be identified by the 2 consecutive time instants thereat the Fven signal assumes the same value of the Floss signal.

The perfect pneumatic sealing of MORI can be controlled by verifying that the value of the inspiratory tidal volume (VCi), which can be calculated as the integral of the Fres signal with respect to the time during inspiration is identical to the value of the expiratory tidal volume (VCe), which can be calculated as the integral of the Fres signal with respect to time during expiration. An additional verification of the perfect pneumatic sealing of MORI can be performed by monitoring and checking the Pma signal.

B) Description of the parameters of the respiratory mechanics in the patient The monitoring of the respiratory mechanics is implemented by the apparatus according to the present illustration by means of detecting and measuring in synchronous way the Paw, Pfa, Pes, Pga and Fres signals, and by processing them in suitable way it is possible calculating the main parameters linked to the respiratory mechanics in the patient and the various components of the effort and the respiratory work performed by the patient himself/herself. By integrating in time, expressed in seconds, the Fres signal, whose values are expressed in millilitres (ml) per second (s), the VC signal in ml is obtained.

Herebelow, the list of the main parameters is shown that is possible to be calculated by processing the above-mentioned signals:

1) Start-Inspiration time (Tstart_ins);

2) End-Inspiration time (Tend_ins);

3) Inspiration duration (Tl); 4) Expiration duration (TE);

5) Ratio between Tl and TE (TI:TE);

6) Breath duration (Ttot);

7) Respiratory frequency (FR);

8) Inspiratory tidal volume (VCi); 9) Expiratory tidal volume (VCe);

10) Minute volume (Vol_min);

1 1) VCi/TI ratio (VCi/TI);

12) VCi/TE ratio (VCi/TE);

13) Start-lnspiratory effort time (Tstart_drop_Pes); 14) Time interval between Tstart_ins and Tstart_drop_Pes (Tdelay);

15) Intrinsic positive end-expiratory pressure (PEEPi);

16) Inspiratory variation in the oesophageal pressure p Pes);

17) Transpulmonary pressure at the end of inspiration (Pp_end_ins); 18) Thoracic resistance (Rt);

19) Pulmonary resistance (Rp);

20) Total pulmonary resistance (RI_tot);

21) Thoracic compliance (Ct); 22) Pulmonary compliance (Cp);

23) Dynamic pulmonary compliance (Cl_dyn);

24) Thoracic compliance in relaxation (Ct_relax);

25) Resistive component of inspiratory effort (Pressure Time Product) (PTP_res); 26) Elastic component (pulmonary expansion) of inspiratory PTP (PTP_elas_pulm);

27) Elastic component (thoracic expansion) of inspiratory PTP (PTP_elas_thorac);

28) Total elastic component of inspiratory PTP (PTP_elas_tot); 29) Elastic component linked to PEEPi of inspiratory PTP (PTP_PEEPi);

30) Inspiratory total PTP (PTPJot);

31) PTPJot per minute (PTP_tot_min);

32) Resistive component of inspiratory work (Work Of Breathing) (WOB_res);

33) Elastic component (pulmonary expansion) of inspiratory WOB (WOB_elas_pulm);

34) Elastic component (thoracic expansion) of inspiratory WOB (WOB_elas_thorac);

35) Total elastic component of inspiratory WOB (WOB_elas_tot); 36) Elastic component linked to PEEPi of inspiratory WOB (WOB_PEEPi);

37) Inspiratory total WOB (WOBJot);

38) WOBJot per minute (WOB_tot_min);

39) WOBJot per litre (WOBJotJit); The above-mentioned disadvantage 4, disadvantage 5 and disadvantage 6 can be overcome by using MORI and 3 PNT. The first PNT (PNT_1) is inserted between GRF and CV_1 and it allows the Fven measurement. The second PNT (PNT_2) is inserted between the output of CV_2 and outside and it allows the Fext measurement. The third PNT (PNT_3) is inserted directly in the main opening of MORI and it allows the Floss measurement. PNT_1 , PNT_2 and PNT_3 are connected to their respective TPD (TPD_1 , TPD_2 and TPD_3) belonging to AMA. In particular, as far as the synchronism between the controlled breaths and the attempts of the spontaneous breaths are concerned, the apparatus according to the present illustration, through the reliable Procedure for the "timing" Identification described hereinafter, offers, intrinsically, optimum performances in terms of effectiveness, response time and auto-trigger associated to the trigger signal. Furthermore, the absence of a PNT inserted between the intersection and NCs, as used in the NIV synchronized conventional modes or techniques, allows obtaining 2 considerable advantage. The first advantage consists in the drastic reduction in the resistance (and then even in the associated effort and respiratory work) which the patient has to contrast for generating an upper inspiratory flow than the threshold fixed for the "trigger". The second advantage consists in the use of circuits connecting the NCs and the clearly less cumbersome and lighter intersection.

As it is shown in Figure 3, the apparatus according to an embodiment of the present illustration can be characterized by the following structure:

Element A : PNT_1 connected in series to CV between CV_1 and GRF for measuring and monitoring the Fven signal. PNT_1 is connected to TPD_1 belonging to AMA;

Element B : PNT_2 connected in series to CV between CV_2 and outside for measuring and monitoring the Fext signal. PNT_2 is connected to TPD_2 belonging to AMA; Element C : small connection tube between MORI and TPD_4, belonging to AMA, for measuring Pma;

Element F : MORI on the main opening thereof the PNT_3 (Element G) is inserted. It is equipped with several outputs with pneumatic sealing for the oesophageal/gastric (Element_D) and pharyngeal (Element_E) catheters for the connector thereon the small tube is inserted for measuring Pma (Element C) and for CNCJine and CNC_ring. MORI is further equipped with systems for fastening to the patient head which guarantee a complete adhesion of the same to the patient face and prevent the flow loss from the mask edges;

Element H : AMA constituted by 7 TPD and by an apparatus for monitoring, filtering, sampling, converting and storing in synchronous way (AMS) the 7 signals outgoing from TDP. The conversion is necessary so that the measuring unit associated to the values of the respective quantity is transformed by a potential difference (volt) to the one congruous for the pressure (cmH₂0) or for the flow (litres/minute or millilitres/second). Each one of the 7 TPD is connected, by means of a double or single small pneumatic tube, to the following devices or critical points already described previously:

1) PNT_1 , for measuring Fven (TPD_1);

2) PNT_2, for measuring Fext (TPD_2);

3) PNT_3, for measuring Floss (TPD_3);

4) connector outgoing from MORI, for measuring Pma (TPD_4); 5) oesophageal/gastric small probe, for measuring Pga (TPD_5);

6) oesophageal/gastric small probe, for measuring Pes (TPD_6); 7) pharyngeal small probe, for measuring Pfa (TPD_7).

Element I : control and processing unit (LAP) connected to a display (MONITOR). In the LAP, interfaced with AMS, there are both SW for managing the acquisition by means of AMS, and the software for the analysis and "on-line" and "off-line" processing of the signals available from AMS developed in MATLAB environment.

By considering the relevance that the Element G (MORI) assumes for the performances of the apparatus according to the present illustration, hereinafter the geometric and functional aspects thereof will be examined deeper.

As it appears evident by observing Figure 3, MORI is constituted by a facial mask with pneumatic sealing, shown in section, whereon 3 openings at corresponding as many outputs are performed. In the main opening (AP_1) PNT_3 dedicated to the Floss monitoring is inserted. A second opening (AP_2) is necessary to make that the small tube connecting the oesophageal/gastric small probe to AMA could cross the MORI, by allowing to measure Pfa. Similarly, a third opening (AP_3) is necessary to make that the 2 small tubes connecting the pharyngeal small probe to AMA could cross the MORI, by allowing to measure Pes and Pga. Both AP_2 and AP_3 are equipped with a mechanism allowing to activate the perfect pneumatic sealing at the same and to deactivate it, with the purpose of making to flow depending upon the patient's needs and the procedure described hereinafter. Such mechanism consists in a hollow conical stiff connector surrounding the small tubes connected to the respective small probes and which can be inserted by interlocking into the AP_2 and AP_3 themselves. In order to deactivate such mechanism it is sufficient extracting the above-mentioned connector from AP_2 and AP_3.

In Figure 3 the presence of an air bearing and 2 hooks for as many elastic belts is highlighted, both applied to the MORI. The bearing, extending along the whole edge in contact with the patient, is equipped with an outer side tongue (adhesive tape-bandage) perfectly adhering to the facial profile even in presence of CNC_line or CNC_ring (see also Figure 9 and Figure 10). The belts, the length thereof can be adjusted depending upon the patient size, are hooked to the MORI in 2 different points, an upper one and a lower one, so as to keep stable the position of MORI itself with respect to the patient head. The bearing and the belts guarantee a perfect pneumatic sealing (absence of flow losses through the side edge of MORI under any operating condition), without worsening the comfort for the patient. The correct procedure for applying the MORI provides the following sequential procedures:

1) deactivating the pneumatic sealing mechanism on AP_2 and AP_3;

2) sliding of the 2 small tubes connected to the small probes for measuring Pfa, Pes and Pga so as to remove MORI from the patient airways and to allow the manoeuvrability required to perform points 3 and 4;

3) inserting the oesophageal/gastric small probe required for measuring Pes and Pga through the nasal nostrils or the oral cavity;

5) inserting NCs in situ required for supplying the flow to the patient;

8) activating the pneumatic sealing mechanism on AP_2 and AP_3.

It is important specifying that the MORI application according to the 8 just described procedures, being necessary for carrying out the Procedure for the "online" monitoring of the respiratory mechanics in the patient in the NCPAP, NBiPAP, NIPPV, NSIPPV and NSIMV modes, described hereinafter, is finalized to optimize the diagnostic and functional performances of the apparatus according to the present illustration. In case such performances are not requested continuously, but only periodically during brief time intervals, the MORI application is reserved only to such time intervals. In this case, outside such "diagnostic" and "functional" time intervals, it will be sufficient to perform the first 5 procedures of the just-described procedure.

- Procedure for the "online" monitoring of the respiratory mechanics in the patient in the NCPAP, NBiPAP, NIPPV, NSIPPV and NSIMV modes MORI represents the specific applicative innovation required to solve the problem of measuring and monitoring the Floss signal. By applying MORI and that is, a sealing orofacial mask on the patient face surrounding nose and mouth, it is possible detecting, measuring and monitoring the flow losses and that is, the Floss signal both during inspiration and expiration. In this way, the Fres signal results to be equal to the difference between the Fnc signal present in CNC and the total loss flow (Floss), in perfect agreement with (8).

A) "Timing" identification

By measuring, monitoring and storing in synchronous way the Fven signal, the Fext signal and the Floss signal and by applying continuously (8), it is possible having available "on-line" and "off-line" the Fres signal and by integration with respect to time, even the VC signal. In particular, "timing" and that is, the start and the end of the inspiration phase, being defined as the 2 consecutive time instants thereat Fres assumes the null value, from (8), are perfectly determined from the following equality:

Fnc = Floss (9)

From (9) it results evident that the start and the end of the inspiration phase result to be identified by the 2 consecutive time instants thereat the Fnc signal assumes the same value of the Floss signal.

The perfect pneumatic sealing of MORI can be controlled by verifying that the value of the inspiratory tidal volume (VCi), which can be calculated as the integral of the Fres signal with respect to time during inspiration is identical to the value of the expiratory tidal volume (VCe), which can be calculated as the integral of the Fres signal with respect to time during expiration. An additional verification of the perfect pneumatic sealing of MORI can be performed by monitoring and checking the Pma signal.

B) Description of the parameters of the respiratory mechanics in the patient

The monitoring of the respiratory mechanics is implemented by the apparatus according to the present illustration by means of detecting and measuring in synchronous way the Paw, Pfa, Pes, Pga and Fres signals, and by processing them in suitable way it is possible calculating the main parameters linked to the respiratory mechanics in the patient and the various components of the effort and the respiratory work performed by the patient himself/herself. By integrating in time, expressed in seconds, the Fres signal, whose values are expressed in millilitres (ml) per second (s), the VC signal in ml is obtained.

1) Start-Inspiration time (Tstart_ins);

2) End-Inspiration time (Tend_ins);

3) Inspiration duration (Tl);

4) Expiration duration (TE);

5) Ratio between Tl and TE (TI:TE); 6) Breath duration (Ttot);

7) Respiratory frequency (FR);

8) Inspiratory tidal volume (VCi);

9) Expiratory tidal volume (VCe);

10) Minute volume (Vol_min); 1 1) Ratio VCi/TI (VCi/TI);

12) Ratio VCi/TE (VCi/TE);

13) Start-lnspiratory effort time (Tstart_drop_Pes);

14) Time interval between Tstart_ins and Tstart_drop_Pes (Tdelay);

15) Intrinsic positive end-expiratory pressure (PEEPi); 16) Inspiratory variation in the oesophageal pressure (□ Pes);

17) Transpulmonary pressure at the end of inspiration (Pp_end_ins);

18) Thoracic resistance (Rt); 19) Pulmonary resistance (Rp);

20) Total pulmonary resistance (RI_tot);

21) Thoracic compliance (Ct);

22) Pulmonary compliance (Cp); 23) Dynamic pulmonary compliance (Cl_dyn);

24) Thoracic compliance in relaxation (Ct_relax);

25) Resistive component of inspiratory effort (Pressure Time Product) (PTP_res);

26) Elastic component (pulmonary expansion) of inspiratory PTP (PTP_elas_polm);

28) Total elastic component of inspiratory PTP (PTP_elas_tot);

29) Elastic component linked to PEEPi of inspiratory PTP (PTP_PEEPi); 30) Inspiratory total PTP (PTP_tot);

31) PTP_tot per minute (PTP_tot_min);

32) Resistive component of inspiratory work (Work Of Breathing) (WOB_res);

33) Elastic component (pulmonary expansion) of inspiratory WOB (WOB_elas_pulm); 34) Elastic component (thoracic expansion) of inspiratory WOB (WOB_elas_thorac);

35) Total elastic component of inspiratory WOB (WOB_elas_tot);

36) Elastic component linked to PEEPi of inspiratory WOB (WOB_PEEPi); ) Inspiratory total WOB (WOBJot); ) WOBJot per minute (WOB_tot_min); ) WOBJot per litre (WOBJotJit);

TABLE

Main parameters of the respiratory mechanics in the patient

Procedure for the optimum Control of the HFNC mode

The purpose of the HFNC mode is to supply to the patient, through NCs, a continuous flow of oxygen-enriched air so as to create inside the oro-pharyngeal cavity a chamber with positive continuous pressure. In this way, the "dead space" is drastically reduced and that is, the volume inside the CV terminated with NCs which does not contribute in effective way to the gaseous exchange at pulmonary level. This is very important, as at the beginning of each inspiration the portion of the immediately available oxygen enriched air is considerably higher. Furthermore, during expiration the outgoing of air enriched with carbon dioxide through the mouth is favoured by the high pressure gradient existing between the oropharyngeal cavity and outside.

The above-mentioned positive intrinsic qualities of the HFNC mode often are not exploited or even nullified due to the fact that there are not yet consolidated and reliable criteria leading to the optimum selection of the Fven value to be set. Nowadays, in fact, in most cases, the clinical personnel selects such value by basing exclusively upon empiric formula which keep into account the patient features and, in particular, his/her body weight. Besides, the clinician has no possibility of modifying the Fven value to be set based upon the current patient requests, but only based upon clinical or hemogasanalytical data, which often are late.

In order to optimize the HFNC mode, then the need arises for identifying objective and effective criteria correlated to some measurement which can be obtained from the monitored signals allowing to set the Fven value at the beginning of the ventilatory treatment and to adjust it continuously, by adapting it to the current requirement of the patient, during the treatment itself.

An air flow can cross any conduit by following 2 different directions which are discriminated by the different (positive or negative) algebraic sign associated to the flow itself. In our case, the scheme thereof is shown in Figure 4, by considering MORI as point ("node") wherein 3 different flows (Fven, Floss, Fres) intersect, it is possible deducing as follows. Fven is a unidirectional flow, that is, always flowing (both during apnea, and during inspiration and during expiration) in the same direction from the ventilation circuit to MORI. Such direction, by definition, is associated to the positive algebraic sign. Floss is a bidirectional flow, that is, which can flow, in different time instants, in the direction from inside to outside of MORI (positive algebraic sign) or viceversa (negative algebraic sign). Fres, which assumes null values during apnea, is a bidirectional flow, flowing from NCs to the lungs during inspiration (inspiratory flow: positive algebraic sign) or from the lungs to MORI during expiration (expiratory flow: negative algebraic sign). In Figure 4, outside the relative conduits, arrows are shown designating the directions of the 3 flows associated to the respective algebraic signs. By expliciting Floss from (1), the following expression is obtained:

Floss = Fven - Fres (3)

By applying (3) to what said previously, it is possible deducing the following considerations about the direction and consequently about the Floss algebraic sign. During apnea, Floss assumes surely positive values as Fven is always positive and Fres is equal to zero. During expiration, Floss assumes surely positive values as Fven is always positive and Fres is always negative. During inspiration, Floss assumes positive or negative values in the time instants wherein the Fres value generated by the patient is lower or higher than the set Fven value.

The primary purpose of the HFNC mode is to make that, during inspiration, only the oxygen-enriched flow coming from CNC (Fven) contributes to the VCi formation, by avoiding then the contribution of the not oxygen enriched flow directed from outside towards inside of MORI (negative Floss). From what said previously, it results clear that, in order to guarantee the above-mentioned primary purpose, it is necessary to make that the value set for Fven is higher than the Fres maximum or peak value required by the patient during inspiration. If this occurs, according to (3), the difference between Fven and Fres is always positive in any instant of inspiration. Differently, the patient would be obliged to take a flow portion from the outer environment which results to be not oxygen-enriched. Such circumstance is to be avoided since, as already said, collides with the primary purpose of the HFNC mode which provides the inspiration of fully oxygen-enriched air coming from CNC. Should this circumstance take place, it would be characterized by time intervals during which Floss assumes negative values, characterizing indeed a flow directed from outside towards inside of MORI. To avoid such circumstance, then, the condition which however should be guaranteed is the one whereby, during inspiration, Floss assumes always positive values characterizing a flow directed from inside towards outside of MORI, according to the following expression:

Floss > 0 (during inspiration) (4) Furthermore, by considering that a flow is always directed between two points therebetween there is a positive pressure difference, the condition (4) is associated to the following condition:

Pma > 0 (during inspiration) (5)

In order that Floss is directed from inside towards outside of MORI, in fact, Pma has to be necessarily higher than the atmospheric pressure pressure which, by assuming the null value by definition, lead to (5). The apparatus according to the present illustration, equipped with MORI, by continuously monitoring the Floss signal and the Pma signal, allows verifying "on-line" the fulfilment of the primary purpose of the HFNC mode during all inspirations. Once set the Fven initial value, by basing upon safety criteria for the patient and upon his/her physiopathologic and clinical conditions, it will be sufficient to verify from the monitoring that the current Fven value is so that the minimum or peak values which Floss and Pma assume during inspiration are all positive and that is, higher than zero. In the contrary case, it will be sufficient to increase the value set for Fven. Obviously, Fven can and has to be adjusted at the end of each breath ("breath to breath" check) by making that the average difference between the above-mentioned peaks of Floss and Pma and the zero line is sufficient to guarantee an appropriate safety margin for satisfying the primary purpose. In any case, how much one can go beyond the value determined by the above-mentioned safety margin is to be verified by checking both VCi and the critical levels of Pes and Pfa, and the values of the features of the mechanic, the effort and the respiratory work. The subject of the present illustration has been sofar described with reference to preferred embodiments thereof. It is to be meant that other embodiments belonging to the same inventive core may exist, all within the protection scope of the here-below reported claims.

Claims

1. An apparatus (10) for a pulmonary non-invasive ventilation, wherein the apparatus (10) includes a ventilation circuit (CV), a nasal cannula circuit (CNC) and a flow generator (GRF), and wherein the apparatus (10) further includes

- an orofacial mask (MORI) provided with one or more passages or recesses for receiving one or more conduits of the nasal cannula circuit (CNC) and configured to create a sealed chamber when associated to the face of a user;

- a first measurement device (PNT_1) connected in series with the ventilation circuit (CV) between the ventilation circuit itself (CV) and the flow generator (GRF) for a measurement and monitoring of a first ventilation signal or ventilation physical magnitude (Fven) ;

- a second measurement device (PNT_3) associated with the orofacial mask (MORI); wherein the second measurement device is apt to measure a second signal or value representative of a flow loss (Floss) that occurs in the airtight chamber of the mask orofacial;

- a calculator apt to calculate and/or to quantify at least an actual ventilation value corresponding to, or based on, a difference between the ventilation signal or ventilation physical magnitude (Fven) and the signal or physical magnitude of loss of flow (Floss).

2. The apparatus according to claim 1 , wherein the first measurement device and the second measurement device are flow transducers and apt to measure a flow of oxygen-enriched air.

3. The apparatus according to claim 1 or 2, wherein the first measurement device and the second measurement device are connected to respective pressure transducers (TPD_1 ; TPD_3)

4. The apparatus (10) according to any one of the preceding claims, comprising an oesophageal catheter and a gastric catheter in order to allow a measurement of oesophageal pressure (Pes) and gastric pressure (Pga), wherein each catheter is connected to respective pressure transducers (TPD_6 and TPD_5).

5. The apparatus (10) according to any one of the preceding claims, further comprising a pharyngeal catheter configured to allow measuring of pharyngeal pressure (PFA), wherein said pharyngeal catheter is connected to a respective pressure transducer (TPD_ 7).

6. The apparatus (10) according to any one of the preceding claims, wherein said ventilation circuit is a first ventilation circuit or primary ventilation circuit, and wherein the apparatus (10) comprises a second ventilation circuit (CV_2) and a third measurement device apt to measure an external flow (Fext) which passes through the second ventilation circuit, wherein the second ventilation circuit is arranged to cross the first ventilation circuit (cv_1) in an intersection area.

7. The apparatus (10) according to any one of the preceding claims, comprising a measuring system comprising a plurality of said pressure transducers (TDP) and a system for monitoring and filtering, sampling, converting and providing synchronous storage (AMS) of output signals from the pressure transducers (TDP).

8. A method for calculating at least one signal of breathing in a system of pulmonary non-invasive ventilation, wherein the method includes the steps of

- creating a sealed chamber on the outside of the face of a user between the face of a user and a orofacial mask (MORI) provided with one or more passages or recesses for receiving one or more conduits of a nasal cannula circuit ( NC);

- measuring a ventilation signal, or ventilation physical magnitude (Fven) of an air flow which is generated by a flow generator (GRF) and fed to a user via the nasal cannula circuit (NC),

- measuring a signal or physical magnitude representative of a flow loss (Floss) that occurs in the chamber of the orofacial mask (MORI);

- calculating and/or quantifying an actual ventilation value corresponding to, or based on, a difference between the ventilation signal or ventilation physical magnitude (Fven) and the signal or physical magnitude of a flow loss (Floss).

9. The method according to claim 8, wherein a calculation and/or quantification of the actual ventilation value (Fres) is performed by integration through time.

10. The method according to claim 9, wherein beginning and end of an inhalation phase are monitored, said beginning and said end being defined as the two consecutive time instants thereat the actual ventilation signal or ventilation physical magnitude (Fres ) is equal to zero value and the flow loss is equal to the ventilation signal or ventilation physical magnitude according to the formula

Fven = Floss (2)

1 1. The method according to claim 9 or 10, wherein in order to check a pneumatic seal of the mask orofacial (MORI), a value of the inspiratory tidal volume (VCi) is calculated as the integral of the signal of the actual ventilation value (Fres) through time during inspiration when it is identical to the value of expiratory tidal volume (VCE), calculated as the integral of the signal of Fres through time during expiration and/or by monitoring and checking the signal of a pressure in the chamber of the mask (Pma).

12. The method according to any one of the preceding claims 8 to 1 1 , wherein it performs a synchronous detection and measurement of one or more pressure signals to airways (Paw), pharyngeal pressure (PFA), oesophageal pressure (Pes), gastric pressure (Pga) in combination with a calculation of a real breathing flow.

13. The method according to any one of claims 8 to 12, wherein said ventilation circuit is a first circuit for ventilation and the method further provides measuring a signal or a physical magnitude relating to an external flow (Fext) which passes through a second ventilation circuit arranged to cross the first ventilation circuit in an intersection area.

14. The method according to any one of the preceding claims 8 to 13, the method providing to feed through the nasal cannulas a continuous flow of oxygenated air such as to establish within the oral cavity and pharynx a zone with continuous positive pressure and reduce a "dead space" that is the volume inside the CV ending with CN that do not actually help gas exchange in the lungs.

15. The method according to any one of the preceding claims 8 to 14, the method providing to supply oxygen-enriched air such that a ventilation signal or ventilation physical magnitude (Fven) is higher than the maximum or peak value of the breathing signal or magnitude (Fres) requested by the patient during inhalation.

16. The method according to any one of the preceding claims 8 to 15, wherein it occurs that during inhalation, a signal of flow loss (Floss) has always positive values that characterize a flow directed from inside to outside of the mask orofacial (MORI) and/or that a pressure in the chamber of the mask (Pma) is greater than the atmospheric pressure.

17. The method according to any of claims 8 to 16, wherein said method is a nondiagnostic method which is performed outside the human body.