Patent Description:
In particular, the ventilation system is suitable for application to CPAP (Continuous Positive Airway Pressure) breathing helmets. By operating in this way, it is possible to provide artificial ventilation to a patient with respiratory difficulties destined for so-called "sub-intensive" therapies.

Breathing helmets of the type with continuous positive pressure mechanical ventilation are known, which allow to provide artificial ventilation to a patient with breathing difficulties. There are numerous models produced by different companies and all have an appearance reminiscent of a diver's helmet, in association with a plurality of tubes that carry oxygen and expel carbon dioxide. Known type helmets are completely transparent and fasten around the head with straps that can pass under the armpits. They are portable devices, sufficiently comfortable and light, which have a fairly low cost for a medical device. The internal volume is several liters (it allows the easy movement of the head) and the most comfortable models weigh a few hundred grams; they are all equipped with various safety systems, such as gauges to measure the internal pressure and anti-suffocation valves. Several clinical studies have shown its effectiveness in treating various conditions that determine respiratory failure, therefore CPAP helmets are versatile and potentially very useful devices to cope with the COVID-<NUM> emergency. These tools are used for patients who require respiratory assistance but are not so severe that ICU (intensive care unit) admission is required.

<CIT> discloses an artificial ventilation system.

Artificial ventilation systems of the known type, however, require very frequent checks by nurses or doctors, for their supervision and monitoring. The regulation of the flows of the respirators of the known systems occurs mostly according to manual control processes, thus requiring the almost constant presence of an operator, that is to say of specialized health personnel. Fully automatic and at the same time extremely safe and efficient artificial ventilation systems are not known.

Therefore, there is a need to define an artificial ventilation system and a related control method that are free from the aforementioned drawbacks.

An object of the present invention is to provide a fully automated artificial ventilation system which does not require frequent checks by specialized medical personnel.

Therefore, according to the present invention, an artificial ventilation system is provided with the characteristics set out in the attached independent product claim.

A control method of the artificial ventilation system is described, but not claimed.

This method allows automatic control of the entire artificial ventilation system and implements innovative control strategies.

Further preferred and / or particularly advantageous ways of implementing the invention are described according to the characteristics set forth in the attached dependent claims.

The invention will now be described with reference to the attached drawings, which illustrate some examples of non-limiting implementation of the housing element, in which:.

With reference now to <FIG>, a first embodiment of the artificial ventilation system <NUM> according to the present invention is described below by way of example only. The system comprises a respiratory helmet <NUM>, for example, a respiratory helmet so-called CPAP (acronym from the English Continuous Positive Airway Pressure) of a known type and therefore not further described except for what will be said below about a device that can be implemented within it. The respiratory helmet <NUM>, worn by a patient who needs artificial ventilation, will be fed by a mixture of air and oxygen and possibly also by a secondary medical gas, for example ozone by means of a supply duct <NUM>, according to the hydraulic scheme that will be described, and the air containing carbon dioxide emitted by the patient will be expelled through the exhaust duct <NUM>.

The supply of the air / oxygen mixture is carried out in a gas supply system <NUM>. In particular, the supply is achieved thanks to a suitable suction means which, in the example of <FIG>, is an ejector <NUM> which works by applying the known Venturi principle. The air is taken from the external environment while the oxygen is contained under pressure in a tank <NUM>. Preferably, the tank <NUM> could be a compressed oxygen cylinder. A first control valve <NUM> regulates the mixing between air or oxygen and a first duct <NUM>' and a second duct <NUM>" branch off from it. The first duct <NUM>' constitutes the supply line to the ejector <NUM>, while the second duct <NUM>" feeds the secondary flow to the ejector <NUM>. As known, for the operation of the ejector according to the Venturi principle, the two flows at the inlet to the ejector <NUM> must have different pressures, since the fluid at a higher pressure will have to "drag" the fluid at a lower pressure, having a single flow at an intermediate pressure at the outlet of the ejector <NUM>. The pressure difference between the two ducts <NUM>' and <NUM>" (and therefore between the two flows entering the ejector <NUM>) is achieved by means of a calibrated orifice <NUM> interposed between the two ducts. A second control valve <NUM> determines the flow rate of the secondary flow of air and oxygen to the ejector <NUM>. Thus, the concentration of oxygen in the air is determined by the first control valve <NUM> while the flow rate of the air / oxygen mixture is determined by the second control valve <NUM>. The mixture of air and oxygen exiting the ejector <NUM>, therefore after exiting the gas supply system <NUM>, reaches a plenum <NUM>, after passing through a filter element <NUM> which will be described below.

Advantageously, the plenum <NUM> can be provided with a light device <NUM> with ultraviolet radiation which guarantees the sterilization of the air / oxygen mixture, avoiding the spread of any contagion.

Preferably, the air-oxygen mixture could be integrated with the presence of a second medical gas, for example, ozone. In fact, as known, ozone is an excellent sanitizer to eliminate germs and bacteria. Its very high oxidizing power makes it an effective sanitizer and deodorant, certainly of interest in the current contingency of the fight against Covid <NUM>. The supply of this secondary gas is very similar to that of the air / oxygen mixture. In fact, it will be sufficient to provide a tank 1A of this "Secondary Medical Gas" (SMG) under pressure and a circuit similar to that described for the air / oxygen mixture in which a first control valve 2A will be present to provide for the mixing of air and SMG, a calibrated orifice 3A to obtain the desired pressure drop and a second control valve 4A to regulate the flow rate of this second air / SMG mixture. The suction effect also for this second mixture will always be guaranteed by the ejector <NUM>.

From the plenum <NUM>, the air / oxygen mixture (possibly the air / oxygen / SMG mixture) reaches the respiratory helmet <NUM> by means of the supply duct <NUM>, along which there is a first non-return valve <NUM> which prevents the backflow of the mixture. The mixture thus fed is then available for inspiration by the patient wearing the helmet <NUM>.

Finally, the exhausted air, i.e. the air rich in carbon dioxide (CO2) exhaled by the patient, is made to flow out by means of the exhaust duct <NUM> and the flow rate is regulated by a third control valve <NUM>. A second non-return valve return <NUM> prevents the backflow of carbon dioxide towards the respiratory helmet <NUM>. The air / CO2 mixture is then filtered into the filter element <NUM> and the air thus purified from CO2 rejoins the main flow of the air / oxygen mixture directed to the plenum <NUM>.

The artificial ventilation system <NUM>, as will be seen below, can be controlled automatically and for this purpose also includes a control unit <NUM> which can manage input data and control the appropriate actuators. The input data may be, according to a non-exhaustive list, the flow rate and pressure of the air / oxygen mixture (possibly of the air / oxygen / SMG mixture), the concentration of oxygen and CO2 in the respiratory helmet <NUM>, as well as pressure and temperature always inside the helmet. In addition, the SpO2 oxygen saturation data is also fundamental, to which additional biomedical parameters, such as heart rate and respiratory rate, can be added. The control unit <NUM>, according to strategies that will be illustrated below, will operate the first control valve <NUM> and the second control valve <NUM> to regulate the oxygen concentration and the flow rate of the air / oxygen mixture in the supply duct <NUM> (as well as, similarly the first control valve 2A and the second control valve 4A to regulate the concentration of SMG and the flow rate of the air / SMG mixture, if a second medical gas is present). The control unit <NUM> will also operate the third control valve <NUM> to adjust the exhaust air flow in the exhaust duct <NUM>.

<FIG> illustrates an artificial ventilation system <NUM> in a second embodiment of the invention. The ventilation system <NUM>, as well as the previous one, includes the respiratory helmet <NUM>. In practice, the ventilation systems referred to in <FIG> and <FIG> differ only by the fact that in the diagram of <FIG> there is a different gas supply system <NUM>' which differs from the previous one only for the suction means which, according to this embodiment, is an electric fan <NUM>. The fan creates an overpressure for the ventilation of the patient inside the helmet <NUM> and creates a low pressure for the intake of breathed air (rich in CO2) from the helmet. The choice of the suction means, ejector rather than fan or other similar means, will be dictated by the specific applications: the ejector, a static organ, may be more reliable, where an electric fan could guarantee greater flexibility within the required pressure head.

According to the present invention, the artificial ventilation system <NUM>, <NUM> is provided with a particular layout involving the supply duct <NUM>, the exhaust duct <NUM> and the respiratory helmet <NUM>, as illustrated in <FIG>.

In these Figures it can be seen that the supply duct <NUM> and the exhaust duct <NUM> are integrated in the first casing <NUM> which connects to a second casing <NUM> inside the respiratory helmet <NUM>. The first casing <NUM> is in turn integrated in a coupling <NUM> which can be attached to the breathing helmet <NUM> by means of a bayonet connection or by means of threaded connections. Advantageously, the coupling <NUM> can be provided with sensors <NUM> in communication with the control unit <NUM> for the transmission of the parameters involved in the control strategies, as described hereafter.

The first casing <NUM>, as mentioned above, groups together the supply duct <NUM> of the air / oxygen mixture (possibly air / oxygen / SMG) and the exhaust duct <NUM> of the exhausted air, rich in CO2. Inside the first casing <NUM> the two flows are evidently separated by means of a separation septum <NUM>, as visible in <FIG>. Similarly, also inside the second casing <NUM> the two flows will remain separated by a similar separation septum (not visible from the drawings). The second casing <NUM>, inside the respiratory helmet <NUM>, is provided with a double plurality of holes. A first plurality of holes <NUM>' allows the air / oxygen mixture to escape inside the helmet <NUM>, while the second plurality of holes <NUM>" serves for the entry into the second casing <NUM> of the exhausted air, exhaled by the patient and therefore rich in CO2. The "flute" conformation of the second casing <NUM> is advantageous for a better circulation of the two flows (oxygen entering the helmet, CO2 exiting the helmet).

Furthermore, this layout has further advantages:.

In particular, with reference to <FIG>, the sanitization of the coupling <NUM> and of the sensors <NUM> is carried out by removing the coupling <NUM> from the respiratory helmet <NUM>, sealing it with a suitable cap <NUM> and leaving the artificial ventilation system in operation. In this way, the mixture of air and oxygen will continue to circulate sterilizing the sensors thanks to its passage through the light device <NUM> with ultraviolet radiation.

As anticipated, the artificial ventilation system <NUM>, <NUM> according to any of the embodiments described above can be managed and controlled automatically by means of the control unit <NUM>.

A first control method <NUM> of the artificial ventilation system has two priority levels and is based on a closed loop control.

According to a first and most important priority level, the control unit maintains the patient's oxygen saturation SpO2 at the desired level, i.e. above a first threshold value and, at the same time, limits the CO2 concentration to helmet interior below a second threshold value.

With a second priority level, the control method optimizes the consumption of the externally supplied oxygen as well as patient comfort by keeping the air / oxygen mixture entering the helmet and the helmet pressure and temperature in corresponding predetermined intervals.

The first control method <NUM> is illustrated in <FIG> which represents a block diagram thereof. A first control line <NUM> has as its objective the complete automation of the management of the respiratory helmet <NUM> according to the first priority level.

Control line <NUM> includes a closed-loop controller <NUM>, such as a proportional-integrative-derivative (PID) controller, which adjusts the patient's oxygen saturation by comparing the input SPO2 saturation (the current value) with the desired level, above a first threshold value; the regulator <NUM> which manages the sequence of the implementation of the control valves; the actuators <NUM> and <NUM> enslaved to the regulator <NUM> which receive the logic command from the regulator <NUM> and give an electric command, respectively, to the third control valve <NUM> which regulates the flow rate of the outgoing flow from the helmet <NUM> (and therefore the CO2 flow rate) and to the second control valve <NUM> which regulates the flow of the air / oxygen mixture; the CO2 controller <NUM> that manages and monitors the amount of CO2 inside the helmet; a logic switch <NUM> which alternately connects the actuator <NUM> with the regulator <NUM> or with the CO2 controller <NUM>.

Once the PID controller <NUM> has calculated the desired SPO2 value, the PID controller <NUM> communicates such a value to the regulator <NUM> which sets the sequence of the control valve actuation, which can be in the following order: first regulation of the exhaust air flow (containing CO2) by means of the actuator <NUM> which activates the third control valve <NUM> and subsequently, if the room for maneuver on the exhaust air flow control is ended (in other words, if the third control valve <NUM> is in an extreme position and is not further adjustable), regulation of the flow of the air / oxygen mixture by means of the actuator <NUM> which operates the second control valve <NUM>.

This strategy is active, as described, when the CO2 concentration value remains below a second threshold value, monitoring chaired by the CO2 controller <NUM>. Should the CO2 concentration exceed the second threshold value, the CO2 controller <NUM> has the authority to reverse the control valve actuation logic. In particular, the regulator <NUM>, "ordered" by the CO2 controller <NUM>, will use the logic switch <NUM> to enslave the actuator <NUM> to control the CO2 concentration. The actuator <NUM> will then actuate the second control valve <NUM> to regulate (in this case increase) the flow of the air / oxygen mixture inside the respiratory helmet <NUM>. The closed-loop control of the patient's oxygen saturation remains active by means of the PID controller <NUM>, but in this case the regulator <NUM> will only manage the actuator <NUM> which operates the third control valve <NUM> to regulate the exhaust air flow.

As mentioned, a second control line <NUM> with lower priority can be dedicated to the patient's comfort and contains suitable algorithms for monitoring some of his biomedical parameters. The second control line <NUM> proceeds in parallel with respect to the first control line <NUM>, of higher priority, obviously subordinated to the correct operation of the parameters controlled by the first control line <NUM>.

With reference to <FIG>, a second variant of the control method of the artificial ventilation system <NUM>, <NUM> is now described.

The second control method <NUM> uses a dynamic model of the process to predict its future evolution and choose the best control action.

Also in this second case, the control method of the artificial ventilation system has two priority levels:.

More specifically, the state observer <NUM> receives as input data (see <FIG>):.

The estimation model implemented in the state observer <NUM> allows instead to have as output data, by way of example, the models of the following physiological parameters of lung functions:
C: flows of oxygen and CO2 in the pulmonary alveoli and blood compartments, instantaneous volume of the lungs, pressure in the alveoli, etc..

The parameters indicated with A, B and C constitute input data for the controller <NUM>. In addition, the controller <NUM> can manage:.

Based on all parameters A, B, C, D and E, the controller <NUM> is able to calculate the optimal values of oxygen saturation and CO2 concentration and to predict the evolution of the model results over a time interval defined by a number N of time steps, using a predetermined sequence of manipulable parameters E within the same time interval.

The algorithm is based on the optimization of an objective function, which evaluates the distance of the control system from the objectives and optimal control constraints, minimizing this distance. The control objectives are assessed in the predetermined time interval in which appropriate penalties are defined on the ability of the control system to follow its objectives and on the effort to implement the control valves.

An example of an objective function structured in this way is the following: <MAT> where:.

In other words, the objective function tends to make the oxygen saturation reach its maximum value of <NUM>, as well as to keep the CO2 concentration below its maximum threshold. These two objectives represent, as in the case of the first control method <NUM>, the first priority level.

According to a lower priority level, the optimization process of the objective function will have to take into account further control constraints related to:.

At each predetermined time instant t, the controller <NUM> will find the optimal sequence of manipulable parameters E (position of the second <NUM> and third control valve <NUM>) which minimize the objective function in the time interval N. Obviously, only the first optimum activation will be used, then the controller <NUM> will act on the regulation of the exhaust air flow by means of the actuator <NUM> which activates the third control valve <NUM> and on the regulation of the air / oxygen mixture flow by means of the actuator <NUM> which activates the second control valve <NUM>.

The procedure will be repeated at the next time instant t + <NUM>.

As seen, the first control method <NUM> and the second control method <NUM> both derive from a single methodology which presents a strategy based on at least two priority levels. They are declined according to different approaches and can be used alternatively depending on the applications.

The first control method <NUM> is certainly easier to be implemented, does not require specific modeling (for example, mathematical models of lung functions) and does not require high computational skills.

The second control method <NUM> is more complex, requiring sophisticated modeling of lung functions and higher computational capacity. On the contrary, however, it allows in a single framework to monitor and assist patients with severe respiratory problems. Furthermore, due to its predictive approach and estimating the internal states of respiratory functions, the second control method is faster in reacting to any worsening of the patient's situation. Finally, it is more adaptable to a wider class of pathologies.

The control method <NUM>, <NUM> for the artificial ventilation system <NUM>, <NUM> may undergo further variations.

For example, it may also be able to control a mixture consisting of air / oxygen / SMG, in this case also acting on the control valve 4A of the air / SMG mixture.

Ultimately, the artificial ventilation system object of the present invention has undoubted advantages: it does not require any fixed infrastructure, since only needs the respiratory helmet, at least one cylinder for compressed oxygen, the electro-hydraulic circuitry, the ultraviolet light device and the control electronics. The artificial ventilation system is therefore completely portable and has ample flexibility for any application. Furthermore, the system is fully automatically controllable, with control strategies also based on sophisticated predictive algorithms, and does not require the presence on site of a health worker.

Claim 1:
Artificial ventilation system (<NUM>, <NUM>) comprising:
- a respiratory helmet (<NUM>),
- suction means (<NUM>, <NUM>) which draw the air from the external environment,
- a tank (<NUM>) for containing pressurized oxygen,
- a first control valve (<NUM>) which regulates the mixing of air/oxygen,
- a second control valve (<NUM>) which regulates the flow rate of the air/oxygen mixture,
- a plenum (<NUM>) for containing the mixture of air and oxygen leaving the suction means (<NUM>),
- a supply duct (<NUM>) which allows the air/oxygen mixture to reach the respiratory helmet (<NUM>),
- a first non-return valve (<NUM>) which prevents the backflow of the air/oxygen mixture from the supply duct (<NUM>),
- an exhaust duct (<NUM>) for the air/CO2 mixture,
- a filter element (<NUM>) of the air/CO2 mixture in fluid communication with the plenum (<NUM>), and
- a control unit (<NUM>) to control at least oxygen saturation and carbon dioxide concentration inside the respiratory helmet (<NUM>);
the artificial ventilation system (<NUM>, <NUM>) being characterized in that:
- the air/CO2 mixture flow rate in the exhaust duct (<NUM>) is regulated by a third control valve (<NUM>),
- the supply duct (<NUM>) and the exhaust duct (<NUM>) are integrated in a first casing (<NUM>) which connects to a second casing (<NUM>) inside the respiratory helmet (<NUM>),
- wherein inside the first casing (<NUM>) and the second casing (<NUM>) the two flows remain separated by means of a separation septum (<NUM>), and
- the second casing (<NUM>) comprises a first plurality of holes (<NUM>') which allows the air/oxygen mixture to flow inside the respiratory helmet (<NUM>) and a second plurality of holes (<NUM>") for the entry of the exhausted CO2-rich air into the second casing (<NUM>).