Patent Application
20230191054
The invention is directed to a device and a method for alternately, intermittently carrying out a measuring functional mode, in particular for measuring the esophageal or thoracic pressure, on the one hand, and a sealing functional mode, in particular with a dynamically adaptive, trans- or intra-esophageal seal, on the other hand, including a catheter that is provided with at least one measuring and/or sealing balloon component that alternates between two filling states, the filling state of the balloon component (i) in the measuring functional mode having a flaccid, volume-defined, static filling of the balloon, and (ii) in the sealing functional mode preferably being set in a pressure-controlled manner, in that respiratory-mechanically caused pressure fluctuations that are transferred from the thorax to the esophageally or tracheally sealing balloon are compensated for via appropriate displacements of filling medium by a controller unit connected to the catheter unit, thus continuously maintaining a sealing target pressure that is specified by the user.
In the machine ventilation of patients, a problem that frequently arises is the transition from a ventilation mode that is completely controlled by the therapist into an assisted ventilation mode that supports the autonomous breathing of the patient. In assisted ventilation modes, the ventilator connected to the patient senses pressure fluctuations or volume movements that arise in the tube system that is connected to the patient. If a decrease in the pressure prevailing in the inspiratory branch of the tube system or a measurable gas movement (flow) directed toward the patient occurs during the initial inspiration by the patient, the ventilator assists the breath that is initiated by the patient until a ventilation pressure, specified by the therapist, to be achieved at the end of the inspiration (end tidal) or a desired end tidal breath volume (tidal volume) is reached.
It is generally the objective of assisted ventilation to maintain to the greatest extent possible the capability of a patient for thoracic autonomous breathing in order to ensure rapid, complication-free disconnection of the patient from the ventilator or removal of the ventilation tube (extubation) if necessary. After the extubation, the patient should continuously perform sufficient respiratory work without subsequently becoming respiratory-mechanically exhausted.
To make the capability for sufficient autonomous breathing measurable and estimatable, measuring catheters are used which are positioned in the esophagus of the patient and equipped with balloon components that are generally filled in situ with air in a flaccid and tension-free manner. The so-called esophageal pressure prevailing in the esophagus corresponds approximately to the so-called intrathoracic pressure, and is used as the standard for clinically measuring same. An optimal approximation of the pressures is achieved when the balloon component of the measuring catheter is placed approximately in the region of the transition from the lower area of the esophagus to the area in the lower third of the esophagus.
The intrathoracic pressure, which is generally converted into an electrical signal outside the patient via a pressure-receiving element, may be plotted as a coordinate with respect to the respiratory gas volume (flow) that is moved by the patient and simultaneously measured by the ventilator. The respiratory work performed by the patient is then depicted as an iterative loop. The particular capability of the patient for autonomous breathing may thus be assessed over time.
The present invention provides esophageal pressure measuring catheters with the capability of sealing the residual esophageal lumen that forms in each case around the catheter shaft, as the result of which the rising up of stomach contents into the pharynx of the patient (gastropharyngeal reflux) may be reduced or largely prevented. The so-called aspiration of gastropharyngeally rising stomach contents is one of the known causes of ventilation-associated lung inflammation. The secretion that rises up into the pharynx during aspiration passes from there into the deep airways, which facilitates the development of inflammatory pulmonary complications.
To reduce the gastropharyngeal reflux, the upper body of the patient is elevated to a certain angle, if possible, thus enabling clinically verifiable reductions in the incidence of ventilation-associated pneumonia. The present invention is intended to enable such an effect even if it is medically indicated that the patient must remain in a horizontal body position. If the thorax of the patient is already in a position with the upper body elevated, the reflux-preventive effect may be further improved by the option, made possible within the scope of the invention, of a continuous balloon tamponade of the esophageal lumen.
It is therefore desirable to be able to change back and forth between two filling states of an esophageally placed balloon element.
On the one hand there is a volume-controlled filling state in which the balloon element is filled with a predefined volume of a filling medium, and on the other hand, a pressure-controlled filling state in which the filling pressure inside the balloon element is held approximately constant.
Furthermore, the balloon on the one hand is intended to fulfill an esophageal sealing function in order to suppress or interrupt the free rising up of secretions from the stomach into the pharynx. This function may be optimally fulfilled when the balloon is controlled to a predefined filling pressure.
On the other hand, the esophageally placed balloon is intended to assume a defined filling state that allows the intrathoracic pressure to be measured, as the result of which the catheter may be used for intermittent respiratory-mechanical monitoring of the actively breathing or machine-assisted thorax. In this regard, pressure regulation would be counterproductive, since in that case only the filling pressure that is held constant would be measured, and not the intrathoracic pressure.
Therefore, the invention utilizes a switchover of the control and regulation module in such a way that the filling pressure of the balloon during a sealing state is adjusted to be as constant as possible, while in a measuring state the pressure is not continuously adjusted, but instead only a defined filling volume of a filling medium is pushed into the balloon and is then “left to itself,” in a manner of speaking, so that it is receptive to the thoracic pressure.
However, this requires a switchover between two different operating modes. It must be kept in mind that a measuring operating mode is to be repeated at certain time intervals in order to track the development of the patient's capability for autonomous breathing, and in each case to adapt the additional machine respiration so that the patient may gradually be led back to strictly autonomous breathing.
However, a manual switchover for such an adaptive modification of the machine respiration to the progressive capability of the patient for autonomous breathing requires the continuous presence of operating personnel in order to switch or program the system in each case into the correct functional mode.
This disadvantage of the prior art has resulted in the object of the invention, to find an option for allowing a ventilated patient to be gradually led to autonomous breathing over the course of his/her recovery process, without the need for constant support from operating personnel.
To achieve this object, the invention provides that a switchover between the two functional states may be triggered manually as well as via a programmable time cycle.
Such a manual switchover may be made at a controller unit that generates the pressure in the catheter balloon for the intermittent measuring function, or maintains it synchronously with the respiratory-mechanically generated pressure changes in the thorax, in the sense of continuous secretion sealing. The ventilator or the controlling unit on the one hand allows the change to be made manually, preferably with the touch of a button. It is thus possible for a medical practitioner or other operating personnel to change into the measuring functional mode, for example, at any time, and to check the present capability of the patient for autonomous breathing and manually adjust the ventilator if necessary.
On the other hand, the invention also provides an automatic switchover, the controller unit automatically switching back and forth between the two functional modes, based on a programmable time cycle. Due to such a functionality, the device according to the invention is able to check at regular time intervals, in a self-adaptive manner, the parameters for machine support for assisted respiration, and to optimize or reset them if necessary. The device according to the invention may therefore be used for prevention of pneumonia and for respiratory planning.
It has proven to be advantageous for the catheter to be a feeding catheter and/or decompression catheter that is nasogastrically or orogastrically inserted into the esophagus, or also into the duodenum or into the jejunum via the stomach.
There is an option for the sealing balloon component to tamponade or seal the entire thoracic esophagus, or to encompass only the upper half or the lower half of the thoracic esophagus.
It is recommended in the invention that the sealing and/or measuring balloon be preformed with a diameter or circumference that exceeds the diameter or circumference of the respective lumen, in particular the esophageal lumen. This results in the advantage that the lumen in question may be tamponaded tension-free, but still in a space-filling and sealing manner. Since in this regard the surface of the measuring balloon does not have to be expanded, the pressure inside the balloon element is equal to the pressure on the outside of the balloon envelope, thus in the present case the thoracic pressure in the area of the lumen, in particular esophageal lumen, in question.
Within the scope of the invention, the sealing and optionally also measuring balloon has a balloon end that is extended in the proximal direction, toward the extracorporeal catheter end, and whose diameter exceeds the outer diameter of the catheter shaft supporting the balloon, and which forms a gap via which the sealing balloon may be filled and acted on by pressure. By fastening the balloon in question only with its distal balloon end to the catheter shaft in such cases, a supply line to the balloon for filling it with a filling medium or also emptying it is obtained in a very simple manner. Moreover, a gap having a comparatively large cross section allows comparatively high flow to/from the balloon, so that dynamic, in particular respiratory-mechanically caused pressure fluctuations, may be adjusted relatively quickly, and an optimal seal is always ensured.
The segment of the balloon that forms the balloon and/or the gap may have a web-like, partially collapsing inner structure that keeps the supply line to the balloon at least partially open. A permanently open flow connection between the intracorporeal, esophageally placed balloon on the one hand and an extracorporeal pressure controller on the other hand ensures that an immediate adjustment of dynamic pressure fluctuations is possible at any time.
The measuring balloon component is to be arranged in such a way that it is situated in the lower half of the thoracic esophagus when the catheter is properly positioned, i.e., in the area of the diaphragm, where the pressure fluctuations are greatest.
In addition to an embodiment in which the same balloon is used for measuring and for sealing, it may also be provided that the sealing balloon and the measuring balloon are designed as structurally separate and separately fillable components. If these components are controllable to different pressures or filling volumes, the pressure of the sealing balloon may be continuously controlled, while the measuring balloon is continuously filled only up to a flaccid state.
There are various options for arranging a measuring balloon and a sealing balloon relative to one another. Within the scope of a first embodiment, the measuring balloon may be situated concentrically inside the sealing balloon.
On the other hand, it is also possible for the measuring balloon to be situated in series, below or distal to the sealing balloon.
Radiopaque markers on the shaft tube of the catheter, in particular in the area of the proximal and/or distal end of a balloon component, allow the length and/or position of the balloon component or balloon components in question to be made visible via X-ray. It is thus possible, if necessary, to correct or optimize the position of an esophageal catheter according to the invention inside a patient to ensure maximum sensitivity to pressure fluctuations or other signals to be recorded.
A control and/or regulation unit is connected or connectable to the measuring and/or sealing balloon components of the catheter; its task on the one hand is to coordinate the various functional modes or their sequence, and on the other hand is to be able to control the filling volume of the particular measuring balloon, in the measuring functional mode, in such a way that it assumes a flaccid, tension-free form due to incomplete, volume-defined filling, while in the sealing functional mode the filling state of the particular sealing balloon is regulated in a pressure-controlled manner.
In particular, a control and/or regulation unit according to the invention may be designed in such a way that at least three operating modes are selectable: namely, a strictly measuring functional mode, a strictly sealing functional mode, and an automatic operating mode in which the automatic controller continuously triggers a change between the measuring functional mode and the sealing functional mode, in particular based on a programmable time cycle. Thus, there are only two different functional modes, namely, either the measuring functional mode with a constant filling volume, or the sealing functional mode with a constant filling pressure. However, there is also a third operating mode in which a switch is made back and forth between these two functional modes.
For definition of the present functional state of the system according to the invention, i.e., the first or second functional mode that is selected in each case, a selection module is provided which includes at least one logical output whose output signal in one functional state is high, but in the other functional state is low. The invention profits from the fact that two possible functional states, namely, a measuring functional mode on the one hand and a sealing functional mode on the other hand, may be represented by a single digital signal, in that the logical value “high” is associated with a first functional state, and the logical value “low” is associated with the other functional state.
The selection module may be designed in the manner of a flip-flop or a bistable toggle circuit, including a setting input, which for a rising flank or for a high level of the input signal at this input sets the output signal at the logical output to “high,” and including a resetting input, which for a rising flank or for a high level of the input signal at this input sets the output signal at the logical output to “low.” Such a bistable toggle circuit thus forms a type of “memory” that remembers the most recently set functional mode in each case, and maintains this functional mode until there is a newer, different manual or machine (switchover) command.
For a manual input, it is provided that the setting input and/or the resetting input of the selection module are/is coupled to a manual input means, for example a switch or button.
On the other hand, the setting input of the selection module may be coupled to a programmable dead time or delay module that is started for a falling flank of the output signal at the logical output or for a rising flank at an inverting output, and after a programmed or programmable time interval elapses, delivers a rising flank to the setting input; and/or the resetting input is coupled to a programmable dead time or delay module that is started for a rising flank of the output signal at the logical output or for a rising flank of the output signal at the inverting output, and after a programmed or programmable time interval elapses, delivers a rising flank to the resetting input. Temporally controlled switching back and forth between two functional modes is thus possible at any time.
If multiple input signals that are associated with the same setting input or the same resetting input are linked to one another by one OR gate each, one or more input signals of at least one OR gate may be locked or unlocked by one or more logical blocking and/or enabling signals, in particular via one AND gate each. Further pursuing this concept of the invention, it may be further provided that one or more logical blocking and/or enabling signals are derived from a further input option, in particular an input button.
Moreover, the invention is preferably further characterized by dynamically adaptive, trans- or intra-esophageal secretion sealing, preferably including a [control loop], the actual value of the filling pressure in the balloon component or in a supply line thereof being detected and held as constant as possible by controlling to a predefined target value, in particular using a controller unit that is designed as an electro-pneumatic or electronic-pneumatic controller, and that in the sealing functional mode, in particular in the state of esophageal or tracheal sealing, continuously maintains a target pressure, specified by the user, inside the sealing balloon, and pressure fluctuations in the sealing balloon, in particular pressure fluctuations that are respiratory-mechanically caused, i.e., occurring in the course of the spontaneous respiration by the patient, being compensated for by appropriate displacements of filling medium into and out of the balloon in order to maintain the seal.
Further advantages may be achieved in that the controller unit, which is connected to the alternately measuring and sealing balloon component of the catheter, has at least one electronic pressure-controlling valve that sets the particular filling pressure in the balloon. This valve is used as an actuator that is acted on by the controller according to a predefined control algorithm, with the objective of holding the filling pressure inside the esophageally placeable balloon component as constant as possible.
In addition, the control and/or regulation unit according to the invention is intended to have a valve function that supplies the balloon and via which volume may be supplied to the balloon in a defined manner, as well as a valve function, parallel thereto, that discharges from the balloon and via which the volume may be withdrawn from the balloon. A constant filling volume of the balloon component may be set in this way.
According to a further design rule, one or both or all controllable valve components is/are designed as piezoelectronically operating actuators. Since only very small filling volumes are necessary for an esophageally placed balloon, solenoid valves are generally not sufficiently fine-tuned, and therefore the use of piezoelectronic actuators is preferred.
According to the invention, an arrangement is preferred in which the pressure-controlling valve has an integrated or connected sensor function that measures the filling pressure in the balloon, in particular via a sensor for the filling pressure in the balloon, the valve controlling the pressure in the balloon in such a way that a predefined filling pressure may be maintained, even continuously, when respiratory-mechanically caused pressure fluctuations occur in the balloon.
Reservoir-like components that have a positive pressure or negative pressure may optionally be provided upstream from the valves in question, or the valves are connected to one or more external pressure sources.
On the other hand, the controller may have a module that applies a defined air volume into the measuring balloon, and optionally subsequently withdraws it from the measuring balloon.
A further, preferred task of a control and regulation module according to the invention is to generate a trigger signal as early as possible for a connected ventilator. For this purpose, the stated control and regulation module is intended to have a settable function and/or module that recognize(s) the measured respiratory-mechanically caused pressure fluctuations in the thorax, in particular an initial intrathoracic pressure drop, as an indication of an incipient active respiratory excursion of the thorax. The advantage is that an esophageal pressure drop may be measured much earlier and also more reliably than a pressure drop in the ventilation tube system itself.
If the control and regulation module has recognized an initial intrathoracic pressure drop as an indication of an incipient active respiratory excursion of the thorax, based on such an intrathoracic pressure drop it may generate a trigger signal for triggering machine-assisted respiration by a ventilator.
To allow an incipient respiratory excursion of the thorax to be distinguished from an incidental pressure fluctuation, a comparator module is provided that compares the pressure signal to a magnitude of a pressure reduction that is necessary for triggering a triggering pulse for a ventilator. Such a comparator may receive at one of its inputs the pressure signal in question or a time derivative thereof, and at another of its inputs may receive a predefined or settable target value.
On the other hand, during assisted machine ventilation the effect regularly occurs that the sealing pressure is to be held as constant as possible in the esophageal balloon component, and an adjusted pressure drop is hardly discernible. Therefore, it is recommended in the invention that the control of the controller module is programmed with a latency or dead time that allows a certain pressure drop in the sealing balloon before the volume compensation that receives the target value takes place, in order to obtain the trigger option for machine-assisted respiration.
Therefore, in the event of a pressure drop in the sealing balloon, the control loop is to remain interrupted until a trigger signal for machine-assisted respiration has been generated. The adaptive sealing function may subsequently be immediately resumed.
Furthermore, the invention allows the visualized continuous thoracic pressure signal to be represented on a display device to inform a medical practitioner or some other operating personnel of the particular present state of the assisted ventilation.
In addition, one or more electrodes for receiving or deriving electrical signals of the patient may be situated at the esophageal catheter. The present invention thus describes a possible combination of an optional measuring and/or sealing esophageal balloon catheter with electrode-like components for deriving electrical signals from the diaphragm of the patient and from the structures that innervate the diaphragm. Such methods are known, for example, within the scope of so-called Edi catheter technology or neurally adjusted ventilatory assist (NAVA) ventilation methods. For appropriate placement of the deriving electrodes in the region where the esophagus passes through the diaphragm, parameters that are important for optimizing the synchronization of the ventilator and of the patient are available. Thus, for example, muscle action potentials of the diaphragm muscle may recognize the initial, early start of the patient's effort to inhale, and may already trigger machine assistance of the breathing initiated by the patient at a point in time when the patient in the connected ventilation tube system is not yet generating gas flow directed toward the patient, or the lungs of the patient have not yet expanded to an extent that triggers such a flow directed toward the patient.
The invention further provides that the electrode(s) are/is situated at the surface of the tube shaft or catheter shaft, in particular distal to the balloon element or to all balloon elements. While the sealing function of the balloon component preferably takes place in an upper area of the esophagus, the electrode(s) should be situated as close as possible to the diaphragm, i.e., distal to the balloon element(s).
Multiple electrodes, situated at the surface of the catheter shaft and distributed in the axial direction and spaced apart from one another, offer the advantage that multiple electrode signals are available which sense a larger range in the surroundings of the diaphragm and are therefore able to more reliably sense fluctuations in potential. For this purpose, it has proved advantageous to arrange multiple electrodes in an axial row one behind the other, similar to a phalanx that extends in the longitudinal direction of the esophagus, so that different phases of the potential may also be detected.
A reference electrode preferably delivers a shared reference potential that is preferably proximal or distal to all other electrode(s).
It is further recommended in the invention to arrange the electrode(s) in an area of the catheter shaft that passes through the diaphragm upon proper placement in the esophagus, since the greatest potential amplitudes naturally occur there.
The electrodes may be connectable to an extracorporeal amplifying, evaluating, and/or monitoring module via a wireless connection, such as Bluetooth, in order to transmit the optionally digitized electrode signals; however, a cable provides a less complicated option for transmitting information, each electrode preferably being individually contacted, in particular via a multicore cable having at least one core each for the individual terminal of each electrode.
Each electrode is preferably individually contacted, in particular via a multicore cable having at least one core each for the individual terminal of each electrode, so that all phases may be individually and separately evaluated.
According to one preferred refinement of the invention, the extracorporeal amplifying, evaluating, and/or monitoring module includes a module or a function for autocorrelation of the electrode signal or the electrode signals in order to recognize cyclically recurring sequences of the electrode signal or of the electrode signals, since it is possible to make repeatable statements regarding a present breathing cycle only on the basis of such cyclically recurring sequences.
Within the scope of such an implemented autocorrelation algorithm, a pattern sequence is correlated with subsequent pattern sequences, the degree of correlation or the correlation coefficient necessary for pattern recognition preferably being settable, preferably on a scale from −1 to +1, via an input element, for example via a rotary knob. Since the period between two successive breaths is not always exactly the same, for a breathing cycle it is possible to recognize typical patterns only by such an autocorrelation.
As soon as a reference pattern that is typical for a breathing cycle has been found via such an autocorrelation, a further module or a further function may determine the correlation of one or more such reference electrode signals with measured, respiratory-mechanically caused pressure fluctuations in the thorax, in particular using an initial intrathoracic pressure drop as an indicator of an incipient, active respiratory excursion of the thorax in order to identify, in the stored reference patterns, cyclically recurring sequences of one or more electrode signals as indicators of the onset of a neuromuscular breathing activity, or also relationships between two or more electrode phases that are typical for an incipient, active respiratory excursion of the thorax. The objective is to find a typical pattern course or typical relationships between multiple pattern courses, from which an incipient neuromuscular breathing activity may be deduced. This process is preferably fully automated, and thus requires no support from operating personnel.
A pattern sequence or phased pattern sequence that is identified within the scope of such an autocorrelation as typical for the onset of a neuromuscular breathing activity may be stored as a reference sequence or as a plurality of time-synchronous, phased pattern sequences, and is then available for a correlation in real time with presently measured electrode signals.
When sufficient agreement is recognized between a presently measured electrode signal and a stored reference sequence that is typical for the onset of a neuromuscular breathing activity, or between multiple presently measured electrode phases and pattern sequences that are typical for the onset of a neuromuscular breathing activity and stored in phases, an early trigger signal for triggering machine-assisted respiration is generated by a ventilator.
According to the invention, it is further provided that within the scope of the correlation algorithm, implemented in a module or as a function, between present electrode measured values on the one hand, and stored pattern sequences that are typical for the onset of a neuromuscular breathing activity on the other hand, the degree of correlation or the correlation coefficient necessary for recognizing an agreement is settable, preferably on a scale from −1 to +1, via an input element, for example via a rotary knob.
There are various options for transmitting a trigger signal, generated by the system according to the invention, for additional machine respiration on a ventilator. The least complicated approach is to output the trigger signal as a pulse signal, for example as a voltage signal having 0 V, corresponding to a low level, and 5 V as a high level, or as a current signal having 4 mA as a level and 20 mA as a high level, provided that the ventilator has a corresponding logical input.
For coupling between the control and regulation unit according to the invention on the one hand and the ventilator on the other hand via a parallel or serial interface, the trigger signal may be transferred as a short command sequence.
Such a command sequence may also be transferred wirelessly, for example via Bluetooth.
Alternatively, for this purpose the invention provides that a trigger signal generated by the system according to the invention is transferred as a pressure signal to a ventilator, in that air is discharged from a ventilation tube, leading from the ventilator to the patient, by means of a pressure relief valve that is controlled by the control and/or regulation unit according to the invention, in order to cause a pressure drop in the ventilation tube that is recognizable by the ventilator. A pressure drop, as would be caused during incipient inspiration due to the contraction of the diaphragm brought about by the patient, and which the ventilator waits for anyway, but at a much earlier point in time than would be possible if the pressure drop had to be effectuated by the patient him/herself, is thus recognizably simulated for the ventilator.
However, this pressure relief valve must be closed as soon as possible after the ventilator has initiated machine-assisted respiration, so that this breath does not escape through the pressure relief valve, but instead reaches the lungs of the patient. For this reason, a pressure sensor that is connected or connectable to the control and/or regulation unit is situated at a ventilation tube in order to signal to the control and/or regulation unit whether the ventilator has triggered machine-assisted respiration.
This sensor may also be used to sense the extent of the pressure drop that is caused by the pressure relief valve, so that it may be recognized whether the pressure drop that has occurred is sufficient for activating the ventilator. The pressure relief valve may then be briefly closed, and if an immediately subsequent pressure rise indicates that the machine-assisted respiration has in fact already been initiated, the pressure relief valve remains closed; otherwise, it may be reopened to increase the pressure drop in the ventilation tube system.
The pressure relief valve and/or the pressure sensor may be situated at a Y-shaped connecting piece where the shared ventilation tube splits off from the endotracheal tube into an inspiration tube and an expiration tube that are connected to the ventilator, or may be situated at a tubular connecting piece that is preferably directly connected to the ventilator.
The invention is further characterized by an endotracheal tube, comprising a tube body through which a lumen passes, and whose proximal end is connectable to a ventilator via one or more ventilation tubes, and comprising a cuff that encloses the tube body.
The cuff may be connected to the control and regulation unit via connecting lines, in particular via tube lines by means of which the cuff communicates with the control and regulation unit. As a result, for the control and regulation unit the option is provided to fill or (partially) empty the cuff according to a predefined, implemented algorithm.
Further pursuing this concept of the invention, a module or a function for the dynamically adaptive tracheal sealing of the cuff with respect to the trachea may be provided in the control and regulation unit, the actual value of the filling pressure in the cuff or in a supply line thereof being detected and held as constant as possible by controlling to a predefined target value. Pressure fluctuations in the cuff that are respiratory-mechanically caused, i.e., that occur during the spontaneous respiration of the patient due to appropriate displacements of filling medium into and out of the cuff, may thus be compensated for in order to also dynamically maintain the seal.
The invention may be refined by means of a signal input at the control and regulation unit for receiving data of a ventilator, in particular the volume flow moved from or to the patient and/or the pleural pressure.
This information may be combined with the information generated by the control and regulation unit itself and, for example, visually represented, preferably in the form of an iterating pie chart or as a respiratory work curve with the continuously measured thoracic or pleural pressure signal plotted with respect to the volume flow that is moved from or to the patient. A graphical display device, for example in the form of an LCD display, is suited for this purpose.
A method for switching a balloon component of a tube unit or catheter unit between two filling states, namely, (i) a first filling state of the balloon component in a measuring functional mode, the balloon component being in a flaccid state and having a filling that is statically set in a volume-defined manner, and (ii) a second filling state of the balloon component in a sealing functional mode, the filling of the balloon component being dynamically set in a pressure-controlled manner, in that pressure fluctuations that are transferred to the balloon component are compensated for by appropriate displacements of a filling medium by means of a controller unit that is connected to the catheter unit, so that a sealing target pressure that is specified by the user is continuously maintained, is characterized by a third functional mode in which an automatic controller continuously triggers a change between the measuring functional mode and the sealing functional mode, in particular based on a programmable time cycle.
On the one hand, for a selection of the measuring functional mode, after initial emptying of the balloon, an injection of a defined, specified volume of a filling medium into the balloon takes place which converts the balloon into a flaccid, unexpanded filling state of the balloon envelope.
On the other hand, for a selection of the sealing functional mode, the controlling module either supplies volume to or removes volume from the balloon in order to achieve and continuously hold a set sealing pressure target value.
The derivation of a relatively early trigger signal for triggering machine-assisted respiration, in a time-delayed manner, for example, may also be made possible by measuring or sensing a thoracic pressure fluctuation, the pressure curve being recorded by a pressure-receiving balloon or cuff placed in the esophagus or in the trachea of the patient, and converted into an electrical signal by the control and regulation unit or by the connected ventilator, visualized, and processed by its controller in a regulating manner.
The invention relates in particular to the combination of a continuous derivation of an electrical signal with the continuous or intermittent derivation of a thorax-mechanical signal. While electrical signals are not able to deliver direct information concerning the extent to which a respiratory excursion of the patient's thorax actually develops, the respiratory-mechanical success of a breathing effort may be detected via the profile of the thoracic pressure or pleural pressure, represented as a curve, analyzed for the ventilator control, and used by the user for ongoing ventilation planning. The combination of the two methods described within the scope of the invention allows in particular:
Further features, properties, advantages, and effects based on the invention result from the following description of preferred embodiments of the invention, with reference to the drawings. In the drawings:
The drawings illustrate the invention by way of example, based on an esophageally sealing catheter 1. However, it is emphasized that virtually all aspects of the present invention are also applicable to an endotracheal tube having a tracheally sealing balloon element in the form of a cuff.
The tube supply line 1d from the controller 5 to the connector 1c should have a circular lumen with a diameter of at least 5 mm in order to avoid, to the greatest extent possible, flow-related pressure losses and damping effects between the balloon and the controller. Two flow- or pressure-regulating valve units D and U are connected upstream from the supply line 1d, the unit D regulating the inflow to the patient and the unit U regulating the outflow or the discharge of volume to the surroundings. The valves D and/or U are preferably based on a piezoelectronic design and mode of operation, and are therefore particularly low in noise and energy-efficient. Connected upstream from the two valves D and U are reservoir chambers PD and PU, respectively, which keep a specified positive pressure (PD) or a negative pressure (PU) as a predefined target value. The valves D and U communicate with the respective associated reservoir PD or PU. Alternatively, a positive pressure or a negative pressure may be provided via a respective connection to an external supply unit ZV.
The module 5 also includes a module Z for volume injection into the balloon element 1a of the catheter 1. A defined quantity of air may be displaced from the cylinder into the balloon element 1a or into the feed lumen 1b, 1d leading to the balloon element 1a via a piston-cylindrical arrangement KZ, for example. This is particularly important for the measuring function of the device, since the measurement per se, but in particular also the constant reproducibility of the measurement, requires flaccid filling of the balloon element 1a with a defined volume of the filling medium. The injection of the volume preferably takes place with a set specification by the controlling software of the module, but may also be variably settable by the user. Other mechanisms are possible as a nonsettable variant which ensures, for example, a spontaneously elastically straightening tube support that is installed in a rigid cylinder enclosing the tube element, the cylinder being acted on by pressure during the injection process, and thus pressing out the contents of the tube support toward the catheter balloon 1a, and automatically elastically re-straightening during the decompression of the cylinder.
At the moment of the switchover from the sealing function to the measuring function of the device, the balloon is emptied by opening the vacuum valve U. The valve U subsequently closes, and a specified quantity of a filling medium is led, via a bypass ZB, from the injecting unit Z to the input of the pressure valve D, which flows to the balloon 1a in the open state of the valve. The valve D then closes.
The valve D and/or the valve U have/has a pressure-measuring function, which in the phase of the esophageal pressure measurement continuously detects the pressure prevailing in the balloon and the supply line to the balloon, and derives it as a signal for the monitoring of the pressure curve. The measurement of the esophageal pressure preferably takes place using a gaseous medium whose volume in combination with the medium-conducting volumes of the catheter unit 1 is dimensioned such that the balloon element 1a goes into flaccid filling in order to avoid in any event an expansion of the balloon envelope that impairs the quality of the measurement. The unexpanded state of the balloon envelope ensures that any deflection of the pressure in the esophagus may be detected, or that values may be detected which, in comparison to an expanded balloon envelope, cannot be measured.
Subsequent to the measurement phase, the valve D opens and the pressure in the balloon element 1a is controlled to the sealing pressure DP that is selected by the user, and is continuously held there in the subsequent phase of the controlled sealing. The control ideally takes place as a result of the interplay between active supply and active withdrawal of filling medium to/to [sic; from] the catheter balloon 1a.
This control may take place using a programmable control, logic, and/or regulation unit, it being possible to use a higher-order control logic system SL in order to switch back and forth between a measuring functional mode FM, in which the filling state of the balloon element 1a is controlled to a constant filling volume, and a sealing functional mode FS, in which the filling state of the balloon element 1a is controlled to a constant filling pressure.
This higher-order control system SL has an input possibility with at least two options that switch the system either into the functional state FS of sealing (button S, sealing) or into the functional state FM of measuring (button M, monitoring [sic; measuring]). On the other hand, the alternation between these two functional states may also be specified automatically or by a control algorithm, for which purpose a button A (automatic unit) may be provided.
The higher-order control system SL may be designed as shown in
As long as a high level is present at the output Q1, the system according to the invention operates in the measuring functional mode FM, the filling state of the balloon element 1a being controlled to a constant filling volume, while the output
In contrast, if a high level is present at the output
The output of a first OR gate 23 is connected to the setting input S1; this first OR gate has two inputs, one of which may be connected to a high level via a button M, but otherwise has a low level. If the button M is pressed, this high level reaches the input of the OR gate 23, and from there is relayed to the setting input S1 of the bistable toggle circuit 22; the output Q1 is set to the high level, and the system immediately goes into the measuring functional mode FM.
In addition, the output of a second OR gate 24 is connected to the resetting input R1 of the bistable toggle circuit 22; this second OR gate likewise has two inputs, one of which may be connected to a high level via a button S, but otherwise has a low level. If the button S is pressed, this high level reaches the input of the OR gate 24, and from there is relayed to the resetting input R1 of the bistable toggle circuit 22; the output Q1 is set to the low level, and instead, the inverting output
As is further apparent from
In addition, there is a second feedback from the noninverting output Q1 of the bistable toggle circuit 22 to the second input of the OR gate 24 via a second timer module or delay module T2. A positive flank at the output Q1 of the bistable toggle circuit 22, i.e., a change from a low level to a high level, accordingly reaches the OR gate−24, delayed by a settable time T2, and from there is immediately relayed to the resetting input R1 of the bistable toggle circuit 22 and then triggers an automatic change of the output signal Q1 from a high level to a low level, while instead, the inverting output
Accordingly, the switchover logic system SL from
The higher-order control logic system SL′ from
In contrast, if the switch A is opened, a low level is present at one input each of the two AND gates 25, 26, and the two gates 25, 26 are thus blocked; i.e., at their outputs they do not respond to the output signals of the timer modules T1, T2, and the automatic unit is switched off.
Instead, a high level now reaches one input each of two further AND gates 28, 29 via an inverting module 27, and these further AND gates now become transparent or respond sensitively to the signal at their respective other input. At this location, for the AND gate 28 a button M is connected, and for the AND gate 29 a button S is connected. Both buttons M, S have their inputs at a high level, and connect this high level through to the respective AND gate 28, 29 when the button M, S in question is manually actuated. The AND gate 28, 29 in question then likewise generates at its output a high level, which for the AND gate 28 is relayed to the OR gate 23, and for the AND gate 29 is relayed to the OR gate 24. As a result, when the button M is pressed, the output Q1 of the bistable trigger element 22 is set and the system immediately goes into the measuring functional mode FM, whereas when the button S is pressed, the inverting output
As long as the automatic unit is switched off, the system remains in the particular most recently selected functional mode FM, FS until either of the respective other functional modes FS, FM is selected, or until the automatic unit is switched on by closing the switch A.
Thus, in this control logic system SL′, each selected functional mode FM, FS, including the automatic unit, is stable until a newer input takes place. However, for manually selecting a functional mode FM, FS it is necessary to first switch off the automatic unit, and then in a second action, to select the particular functional mode FM, FS by pressing a button M, S. In contrast, directly pressing a button M, S has no effect unless the automatic unit is switched off.
For technical laypersons, this could result in misunderstandings concerning the particular valid operating mode. To rule this out, there is a further embodiment of a higher-order control logic system SL″, illustrated in
Here, the function of the switch A from
The noninverting output Q2 of the second bistable toggle circuit is connected to one input each of the two AND gates 28, 29, and the respective other input of the two AND gates 28, 29 is connected to the button M or to the button S. Thus, for a high level at the output Q2, the AND gates 28, 29 are transparent, and by pressing a button M or S, via the downstream OR gates 23, 24 either the setting input S1 is activated in order to select the functional mode FM, or the resetting input R1 is activated in order to select the functional mode FS.
On the other hand, the inverting output
As is further apparent in
As long as the button A is not pressed, the bistable trigger element 30 cannot be reset, and remains in this state, which may be referred to as manual operation and in each case one of the two manually selectable functional modes FM or FS being carried out, it being possible at any time to switch between these two functional modes FM, FS by pressing the respective other button S, M.
In contrast, if the button A is pressed, the bistable trigger element 30 is reset, and a high level is then present at the inverting output
In other words, pressing a button M, S, A immediately results in the respective operating mode FM or FS or the automatic operating mode, and the particular operating mode remains active until some other button M, S, A is pressed.
The monitoring of the measured pressure values may take place in various ways. The pressure signal is displayed as a continuous absolute value, for example. It may also be displayed in combination with the volume (flow) that is actively moved by the patient, as an iterating loop KK, to make the respiratory work of the patient representable over time. In addition, the so-called transpulmonary pressure, which results from subtracting the pleural pressure from the so-called alveolar pressure, may be determined.
As a further application option, the unit may also be utilized in both functional states for triggering machine-assisted respiration. Corresponding deflections of the intrathoracic or pleural pressure are temporally accompanied by the start of mechanical respiration of the patient's thorax, even before measurable movements of respiratory gas occur in the tube system connected to the patient. The user specifies a certain thoracic or pleural pressure drop, to be generated by the patient, as a trigger threshold, it being possible for the particular pressure difference to be set via a rotary knob or control knob T, for example in a stepless or rastered manner.
For the combined measuring and sealing balloon 1a described, the invention proposes an approximately cylindrically formed balloon body having a diameter of 15 to 35 mm, preferably 25 to 30 mm. The length is 6 to 12 cm, preferably 8 to 10 cm. The balloon 1a is to be made of a thin-walled material having low volume expansibility. Polyurethanes having a Shore hardness of 90 A to 95 A or 55 D are preferably used. The wall thickness of the balloon body 1a is in the range of 5 to 30 μm, preferably 10 to 15 μm. The sealing pressures, which are set to avoid gastropharyngeal reflux in the balloon 1a, are typically in a range of 5 to 30 mbar, preferably in a range of 15 to 25 mbar.
The measuring balloon 9 preferably has a diameter of 8 to 12 mm, is likewise made of a soft film with a preferably low volume expansibility, and is manufactured, for example, from a PUR having a Shore hardness of 95 A. The dimensions and used materials of the sealing tamponading balloon 8 correspond to the information described above for the esophageal seal.
The method for handling the system made up of the catheter unit 1 and the controller module 5 according to
The catheter unit 1 is typically nasogastrically positioned. The correct positioning of the tamponading sealing and measuring catheter balloon 1a between the upper and the lower sphincter muscles of the esophagus is confirmed by an X-ray of the thorax, the upper and lower ends of the balloon 1a being emphasized by appropriately contrasted markers 14 on the shaft tube SS of the catheter 1.
After the position of the balloon 1a is checked and the catheter 1 is fixed in the area of the nasal opening, the catheter is connected to the controller unit 5.
As the first function step of the controller unit 5, the valve U is opened, as the result of which the balloon body 1a is completely emptied. After the valve U is closed, a predefined volume of a filling medium is led directly to the opened valve D via a volume injection unit Z, and is displaced across the valve into the catheter balloon. The valve D closes, and via a pressure-receiving function that is preferably integrated into the valve, now measures the filling pressure prevailing in the balloon 1a, which corresponds approximately to the intrathoracic pressure, as a continuous value. A first visualization of the intrathoracic pressure then takes place, either as a continuous pressure curve or as a continuous iterating pie chart of a respiratory work diagram. The correct positioning of the balloon 1a is confirmed by a typical diagram of the esophageal pressure curve.
The user checks the continuous thoracic pressure signal for typical depressions, triggered by the resulting thoracic autonomous breathing of the patient. These depressions, when imaged sufficiently clearly, may be used for triggering machine-assisted respiration. The trigger threshold or pressure difference to be achieved may then be set by the user via a rotary controller T.
In the measuring mode, the user may observe the thoracic pressure as a continuous curve/signal, and may have iterating pressure-volume curves (respiratory work curves), or also the computed, so-called transpulmonary, pressure, represented.
The transition from the measuring mode into the sealing mode takes place via a manual switchover (button S) by the user. At this moment the pressure reservoir PD is connected to the valve P, and the negative pressure reservoir PU is connected to the valve U. Volume is now either supplied to or withdrawn from the balloon in order to reach the particular set esophageal sealing target pressure value DP or to continuously maintain it.
To obtain the trigger option for triggering machine-assisted respiration, the control by the controller may be programmed with a certain latency that allows a certain pressure drop in the balloon body before the volume displacement that is directed toward the balloon and that maintains the sealing target value occurs.
The switchover or switchback from the sealing mode to the measuring mode may be triggered by actuating the M button, or may also take place in cycles that are specified by the user.
The distal end 13 of the catheter is optionally designed in such a way that it opens into the stomach of the patient, or also extends through the stomach into the duodenum, or through the duodenum into the jejunum of the patient.
An amplifying and monitoring module 15 on the one hand and a respiratory-mechanical module 19 on the other hand are illustrated. The respiratory-mechanical module 19, in addition to the functions and elements described below, may also contain the functions and elements mentioned above with regard to the controller module 5, in particular valves D and/or U, pressure reservoirs PD and/or PU, a module Z for volume injection into the balloon element 1a of the catheter 1, a control logic system SL, input elements M and S for manually selecting a measuring function on the one hand or a sealing function on the other hand, and optionally also rotary knobs DP, T for inputting an esophageally sealing target pressure value or a trigger threshold.
The amplifying and monitoring module 15 is connected to one or more electrodes 12, 12c via cables 12a, 12d and preferably a detachable plug connection 12b, 12b′, and allows the continuous visualization of the electrical diaphragm activity in the form of a continuous signal curve 16. By use of an appropriate algorithm that analyzes the signal, certain cyclically recurring segments of the signal may be recognized and identified as the effective onset of “neuromuscular” breathing activity. The point in time when the patient-generated neuromuscular activity 17 is recognized may be led to the ventilator V of the patient and may trigger assisted respiration there, which provides optimal early assistance to the spontaneous breathing effort by the patient at a point in time that precedes the effective autonomous breathing that triggers a volume flow to the patient, i.e., already in the state of “isometric” patient breathing, wherein the thoracic lumen has experienced little or no enlargement, or the elastic restoring force of the lungs is not yet overcome. This option for particularly early assistance is important for many patients. To prevent fatigue of the respiratory apparatus due to frustrating breathing efforts of the patient with no volume displacement, which generally result in resetting a patient from an assisted ventilation mode into a monitored ventilation mode, respiratory-mechanically weak patients may be weaned from the ventilator more quickly, with better efficiency and targeted ventilation planning.
The signal recognition or the computation and triggering of a trigger pulse may take place using an autocorrelation algorithm, for example, that correlates a sample action with subsequent actions. The degree of correlation or the correlation coefficient necessary for a triggering may be set, preferably on a scale from −1 to +1, by the user by manual input on an input element such as a rotary knob 18a.
Parallel to the electrical signal, a mechanical signal is derived from the thorax of the patient, the thoracic pressure prevailing at the time being recorded in each case via the esophageal balloon 8, 9, 1a, and this information being led to the respiratory-mechanical module 19 via one or more tube-like supply lines 1b, 1d and preferably via a detachable plug or screw connection 1c, 1c′. The thoracic or pleural pressure curve is represented as a continuous pressure curve, for example, in this respiratory-mechanical module 19. The curve allows the user to track the progression of the thoracic capability of the patient for spontaneous respiration.
Relative deflections of the pressure curve into the negative region may be interpreted by an identifying, correlating algorithm as the start of mechanical respiration action and transmitted to the ventilator V as a trigger pulse. The signal recognition or the computation and deflection of a trigger pulse may take place using an autocorrelation algorithm, for example, that correlates a pattern course of the pressure curve with subsequent signal patterns of the pressure curve. The degree of correlation or the correlation coefficient necessary for a triggering may be set, preferably on a scale from −1 to +1, by the user by manual input on an input element such as a rotary knob 18b.
In addition to a continuous representation of the pleural pressure, the pleural pressure may be plotted as a function of the volume flow moved by the patient, and visualized as an iterating pie chart or as a respiratory work curve 20 in the respiratory-mechanical module 19. The number of iterations of the respiratory work curve 20 to be represented on the display may be manually input by the user on an input option such as an input rotary knob 21.
The respiratory-mechanical module 19 interacts with the ventilator V in both directions; i.e., it receives present measured flow values from the ventilator V, and transmits controlling or triggering pulses to the ventilator.
The described combination of electrical and mechanical signals allows in particular the correlation of neuromuscular electrical activity with effective, mechanically performed respiratory work, and on the one hand permits the user to identify that an electrical signal is related to a mechanical response. On the other hand, the evaluating algorithm can correlate the particular signal intensities of the two signals with one another. An electrical signal may also be differentiated into a supplying, motor-efferent neural signal and the subsequent muscle action potential. The user may also verify whether a neurally efferent electrical signal is transformed into a muscle action potential, or may determine the intensity of the potential. Similarly, the user may determine whether, and with what intensity, a muscle action potential is transformed into a mechanical contraction of the diaphragm muscle.
In all preferred embodiments of the balloon catheter 1, the shaft tube SS is provided with radiopaque markers 14 that make the upper and lower ends of the esophageally positioned balloon 1a or of the balloon arrangement 1a, 8, 9 visible in the X-ray image. In principle, the sealing effect of the balloon 1a, 8 should occur in the entire area between the upper and the lower esophagus sphincter. The positioning of the preferably ring-shaped markers 14 on the shaft tube SS should then correspond approximately to the respective sphincters.
Moreover, the invention describes a method for machine ventilation of patients that minimizes reflux and prevents pneumonia, it being possible for the user to change from an esophageal dynamically sealing mode into an esophageal statically measuring mode in the course of the ventilation.
Furthermore, the invention describes a method for the alternating esophageal measuring application and esophageally sealing application to a catheter unit 1, the detection of neuromuscular electrical signals of the diaphragm of the patient being made possible via an electrode arrangement 12 situated transdiaphragmally or near the diaphragm.
Accordingly, the catheter unit 1 has a structural combination of an esophageally positioned measuring and/or sealing catheter balloon 1a and electrical drain electrodes 12.
The method for handling the system made up of the catheter unit 1 and the modules 15, 18 according to
The catheter unit 1 is typically nasogastrically positioned. The correct positioning of the tamponading sealing and measuring catheter balloon 1a between the upper and the lower sphincter muscles of the esophagus is confirmed by an X-ray of the thorax, the upper and lower ends of the balloon 1a being emphasized by appropriately contrasted markers 14 on the shaft tube SS of the catheter 1. The probe-like catheter 1 has the functions of a nasogastric feeding catheter, and allows the gastric decompression as well as the gastric feeding of the patient.
The drain electrodes 12 positioned distal to the balloon component 1a are preferably positioned in such a way that they come to rest on both sides of the diaphragm, i.e., transdiaphragmally.
After the position of the balloon 1a is checked and the catheter 1 is fixed in the area of the nasal opening, the drain electrodes 12 are connected to the amplifying and monitoring module 15 via the cable supply line 12a, 12b, 12b′, and 12d, for example, and the balloon 1a, 8, 9 is connected to the respiratory-mechanical module 19 via the tube supply line 1b, 1c, 1c′, and 1d.
A summed potential of multiple individual electrodes 12 or also a signal of one or more individual electrodes 12 may then be depicted in the display of the monitoring module 15 as a continuous signal curve 16. The derivation takes place relative to the signal of a reference electrode 12c that is likewise situated on the catheter shaft SS. By comparing multiple potential cycles, a module-integrated control algorithm determines the earliest possible signal identification spike 17 within the signal 16, and the specific morphology of this identification spike is correlated with the cyclically following potentials. The precision of the correlation may be set by the user by inputting a correlation coefficient that is necessary for recognizing the signal spike. If such a sample spike is recognized in a signal, the module sends a triggering pulse to the ventilator V that is connected to the patient, as the result of which the ventilator is informed of an incipient electrical diaphragm activity. The trigger pulse may be used by the ventilator V for triggering respiration that assists the breathing effort of the patient.
The respiratory-mechanical module 19 visualizes the course of the thoracic or pleural pressure in a display, either as a continuous curve or as an iterating loop. A continuous loop is created in that the ventilator V continuously determines the flow of respiratory gas to and from the patient, and leads this information as a corresponding electronic signal, for example as a voltage curve, to the respiratory-mechanical module 19, which plots the information as a function of the continuously determined thoracic pressure.
The combination of both modules 15, 19 allows, in a manner that is optimal for ventilation planning by the user, the start of a muscular action (diaphragmal action potential) to be connected to the start of an associated respiratory-mechanically active contraction of the diaphragm, and an associated deflection or depression of the thoracic pressure, in a correlating manner. In particular, based on a triggering by a potential that is derived by the diaphragm, a volume support that assists the breathing or the inspiration effort of the patient may already be initiated, even if the patient has developed little or no mechanical breathing effort. This is crucial in particular for patients who are not able, via their autonomous breathing, to generate a sufficient depression of the thoracic pressure in order to overcome the particular elasticity of the patient's lungs, or to expand the lungs in the thorax to the extent that a volume flow directed toward the patient results inside the ventilating tube system. By use of the described method, such patients may be put into an assisted ventilation mode, and continuously held there and supportively ventilated without repeated fatigue of the respiratory muscles.
As an alternative to the “early” triggering by an electrical signal, the user may change to a triggering by a “late” thoracic-mechanical signal, the trigger signal being determined from a specified settable deflection or depression of the thoracic pressure from thoracic resting pressure. Depending on the specification of the pressure deflection that is necessary for triggering the signal, the patient may make a fairly large self-contribution to achieve a certain breathing volume. The specification thus allows optimized “training of the respiratory apparatus” without the patient experiencing respiratory fatigue and having to quit the assisted autonomous breathing.
If the respiratory-mechanical module 19 does not already integrate or have the functionalities and elements of the controller module 5, in parallel or as an alternative to a connection of the catheter balloon 1a to a respiratory-mechanical module 19, the tube-like supply line 1b to the catheter balloon 1a may also be connected to a module 5 which displays the thoracic pressure curve, and which, in addition to the option of intermittently measuring the thoracic pressure, also offers the option of a continuous pressure regulation in the catheter balloon 1a with a sealing tamponading action, wherein the sealing balloon pressure, regulating in a dynamic manner, compensates for the thoracic pressure fluctuations caused by the autonomous breathing of the patient. With such a combination of the modules, continuous triggering of a ventilator assisting the patient respiration may take place via an action potential of the diaphragm, regardless of a pressure situation that has primarily a sealing effect and that is controlled by a target value, and/or regardless of an esophageal measuring function in the esophageal balloon. In the sense of respiratory training or respiratory planning, the point in time when the ventilator is triggered may once again be predefined with a certain time offset, settable by the user, for using an electrical diaphragm signal.
For this purpose, an adapter 33 is connected to the control and regulation unit 5 via a cable 32a, the adapter being connected to a ventilation tube 34a of the ventilator V, for example to a Y-shaped connecting piece 35 as illustrated in
In one embodiment according to
The main component of the adapter 33 is a pressure relief valve 37 that is opened and closed by a magnet 38 that is controlled by the control and regulation unit 5 via the cable 32a.
As soon as a trigger signal has been generated by this control and regulation unit 5, i.e., machine-assisted respiration is requested by the ventilator control and regulation unit 5, this trigger signal must be communicated to the ventilator V. For this purpose, the trigger signal, optionally in a sufficiently amplified form, is switched to the magnet 38 via the cable 32a, and causes the magnet to open the pressure relief valve 37. Air may thus escape from the mutually communicating ventilation tubes 34a, 34b, and/or from the Y-shaped distributing [sic; connecting] piece 35 or from the tubular connecting piece 36. The resulting pressure drop in the ventilation tube 34b leading to the ventilator V is sensed by the ventilator V and interpreted as an attempt by the patient to lift his/her thorax in order to draw air into the lungs by means of negative pressure, and the ventilator V then triggers the desired machine-assisted respiration.
The pressure relief valve 37 is to remain open only until the desired machine-assisted respiration has been triggered. The pressure relief valve 37 is to be subsequently closed as quickly as possible so that the positive pressure generated by the ventilator V does not escape, but instead reaches the lungs of the patient. Therefore, it is further provided according to the invention that in the area of the pressure relief valve 37 a pressure sensor 39 is situated, which is connected to the control and regulation unit 5 via a cable 32b and which allows the control and regulation unit to recognize an increasing pressure in the ventilation tube 34b due to the now active ventilator V, and to immediately close the pressure relief valve 37.
In the arrangement according to
The cuff 42a of the ventilation tube 40 is also subject to a sealing problem similar to that of the balloon element 1a of the esophageal catheter 1. This sealing problem is based on the fact that during a breathing cycle of the patient, the intrathoracic pressure undergoes regular fluctuations, which in particular during a temporary pressure reduction may result in the cuff 42a as well as the balloon element 1a no longer being completely seal-tight.
To minimize this effect, the invention, the same as for the esophageally placed balloon element 1a, also provides adaptive pressure regulation for the cuff 42a of the ventilation tube 40 so that the cuff 42a is continuously seal-tight over the entire breathing cycle, without resulting in atraumatic impairment when it remains in the patient for an extended period.
In other words, the pressure inside the cuff 42a is measured, either directly in the cuff 42a itself or in a supply line 42b, 42c, 42d thereof, and this measured pressure is then adjusted as closely as possible to a predefined target value by the control and regulation unit 5. This may involve the same control algorithm as for the esophageally placed balloon element 1a, with the sole difference that no switchover to a measuring functional mode is necessary for the cuff 42a.
Various operating principles of the invention are depicted in
Whereas the breathing cycle 46 takes place in each case via conventional triggering by the ventilator V, for the breathing cycle 47′ a triggering takes place based on the pressure curve inside the esophageally placed balloon element 1a, and during the breathing cycle 47″ a triggering takes place based on the potential curve at the diaphragm ZF, which is measured by means of electrodes 12, 12c at the shaft 4a of the esophageally placed catheter 1.
All breathing cycles 46, 47′, 47″ share the common feature that at the end of a complete, preceding expiration phase 45, the pressure inside the ventilation tube 34a, 34b has dropped to an approximately constant value 48, which is referred to as the positive end expiratory pressure (PEEP) and is approximately +5 mbar.
For the conventional triggering method, as soon as the patient, consciously or unconsciously, has the need for a further breathing cycle 46, an appropriate stimulus reaches the diaphragm ZF via the phrenic nerve. This autonomous breathing capability, which in any case is present for the patient at least to some extent, then begins to contract. After a certain time, it deforms in an approximately conical manner, with simultaneous enlargement of the pleural cavity. As soon as the pleural cavity has noticeably enlarged, the pressure inside the ventilation tube system 34a, 34b drops slightly according to curve a. This pressure drop 49 is referred to as the initial respiratory pressure drop (IRPD). As soon as this pressure drop 49 has reached a range of approximately 2 to 3 mbar below the positive end expiratory pressure level 48, it is recognized by the ventilator V and interpreted as the desire of the patient for an inspiration phase 44, and the ventilator V now increases the pressure in the ventilation tube system 34a, 34b in order to press additional air into the lungs of the patient. In the process, the pressure in the ventilation tube system 34a, 34b increases steeply according to curve a up to a peak pressure value 50 (PEAK), which is typically approximately 35 mbar. With increasing filling of the lungs, this value drops to an elevated inspiratory pressure plateau (PLATEAU) 51, which is approximately 25 mbar. This is once again followed by an expiration phase 45, while the curve a returns once again to the original [positive] end expiratory pressure (PEEP) level 48.
Concurrently with the pressure curve a inside the ventilation tube system 34a, 34b according to curve a, the pressure curve b is measured in the cuff 42 of the endotracheal tube 40. This pressure curve has reached a constant pressure value 52 of approximately 25 mbar, for example, at the end of an expiration phase 45. As soon as the diaphragm ZF begins to contract, an onset of patient breathing (OPB) is discernible as a slight pressure drop 53 inside the cuff 42. The pressure drop 53 is only approximately 2 to 3 mbar below the initial, constant pressure value 52 of approximately 25 mbar. For the machine-assisted respiration, this pressure drop 53 remains approximately constant until the ventilator V becomes active and air is pressed into the lungs. In the process, the cuff pressure b also increases approximately to the PEAK value 50, and then follows the pressure curve a inside the ventilation tube system 34a, 34b up to the elevated inspiratory pressure plateau 51 (PLATEAU), which is already close to the initial pressure value 52 of the curve b of approximately 25 mbar, which the curve c ultimately once again seeks to attain in the expiration phase 45.
In a similar manner, the pressure curve c may be measured concurrently with the pressure curves a and b in the esophageally placed balloon element 1a of the catheter unit 1. This pressure curve has reached a constant pressure value 54 of approximately 15 mbar, for example, at the end of an expiration phase 45. As soon as the diaphragm ZF begins to contract, once again the onset of patient breathing OPB is discernible as a pressure drop 55 inside the esophageal balloon element 1a. However, the pressure drop 55 at the curve c is much more strongly pronounced than for the curve b, and is typically approximately 6 to 7 mbar below the initial constant pressure value 54 of approximately 15 mbar. During the machine-assisted respiration, this pressure drop 55 remains approximately constant or drops slightly further until the ventilator V becomes active and air is pressed into the lungs. The pressure c in the esophageally placed balloon element 1a also increases approximately to the peak value 50 of the curve a, i.e., to approximately 45 mbar, and then follows the pressure curve a inside the ventilation tube system 34a, 34b up to the elevated inspiratory pressure plateau 51, PLATEAU at approximately 25 mbar, to ultimately return to the initial pressure value 52 of approximately 15 mbar in the expiration phase 45.
Since the pressure drop 55 inside the esophageally placed balloon element 1a at the onset of patient breathing OPB is much more strongly pronounced than the approximately simultaneous pressure drop 53 inside the cuff 42a at the endotracheal tube 40, this pressure drop 55 may be more easily and quickly recognized by the control and/or regulation unit 5 according to the invention than the pressure drop 53 in the cuff 42a, and may be used to generate a trigger signal for the ventilator V.
The left portion of
As is apparent in the left portion of
In comparison, in the method according to the right portion of
As yet a further case,
Since the esophagus 3, OE passes through the diaphragm ZF at the esophageal hiatus, the electrodes 12 may come into direct contact with the diaphragm ZF in order to measure its electrical muscle activity within the scope of electromyography (EMG), in particular when the electrode phalanx 12 at the catheter shaft 4a is positioned approximately one-half distally and one-half proximally with respect to the diaphragm ZF. Such positioning may be ensured with the aid of optional additional marker elements 14 at the catheter shaft 4a, for example at the proximal and distal ends of the electrode phalanx 12.
As a result, it is then no longer necessary at all for the diaphragm ZF to go into action in order to determine a trigger point in time 56″. This is important in particular since it is often difficult, specifically for elderly and/or feeble persons, to bring about any measurable pressure drop 49 at all in the ventilation tube system 34a, 34b via muscular contraction of the diaphragm ZF. Even the generation of the typically well perceivable pressure drop 55 in the esophageally placed balloon element 1a requires comparatively great physical exertion by very feeble patients, which additionally burdens and fatigues such patients.
For a triggering upon a detectable electrode signal that has been interpreted, by a preceding correlation with the esophageal pressure signal according to curve c, as an initiation 57″, BMO of the muscular activity of the diaphragm ZF, the trigger point in time 56″ may thus be determined before an esophageal pressure drop 55 has even occurred, namely, directly at the point in time 57″. This is apparent in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2020 002 932.9 | May 2020 | DE | national |
| 10 2021 000 220.2 | Jan 2021 | DE | national |
| 10 2021 000 221.0 | Jan 2021 | DE | national |
This patent application is a 371 national stage entry of pending prior International (PCT) Patent Application No. PCT/IB2021/054222, filed 17 May 2021 by Creative Balloons GmbH and Fred Göbel for DEVICE AND METHOD FOR ALTERNATELY MEASURING THORACIC PRESSURES AND FOR SEALING ESOPHAGEAL SECRETION, which patent application, in turn, claims benefit of: (i) German Patent Application No. DE 10 2020 002 932.9, filed 15 May 2020, (ii) German Patent Application No. DE 10 2021 000 220.2, filed 19 Jan. 2021 and (iii) German Patent Application No. DE 10 2021 000 221.0, filed 19 Jan. 2021. The four (4) above-identified patent applications are hereby incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB21/54222 | 5/17/2021 | WO |
