VENTILATION APPARATUS FOR VENTILATING A PERSON, CONTROL METHOD FOR CENTRIFUGAL FAN OF A VENTILATION APPARATUS, AND VENTILATION METHOD

Abstract

An apparatus comprises a centrifugal fan having an inlet and outlet, the fan receives ventilation air at the inlet and provides the ventilation air at an adjustable pressure at the outlet, a first respiration line with a first end connected to the inlet and a second end for receiving inhalation air, a second respiration line having a first end connected to the outlet and a second end for coupling a filter and a ventilation mask, the second respiration line having a sensor, to measure a flow parameter in the second respiration line, and a device for controlling the fan according to an output signal of the sensor, the fan and second respiration lines forming a continuous bidirectional flow path, the adjustable ventilation pressure at the outlet comprises an inhalation or an exhalation pressure less than or equal to the inhalation pressure, and the second respiration line has an air filter.

Claims

1-17. (canceled)

18. A ventilation apparatus which is adapted for non-invasive ventilating of a person, comprising: a centrifugal fan having an inlet opening and an outlet opening, the centrifugal fan being adapted to receive ventilation air at the inlet opening and to provide the ventilation air at an adjustable ventilation pressure at the outlet opening, a first respiration line having a first end connected to the inlet opening of the centrifugal fan, and having a second end arranged for receiving inhalation air, a second respiration line having a first end connected to the outlet opening of the centrifugal fan, and having a second end adapted for coupling a ventilation mask, the second respiration line being provided with a sensor device, by means of which at least one flow parameter in the second respiration line can be measured, and a control device adapted for controlling the centrifugal fan in dependency on at least one output signal of the sensor device, wherein the centrifugal fan and the second respiration line form a continuous bidirectional flow path, the adjustable ventilation pressure at the outlet opening of the centrifugal fan comprising an inhalation pressure or an exhalation pressure which is equal to or less than the inhalation pressure, and the second respiration line is provided with a filter device (60) which is arranged for air flow filtering.

19. The ventilation apparatus according to claim 18, wherein: the flow path between the second end of the second respiration line and the inlet opening of the centrifugal fan is free of valves.

20. The ventilation apparatus according to claim 18, wherein: the first respiration line includes a valve device arranged between the inlet opening of the centrifugal fan and the second end of the first respiration line and arranged as an expiration exit for the outlet of exhalation air.

21. The ventilation apparatus according to claim 20, wherein: the valve device is a passive outlet valve.

22. The ventilation apparatus according to claim 18, wherein: the second end of the first respiration line opens into surroundings of the ventilation apparatus.

23. The ventilation apparatus according to claim 18, wherein: the second end of the first respiration line is adapted for coupling to a respiration air reservoir.

24. The ventilation apparatus according to claim 18, comprising: a respiration air conditioning device which is coupled to the second end of the first respiration line.

25. The ventilation apparatus according to claim 24, wherein: the respiration air conditioning device is adapted for adjusting at least one of the parameters moisture, temperature and oxygen content of the inhalation air.

26. The ventilation apparatus according to claim 25, wherein: the respiration air conditioning device comprises a temperature control device which is adapted for controlling the temperature of the ventilation apparatus.

27. The ventilation apparatus according to claim 26, wherein: the temperature control device is adapted for controlling the temperature of the second respiration line.

28. The ventilation apparatus according to claim 18, having at least one of the features: the filter device comprises a HEPA filter, and the filter device comprises a plug connection to at least one of the centrifugal fan and the second respiration line.

29. The ventilation apparatus according to claim 18, having at least one of the features: the control device is provided with an interface for receiving an output signal of an oxygen saturation sensor, the control device is arranged directly adjoining the centrifugal fan, and the control device is adapted for outputting an alarm signal in the event of at least one of a malfunction of the ventilation apparatus and a critical state of the ventilated person being identified.

30. The ventilation apparatus according to claim 18, wherein: the control device is adapted for controlling the centrifugal fan using a first control loop, by means of which the ventilation pressure at the outlet opening of the centrifugal fan can be adjusted.

31. The ventilation apparatus according to claim 30, wherein: the control device is adapted for controlling the centrifugal fan using a third control loop, by means of which target variables of the first control circuit are adjustable in such a way that at least one of the parameters of tidal volume and minute volume of the ventilation can be matched to predetermined volume reference variables of the tidal volume or of the minute volume.

32. The ventilation apparatus according to claim 31, wherein: the control device is adapted for controlling the centrifugal fan in dependency on an output signal of an oxygen saturation sensor using a fourth control loop, by means of which a target variable of the third control loop is adjustable such that an oxygen saturation in the blood of the ventilated person is matched to a predetermined oxygen saturation reference variable.

33. The ventilation apparatus according to claim 18, wherein: the control device is adapted for controlling the centrifugal fan using a second control loop, by means of which at least one of the following can be adjusted: a frequency of inhalation phases, in which the inhalation pressure is established at the outlet opening of the centrifugal fan, and a duty cycle of the duration of the inhalation phases relative to the duration of exhalation phases, in which the exhalation pressure is established at the outlet opening of the centrifugal fan.

34. The ventilation apparatus according to claim 33, wherein: the control device is adapted for controlling the centrifugal fan using a third control loop, by means of which target variables of the second control circuit are adjustable in such a way that at least one of the parameters of tidal volume and minute volume of the ventilation can be matched to predetermined volume reference variables of the tidal volume or of the minute volume.

35. The ventilation apparatus according to claim 34, wherein: the control device is adapted for controlling the centrifugal fan in dependency on an output signal of an oxygen saturation sensor using a fourth control loop, by means of which a target variable of the third control loop is adjustable such that an oxygen saturation in the blood of the ventilated person is matched to a predetermined oxygen saturation reference variable.

36. A control method for controlling a centrifugal fan for ventilating a person, comprising at least one of the steps of: controlling the centrifugal fan using a first control loop, by means of which the ventilation pressure at an outlet opening of the centrifugal fan can be adjusted to an inhalation pressure or an exhalation pressure which is equal to or less than the inhalation pressure, and controlling the centrifugal fan using a second control loop, by means of which at least one of the following can be adjusted: a frequency of inhalation phases, in which the inhalation pressure is established at the outlet opening of the centrifugal fan, and a duty cycle of the duration of the inhalation phases relative to the duration of exhalation phases, in which the exhalation pressure is established at the outlet opening of the centrifugal fan.

37. The control method according to claim 36, comprising the step of: controlling the centrifugal fan using a third control loop, by means of which target variables of at least one of the first control loop and the second control loop are adjustable in such a way that at least one of the parameters of tidal volume and minute volume of the ventilation can be matched to predetermined volume reference variables of the tidal volume or of the minute volume.

38. The control method according to claim 37, comprising the step of: controlling the centrifugal fan according to an output signal of an oxygen saturation sensor using a fourth control loop, by means of which a target variable of the third control loop is adjustable such that the oxygen saturation in the blood of the ventilated person is matched to a predetermined oxygen saturation reference variable.

39. The control method according to claim 36, wherein: the centrifugal fan is included in the ventilation apparatus according to claim 35.

40. The method for operating the ventilation apparatus according to claim 35, comprising the steps of: operating the centrifugal fan, measuring at least one flow parameter using sensor device, and controlling the centrifugal fan by means of a control method according to claim 36.

Description

DESCRIPTION OF THE DRAWINGS

[0040] Further details and advantages of the invention will be described in the following, with reference to the accompanying drawings. The drawings, schematically in each case, show:

[0041] FIG. 1 is a perspective view of a preferred embodiment of the ventilation apparatus according to the invention;

[0042] FIG. 2 depicts side views of the ventilation apparatus according to FIG. 1;

[0043] FIG. 3 depicts sectional views of the ventilation apparatus along the lines 3A and 3B in FIG. 2;

[0044] FIG. 4 is a flow diagram of the ventilation apparatus according to preferred embodiments of the invention; and

[0045] FIG. 5 is a flow diagram of a preferred embodiment of the control according to the invention of a centrifugal fan of a ventilation apparatus.

DETAILED DESCRIPTION

[0046] Features of preferred embodiments of the invention are described by way of example in the following, with reference to a design of the ventilation apparatus in a spherical housing, a flow diagram of the ventilation apparatus, and a flow diagram of the control loops which are preferably provided. It is emphasized that the implementation of the invention in practice is not limited to the examples shown, but rather can be modified in particular with respect to the dimensions, shapes, materials and design of the control loops.

[0047] An embodiment of the ventilation apparatus 100 is shown schematically in a perspective view in FIG. 1 and in side and sectional views in FIGS. 2 and 3, comprising the centrifugal fan 10, the first respiration line 20 (shown in part), the second respiration line 30 (shown in part), the sensor device 40, and the control device 50, in a substantially spherical housing 101. In a manner known per se, the centrifugal fan 10 contains, in a fan housing 13, an electric motor 14 and an impeller having fan blades 15 (see FIG. 3A). The electric motor 14 is for example a brushless direct current motor (BLDC motor). The axis of rotation of the electric motor 14 define a main axis (z-direction) of the ventilation apparatus 100. The fan housing 13 extends perpendicularly to the main axis, and comprises a central inlet opening 11 which opens along the main axis, and a tangential outlet opening 12 which opens perpendicularly to the main axis. The first end 21 of the first respiration line 20 is connected to the inlet opening 11, and the first end 31 of the second respiration line 30 is connected to the outlet opening 12.

[0048] During operation of the centrifugal fan 10, ventilation air is sucked in via the inlet opening 11 and provided at the outlet opening 12 at a ventilation pressure dependent on the respiration phase. The centrifugal fan 10 is preferably provided with straight, radially extending fan blades 15, wherein the centripetal effect of the fan blades 15, and no aerodynamic effects, preferably is used for pressure build-up. Particularly preferably, the fan blades 15 are slanted with respect to the peripheral direction of the centrifugal fan. This reduces the effectiveness, but also the operating noise, of the fan. In the case of a maximum rotational speed, given by the operating voltage, of 40,000 rotations/min, for example a maximum ventilation pressure of approximately 35 mbar is generated at a flow of at most approximately 100 1/min.

[0049] The first respiration line 20 and the second respiration line 30 are each formed of a rigid or flexible line material and preferably each comprise a plastics tube. The second end 22 of the first respiration line 20 is connected to the respiration air conditioning device 70 and arranged for receiving inhalation air (see FIG. 4). The second end 32 of the second respiration line 30 is connected to the face mask 110 via a filter device 60 (see FIG. 4).

[0050] The valve device 23, comprising a passive outlet valve, is provided at the second end 22 of the first respiration line 20, directly at the inlet opening 11 of the centrifugal fan 10. The valve device 23 closes in the inhalation phases, such that inhalation air is supplied to the centrifugal fan 10, and it opens in the case of an increased pressure in exhalation phases, such that exhalation air is diverted past the first respiration line 20 and into the surroundings. The outlet valve is preferably a simple expiration valve, which is located directly in front of the inlet opening of the fan 11. The inlet opening of the fan 11 is thus switched between oxygen / humidification and expiration exit, depending on the sign of the airflow flowing through the centrifugal fan 10.

[0051] The sensor device 40 comprises a pressure sensor 41 and a flow sensor 42, by means of which the pressure or the flow speed in the second respiration line 30 can be acquired. The measurement takes place at a narrowing 43 in the second respiration line 30 (see FIG. 4). The narrowing 43 comprises e.g. a nozzle. The pressure sensor 41 and the flow sensor 42 are connected to the control device 50, which controls the centrifugal fan 10 according to output signals of the sensors, as is described below with reference to FIG. 5.

[0052] The control device 50 comprises, as shown schematically in FIG. 1, a motor controller 51 for providing a control signal for the operation of the electric motor 14, and a control circuit 52 for implementing the control loops for controlling the centrifugal fan 10. The motor controller 51, such as a BLDC controller, is preferably arranged directly on the electric motor 14, in order to minimise electromagnetic interference (EMI). For the purpose of controlling the ventilation apparatus 100, the control circuit 52, such as an Arduino microcontroller, is preferably located directly on the centrifugal fan 10, in order to minimise the interfaces to the sensors and actuators.

[0053] The ventilation apparatus 100 is furthermore provided with an electrical interface 102 (see FIG. 1), which is configured for connecting at least one electrical connection for energy supply and for data exchange, and/or for a wireless connection of the ventilation apparatus 100 to an external network or control apparatus. The interface 102 is adapted for example for a 4-pole cable (2 poles for supply voltage, e.g. 12 V, and 2 poles for a USB port), and is adapted having an interface for the SpO.sub.2 sensor, an interface for an optical and/or acoustic alarm, and a Bluetooth interface for remote control and/or a datalogger, e.g. having a computer or Smartphone.

[0054] In the following, the pneumatic configuration of the centrifugal fan 10 is described, which operates as a pressure generator for generating a flow-independent ventilation pressure of e.g. 5 mbar to 30 mbar. In the case of the centrifugal fan 10, comprising straight, radially extending fan blades 15, the ventilation pressure at the outlet opening of the centrifugal fan 10 generally results according to

[00001]$\text{p}\text{=}1/2*\rho *{\left(2*{\text{p}}_{\text{i}}*\text{f}\right)}^2*\left({\text{r}}_{\text{a}}{}^2\text{}-{\text{r}}_{\text{i}}{}^2\right)$

wherein: p = air density, f = rotational speed, r.sub.a = outside diameter of the impeller, r.sub.i = inside diameter of the impeller. In the case of a maximum rotational speed, achieved using a BLDC motor, of 40,000 rpm (670 Hz), a minimum outside diameter of approximately 40 mm results. In order to be able to achieve a flow of e.g. 100 1/min, the fan blades 15 preferably have a height of approximately 4 mm at the periphery. With the fan housing 13, a size of the centrifugal fan 10 of approximately 60 mm diameter and approximately 15 mm height results, at a mass of approximately 20 g. The dead volume of the centrifugal fan 10 is only approximately 10 ml.

[0055] These parameters, given by way of example, result in an average power P according to P = 0.001 m.sup.3/s * 2,500 Pa = 2.5 W. With an assumed efficiency of the ventilation apparatus 100 of 25%, the average power input into the electric motor 14 of from approximately 10 W to 12 W results. A motor of this power class weighs approximately 10 g and has a diameter of approximately 18 mm and a length of approximately 15 mm. A form factor of the fan (diameter >> length) allows for the integration of the fan, the measuring path for the flow measurement and the pressure measurement, the motor controller, and the expiration valve in a spherical housing 101 of the size of a tennis ball and having a mass of approximately 50 g. This advantageously achieves comparable sizes as in the case of a respiration gas filter of the Pall Ultipor 50 type, which has a mass of 26 g (dry) and 35 ml dead volume.

[0056] The flow diagram according to FIG. 4 schematically illustrates the pneumatic and electrical configuration of the ventilation apparatus 100 with the centrifugal fan 10, the first and second respiration lines 20, 30, the sensor device 40, the control device 50, the filter device 60, and the respiration air conditioning device 70. The pneumatic interfaces of the centrifugal fan 10 comprise the inlet opening 11 having a hose connection for the air supply and having the expiration valve of the valve device 23, and the outlet opening 12 which opens towards the sensor device 40 and the filter device 60. The continuous bidirectional flow path (see double arrow B) is formed, on which air flows either towards the face mask 110 or in the reverse direction into the surroundings (arrow B).

[0057] The filter device 60 is arranged in the second respiration line 30, between the sensor device 40 and the face mask 110. The filter device 60 comprises a preferably replaceable HEPA filter 61. The HEPA filter 61 is preferably positioned directly on the face mask 110, such that advantageously the dead volume of the ventilation apparatus 100 is minimised.

[0058] For the purpose of humidification, temperature control and adjustment of the oxygen content of the respiration air, the respiration air conditioning device 70 is provided at the second end 21 of the first respiration line 20. The respiration air conditioning device 70 is located outside of the housing 101 of the ventilation apparatus 100 (see FIG. 1). In the respiration air conditioning device 70, inhalation air from the surroundings, optionally enriched with oxygen from an oxygen bottle, flows over heat exchangers from a resistance heating element and/or a Peltier element. Furthermore, the respiration air conditioning device 70 contains a humidifier, which loads the inhalation air with water vapour and/or aqueous aerosol droplets.

[0059] The pressure sensor 41 and the flow sensor 42 of the sensor device 40, as well as the oxygen saturation sensor 120, are connected via signal lines (shown dashed) to the control device 50, in particular the control circuit 52. During operation of the ventilation apparatus 100, the oxygen saturation sensor 120, e.g. a pulse oximeter, is coupled to the person to be ventilated, in order to acquire the oxygen saturation in the blood. The control device 50 is connected to the centrifugal fan 10, in particular the motor controller 51 thereof, via a control line 53. If, instead of the passive expiration valve, an actively actuatable three-way valve of the valve device 23 is provided, this is also actuated by means of the control device 50 (see dotted control line), in order to open alternately into one of the two branches of the first respiration line 20, according to the breathing rhythm. Optionally, the respiration air conditioning device 70 can also be actuated using the control device 50 or using an external controller.

[0060] The diameter of the first and second respiration lines is e.g. 15 mm. The length of the second respiration line 30 from the centrifugal fan 10 to the filter device 60 is e.g. 30 mm. At the narrowing 43, the second respiration line 30 has a diameter of e.g. 8 mm.

[0061] In a manner deviating from FIG. 4, the valve device 23 may be arranged having the valve opening to the surroundings on the side of the second respiration line 30, e.g. at the face mask 110 or between the sensor device 40 and the centrifugal fan 10. In this case, the first respiration line 20 preferably has one single branch only. If the expiration is intended to be pressure-controlled, however, the centrifugal fan 10 must be arranged on the mask side, before the expiration exit.

[0062] The compact design of the ventilation apparatus 100 illustrated in FIG. 4 offers in particular the following advantages. A hose system is not required, since the centrifugal fan 10, together with the sensor device 40, can be plugged directly onto the HEPA filter 61. Valves are not necessarily required. In particular an external expiration valve, as is conventional in the case of one-hose systems, is not required. The rest resistance of the ventilation apparatus 100 is in the order of magnitude of that of the HEPA filter, e.g. approximately 3 mbar*s / 1. Since the pneumatic system can be temperature-controlled to temperatures of over 40° C. within a few seconds, condensation can be effectively prevented. An air stream used for system cooling can even be used with a simple air hood for heating the connected HEPA filter. The mechanical structure of the ventilation apparatus 100, comprising the housing and the respiration lines, is simple, e.g. can be produced using 3D printing, from plastics material.

[0063] The ventilation pressure at the outlet opening 12 of the centrifugal fan 10 is adjusted alternately, using the multi-stage control method shown in FIG. 5, to an inhalation pressure or an exhalation pressure, as is explained in the following. The control method comprises four control loops I to IV, of which the first (I) and the second (II) control loop are necessary for the operation of the ventilation apparatus 100, while the third (III) and the fourth (IV) control loop are provided according to preferred embodiments of the invention. The control loops form a cascade, in which each control loop manipulates the target values of the control loop of the next-lowest level.

[0064] Actual values (reference variables) of the control loops are delivered in each case by the pressure sensor 42 for the first control loop I, the flow sensor 42 for the second control loop II, an output 54 of the control circuit 52 for the third control loop III, and the oxygen saturation sensor 120 for the fourth control loop IV. Limiters, denoted IA to IVA are provided in the control loops in each case, which limiters keep the control loops within specified limit values of time and pressure parameters. In the case of the test steps IB to IVB, predetermined target values are compared with the actual values, as is explained below. The “Δ” function calculates, in steps IC to IVC, the change in the respective controller target value on the basis of the pre-set parameters.

[0065] The first (innermost) control loop I comprises a pressure control, by means of which the ventilation pressure (inhalation pressure IPAP and exhalation pressure) is adjusted, using predetermined PIP and PEEP parameters (IA) as upper and lower limit values, respectively. The upper limit value PIP is selected by the treating operator, e.g. a doctor, such that the lung is not overexpanded during ventilation, and the lower limit value PEEP is selected such that the alveolae do not fall together upon exhalation. The PEEP parameter is preferably selected in the range of 5 mbar to 15 mbar, e.g. 8 mbar. The first control loop I is a PI controller, by means of which the ventilation pressure is adjusted using the rotational speed of the centrifugal fan 10, and the integration constants of which are given by the PIP and PEEP parameters.

[0066] At rest, a healthy person requires a respiration volume of approximately 8 ml air / (kg [body weight] * min). In general, the state of the patient will change over time, e.g. an improvement in the phase of weaning off the ventilating, or a worsening e.g. on account of advancing atelectasis (alveolar collapse). In order to prevent the collapse of the alveolae at the end of the expiration phase, it is provided for the minimum pressure (PEEP, positive end-expiratory pressure) to be maintained. Accordingly, the ventilation apparatus 100 has to generate only varying positive pressures.

[0067] The next highest level comprises, with the second control loop II, a time control, the target values of which for frequency (f) of the inhalation and duty cycle of inhalation and exhalation (I:E) are adjusted (in a parameterisable manner) within physiologically reasonable limits. Together with the subordinate pressure control, the BIPAP functionality is already implemented. The frequency is selected for example in the range of from 25 min.sup.- .sup.1 to 12 min.sup.-1. The duty cycle is selected for example in the range of from 30% (at low frequencies) to 50% (at high frequencies).

[0068] At the second-lowest level the third control loop III implements a control of the tidal and/or minute volume (TV, MV), in order to be able to react to changes in the stiffness of the lungs and the airway resistance within specified limits (parameterizable). The reference variable is the tidal volume which is calculated by the temporal integration of the measured flow during inspiration and expiration phases, and is provided by the control circuit 52 at the output 54. The target value for the third control loop III is specified by the minute volume parameter. The output of the third control loop III modifies the target value specifications of the pressure control of the first control loop I and the time control of the second control loop II.

[0069] At the highest level, the fourth control loop IV specifies the target value of the minute volume by an i-controller, which has the oxygen saturation as the reference variable and compares this with its local target value. As a result, the entire control loop is closed. Too low an oxygen saturation for examples leads to a gradual increase in the minute volume specification, and this leads to an increase in the target values for PIP, breath frequency, inspiration/expiration ratio, and PEEP.

[0070] The limits of the ranges of all target values are parameterised. Thus, the controls of the individual control loops, in the absence of a reference variable or control variable of a higher level, automatically remain in the range of that which is specified by the local parameterisation thereof. A failure of the oxygen saturation sensor 120 would lead for example to freezing of the target value for the minute volume and, in the case of activated control in the fourth control loop IV, would lead to a warning. If desired minute volumes cannot be achieved within the specified limits of the time control or pressure control, e.g. on account of too high a compliance, the system automatically remains within these limits and issues a warning.

[0071] During operation of the ventilation apparatus 100, preferably at least one of the following safety measures is provided. In the case of a power failure, the behaviour of the ventilation apparatus 100 transitions into that of an FFP3 mask. The maximum rotational speed of the centrifugal fan 10, and thus the achievable system pressure, are fixed in an invariable manner by the fan design, the operating voltage, and the diameter of the fan wheel. A failure of the motor controller 51 cannot lead to a motor wearing out, and a blow out as in the case of DC motors is not possible. There are no blocking valves; inhalation and exhalation airways are always completely open and are only dynamically pressurised. Non-ventilated masks can thus be used without limitation. After a short warming phase, formation of condensate is prevented by the design, inter alia on account of the lack of hose lines.

[0072] There are at least two possibilities in order to be able to estimate possible losses by leakage of the face mask during NIV ventilating. Firstly, a measurement and extrapolation of the flow and pressure data at the end of the inspiration phase results in an estimation of the flow caused by mask leakages, at a constant pressure. Secondly, a bidirectional measurement of the flow in front of the centrifugal fan can be provided.

[0073] In summary, the ventilation apparatus 100 advantageously has at least one of the following features. The ventilation apparatus 100 ensures that the ventilated person obtains enough oxygen (oxygen saturation typically > 90%), and that enough CO.sub.2 is removed in order to maintain their vital functions. The system is adapted to acquire the reference variable oxygen saturation (SpO.sub.2). Additional oxygen can be fed in. The ventilation apparatus 100 can autonomously compensate for changes in the lung condition of the ventilated person, within physiologically reasonable limits, by changing the tidal or minute volume. The ventilation apparatus 100 can signal to the clinicians, via acoustic, optical and/or digital alarms, when there is a risk of the treatment destabilising.

[0074] The features of the invention disclosed in the above description, the drawings, and the claims, can be of significance both individually and in combination or subcombination for implementing the invention in the various embodiments thereof.