WO2022149990A1

WO2022149990A1 - Method and system for controlling the volume of a patient's inspiratory gas mixture and related method and system for multi-station ventilation

Info

Publication number: WO2022149990A1
Application number: PCT/PL2022/050001
Authority: WO
Inventors: Marek Darowski; Maciej KOZARSKI
Original assignee: Instytut Biocybernetyki I Inżynierii Biomedycznej Im. M. Nałęcza Polskiej Akademii Nauk
Priority date: 2021-01-08
Filing date: 2022-01-10
Publication date: 2022-07-14
Also published as: PL436618A1

Abstract

The subject matter of the invention is a method and a system for controlling the volume of a patient's inspiratory gas mixture delivered by means of distributing a ventilator inspiratory gas mixture into at least one of two respiratory tracks from a single ventilator, comprising distribution by pneumatic means of a patient's inspiratory gas mixture and electronic adjustment of the volume of a patient's inspiratory gas mixture. The method is characterized in that adjusting of the volume of a patient's inspiratory gas mixture is performed automatically and by means of an electronic system comprising a control circuit (21) comprising only analogue elements, and in that adjusting of the volume of a patient's inspiratory gas mixture is performed downstream of a pneumatic distributor of a ventilator inspiratory gas mixture in a single respiratory track, and in that adjusting of the volume of a patient's inspiratory gas mixture is performed based only on one, variable setting.

Description

METHOD AND SYSTEM FOR CONTROLLING THE VOLUME OF A PATIENT’S INSPIRATORY GAS MIXTURE AND RELATED METHOD AND SYSTEM FOR MULTI-STATION VENTILATION

DESCRIPTION The present invention relates to a method of controlling the volume of a patient’ s inspiratory gas mixture delivered to at least one of two respiratory tracks from a single ventilator and a method of multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator comprising such method of control. The invention further relates to a system for controlling the volume of a patient’ s inspiratory gas mixture delivered to at least one of two respiratory tracks from a single ventilator and a system for multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator comprising such control system. The invention applies during a simultaneous ventilation therapy of several patients by means of a single ventilator operating in a mode of forced constant pressure ventilation, especially in pandemic situations, when an alternative for a ventilator is a manual breathing pump engaging one medical employee per each patient while medical personnel is dramatically scarce.

Since the beginning of 2020, we have been facing a rapid, worldwide spread of the COVID- 19 virus. The virus causes an acute respiratory failure requiring a ventilation therapy in so many patients, that their number has exceeded the number of ventilators available for this purpose. This is a global problem and hence cannot be solved quickly by producing more ventilators. This regards especially poor countries, which cannot afford to purchase very expensive ventilators.

In prior art there have been attempts to use a single ventilator for simultaneous ventilation of more than one patient. This is possible due to a significant excess stream of an inspiratory gas from a ventilator relative to the needs of a single patient. In one solution type there has been proposed a modification of the ventilator-patient configuration such that the inspiratory port of a ventilator is connected to endotracheal tubes of two or more “dummy patients” by means of widely available Y-shaped pneumatic connectors. In simulation tests simple pneumatic valves for adjusting the flow rate for the separation of the gas stream from a ventilator were used.

However, the results of these tests have shown that such simple ventilation configurations would serve their purpose only if the lungs of all patients displayed the same compliance and resistance of the airways. This is not the case in clinical conditions. Consequently, distribution of ventilation between patients in absence of an automatic adjustment of inspiratory flows is uncontrolled. This may result e.g., in excessive ventilation of one patient while causing damages (impairment of ventilation) in another. This may be the case especially where the mechanics of patient’s lungs changes during a long-term ventilation therapy.

A critical opinion regarding the risk related to using a single ventilator for ventilation of two and more patients using the above-described method has been expressed by renowned professional international organizations, e.g.: The Society of Critical Care Medicine (www. sccm.org /Disaster/ Joint-Statement-on-Multiple-Patients-Per-Ventilator). Already on 26 March 2020, these organizations advised against using such simple technical means.

Known from prior art are also systems and methods for multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator, where the stream of a patient’ s inspiratory gas mixture (ventilation flows) is controlled automatically using the same mechanical means for at least two respiratory tracks simultaneously. An example of such solution has been disclosed in the Polish application no. PL434417, disclosing a system for mechanical adjustment of the stream of an inspiratory gas mixture located upstream of the pneumatic distributor of a ventilator inspiratory gas mixture. This system comprises a pneumatic capacitor to stabilize the transitory states of the system, dangerous to patients. However, a functional restraint of this solution is that despite the adjustment of the gas stream for two patients being automatic, it does not fully prevent the problems resulting from the interaction between at least two inspiratory tracks, caused by dynamic changes in the compliance of the lungs and resistance of the airways of two patients (e.g., one patient coughing). In addition, this known system makes it practically possible to prevent the problems of the interaction between at least two inspiratory tracks caused by significantly different static mechanical parameters of the respiratory systems of two patients solely by pairing patients with similar mechanical parameters of the respiratory system i.e. with a similar resistance of the airways and compliance of the lungs. Pairing patients is difficult to implement for the medical personnel in a situation where a significant number of patients require immediate care over a given time. There are also know from prior art methods and systems for controlled adjustment of inspiratory flows dedicated for a single patient and integrated into ventilators. Systems for adjusting inspiratory flows are applied to stabilize the volume of a respiratory gas mixture of a ventilator i.e., for the purpose of adapting to handling a single patient, the volume of a patient’s inspiratory gas mixture, that is the so-called tidal volume. Tidal volume is an important parameter of a respiratory therapy under dynamic changes of a patient’s respiratory system parameters (compliance and resistance of the airways). A characteristic feature of known systems for adjusting the tidal volume is that they use the difference of the current values of the measured and setpoint tidal volume as a feedback signal for controlling the inspiratory valve of the ventilator. The systems for adjusting the tidal volume integrated into constant-pressure ventilators operate in a similar way, using a feedback signal. An example of a known system for adjusting the tidal volume of this type was revealed in the American patent application no. US448192A. However, known systems for adjusting the tidal volume are digital electronic systems and are usually provided by means of microchips. A disadvantage of these systems is that they cannot be used with more than one patient as they are integrated into a single ventilator. In addition, they are digital electronic systems and are vulnerable to interference from the electromagnetic field of other devices. Hence, they are required to undergo a long-term licensing and certification process before they can be put into use together with a ventilator. In the time of the pandemic and a huge, immediate demand for medical equipment, the time required for certification of the digital system solution is unacceptably long.

The aim of the invention is to provide a method and a system for multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator, free from the above- mentioned drawbacks indicated in the description of the state of the art. In particular, the aim of the invention is to provide a method and a system for multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator for more than one patient, which would ensure automatic and patient-safe adjustment of inspiratory flows, reducing the possible mutual interaction between the inspiratory tracks of the patients connected to the same ventilator. Secondly, the aim of the invention is to provide a method and a system for multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator for more than one patient, which would ensure quick and easy scalability of a system of distribution of a ventilator inspiratory gas mixture.

Thirdly, the aim of the invention is to provide a method and a system for multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator for more than one patient, which would ensure quick and easy decision-making by the medical personnel regarding the necessary changes to the system settings and a better-targeted inspiratory therapy i.e., better suited to the individual needs of a patient. Fourthly, the aim of the invention is to provide a method and a system for multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator for more than one patient, which would be less vulnerable to electromagnetic interference, and which would require a shorter process of certification and obtaining permits to be put into operation.

The essence of the invention is that the method of controlling the volume of a patient’s inspiratory gas mixture delivered by means of distribution of a ventilator inspiratory gas mixture into at least one of two respiratory tracks from a single ventilator, comprising distribution by pneumatic means of a patient’s inspiratory gas mixture and electronic adjustment of the patient’s inspiratory gas mixture is characterized in that adjusting a patient’ s inspiratory gas mixture is performed automatically and by means of an electronic system comprising a control circuit comprising only analogue elements and in that adjusting the volume of the delivered gas mixture is performed downstream of the mechanical pneumatic distributor of a patient’s inspiratory gas mixture in a single inspiratory track and in that adjusting the volume of a patient’s inspiratory gas mixture is performed based only on one variable setting.

Preferably, the volume of the delivered patient’s inspiratory gas mixture is adjusted by means of an electronic system comprising a circuit of a programming device (21) based on a single variable setting expressing the desired minute volume Vm. Preferably, the volume of the delivered patient’s inspiratory gas mixture is adjusted by means of an open-loop electronic system based additionally on a permanent setting expressing the desired inspiration frequency.

Preferably, the volume of the delivered patient’s inspiratory gas mixture is adjusted by means of an electronic system operating in a closed loop based additionally on permanent setting expressing the desired value of the Te/Ti ratio.

In another embodiment the essence of the invention consists in that the system for controlling the volume of a patient’s inspiratory gas mixture delivered by means of distributing the ventilator inspiratory gas mixture into at least one of two inspiratory tracks from a single ventilator comprising pneumatic means for the distribution of a patient’s inspiratory gas mixture and an electronic system for adjusting the volume of a patient’s inspiratory gas mixture is characterised in that it is adapted to be mounted downstream of the pneumatic distributor of the ventilator inspiratory gas mixture in a single inspiratory track, and in that the electronic system for adjusting the volume of a patient’s inspiratory gas mixture is adapted for automatic adjustment of the volume of a patient’s inspiratory gas mixture and comprises a control circuit comprising only analogue elements, and in that the electronic system for adjusting the volume of a patient’s inspiratory gas mixture adjusts the volume of a patient’s inspiratory gas mixture based only on a single, variable setting.

Preferably, the electronic system for adjusting the volume of a patient’s inspiratory gas mixture comprises a circuit of a programming device and adjusts the volume of the delivered patient’s inspiratory gas mixture based on a single variable setting expressing the desired minute volume Vm.

Preferably, the system operates in an open-loop control mode, and the electronic system for adjusting the volume of a patient’s inspiratory gas mixture adjusts the volume of the delivered patient’s inspiratory gas mixture based additionally on a permanent setting expressing the desired inspiration frequency.

Preferably, the system operates in a closed-loop control mode, and the electronic system for adjusting the volume of a patient’s inspiratory gas mixture adjusts the volume of the delivered patient’s inspiratory gas mixture based additionally on a permanent setting expressing the desired value of the Te/Ti ratio.

Preferably, the system has a housing in which there is located a pneumatic track preferably comprising an execution valve, gas stream sensor and a check valve, connected in series.

Preferably, the execution valve is an analogue valve, preferably constituting an electropneumatic valve, more preferably a stepper motor valve.

Preferably, the system comprises digital voltmeters Vm, pmax and pmin, each connected to a display located on the housing.

In yet another embodiment, the essence of the invention consists in that the method of multi station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator including distribution of a gas mixture into at least two inspiratory and expiratory tracks is characterised in that it also comprises stages of the method of control according to the invention.

In yet another embodiment, the essence of the invention consists in that the system for multi station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator comprising a system of distribution of a gas mixture into at least two inspiratory and expiratory tracks is characterised in that it also comprises a control system according to the invention in each inspiratory track.

The method and the system for controlling the volume of a patient’s inspiratory gas mixture delivered by means of distribution of a ventilator inspiratory gas mixture into at least one of two inspiratory tracks from a single ventilator operating in a constant pressure mode according to the invention provides customised, automated adjustment of the tidal volume of each of the patients connected to a single ventilator and monitoring of the minute ventilation and the pressures (minimum and maximum) in the airways of each of them.

The analogue electronic control circuit for adjusting the tidal volume applied in the system according to the invention has an original design adapted for a specific use such as simultaneous and, consequently, synchronous constant-pressure ventilation of several patients by means of a single ventilator.

Mounting of the system for controlling the volume of a patient’s inspiratory gas mixture according to the invention on an inspiratory track downstream of the first pneumatic distributor of a ventilator inspiratory gas mixture allows to provide an electronic device, external relative to the ventilator, which is mounted individually onto each respiratory track, allowing automated control of the volume of a patient’ s inspiratory gas mixture separately for each patient, individual adaptation to the needs of a specific patient, without disturbing the operation of the other respiratory tracks of the multi-station ventilation system. Application in the method and the system for controlling the volume of a patient’s inspiratory gas mixture in an electronic control circuit of only analogue elements eliminates the risk of vulnerability of the system and the method according to the invention to electromagnetic interference from other medical and non-medical devices. Furthermore, the process of certification of a medical device comprising analogue electronics is much simpler and thus shorter.

Moreover, thanks to integrating a pneumatic part and an electronic control system, together with an appropriate control interface for medical personnel, in a system for controlling the volume of a patient’s inspiratory gas mixture, a device suitable for easy and fast integration with a multi-station ventilation system has been arrived at. To install the device in a multi- station ventilation system it is enough to connect it via an appropriate input to one of the outputs of the mechanical distributor of a ventilator inspiratory gas mixture located downstream of the ventilator, and via an appropriate output to the input port of the collective expiratory track. The numerous advantages result also from the fact that the only parameter subject to adjustment from the level of the housing of the device, entered during a therapy using the method and the system of control of the volume of a patient’s inspiratory gas mixture according to the invention, is minute ventilation Vm (by means of a potentiometer R46). Owing to the fact that this is just a single setting, and that this parameter can be easily linked by medical personnel to a patient’s condition, the personnel’s response time is significantly shorter, especially when attending to several patients at the same time.

A system for controlling the volume of a patient’s inspiratory gas mixture and, comprising the same, a system for multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator according to the invention are presented in detail by way of embodiments in relation to the attached figures of the drawing, where:

Fig. 1 illustrates a general diagram of a system for multi-station ventilation according to the invention;

Fig. 2 illustrates a diagram of a system for controlling the volume of a patient’s inspiratory gas mixture according to the first embodiment of the invention;

Fig. 3 illustrates a diagram of a system for controlling the volume of a patient’s inspiratory gas mixture according to the second embodiment of the invention;

Fig. 4 illustrates a longitudinal section of an exemplary execution valve controlled by a system for controlling the volume of a patient’s inspiratory gas mixture according to the invention;

The terms used in the description shall have the following meaning: ‘a system for controlling the volume of a patient’ s inspiratory gas mixture’ is a part of a larger medical device or an independent medical device contained in a housing and connected externally relative to a ventilator, ‘control circuit’ is an electronic circuit located within a larger electronic unit of a system for controlling the volume of a patient’s inspiratory gas mixture, which circuit generates at its output a signal controlling an external element, for example an electromechanical element, preferably a pneumatic valve in a single respiratory track.

Generally, application of a ventilator, that is a mechanical support of breathing by means of generating positive inspiratory pressures, results in an adverse increase in the mean chest pressures, which usually causes a drop in the left ventricle output and reduces the venous return to the heart and, consequently, results in more difficult gas exchange conditions. Non-optimal choice of ventilation parameters e.g., too big inspiratory volume, causes a drop in lung compliance, thus deteriorating the gas exchange conditions, and increases the risk of damage to the alveoli and deterioration of the hemodynamic conditions of the pulmonary and systemic blood flow. This issue is of great importance for the clinical practice with regard to intensive respiratory therapy, both with respect to mechanical ventilation of a single patient and several patients simultaneously.

In a multi-station system for ventilation of several patients by means of a single ventilator the mode of operation of the latter is of primary importance. Apart from special methods of individualised ventilation, most ventilators have two modes of operation: the pressure mode, where the pressure generated by a ventilator is constant and independent of the stream of gas delivered to a patient, and the flow mode, where the volume of the gas delivered by a ventilator is constant and independent of the pressure in the inspiratory tip of a ventilator.

Simultaneous ventilation of several patients connected in parallel to a ventilator differs significantly in each of the described modes of operation. The pressure mode means that a ventilator operates as a source of pressure of a very small own resistance, maintaining in a network of parallel connected patients a pressure independent of the amount of air they take in. This also means that a change in the respiratory resistance or pulmonary compliance of any of the patients has no impact on the conditions of ventilation of the other patients. In the flow mode, a constant, independent of the pressure volume of a gas delivered cyclically by a ventilator must be distributed among patients. A ventilator operates as a source of a gas of a very high self-resistance. A change in the air intake by one of the connected patients introduced by a physician or caused otherwise immediately changes the pressure in the network and, consequently, the conditions of ventilation of all patients. While handling such changes with only two patients connected is relatively easy, it may prove to be practically impossible where a bigger number of patients is involved. Therefore, in the case of multi station ventilation the only suitable mode of ventilation is the pressure mode. Therefore, the method and the system for controlling the volume of a patient’s inspiratory gas mixture delivered to at least one of two respiratory tracks from a single ventilator according to the invention is dedicated for ventilators operating in the constant pressure mode.

A control system 9 of the volume of a patient’s inspiratory gas mixture singled out from a ventilator inspiratory gas mixture from a single ventilator 1 according to the invention may operate in a multi-station ventilation system in which at least two inspiratory and two expiratory tracks are provided.

According to the first embodiment shown in Fig. 1, the control system 9 of the volume of a patient’s inspiratory gas mixture delivered by distributing a ventilator inspiratory gas mixture into at least one of two respiratory tracks is incorporated into a multi-station ventilation system. The multi-station ventilation system comprises a ventilator 1. The ventilator 1 works best in the constant pressure mode and cyclically, in the inspiration phase, generates overpressure in its pneumatic inspiratory tip 2. It is delivered to a pneumatic distributor 6a of a ventilator inspiratory gas mixture stream, preferably a tee 6a, which on one side constitutes the beginning of the first inspiratory track and on the other forms a second distributary of the stream, allowing to introduce therein the second and the subsequent inspiratory track via another pneumatic distributor, preferably a tee 6b. The said distributary constitutes a pneumatic inspiratory manifold 6. The pneumatic distributor 6a, 6b of a ventilator inspiratory gas mixture and the pneumatic inspiratory manifold 6 constitute elements of the pneumatic system for the distribution and separation of the gas mixture stream from a ventilator. Subsequently, a patient’s inspiratory gas mixture moves from the tee 6a to the control system 9 of the volume of a patient’s inspiratory gas mixture via a pneumatic input tip 8. The control system 9 of the volume of a patient’s inspiratory gas mixture according to the invention ensures delivery of a suitable tidal volume to a patient, having regard for the static and dynamic conditions in a single inspiratory track. In addition to the first pneumatic input tip 8, the control system 9 of the volume of a patient’ s inspiratory gas mixture also comprises a second pneumatic input tip 10, via which the gas mixture from a tee 16 is delivered to the control system 9. The tee 16 is mounted in the respiratory track just upstream of a tee 17 situated at a patient’ s mouth. The tee 16 allows to capture the stream of a patient’ s inspiratory gas mixture, which must be observed in order to read its parameters . Preferably, an observed parameter may be pressure. By observing the parameters of a patient’ s inspiratory gas mixture reaching the patient’ s mouth we obtain a feedback signal which may be used by the control system 9 or for monitoring and/or controlling. Moreover, the control system 9 of the volume of a patient’s inspiratory gas mixture comprises a pneumatic output tip 11 via which a patient’ s inspiratory gas mixture enters a pneumatic input tip 14a of a check valve 14. The check valve 14 constitutes an element forcing a specified direction of the flow of a patient’s inspiratory gas mixture. Preferably, the check valve 14 in the inspiratory track forces the flow of a gas mixture from the ventilator toward a patient, preventing a patient’ s inspiratory gas mixture from flowing back in the inspiratory track. Subsequently, from the check valve 14 via its pneumatic output tip 14b, a patient’s inspiratory gas mixture preferably enters an antibacterial filter 15, preferably of the HEPA type via a pneumatic input tip 15a. An expert in the field will know, however, that the antibacterial filter may be located elsewhere in the multi-station ventilation system. Next, a patient’s inspiratory gas mixture is moved from the antibacterial filter 15 via its pneumatic output tip 15b and then the tee 16 and its first and second pneumatic tips 16a, 16b, to finally reach the patient. A respiratory tee 17 located at the patient’s mouth constitutes the end of the inspiratory track on one side - a pneumatic tip 17a, and on the other - the beginning of the expiratory track - a pneumatic tip 17c. The air exhaled by a patient moves through the second pneumatic tip 17b of the respiratory tee 17, this time in the other direction, and subsequently through the third pneumatic tip 17c of the respiratory tee 17, where the expiratory track begins. Via its pneumatic output tip 17c and input tip 18a of the check valve 18, the said respiratory tee 17 is serially connected to the check valve 18 forcing a specific direction of flow of the exhaled air. Subsequently, the check valve 18 connects to a valve 19 determining the end-expiratory pressure by the pneumatic output tip 18b of the check valve 18 and the pneumatic input tip 19a of a valve 19 determining the end-expiratory pressure.

This valve, usually referred to as the PEEP valve, limits the decrease in the pressure in the patient’s lungs in the expiration phase at a pre-set level, which prevents the alveoli from collapsing and determines the functioning of the lungs withing a favourable range of their top compliance and is necessary for a therapy to be administered properly. The end portion of the expiratory track is a serial connection between the valve 19 determining the end- expiratory pressure via the pneumatic output tip 19b and the tee 7a and the expiratory tip 3 of the ventilator 1. The tee 7a is a pneumatic element connecting the ventilator 1 with the collective distributary of the expiratory air stream from the other expiratory tracks of the consecutive patients. The said consecutive expiratory tracks are connected parallel to the collective stream moving down the pneumatic manifold 7 via consecutive tees, preferably the tee 7b. The pneumatic tee 7a, 7b of the gas mixture and the pneumatic expiratory manifold 7 constitute elements of the pneumatic system for the distribution and separation of a ventilator inspiratory gas mixture stream from a ventilator. The maximum number of inspiratory tracks (and, by analogy, expiratory tracks) depends on one hand on the total minute ventilation required by patients PI, P2, P3, P4, and on the maximum minute ventilation available to the ventilator 1. By way of example, in the presently manufactured ventilators a ventilator’s maximum available minute ventilation reaches the value of approximately 2001/min. The control system 9 according to the invention is shown in more detail in Fig. 2 and Fig. 3 in the first and the second embodiment, respectively, as a device installed in a single inspiratory track of a multi-station patient ventilation system.

In the first embodiment, the control system 9 of the volume a patient’s inspiratory gas mixture according to the invention is an open-loop control system, hereinafter referred to as an tidal volume open-loop controller 9. In this description, the term ‘tidal volume’ is equivalent to the term “inspiratory volume of a patient’s gas mixture,’ which is a certain part of ‘a respirator gas mixture.’

A more detailed method of use and operation of the tidal volume open-loop controller 9 is shown in Fig. 2. As previously mentioned, in a multi-station ventilation system the ventilator 1 is connected to two pneumatic manifolds 6, 7: by means of the tee 6a to the pneumatic inspiratory manifold 6 pumping a ventilator inspiratory gas mixture produced by the ventilator 1 and by means of the tee 7a to the pneumatic expiratory manifold 7 evacuating the gas exhaled by patient PI via the ventilator. More patients can be connected to the manifolds 6 and 7, and the limitation regarding their number results only from the capacity of the ventilator as a pump. Assuming that the stream of the pumped ventilator inspiratory gas mixture is at the level of 200 1/min, it is feasible to connect even 6 patients to a single ventilator 1, while maintaining control over the ventilation conditions of each of the connected patients, which may radically and beneficially change the situation regarding battling the pandemic.

The tidal volume open-loop controller 9 according to the first embodiment of the invention is mounted in the inspiratory track downstream of the first pneumatic distributor 6a of a ventilator inspiratory gas mixture and comprises a pneumatic track beginning in the pneumatic input tee 4, whose pneumatic input tip 4a constitutes the pneumatic input tee 8 of the controller 9, and the pneumatic output tip 13b of the gas stream sensor 13 constitutes its output tip 11. Hence, the pneumatic track of the open-loop controller 9 constitutes a part of the entire inspiratory track, running through the pneumatic output tip 4b of the tee 4 down the pneumatic channels through the pneumatic input tip 5a of the first check valve 5 and its pneumatic output tip 5b into the pneumatic input tip 12a of the execution valve 12 and its pneumatic output tip 12b into the pneumatic input tip 13a of the gas stream sensor 13 and into the pneumatic output tip 13b. Subsequently, the pneumatic output tip 13b of the gas stream sensor 13, constituting the pneumatic output tip 11 of the tidal volume controller 9 connects with the pneumatic input tip 14a of the second check valve 14 and, via its pneumatic output tip 14 b, with the pneumatic input tip 15a of the antibacterial filter 15 and then, via the pneumatic output tip 15b of the antibacterial filter 15 and the pneumatic tips 16a, 16b of the pneumatic output tee 16, with the pneumatic input tip 17a of the respiratory tee 17 of patient PI.

The role of the check valve 5 of the pneumatic controller 9 track is to force the suitable direction of the flow of a patient’ s inspiratory gas mixture in the pneumatic controller 9 track, among other things along the adjustment section (comprising the said electropneumatic valve 12) and the measuring section (comprising the said patient’s inspiratory gas mixture stream sensor 13). The execution valve 12 is an execution element of the control system 9 and is intended for adjusting the tidal volume in the inspiratory track. Preferably, the execution valve 12 is a solenoid valve, preferably an electropneumatic valve, whose structural diagram is shown in Fig. 4, preferably controlled by means of an analogue signal and can be replaced by a different solenoid valve ensuring the same functionality e.g., a stepper motor valve. The air stream sensor has the function of an element measuring at least one of the parameters of a patient’s inspiratory gas mixture, preferably the pressure differences. A measurement from the gas stream sensor 13 can be used to monitor and/or control the executive element for adjusting the tidal volume.

In addition to the pneumatic track, the tidal volume open-loop controller 9 according to the first embodiment of the invention comprises an electronic system comprising a control circuit 20, a circuit of the programming device 21 and a circuit of a respiratory monitor 63. The control circuit 20 is intended for controlling the execution valve 12 in the pneumatic track based on the voltage received from the circuit of the programming device 21. The circuit of the programming device 21 comprising potentiometers allows the medical staff to apply suitable settings.

The basic patient ventilation parameter used by the medical staff is tidal volume. Tidal volume Vo delivered to the lungs during a single breathing cycle is linked to minute ventilation i.e. the volume of a patient’s inspiratory gas mixture Vm flowing through the inspiratory track during one minute and to the breath frequency f by the following relationship:

Vo = Vm/f In a multi-station system, the breath frequency set as a constant value and equal for all patients is a frequency set on the ventilator and transferred by the doctor as a setting for the open-loop controller 9 according to Fig. 2. Whereas in the case of a closed-loop controller 9 according to Fig. 3 a second ventilator setting is transferred, constant for all patients, i.e., a setting defining the ratio of the expiration time Te to the inspiration time Ti. The adjustable parameter which can and must be adjusted during therapy in the respiratory track before a patient’s inspiratory gas mixture reaches Patient PI is the minute volume of a patient’s inspiratory gas mixture Vm (abbreviated as minute volume Vm). In an ideal case, thanks to the operation of the closed-loop controller 9 (or the open-loop controller - see the second embodiment) according to the invention, in the inspiratory track, at the end of an inspiration, a tidal volume Vo should be reached corresponding to the pre set minute ventilation Vm. In reality, it will always be a little lower due to the adjustment error at the initial phase of inspiration and a non-ideal constant pressure mode of the ventilator. This error should be corrected by a physician and hence the importance of measuring the actual minute ventilation Vm between the cycles. It should be pointed out that more dangerous than an initial “underventilation” of a patient would be their “overventilation” as in the constant flow mode in which the control circuit 20 operates the risk of volutrauma would arise resulting in a permanent damage to alveoli. Prior to connecting patient PI to a multi- station ventilation system, the medical staff sets the breathing frequency f and the initial minute ventilation Vm in the open-loop controller 9 by means of knobs (potentiometers) accessible on the housing of the controller 9, which constitute elements of the programming device circuit 21. The programming device circuit 21 of a pre-set tidal volume Vo of the tidal volume controller 9 is designed based on an operating amplifier 51 adapted also for setting the values of the breath frequency parameters f and for minute ventilation Vm related to tidal volume Vo. The non-inverting input “+” 51b of the operating amplifier is typically connected via a compensation resistor R_k to the circuit ground. Between the inverting input 51a of the operating amplifier 51 and the source of negative reference voltage -Uz connected to the input 21a of the programming device circuit 21, there is incorporated a potentiometer R1 used for setting the respiratory frequency f set in the ventilator. Further, the common point of connection of the inverting input 51a of the operating amplifier 51 and the potentiometer R1 is connected via the resistor R2 to the output 51c of the operational amplifier 51, thereby forming a voltage divider incorporated between the negative reference voltage source -Uz and the output 5 lc of the operational amplifier 51. The common point of connection of the output 51c of the operating amplifier 51 and the resistor R2 is connected to the circuit ground through the extreme terminals of the potentiometer R3R4 with the total resistance R3 and the resistance R4, used to set the minute ventilation Vm. The adjustment terminal of the potentiometer R3R4 constituting the voltage output of the voltage divider formed by this potentiometer R3R4 is at the same time the output 21b of the programming device circuit 21. The voltage Uv present at the output 21b of the programming device circuit 21, is the output voltage Uv of the programming device circuit 21 and is the set point of the tidal volume Vo at the input 47a of the comparator 47.

As mentioned previously, the tidal volume open-loop controller 9 according to the first embodiment of the invention further comprises a control circuit 20. The control circuit 20 comprises: a pressure transducer 25 connected to a zero crossing detector 28, a differential pressure difference transducer 36, a programming device circuit 21, an integrating system 43, a comparator 47 and a power amplifier 31.

As shown in Fig.2, the control circuit 20 comprises a comparator 47, one input 47a of which is connected to the programming device circuit 21 through connection with the adjustment terminal of the potentiometer R3R4 constituting the output 21b of the programming device circuit 21, while the other input 47b is connected to the output 43c of the integrating system 43, and the output 47c of the comparator 47 is connected to the input 31a of the power amplifier 31. The comparator 47 is used to compare the value of the output voltage Uv present at the output 21b of the programming device circuit 21, i.e., the value of the set tidal volume Vo with the value of the voltage present at the output 43c of the integrating system 43, which is proportional to the current value of the volume V of air delivered to the patient’s lungs. If the value V exceeds the value Vo, a signal appears at the output 47c of the comparator 47 to close the hitherto open execution valve 12. The electrical signal thus developed from the comparator 47 is fed to the input 31a of the power amplifier 31, whose output 31b is connected to the control input 12c of the execution valve 12, thus enabling the operation of the said execution valve 12 to be controlled, and thus sending in a controlled manner the inspiratory gas mixture in the inspiratory track from the ventilator 1 to patient PI . The control circuit 20 acquires information about the state of the tidal volume control system by means of components connected to the pneumatic track downstream of the executive valve 12. The control circuit 20 serves to produce, in the inspiration phase, i.e., when the pressure at the tip 2 of the ventilator 1 is greater than that determined by the switching threshold of the detector 28, a flow of respiratory gas giving the preset tidal volume Vo. It is therefore the control circuit 20 portioning (titrating) in successive inspirations equal doses (volumes) of air into the airways of patient PI. For this purpose, to the zero-crossing input 43b of the integrating system 43 there is connected the output 28b of the zero crossing detector 28 of the signal coming from the pressure transducer 25, the output 25b of which is connected to the input 28a of the zero crossing detector 28. The pneumatic input tip 25a of the pressure transducer 25 is connected with the pneumatic tip 4c of the tee 4. The pressure transducer 25 converts the current pressure value of the gas stream pressure of the inspiratory track located in the tee 4, and derived by the pneumatic tip 4c, into a voltage signal which is fed to the zero-crossing detector 28. The detector 28 is used for detecting the minimum pressure level in the inspiratory track and based on this for cyclically activating integration and/or for zeroing the integrating system 43. Furthermore, the input 43a of the said integrating system 43 is connected to the output 36c of the transducer 36 converting the pressure difference into an electrical signal, whose first pneumatic measuring tip 36a is connected by means of the antibacterial filter 34 to the first pneumatic impulse tip 13c of the gas stream sensor 13, and the second pneumatic measuring tip 36b is connected by means of the antibacterial filter 35 to the second pneumatic impulse tip 13d of the gas stream sensor 13. Preferably, the gas stream sensor 13 is a leaf orifice with a variable cross-section. The pressure difference transducer 36 is responsible for converting the pressure difference signal generated in the gas stream sensor 13 in the inspiratory track present downstream of the execution valve 12 into a proportional electrical signal fed into the input 43 a of the integrating system 43.

The control circuit 20 according to the first embodiment of the invention operates such that the pressure difference signal generated in the sensor 13 by the gas stream is converted by means of the pressure difference transducer 36 into a proportional electrical signal fed into the input 43 a of the integrating system 43. Integration is an operation activated only in the inspiration phase when the ventilator 1 is pumping an inspiratory gas mixture into the lungs of patient PI. During the expiration phase, when the pressure at the ventilator 1 output falls to zero, the output signal V of the integrating system 43 takes the value of zero, which causes the execution valve 12 to open. Enabling the integration and zeroing the integrating system 43 is done cyclically. This process is controlled by the zero-crossing detector 28, which detects the minimum level of the voltage signal set on the detector 28 proportional to the minimum pressure level in the inspiratory track, converted by the pressure transducer 25 into a voltage signal. The voltage signal at the output 28b of the detector 28 is fed to the control input 43b of the integrating system 43, which allows integration only during the inspiration phase. The voltage signal at the output 43c of the integrating system 43 is proportional to the current volume V of a patient’s inspiratory gas mixture delivered to the lungs of patient PI .

As previously mentioned, this signal, delivered to the input 47b of the comparator 47, is compared against the signal of the preset value Vo of the minute ventilation Vm delivered to the input 47a of the comparator 47 from the output 21b of the programming device circuit 21. If the value V exceeds the value Vo, a signal appears at the output 47c of the comparator 47 to close the hitherto open execution valve 12. This signal is fed into the input 31a of the power amplifier 31, at whose output 31b a suitable electrical signal is acquired controlling the valve 12.

As previously mentioned, the preset Vo value signal of the minute ventilation Vm is generated in the programming device circuit 21 together with the operating amplifier 51. In the programming device circuit 21 of the first embodiment of the invention the Uf pressure at the output of the amplifier 51 is inversely proportional to the resistance value of preset on the potentiometer R 1.

Uf = Uz * R2/R1

Ultimately, the Uv pressure at the potentiometric divider R3R4 will be expressed by the following formula:

Uv = Uz (R2/R1) (R4/R3) = (UzR2)/R3 * R4/R1 and as the minute ventilation Vm and the inspiration frequency f are linked to the Vo volume supplied to the lungs during one inspiratory cycle by the following relationship:

Vo = Vm/f in the programming device circuit 21 in question the preset tidal volume value Vo is ultimately determined by the line potentiometers R1 and R3R4, where the potentiometer R1 is responsible for setting the frequency f, and the potentiometer R3R4 is responsible for setting the minute volume Vm. As mentioned previously, this means that the physician determining the ventilation conditions of a patient has to perform only two activities: first, they must set the frequency f by means of the potentiometer R1 calibrated using the same frequency units as the preset frequency of the ventilator 1 , and then, by means of a knob - the potentiometer R3R4, calibrated in the minute ventilation units, enter the assumed minute ventilation Vm = Vo*f. With the assumed frequency f imposed by the setting of the ventilator 1, a physician will only change the minute ventilation Vm during therapy, optimising the ventilation conditions of patient PI. Since the tidal volume control system 9 according to the invention allows the medical personnel to monitor and adjust only one parameter, the system is easy and intuitive to handle. This significantly reduces the response time of the medical staff in the event of a change in a patient’s condition. The tidal volume open-loop controller 9 according to the first embodiment of the invention also comprises a breath monitor circuit 63, comprising a pressure transducer 40 connected to a peak respiratory pressure pmax detector 57 and minimum respiratory pressure pmin detector 60, to which there are connected digital pmax and pmin voltmeters, respectively, and comprises a minute ventilation Vm measuring system 54, to which there is connected a digital voltmeter Vm.

The respiratory monitor circuit 63 according to the first embodiment of the invention is used for measuring the current values of: the peak respiratory pressure pmax, the minimum respiratory pressure pmin and the minute ventilation Vm. The circuit 63 is designed, among other things, based on the pressure transducer 40, whose pneumatic input tip 40a constituting the pneumatic input tip 10 of the controller 9 is connected to the pneumatic tip 16b of the output tee 16, and the electrical output 40b is connected to the input 57a of the respiratory pressure peak value detector 57, which value is indicated on the pmax voltmeter connected to the output 57b of the detector 57. Furthermore, the electrical output 40b of the pressure transducer 40 connected to the input 60a of the detector 60 of the minimum respiratory pressure value pmin , which value is indicated on the pmin voltmeter connected to the output 60b of the detector 60, respectively. Additionally, in the measuring-monitoring circuit 63, i.e., in the respiratory monitor circuit 63 there is present a minute ventilation Vm measuring system 54, to the output 54a of which there is connected the output 36c of the pressure difference transducer 36. Preferably, the minute ventilation Vm measuring system 54 is a low-pass filter of a signal transmitted from the output 36c of the pressure difference transducer 36. A digital voltmeter Vm is connected to the output 54b of the ventilation measuring system 54, which provides a signal of the average gas flow rate proportional to the minute ventilation Vm of a patient’s lungs. The Vm, pmax and pmin measurements are taken by means of digital voltmeters indicated in Fig. 2 of the drawing by means of the measured values Vm, pmax, pmin. The respiratory monitor circuit 63 allows the medical personnel to follow the therapy on the displays of the Vm, pmax, pmin voltmeters - especially with regard to the minute ventilation Vm, which is the most critical value determining blood oxygenation and elimination of CO2. In turn, observation of the maximum pressure pmax, allows the assessment of changes in the patient’s airway resistance, while knowledge of the minimum pressure pmin is used to assess the correct operation of valve 19.

According to the second embodiment of the invention shown in Fig. 3, the control system 9 for controlling the volume of a patient’ s inspiratory gas mixture delivered by distributing a ventilator 1 inspiratory gas mixture into at least one of two respiratory tracks is a closed- loop control system, hereinafter referred to as the tidal volume closed-loop controller 9 and is incorporated into a multi-station ventilation system. As in the previous embodiment, the multi- station ventilation system comprises a ventilator 1, and the general method of incorporating the closed-loop controller 9 into the multi-station system for ventilation of patients (PI, P2...) is identical with the method of incorporating the open-loop controller 9, which was previously illustrated in Fig. 1. Similarly to the open-loop controller 9, the closed- loop controller 9 is mounted onto the respiratory track downstream of the first pneumatic distributor 6a of a ventilator inspiratory gas mixture. The pneumatic track of the tidal volume closed-loop controller 9 according to the second embodiment of the invention also constitutes a part of the inspiratory track following incorporation of the closed-loop controller 9 into a multi-station ventilation system. The pneumatic track begins with the first check valve 5, whose pneumatic input tip 5a constitutes the pneumatic input tip 8 of the closed-loop controller 9. Hence, a patient’s inspiratory gas mixture transferred from the ventilator 1 following separation out of a ventilator inspiratory gas mixture into the pneumatic input tip 8 of the closed-loop controller 9 moves down the pneumatic output tip 5b of the first check valve 5 to the pneumatic input tip 12a of the execution valve 12 and from its pneumatic output tip 12b into the pneumatic input tip 13a of the gas stream sensor and its pneumatic output tip 13b. Subsequently, a patient’s inspiratory gas mixture moves down the pneumatic output tip 13b of the gas stream sensor 13 constituting the pneumatic output tip 11 of the tidal volume closed-loop controller 9. Next, the pneumatic output tip 11 of the tidal volume closed-loop controller 9 connects with the pneumatic input tip 14a of the second check valve 14, and the pneumatic output tip 14b is connected to the pneumatic input tip 15a of the antibacterial filter 15. Next, a patient’s inspiratory gas mixture exits via the pneumatic output tip 15b of the antibacterial filter 15 and reaches the pneumatic tips 16a, 16b of the pneumatic output tee 16 connected to the pneumatic input tip 17a of the respiratory tee 17 of patient PI. The check valve 5 of the pneumatic controller 9 has a similar function as in the controller 9 of the first embodiment. The check valve 5 forces the suitable direction of the flow of a patient’s inspiratory gas mixture in the pneumatic controller 9 track, among other things along the adjustment section (comprising the said electropneumatic valve 12) and the measuring section (comprising the said patient’s inspiratory gas mixture stream sensor 13). Similarly, the execution valve 12 is an execution element of the controller 9 and is used for adjusting the tidal volume in the inspiratory track. Preferably, the execution valve 12 is a solenoid valve, preferably an electropneumatic valve, whose structural diagram is shown in Fig. 4, preferably controlled by means of an analogue signal and can be replaced by a different solenoid valve ensuring the same functionality e.g., a stepper motor valve. The air stream sensor 13 has the function of an element measuring at least one of the parameters of a patient’s inspiratory gas mixture, preferably the pressure differences. A measurement from the gas stream sensor 13 can be used to monitor and/or control the executive element 12 and, consequently, for adjusting the tidal volume. The only difference in the design of the internal pneumatic tracks of the open- loop controller 9 and the closed-loop controller 9 results from the necessity of an additional pressure measurement (in the tee 4 of the open-loop controller 9) required to control the operation of the integrating system 43, which is not required in the closed-loop controller 9 system. The tee 4 must be used to ensure independent operation of the open-loop controller 9 according to the invention. In the absence thereof, an additional controller 9 input would have to be introduced (for measuring the pressure) connected to the input tip 25a of the transducer 25.

In addition to the pneumatic track, the tidal volume closed-loop controller 9 according to the second embodiment of the invention comprises an electronic system comprising a control circuit 20 for controlling the check valve 12, the programming device circuit 21 and the respiratory monitor circuit 63, where the control circuit 20 comprises: the regulator 32, preferably a PID regulator, connected to the power amplifier 31 and a pressure difference transducer 36. The output 36c of the pressure difference transducer 36 in the control circuit 20 of the tidal volume controller 9 according to the second embodiment is connected to the second input 32b of the regulator 32 and to the input 54a of the minute ventilation Vm measuring system 54 located in the respiratory monitor circuit 63. Furthermore, the output 51c of the circuit of the programming device 21 of the minute ventilation Vm is connected to the first input 32a of the regulator 32, while the output 32c of the regulator 32 is connected to the input 3 la of the power amplifier 31, whose output 31b is connected to the control input 12c of the electropneumatic valve 12.

This part of the closed-loop controller 9 operates such that the electrical signal from the electrical output 36c of the transducer 36, which is proportional to the gas stream flowing through the gas stream sensor 13, is transferred to the second input 32b of the regulator 32 and to the input 54a of the minute ventilation Vm measurement system 54. By contrast, to the first input 32a of the regulator 32 the signal from the output 51c of the programming device circuit 21 of the minute ventilation Vm is fed. Next, a properly converted signal from the output 32c of the regulator 32 is fed to the input 31a of the power amplifier 31, from whose output 31b a suitable electrical signal is sent to the controlling input 12c of the electropneumatic valve 12. This way the regulation loop of the negative feedback determining the preset stream of the respiratory gas flowing through the execution valve 12 to patient PI is closed. Similarly to the open-loop controller 9 according to the first embodiment of the invention, for the closed-loop controller 9 according to the second embodiment of the invention, prior to connecting patient PI to a multi-station ventilation system, by means of the knobs (potentiometers) accessible on the housing and constituting elements of the programming device circuit 21, the medical staff sets the ratio of the expiratory time Te and the inspiratory time Ti, in this case constant for all patients, and the initial minute ventilation Vm, set for each patient individually.

The programming device circuit 21 of the minute ventilation Vm of the tidal volume closed- loop controller 9 according to the second embodiment is designed based on the operating amplifier 51 capable of simultaneously setting the values of the k parameter i.e., the ratio of the expiratory time Te to the inspiratory time TI (Te/Ti) set on a ventilator and the minute ventilation Vm, related to the tidal volume Vo. The inverting input

51a of the operating amplifier is connected by means of the resistor R43 to the output 5 lc of the amplifier 51 and by means of the potentiometer R44 to the system ground thus forming a negative feedback loop with the resistance divider on the resistor R43 and the potentiometer R44, where the potentiometer R44 is used for setting the previously mentioned k parameter i.e. the ratio Te/Ti of the expiratory time Te to the inspiratory time TI transferred from the Te/Ti setting on the ventilator 1. To the non-inverting input “+” 51b of the operating amplifier 51 there is connected a common connection point of the resistor R45 and the potentiometer R46, which form a resistance divider incorporated between the Uz voltage and the system ground. The potentiometer R46 is used for setting the desired value of the minute ventilation Vm supplied by the ventilator 1 to patient PI.

The function of the programming device 21 of the minute ventilation Vm of the controller 9 according to the second embodiment can be illustrated by the following ratio:

Vm = q * Ti * f where q is a gas stream, constant during the inspiration phase, and moreover, the respiratory frequency f is expressed by the formula: f = l / (Ti + Te) Where

Vm = q (Ti / (Te + Ti)) = q / (1 + k); k = Te/Ti Ultimately, the preset value q for the regulator 32 will be q = Vm (1+k)

The same function is performed by the previously described programming device circuit 21 designed on the operating amplifier 51.

The difference in the design of the programming device circuit 21 between the open-loop and the closed-loop controller 9 results from the characteristics of the adjusted parameters. This follows from the fact that in the case of the closed-loop controller 9 the required minute ventilation Vm is arrived at by setting in the regulator 32 an analogously calculated gas flow setpoint, whereas in the case of the open-loop controller 9 the minute ventilation Vm is arrived at by setting in the comparator 47 an analogously calculated tidal volume Vo setpoint.

The operation of the tidal volume controller 9 according to the second embodiment is as follows. At the beginning of inspiration, the execution valve 12 is fully open because in the absence of pressure and flow at the output 2 of the ventilator 1, the control circuit 20 of the controller 9 will force the execution valve 12 fully open.

When pressure is applied to the outlet 2 of the ventilator 1 (during the inspiration phase), the control circuit 20 will close the valve 12 sufficiently to provide a preset stream of a patient’ s inspiratory gas mixture in the rubber tube of the valve 12. Similarly, to the operation of the controller 9 according to the first embodiment, ideally, a tidal volume corresponding to the preset minute ventilation Vm should be reached at the end of inspiration. In reality, it will always be a little lower due to the adjustment error at the initial phase of inspiration and a non- ideal constant pressure mode of the ventilator 1. This error should be corrected by a physician and hence the importance of measuring the actual minute ventilation Vm between the cycles. It should be pointed out that more dangerous than an initial “underventilation” of a patient would be their “overventilation” as in the constant flow mode in which the tidal volume closed-loop controller 9 operates the risk of volutrauma would arise resulting in a permanent damage to alveoli. During the expiration phase, the pressure in the tip 2 of the ventilator 1 drops to zero, which causes the valve 12 to fully open again. As mentioned earlier, the check valve 5 protects against a backflow from the valve 12 to the ventilator 1. As mentioned earlier, in addition to the described control circuit 20 of the tidal volume closed-loop controller 9, the closed-loop controller 9 comprises an additional functional block, i.e., a respiratory monitor circuit 63 for controlling the course of the therapy of the ventilated patient PI. Two electrical signals are fed to the monitor 63. The first signal is fed from the output 36c of the pressure difference transducer 36 (proportional to the respiratory gas flow), which, through the measuring circuit 54, advantageously a low-pass filter, is converted into a voltage signal proportional to the minute ventilation Vm and fed from the output 54b of the circuit 54 to the digital voltmeter Vm.

The second signal from the output 40b of the pressure transducer 40 present in the tee 16 and in the tee 17 is applied to the input 57a of the system 57 for measuring the maximum value pmax of the pressure, and furthermore the same second signal from the output 40b of the pressure transducer 40 is applied to the input 60a of the system 60 for measuring the minimum value pmin of the pressure. The voltage signal at the output 57b of the system 57 is measured by a digital voltmeter pmax, and the voltage signal at the output 60b of the system 60 is measured by a digital voltmeter pmin. The measurement results from the voltmeters Vm, pmax and pmin are displayed to the medical personnel on corresponding displays (not shown) located on the closed-loop controller 9 housing. This allows the medical personnel to monitor the course of the therapy. The procedure for inputting the settings of the closed-loop controller 9 is different from that illustrated previously for the open-loop controller 9 in fig. 2. First, the parameter k common to all connected patients, i.e., the Te/Ti ratio (using the potentiometer R44) should be input, followed by a preset minute ventilation Vm (using the potentiometer R46), which is the only parameter subject to adjustment during therapy, as in the case of fig. 2. This means that, in each of the presented embodiments of the method, during the therapy of a patient the medical personnel needs only to select a suitable minute ventilation Vm to arrive at the suitable level of blood oxygenation and elimination of CO2· This greatly facilitates the management of simultaneous ventilation of several patients by a single medical personnel member and reduces the risk of error.

If it is assumed that the period of operation of the controller in repeated cycles is limited to the inspiratory time Ti, then in the case of the controller 9 of Fig. 2 one deals with a typical open-loop system, in which a preset minute ventilation Vm is achieved, while the inspiratory gas flow is not adjusted. By contrast, the case of Fig. 3 during inspiration one deals with a continuous operation of a closed-loop adjustment system (with a PID regulator) maintaining a constant gas stream in the inspiratory track. Fig. 4 of the drawing illustrates an embodiment of the executive valve 12, preferably an electropneumatic valve controlled by an analogue signal. This is a valve in which the airflow throttling element is a rubber tube 71 provided with two rigid pneumatic tips 68 and 70 having two circlips 72 and 79 fixing the position of the tube 71 in the sockets of the body 73 of the valve 12 and in identical sockets of a pressure plate 81 fixed to the body, preferably with screws 80. The pressure plate 81 has a centrally located prismatic rib 82 which is a fixed clamping jaw. The second, movable clamping jaw is a similarly prismatic tip 74 of a pusher 75 guided in an opening of a ferromagnetic shell 76 and in a coaxial opening of a permanent magnet 78 of an electromagnetic actuator. On the pusher 75 there is rigidly fixed a coil 77, the leads of which are connected to an electrical socket 69. The force of the pusher 75 on the rubber tube 71 is proportional to the current flowing through a coil winding 77. The above-described design of the valve 12 has a number of advantages and, primarily, very good dynamics (closing and opening times calculated in ms) and, moreover, the entire pneumatic path of the valve, i.e., the tips 68, 70 and the rubber tube 71 can preferably be made as easily replaceable disposable elements.

As mentioned and illustrated in fig.l, in each of the at least two inspiratory tracks downstream of the pneumatic stream distributor 6a there is located a tidal volume control system 9 according to the invention. In this context, it is very important that the ventilator 1 provides the possibility of using a constant-pressure mode, because then the operation of the individual control systems 9 of a patient’s inspiratory gas mixture stream located downstream of the pneumatic distributors 6a, 6b, ... of the ventilator’s inspiratory gas mixture stream is independent, i.e. a change in the respiratory gas stream taken by one patient does not affect the operation of the other patients, i.e. there is no interaction between them.

The tidal volume control system 9 according to the invention, i.e., the open-loop controller 9 according to the first embodiment, or the closed-loop controller 9 according to the second embodiment, comprises an electronic control circuit 20 which is fully analogue. Thus, the control system 9 of a patient’s inspiratory gas mixture is not susceptible to electromagnetic interference from other equipment operating in the hospital. Thanks to this, also the procedures for certification of a multi-station ventilation system using the control system 9 according to the invention take considerably less time. This provides an opportunity for a faster putting into operation of a life-saving equipment so necessary during a pandemic.

Claims

CLAIMS:

1. A method of controlling the volume of an inspiratory gas mixture delivered by means of distribution to at least one of two respiratory tracks from a single ventilator, comprising distribution by pneumatic means of an inspiratory gas mixture distributed from a ventilator and electronic adjustment of a volume of a patient’s inspiratory gas mixture, characterized in that

- adjustment of the volume of a distributed inspiratory gas mixture is performed automatically and by means of an electronic system comprising a control circuit (21) comprising only analogue elements and

- adjustment of the volume of a patient’s inspiratory gas mixture is performed downstream of a pneumatic inspiratory gas mixture distributor in a single inspiratory track and

- adjustment of the volume of a patient’s inspiratory gas mixture is performed based only on one, variable setting.

2. The method according to claim 1, characterized in that the adjustment of the volume of a patient’ s inspiratory gas mixture is performed by means of an electronic system comprising a programming device circuit (21) based on a single, variable setting expressing the desired minute volume Vm.

3. The method according to claim 2, characterized in that the adjustment of the volume of a patient’s inspiratory gas mixture is performed by means of an open-loop electronic system, based additionally on a permanent setting expressing the desired inspiration frequency.

4. The method according to claim 2, characterized in that the adjustment of the volume of a patient’s inspiratory gas mixture is performed by means of a closed-loop electronic system based additionally on permanent setting expressing the desired value of the Te/Ti ratio.

5. The method according to any one of claims 1 to 4, characterized in that during the controlling the stream of gas in the pneumatic track for the distribution of a separated inspiratory gas mixture is measured by means of a gas stream sensor (13) and the gas stream in the pneumatic track for the distribution of a separated inspiratory gas mixture is controlled by means of an execution valve (12).

6. The method according to any one of claims 1 to 4, characterized in that during controlling of the volume of a separated inspiratory gas mixture the voltage levels representative for Vm, pmax and pmin are measured at the output of the gas stream sensor (13) and their values are displayed on the displays located on the housing.

7. A system for controlling the volume of an inspiratory gas mixture delivered by means of distribution to at least one of two respiratory tracks from a single ventilator comprising pneumatic means for the distribution of an inspiratory gas mixture distributed from the ventilator and an electronic system for adjusting the volume of a patient’s inspiratory gas mixture, characterized in that

- it is adapted to be mounted downstream of the pneumatic distributor of an inspiratory gas mixture in a single inspiratory track, and in that the electronic system for adjusting the volume of a patient’s inspiratory gas mixture is adapted for automatic adjustment of the volume of a patient’s inspiratory gas mixture and comprises a control circuit (20) comprising only analogue elements, and

- the electronic system for adjusting the volume of a patient’s inspiratory gas mixture adjusts the volume of the separated inspiratory gas mixture based only on a single, variable setting.

8. The system according to claim 7, characterized in that the electronic system for adjusting the volume of a patient’s inspiratory gas mixture comprises a programming device circuit (21) and adjusts the volume of the delivered patient’s inspiratory gas mixture based on a single, variable setting expressing the desired minute volume Vm.

9. The system according to claim 8, characterized in that it operates in an open-loop control mode, and the electronic system for adjusting the volume of a patient’s inspiratory gas mixture adjusts the volume of the delivered patient’s inspiratory gas mixture based additionally on a permanent setting expressing the desired inspiration frequency.

10. The system according to claim 8, characterized in that it operates in a closed-loop control mode, and the electronic system for adjusting the volume of a patient’s inspiratory gas mixture adjusts the volume of the delivered patient’s inspiratory gas mixture based additionally on a permanent setting expressing the desired value of the Te/Ti ratio.

11. The system according to any one of claims 8 to 10, characterized in that it has a housing in which there is located a pneumatic track, preferably comprising an execution valve (12), a gas stream sensor (13) and a check valve (5), connected in series.

12. The system according to claim 11, characterized in that the execution valve (12) is an analogue valve, preferably constituting an electropneumatic valve, more preferably stepper motor valve.

13. The system according to any one of claims 8 to 12, characterized in that it comprises digital voltmeters Vm, pmax and pmin, each connected to a display located on the housing.

14. A method of multi-station ventilation by means of a ventilator inspiratory gas mixture from a single ventilator, comprising distribution of a ventilator inspiratory gas mixture into at least two inspiratory and expiratory tracks, characterized in that it also comprises stages of the control method according to any one of claims 1 to 6.

15. A method of multi-station ventilation by means of a gas mixture from a single ventilator, comprising a system of distribution of a ventilator inspiratory gas mixture into at least two inspiratory and expiratory tracks, characterized in that in each inspiratory track it also comprises a control system according to any one of claims 7 to 13.