DE2432932C3 - Pressure comparator for patient-controlled triggering of the inhalation and exhalation phase - Google Patents

Description

The invention relates to a ventilator with a pressure curve in the at its signal output Respiratory line of the patient reflecting monitoring signal emitting sensor and with a two Signal inputs and a signal output having a comparator, one of which is a signal input with the Signal output of the sensor is connected while on

ίο a reference signal is applied to its second signal input, and its signal output on switching the ventilator from the Ausaimungsphase to the Emits a trigger signal that triggers the inhalation phase when the monitoring signal has dropped below a specified value Value deviates from the reference signal.

Such ventilators, as can be found, for example, in US Pat. No. 3,385,295, are above all Od in the intensive care units of clinics. Like. Used and are used to help patients breathe support or maintain those who are so weak, so sick, or so badly injured that they become them Not being able to carry out bodily functions on their own.

In the past, devices that forced the patient's respiratory cycle, i. H. maintained according to a fixed time schedule. On the other hand, there is already one at State of the art improvement in providing the patient's lungs with a pressurized, Oxygen-containing gas only ever in response to an attempt at inhalation by the patient to feed. The patient's airway or breathing line is typically used for this purpose equipped with a pressure sensor that reacts when the patient tries to inhale based negative pressure of a predetermined size to which the lungs of the patient the respiratory gas supplying device emits a trigger or release signal.

For most treatment cases, a ventilation device with a pressure sensor is sufficient. which only responds when in the airways or the breathing line of the patient a negative pressure compared to the atmospheric pressure of the environment Occurs in some cases, however, it is necessary also in the exhalation phase ic the lungs of the Maintain positive pressure in the patient, for example to prevent the alveoli from collapsing to prevent. In these cases, too, the ventilator has to be assisted by an attempt to inhale the patient-based pressure drop are triggered in the patient's breathing line; however, the pressure must not fall below the patient's breathing line or within the airways the atmospheric pressure will drop; rather it should the inhalation process can still be triggered at a certain overpressure in relation to the ambient atmosphere. The previously common ones Trip sensors cannot be used in such a case for those above atmospheric pressure Determine pressure drop; this is especially true for patients who are too weak to handle the excess pressure. level and to create a vacuum that can respond to the sensor and the ventilator into an inhalation phase

To overcome these difficulties, various devices have been used to the To preload the triggering device so that a patient enters the ventilator in an inhalation phase can switch over without creating a negative pressure in relation to the surrounding atmosphere.

In these known devices, the pressure in the surrounding area is generally used as a reference level Atmosphere corresponding signal, which in those cases where a during the entire respiratory cycle certain overpressure in the patient's respiratory tract should not be fallen below, to one of The value can be set manually, but can be increased in the further course of the process. There is the There is a risk that a slow-acting leak in the ventilation line to the patient caused by the im general provided warning system because of its small size is not detected, a pressure drop is generated by the system triggering the switchover incorrectly as an attempt to inhale by the patient is interpreted. The system that triggers the switch then reacts by switching prematurely from the exhalation to the inhalation phase, which makes it very easy to over-ventilate the Patient can come.

Building on this prior art, the invention is based on the object of a ventilator of the type mentioned so that it goes from an exhalation phase to an inhalation phase even if there is a slow-acting leak in the breathing line or airway of the The patient is not switched prematurely before the patient actually attempts to inhale will.

To solve this problem, the invention provides that a monitoring signal delaying and smoothing integrator with its signal input to the signal output of the sensor and with its signal output is connected to the reference signal input of the! Comparator.

This arrangement according to the invention ensures that the reference signal expires slowly Changes in pressure in the patient's breathing line follow as well as the pressure in that line Monitoring signal that is immediately reproduced, but not rapid pressure changes, as is the case, for example triggered by an attempt to inhale by the patient. As a result, the monitoring signal can only then reach the value that is a predetermined amount beyond the reference level and a Switching to the inhalation phase only triggers ίο when the patient actually inhales spontaneously tried On the other hand, a slow pressure drop due to a small leak is carried over into to the full extent to the reference level, which thereby changes in the same direction as the monitoring signal Due to such a slow pressure drop, the monitoring signal can exceed the reference level not reach the lying value and there will be a premature triggering of the switchover from the Exhalation to inhalation phase is definitely prevented

A particular advantage of the device according to the invention is the fact that it is extremely can be implemented in a simple manner and thus low manufacturing costs with high operational reliability connects

Advantageous further developments of the ventilator according to the invention are set out in the subclaims laid down.

The invention is described below, for example, with reference to the drawing; it shows

F i g. 1 is a graph showing a patient's respiratory cycle in a prior art Technique in the "control mode" of the ventilator operating, with the phase of inhalation is triggered independently of a corresponding attempt at inhalation by the patient,

F i g. Figure 2 is a graph showing the respiratory cycle of a patient in a prior art represents a corresponding ventilation device working in the »support mode«, with an inhalation phase triggered by the patient attempting to inhale,

F i g. 3 shows a schematic representation of a known ventilation device which is used for this purpose can, in the F i g. 2 to perform the respiratory cycle shown,

FIG. 4 is a graph showing the respiratory cycle of a patient through a dem State-of-the-art ventilation equipment is supported, which is in the lungs of the patient At the end of the exhalation phase, positive pressure is generated and the patient attempts to inhale is triggered,

F i g. 5 a schematic representation of a known, mechanically pre-stressed ventilation device, which is triggered by the patient and used to the in F i g. 4 to generate the respiratory cycle shown, FIG. 6 is a schematic representation of a known one pneumatic, differential device that is triggered by the patient and is used to provide a Specify the reference inlet pressure,

F i g. 7 is a graphical representation of a patient's exhalation cycle corresponding to FIG. 7, but in the presence of a relatively large _h5 leak,

9 shows a schematic representation of an inventive Device during the inspiratory portion of a respiratory cycle,

10 shows the schematic representation of the switching valve the device from FIG. 9 in the position during the exhalation portion of a respiratory cycle,

F i g. FIG. 11 is a graph showing a patient's respiratory cycle using the method shown in FIGS 9 and 10 shown ventilation device according to the invention reproduces,

12 is a graph showing a patient's respiratory cycle using the inventive Device and in the presence of a small leak in the breathing line reproduces, and

F i g. 13 is a graphical representation of a patient's respiratory cycle using the device according to the invention in the event of a relatively large leak in the respiratory line. ι ⁵

In Fig. 1 a graphic representation is shown, showing a patient's breathing cycle while a ventilator is in "control mode" works, in which the inhalation phase is triggered independently of an inhalation attempt by the patient will.

It can be seen that forced ventilation is generated in the control mode, and this mode is for one Patients especially helpful when a patient is actually unable to breathe on their own trigger or entertain. Of course, the breathing cycle generated in the control mode is not necessarily synchronized with the patient's natural respiratory cycle and can affect the patient May become hypoxic or over-ventilated to lead. It is therefore advisable that the patient's respiratory cycle should be controlled by the natural one The patient's need for air is controlled and thus dependent on the normal inhalation and Exhalation characteristics of the patient.

For this reason, most ventilators only generate the control mode mentioned above during those times when the patient is unable to achieve a minimum of breathability. Accordingly there is generally a device that can be triggered by the patient in order to trigger the inhalation phase when the patient has the Attempt to inhale is noted.

The F i g. Figure 2 illustrates a patient's breathing cycle under the influence of a ventilator operating in assist mode. In general, a patient release is preselected in such a way that the determination of a certain negative pressure difference "s" serves to control the device in such a way that it goes into an electrical phase.

It can be seen that the one shown in FIG. 2 requires that the patient create a negative pressure, ie a vacuum, before the ventilator initiates the inhalation phase. If the patient had not been able to create the required vacuum, the pressure difference "s" would not have arisen and the machine would in the one shown in FIG. 1 work shown control mode, through known equipment. In & o this sense, the support mode is overridden by the control mode if the patient is unable to produce the required pressure difference "s" to begin the inhalation phase of his respiratory cycle.

FIG. 3 schematically illustrates a known device which is used for this purpose which can be shown in FIG. 2 to generate patient breathing pressure curve shown. Necessarily the device has a housing 10 which represents an input chamber for a ventilation line, which is closed by a flexible membrane 14. A gas line 16 provides a connection between the Chamber 12 and the breathing line 18 of the patient, which in turn are connected to the ventilation unit 20 in Connection. In the present description, the term »patient's breathing line« is used used in the sense that it is understood to mean any gas line that connects with the lungs of the Is in communication with the patient, and this gas line can comprise any other gas line, which is designed in such a way that it detects the pressure in the lungs of the Palienien.

A ventilation control unit 22 can be provided which responds to the movement of the flexible membrane 14 appeals to. Any variety of devices can be used to control movement of the diaphragm 14 in response to the patient creating a vacuum in chamber 12. Such Motion sensors contain correspondingly sensitive electrical switches and direct electrical contact devices (one of which moves with the membrane), arrays of light sources and photocells as well Fluid sensor.

Only for the purpose of schematic illustration is an element 24, which is from the flexible Membrane 14 extends out into electrical switching relationship with electrical control unit 22

While the trip system described above is sufficient for most use cases, it is sometimes it is desirable to maintain positive pressure in the alveoli of the patient at all times. In in such cases, positive pressure is permanently maintained in the patient's lungs, too throughout the exhalation phase.

Figure 4 is a graphic representation of a A patient's respiratory cycle in which positive pressure is constantly maintained in the patient's lungs will. The pressure curve 26 represents the minimum positive pressure in the patient's lungs should be maintained, except for a momentary pressure drop that occurs during the patient's attempt to Inhalation Occurs Pressure level 26 is commonly referred to as Positive Exhalation Pressure (AAÜD) and hereinafter briefly mentioned as AAÜD

From Figure 4 it can be seen that in a ventilated patients if an AAÜD is maintained, a device according to Figure 3 not is effective as it is even for a healthy one. Patients would find it difficult to find a suitable adequate vacuum within the chamber 12 to initiate the inhalation phase of its respiratory cycle. Therefore, a known device according to FIG. 5 sometimes used to assist the patient in the Support triggering the inhalation phase.

In particular, FIG. 5 illustrates a modification the one shown in FIG. 3 device shown, in which a mechanical preload on the flexible membrane 14 acts. The bias has the same polarity as the force exerted by the The patient's attempt to inhale is generated so that the patient is supported in using the flexible To move the membrane against the overpressure in the chamber 12. Accordingly, a spring 28 or a Similar means may be operatively connected to the membrane 14 such that the membrane faces towards

7 8

a position is biased which is in communication with triggering breathing line 18 A switching valve

corresponds to an inhalation phase. The size of 42 is used to move the reference pressure chamber 32 into the

Biasing force exerted by spring 28 to vent atmosphere through tube 46 when up

is brought, the device shown in FIG. 9 by a corresponding adjusting screw

be set or by a similar position 5, and around the reference pressure chamber 32

Means so that the pressure drop difference in advance with the breathing line 18 of the patient in communication

can be set that is required to bring the when the facility is in the in the

To move membrane 14. Fig. 10 is the position shown. If this The device according to FIG. 6 works in the latter case, both the reference

chen in the same way as the device according to ι ο pressure chamber 32 and the associated pneumatic

Fig. 5. A pneumatic bias is gradually applied to the condenser 40 to the pressure that Membrane 114 applied by a pressurized in the line 18 is present

standing gas introduced into a reference chamber 32. The device according to the invention operates in the

that is in the overall housing 10 of the trip device, that the reference pressure in response to changes

device is present, the reference pressure by means of a 15 wrestling of the pressure in the breathing line 18 in such a way

Eineiiventiis 34 can be set by changing ais that a trip in response to Reference pressure in the chamber 32, an overpressure, a pressure drop in such "rates" as it occurs

is produced, the flexible membrane 14 can correspond to the rates, polygamy through the efforts

Direction of actuation are moved, namely in gene of the patient for inhalation are generated, wherein Response to the pressure drop in the chamber 12, 20 but no inhalation phase in response to the

thereby triggering the pressure to a predetermined pressure-pressure drop at rates as determined by

difference below the reference pressure is reduced. small or minor leaks in the overall system

During the operation of those in Figs. 5 and 6 arise which cares for the patient

tripping devices shown, it is in general- For the purpose of illustration, FIG. 11 a

sufficient if, under ideal conditions, a pressure curve (solid line) for a respiratory

Thick in the patient's lungs, the patient's sustaining cycle, one during the AAÜD

th is if there is a leak in the breathing line of the continuously drawn curve 44. Die

The patient should show, however, that there is a reference pressure curve which shows the pressure in the chamber

known devices, the danger that the input 32 represents is shown as a dashed line 46 Es

is triggered too early. 30 must be taken into account that an inhalation phase

In particular from FIG. 7 it can be seen that it is triggered when the solid pressure curve

if a small leak in the breathing line falls below the reference pressure curve 46 by "s"

The patient puffs, the pressure in the breathing line of the valve 42 is opened during the inhalation phase The patient is switched by the amount "s" below the reference pressure in such a way that the reference pressure chamber through

can drop (which in this case is equal to AAÜD) 35 vented the outlet opening 47 into the atmosphere

and that an inhalation phase is triggered prematurely. will.

FIG. 8 illustrates the condition which a coil 48 can be connected to the switching valve 42

would be present if a major leak in the connected so that the valve 42 in the

Respiratory line of the patient would occur, which venting position is held, as shown in FIG. 9

may not be large enough to accommodate a corresponding 40 is shown while a patient is in the

The corresponding alarm for a too low pressure is to be triggered. Inhalation phase

or to activate another alarm system as it is certain time after the start of the exhalation phase

typically be switched on in known ventilators. The switching of the valve 42

is provided in the position shown in Fig. 10 must, however

It can also be seen from FIG. 8 that a 45 is delayed by a time period T _D. These

Larger leak the inhalation phase much too early period should generally be in the range of 0.2 to 0.5

would trigger, with the ventilator being in seconds.

a free running condition would be brought about during the time period T _D the pressure in the

which runs the risk of overbreathing a patient's lungs and airways

Patient occurs 50 about the ideal AAÜD level 44 from. At the end of Of course, such a condition is at the highest period T _D , the switching valve 42 is in the one shown in FIG. 10

undesirable. shown position switched, se that thereby the

According to FIGS. 9 and 10, a release reference chamber 32 according to the invention and the pneumatic one Device according to the schematic representation, a condenser 40 with the airways and the lungs of the Housing 10, which has a flexible membrane 14, 55 patients through the breathing line 18 of the patient

mounted therein to connect to a breathing line and pneumatic resistor 38.

Pressure chamber 12 and a variable reference pressure- The resulting exponential pressure increase in the

chamber 32 to be fixed a gas line 16 brings the pneumatic condenser 40 and in the release level

Chamber 12 with the breathing line 18 of the patient in pulling chamber 32 takes place gradually, because of the Connection, which in turn with the ventilation unit 20 eo time delay effect of the capacitor 40 and the

is connected to pneumatic resistance 38. The condenser 40

The reference pressure chamber 32 is connected to the breathing duct with an elastic, resilient wall 50 in this way

Device 18 of the patient via lines 16, 17 and 36 connected that the damping effect of a

tied together. A pneumatic resistor 38 and a large capacitor is achieved without the

pneumatic condenser 40 are operationally large within 65 correspondingly large physical dimensions

half of the lines 17 and 36 connected to that of a capacitor with a rigid wall required

To be pressure build-up in the reference pressure chamber 32, the equivalent damping or a

decelerate when the chamber 32 has the equivalent time delay effect with the pressure

As shown in FIG. 11, the reference pressure curve 46 gradually approaches the pressure level in the patient's lungs (solid curve) during the exhalation phase. When the patient tries to inhale, the pressure in the inlet pressure chamber 12 drops relatively quickly. The pressure in reference chamber 32 cannot drop as rapidly because of the time delay action of pneumatic resistor 38, and thus the pressure in chamber 12 soon drops to a pressure "s" below the pressure in reference chamber 32, thereby lifting the membrane 14 up to bring the main ventilation unit 20 into the inhalation phase.

In Fig. 12 is a respiratory cycle of a patient illustrated during a condition in which the patient's breathing line has a small leak It can be seen that the reference pressure 46 has the tendency to follow the falling pressure in the breathing line 18 such that the premature release of the inspiratory cycle in response to such a leak is prevented.

The F i g. 13 shows the condition of FIG. 12, there being a major leak in the breathing line 18 which may not be sufficient to activate an alarm system but which may be sufficient to relieve the overpressure in the patient's lungs at the end of the exhalation phase. It can be seen, however, that even under such an extreme condition the reference pressure approximately follows the falling pressure in the patient's breathing line and thus an inhalation phase is not triggered until the patient attempts to inhale himself when the breathing tube pressure line (solid line) »s « With respect to the variable reference pressure 46 drops

In order to ensure such a mode of operation, the pneumatic resistance 38 should be selected in such a way that that the variable reference pressure curve 46 has the proper response time

It can thus be seen that the synergetic interaction of the elements of the Ben device the device according to the preferred th embodiment is extremely straightforward, which means that they are very easy to manufacture is economical and very reliable in operation According to the invention is an essential technical one

to progress achievable by namely, when operating the device according to the invention, a ventilation device works with an AAÜD, which in the It is crucial that the inhalation phase in the patient's respiratory cycle is only responsive is triggered on the patient's attempt to inhale. Therefore, the operation of the device according to the invention is not due to a leak in a line to affect. While above a preferred embodiment of the

Subject of the invention has been described, is

it can be seen that various modifications and

Changes are possible without leaving the framework of the Invention to leave. For example, the inlet pressures can be in others

Parameters such as electrical voltages are converted, which would then have corresponding phases, such as it is shown in Figs. 11 to 13 and as Input signals would be fed to an electrical release device in a manner known per se. In similarly, it is not necessary that the changeable reference pressure exactly follows the pressure in the breathing line essentially follows so that a distance of the two

Pressure lines from each other is permissible For this purpose 4 sheets of drawings

Claims (12)

Patent claims: 1. Ventilator with a signal output on the pressure curve in the breathing line the patient's reflective monitoring signal emitting sensor and with a two Signal inputs and a signal output having a comparator, one of which is a signal input with the signal output of the sensor is connected, while at its second signal input a Reference signal is applied, and its signal output on the switching of the ventilator from the Exhalation phase emits a trigger signal that triggers the inhalation phase when the monitoring signal deviates from the reference signal by a specified value, characterized in that that an integrator (38, 40) delaying and smoothing the monitoring signal with its signal input to the signal output of the sensor (16) and with its signal output to the reference signal input of the! Comparator (10) is connected 2. Ventilator according to claim 1, characterized in that the signal output of the Sensor (16) via the integrator (38, 40) with the reference signal input of the comparator (10) Line (17, 30) a changeover switch (42) is arranged which is controllable so that the delayed and smoothed monitoring signal only during part of each exhalation phase is applied to the reference signal input of the! Comparator (10) 3. Ventilator according to claim 2, characterized in that the part of each exhalation phase during which the delayed and smoothed monitoring signal is applied to the reference signal input of the comparator (10) starts 02 to 0.5 seconds after the beginning of each exhalation phase and at the beginning the next inhalation phase ends. 4. Ventilator according to claim 2 or 3, characterized in that during the period in which the delayed and smoothed monitoring signal is not at the reference signal input of the comparator (10) is applied, through the switch (42) another sensor (47) emits, Signal representing the ambient pressure to the reference signal input of the comparator (10) is applied. 5. Ventilator according to one of the preceding claims, characterized in that the from the sensor (16) emitting the monitoring signal, the comparator (10) and the integrator (38, 40) existing control device is a pneumatically operating control device. 6. Ventilator according to claim 5, characterized in that the monitoring signal The emitting sensor (16) is a pipe branched off from the patient's breathing line (18). 7. Ventilator according to claim 5 or 6, characterized in that the comparator (10) comprises a housing, the interior of which is passed through a flexible membrane (14) into a via the sensor (16) with the ventilation line (18) in connection with the first chamber (12) and one with the Second breathing line (18) connected via the sensor (16) and the integrator (38, 40) Chamber (32) is divided, the switching of the ventilator from the exhalation phase se trigger signal that triggers the inhalation phase depending on the degree of deflection of the flexible membrane (14) can be released into the first chamber (12) 8. Ventilator according to one of claims 5 to 7, characterized in that the integrator (38, 40) a pipe section (17) having a pneumatic resistance (38) and an im essentially comprises a pneumatic condenser (40) consisting of a gas storage space 9. Ventilator according to claim 8, characterized in that the pneumatic resistance (38) consists of a constriction in the pipe section (17) 10. Ventilator according to claim 8 or 9, characterized in that at least one wall of the gas storage space of the pneumatic condenser (40) is formed by an elastic membrane (50) 11. Ventilator according to one of claims 5 to 10, characterized in that the switch (42) is a switching valve which can be actuated by an electromagnetic actuating device (48). 12. Ventilator according to claim 11, characterized in that the switching valve (42) between the pneumatic resistor (38) and the pneumatic condenser (40) of the integrator is arranged.