WO1986000793A1

WO1986000793A1 - Apparatus for determining the respiratory behaviour of a patient

Info

Publication number: WO1986000793A1
Application number: PCT/NL1985/000030
Authority: WO
Inventors: Erna Peltzer
Original assignee: Erna Peltzer
Priority date: 1984-07-19
Filing date: 1985-07-16
Publication date: 1986-02-13
Also published as: NL8500314A; EP0188508A1

Abstract

An apparatus for determining the respiratory behaviour of a patient, comprises first and second measuring elements (9, 10, 25, 28) for determining the rythm and the amplitude of the abdominal respiration and the costal respiration respectively, and a third measuring element (14, 34) for determining the evolution of the heart rate, and means (18, 30) for simultaneously displaying and/or recording the output signals from these three measuring elements on the same time base. Further means (38, 40) are provided for determining the flow rate of the blood from the legs and/or from the arms and/or from the head of the patient.

Description

Apparatus for determining the respiratory behaviour of a patient

The invention relates to an apparatus for determining the respiratory behaviour of a patient. The natural respiration in the rest state is the so-called abdominal respiration, also termed full, breathing at rest. In this process the diaphragm, which is convex, contracts, as a result of which it becomes flatter in the centre, while it lifts the lowermost ribs at the sides. As a result of this last effect the chest already to some extent expands without there being as yet any question of work being done by the outermost intercostal muscles. When the abdominal muscles have to some extent relaxed at the beginning of the respiration, the abdominal capacity will increase somewhat as a result of the higher pressure in the abdominal cavity, which can be seen as the "precursory start of abdominal respiration". This slight relaxation of the abdominal muscles at the beginning of inspiration is necessary to allow the venous bloodstream in the thigh and pelvic veins to proceed since this bloodstream can stagnate with a high pressure in the abdominal cavity. The slight rise and lateral rotation of the lowermost ribs forms a stimulus for the costal respiration by the outer intercostal muscles and assessors, which costal respiration is, however, hardly necessary in the rest state. As a result of the raising of the chest a contraction of the abdominal muscles is produced by reflex action and the chest is again pulled downwards, as a result of which expiration sets in, in which process the diaphragm relaxes again and again becomes convex.

In this respiration the diaphragm exerts a doubleaction pump action on the venous blood, which is especially necessary in the rest state because there is then little muscle action to cause this blood to flow back to the heart from the whole body.

The inspiration and expiration are attended by a pressure change in the interpleural cavity and, inherent in this, by a pressure chang in the intrathoracic cavity and the right atrium. During the inspiration, because of the drop in pressure which occurs at that time, the blood is as it were sucked in, which increased venous supply is signailed by mechanoreceptors and leads to an acceleration of the heart rate. As soon as an increase in pressure again occurs, which in any case occurs during the expiration, a deceleration of the heart rate occurs in a contrary manner. This phenomenon of varying heart rate is termed respiratory sinus arrhythmia, and for normal efficient respiratory behaviour this respiratory sinus arrhythmia must therefore be synchronous with the respiratory movements.

A deviating inefficient respiratory behaviour may manifest itself in various ways. If, for example, inspiration proceeds for such a long time that the uppermost outer intercostal muscles and the assessors are still contracting while the diaphragm, possibly together with the abdominal muscles, has already started the expiration contraction, as a result of which the lowermost ribs are being pulled inwards and downwards, an interpleural increase in pressure may nevertheless take place in spite of the inspiration condition. As a result the mechanism of the interpleural pressure drop and the intrathoracic pressure drop inherent in it and the drop in pressure in the atrium is nullified. This has an adverse effect on the venous return of the blood and is moreover a sign that the respiratory work is itself inefficient. The curve of the respiratory sinus arrhythmia loses its synchronism with the respiration curves. In the case of efficient respiration the expiration terminates at the level of the functional residual capacity σf the lungs. If further forced expiration occurs, this is also inefficient. In the case of excessive inhalation the curve of the respiratory sinus arrhythmia, as indicated above, therefore moves downwards earlier than the respiration curves, while in the case of excessive expiration exactly the opposite occurs.

The invention is therefore based on the view that ft is possible to teach a patient an optimal efficient respiratory behaviour by measuring the abdominal respiration, costal respiration and the resp iratory sinus arrhythmia simultaneously and to make them directly observable for the patient so that the latter can check for himself whether there is abdominal respiration (precursory abdominal start), whether in this process loss of the respiratory sinus arrhythmia me, be occurring and whether the respiration curves are synchronous with the latter.

Starting from this view, the invention therefore aims to create a practical apparatus for determining the respiratory behavior and pulmonary function of a patiet, the patient being able to check this behavior for himself and if necessary correct it.

The apparatus according to the invention is characterised by a first and a second measuring element for determining the rhythm and the amplitude respectively of the abdominal respiration and the costal respiration respectively, a third measuring element for determining the behaviour of the heart rate, and means for simultaneously making observable and/or recording the output signals from these three measuring elements with the same time base.

Because the costal and abdominal respirations are thus separately and simultaneously made visible on, for example, a suitable screen, the patient can observe faults in his respiratory behaviour directly and, through training, learn to correct it, the respiratory sinus arrhythmia also displayed at the same time forming a check on the efficiency of the respiration both as regards muscles usage and with regard to the perfusion/ventilation or the gas exchange. With the aid of the apparatus according to the invention it is thus possible to practise an exact respiratory behaviour without strain, the result being directly visible. In this process the venous return of the blood can at the same time be influenced in a manner such that it can become optimally efficient. By means of the equipment according to the invention there is the possibility of combating stress phenomena in the manner described and of breaking many patients with chronic aspecific respiratory disorders and hyperventilation patients of their tendency to excess respiration. Generally speaking, by using the apparatus according to the invention patients with respiratory difficulties or an incorrect breathing habit can be enabled to find and acquire the respiratory behaviour which is most efficient for them personally.

As has already been noted, if inspiration continues too long, a premature interpleural increase in pressure will occur, as a result of which the venous return of blood, especially from the legs, is reduced. Moreover, if inspiration continues too long, the more highly placed sections of the lungs will be used to an ever increasing extent and the ever increased expansion of these more highly placed lung sections may have the result that the veins which are responsible for the return of blood from the arms and from the head are more or less shut off so that the return bloodstream from these parts of the body is also reduced and in the most serious case is even cut off.

In order therefore to obtain an insight into the extent of the venous return of blood both from the legs and from the arms and the head, means are introduced according to a further development of the apparatus for the determination of the flow rate of the blood from the legs and/or from the arms and/or from the head, the output signals from these additional means also being capable of being made observable and/or being capable of being recorded.

The apparatus according to the invention cannot only be used by a patient as an aid for regulating or correcting his respiratory behaviour himself, but can also be used by patients under an anaesthetic, in which case the observation is of course made by another person, for example the anaesthetist.

If a patient has to be artificially respirated, the mechanism described above of a low interpleural pressure during the inspiration and high interpLeural pressure during the expiration is as it were stood on its head. In the case of artificial respiration air is pumped into the lungs at a predetermined overpressure during the inspiration phase, whereas during the expiration phase the pump pressure is reduced so that the air can flow back out of the lungs. In this case there is no question of a relative reduction of the interpleural pressure while air is pumped in as is ^'the case in natural breathing (see above) but rather of an increased-interpLeural pressure. Moreover, the pressure in the abdominal cavity becomes higher. The result of this is that the venous return of blood from the Legs is hampered. Moreover, when air is being pumped into the lungs, a movement of the chest will occur which is similar to the movement which occurs in costal respiration. As a result of this tjie more highly placed sections of the

Lungs are used to a much greater degree than for efficient natural respiration, as a result of which, as was already pointed out, the veins which cater for the return of the blood from the arms and from the head are more or less shut off by the expanding higher lung sections so that the return of blood from these parts of the body is also hampered. This wholesale reduction of the venous return bloodstream has the result that the quantity of blood pumped out by the heart also decreases. The entire blood circulation is, as it were, slowed down, which can under certain circumstances even have very damaging consequences because as a result of this restricted blood flow the gas exchange in the lungs is adversely affected and the perfusion/ventilation ratio is negatively influenced or the supply of (oxygen-containing) blood to the brain may reach too low a level.

A slight overpressure (the so-called "PEEP") is also (often) nevertheless maintained during the expiration phase, in which the air-pump pressure is reduced, in order to prevent the lungs collapsing. The result of this is that the interpleural pressure also remains relatively high during this phase and the venous bloodstream is thus certainly not increased.

According to a further development the apparatus according to the invention is therefore coupled to means by which the venous return of blood, especially from the legs, is promoted, which means are activated if the means which determine the bloodstream flow rate deliver a signal below a predetermined threshold level. The invention will now be explained in more detail on the basis of the accompanying figures.

Figure 1 is a diagrammatic representation of a possible embodiment of the apparatus according to the invention.

Figure 2 is a graph which can be obtained with the apparatus of Figure 1.

Figure 3 shows diagrammaticaIly a second embodiment of the apparatus according to the invention. Figure 4 shows the bar diagrams which are obtained on the screen of the monitor.

Figure 5 illustrates diagrammaticaIly a third embodiment of the apparatus according to the invention.

Figure 6 shows di agrammatically an embodiment of the means with which the venous return bloodstream can be increased.

Figure 7 shows diagrammaticaIly an embodiment of the apparatus according to the invention connected to a respirating unit. The apparatus of Figure 1 has a frame consisting of two semi-circular brackets 1 and 2 placed parallel to each other which at their highest points are connected by a connecting rod 3 telescopically adjustable in length and which can be placed over a patient lying on a bench 4 or the like. On each of the brackets 1, 2 is fixed a rod 5 which projects downwards and on which a tube 6.can be adjusted vertically and fixed by means of a clamping screw 7. The tube 6 has on its lower end a spring element in the form of a horizontal arm 8 of an elastic material such as spring steel, to the free end of which is secured a knob-shaped sensor 9 or 10 which projects downward. Against each of the arms 8 is fixed a strain gauge (not visible in the drawing) which is connected by connecting Leads 11 and 12 to two inputs of an electronic processing unit 13. The apparatus has moreover two handle electrodes 14 to be gripped by the patient which are connected by leads 15 to a heart-rate meter or tachometer 16. The equipment 13 is connected by output leads 17 to a monitor with a display screen 18 and, if required, also to a chart recorder 24 (shown in the figure by dotted lines). The heart-rate meter 16 may be a per se known meter. The processing unit 13 is designed in such a manner that the signals received by the strain gauges on the arms 8 and by the heart-rate meter 16 are processed separately and transmitted with a common time base to the monitor on which these signals are made visible as three wavy-line curves above each other on the display screen 18.

It will be clear that the measuring elements and the sensors 9 and 10 for the determination of the excursions of the abdominal and costal respirations may also be supported in a different manner and may, for example, be secured above each other in a horizontally adjustable position on a stand for use by a sitting patient. In place of the handle electrodes 14 shown, for the measurement of the heart rate, for example, adhesive electrodes for attachment to the wrists or other known means can of course be used.

In using the apparatus shown in Figure 1 the brackets 1 and 2 of the frame are placed over the patient lying on the bench 4 in a position in which the sensor 9 rests in a point on the abdomen of the patient approximately 4 cm below the navel and the sensor 10 is supported against the chest at approximately one third of the length of the breast bone calculated from below. The patient receives the two electrodes 14 in his hands.

Figure 2 shows an example of the graphic pattern appearing on the display screen 18 in which the uppermost curve 19 represents the heart rate as a function of time, the curve 20 represents the amplitude of the abdominal respiration and the curve 21 the amplitude of the costal respiration also as a function of time. The inspiratory thoracic recession may also be recorded and/or displayed. The graph in Figure 2 represents the situation for a normal respiratory behaviour in the rest condition, in which case approximately 8 respirations occur per minute. As is evident from the graph, the amplitude of the abdominal respiration (curve 20) is approximately three times as large as the thoracic amplitude (curve 21). At the same time it is evident that the start of the abdominal respiration (point 22) precedes the start of the thoracic respiration (point 23) and indeed by approximately 1/2 to 1 second. A comparison of the curve 19 with the curves 20 and 21 shows that the respiratory sinus arrhythmia is synchronous with the respiration, the acceleration of the heart rate occurring during the inspiration (the arising portion of the wavy line) and the deceleration of the heart rate during the expiration (the descending portion of the wavy line). As is explained above, this implies that for a correct abdominal respiration the heart rate increases with a lower pressure in the chest during the inspiration and decreases with a higher pressure in the chest during the expiration. This occurs under the influence of mechano-receptors which are sensitive to change in volume. Figure 3 describes another embodiment of the apparatus according to the invention. In this apparatus, for the measurement of the respiratory movements, use is made of two tapes 25, 28 of elastic material which are secured around the chest and the abdomen respectively of the patient, for example by means of strip fasteners, and indeed at positions corresponding to the positions of the detectors 9 and 10 in Figure 1. In each of the tapes 25 and 28 respectively there is a mercury wire 26 and 29 respectively and these mercury wires are connected to the measuring apparatus 33 via the connections 24 and 27. During the respiratory movements the length of each of the mercury wires in each case becomes longer and then shorter again in time with the respiratory movements. As a result the resistance of the mercury wire changes with the same rhythm. This change in resistance can therefore be detected in the measuring circuit 33 and a signal derived from it which can be made visible on the monitor 30. It should be noted that such mercury-wire tapes are per se known in medical engineering.

The apparatus in Figure 3 is further provided with electrodes 34 or a finger or ear plethysmograph which, for example, can be fixed to the lower arm and which delivers a signal via a connection 35 to the heart-rate meter 36. Such probes are also known in medical engineering.

The apparatus is further provided with one or two e ec ors with which the bloodst ream flow rate can be measured; in many cases one detector is sufficient. These detectors 38 and 40 are connected via the respective connections 37 and 39 to the bloodstream flowmeters 32a/32b. These bloodstream flowmeters may operate, for example, on the Doppler principle. Such bloodstream flowmeters and the associated detectors are per se known. Other types of bloodstream flow rate meters, for example provided with detector elements introduced into the bloodstream itself, can be used within the scope of the invention.

The apparatus according to Figure 3 is further provided with a display screen 30 on which now, in contrast to the embodiment of Figure 1, it is not analogue signals which are made visible but bar diagrams, the length of which is proportional to the amplitudes of the corresponding analogue signal. Instead of vertical bar diagrams horizontal ones can also be used.

It is further possible to make visible in the form of figures the inspiration time in seconds, the expiration time in seconds, the various amplitudes, the heart beat rate, the minimum and maximum of the heart beat rate, the time difference between the changeover points of sinus arrhythmia and abdominal respiration ( inspiration and expiration), time difference between the changeover points of abdominal and costal respiration (and, if necessary, between abdominal respiration and inspiratory thoracic recession). The processor 33 may accomodate suitable calcu-lating units for this purpose, which can also calculate averages, or the means present in the processor 33 may be programmed in a suitable manner for reproducing the above parameters.

Figure 4 shows a diagrammatic example of the picture which may become visible on the monitor. All the bar diagrams start at the same height. By means of the first three vertical bars 60, 61 and 62 on the screen, for example, the amplitudes of the costal respiration, the amplitude of the abdominal respiration (if necessary, a further bar for the inspiratory flank respiration ) and the heart rate can again be reproduced, the patient being able to draw in a similar manner as in Figure 2 conclusions from the synchronism of the upward and downward movements of these bars about the efficiency of his respiration. The two other bars 63 (and 64) may be used for reproducing the output signals of the two bloodstream flowmeter(s) 32a/32b. The Doppler sensors 38 and 40 are, for example, used on the main veins of the legs (or leg) or arms (or arm) of the patient. The output signals of the bloodstream flowmeter 32 form in that case an indication of the venous bloodstream from the legs or from the arms/the head of the patient. The patient can learn to influence the venous bloodstream through the manner of respiration in a manner such. that it is optimally efficient for him/her.

A separate recording apparatus 31 can also be connected in Figure 3 for the permanent recording of the analogue or, if necessary, digitised output signals from the measuring apparatus 33.

When the apparatus described is used to teach the patients precise respiratory behaviour, the curve 19 of the respiratory sinus arrhythmia appearing on the screen 18 can be used by the patient to check whether the respiration is as efficient as possible, i.e. whether the curves 19 and 20 retain their synchronism. If, for example, expiration takes place to below the residual volume of the Lungs, the expiration is inefficient in relation to the respiratory muscles and the perfusion/ventilation or gas exchange is not optimal, so that more oxygen is used by these muscles than would be necessary in a more efficient respiration. During the expiration the pressure in the chest becomes higher until expiration is taken below this residual volume. Only at that instance does the pressure in the chest again become lower so that the line of the respiratory sinus arrhythmia again begins to rise, which is a signal to the patient to start inspiring again. Efficient inspiration is also subject to limits. Normally the pressure in the chest becomes lower during inspiration. As has been described previously, however, if inspiration is continued too l o n g (and to too great an extent), an increase of the pressure in the chest occurs so that the line of the respiratory sinus arrhythmia again begins to fall. There is a certain individual respiratory behaviour which is the most efficient. By means of the apparatus described the patient can observe whether his respiratory behaviour is correct and at the same time the patient can also check whether there is abdominal breathing by comparing the. amplitudes of the two respiration curves 20 and 21 and from the position of the start points 22 and 23. If necessary, he can reduce the rate and thereby increase the amplitude, in particular the abdominal amplitude, in a manner such that the synchronism of the curves 19 and 20 aimed for occurs or remains in existence.

The acquisition of an efficient abdominal respiration at rest is of importance for patients with chronic aspecific respiratory disorders and heart patients because through it, as described in the above, the efficiency of the venous bloodstream can be adjusted to the individual optimum. In particular, by doing this it is possible to prevent the heart muscle working under strain, consuming an excessive amount of oxygen in the process and squeezing shut its own coronary vessel branches during contraction as a result of a forced contraction of the heart muscle.

For patients with chronic aspecific respiratory disorders and patients with hyperventilation the apparatus according to the invention is also of importance. Such patients can learn to reduce their respiration rate by means of the apparatus and at the same time learn to get the starting point 22 of the abdominal respiration in the correct manner ahead of the starting point 23 of the thoracic respiration.

Other patients, too, such as inter alia hypertensive patients, asthma patients, patients with chronic aspecific respiratory disorders and patients with psychosomatic disorders, can learn to break the vicious circle which is caused by a hyperactivity of the thoracic respiration by means of the apparatus and thereby attain a more adjusted and more efficient respiratory behaviour and better matching of perfusion and ventilation.

Both the apparatus of Figure 1 and that of Figure 3 can be used to help patients with poorly functioning intercostal muscles, which patients are dependent upon an as efficient as possible abdominal respiration, in the training of the diaphragm. This can be done in the case of these patients by fitting a harness on the diaphragm, for example by stretching an elastic tape around the body of the patient at the right point or a tape of non-yielding material, the ends of which are coupled to each other by means of a. adjustable spring mechanism. In this case the patient must overcome this extra external tension in carrying out the respiratory movements and in doing this maintain, in fact, the correct respiratory behaviour, as a result of which the diaphragm is trained to be able to keep functioning optimally even under load.

Figure 5 shows a further development of the apparatus according to the invention. In this embodiment the components 24'... 41' correspond to the components 24 ... 41 from Figure 3 and also have the same function as the corresponding components in Figure 3. More detailed discussion of this is therefore superfluous.

In Figure 5 a unit 43 has been added which receives a signal via a connection 42 from the multi-core connection cable 41', which signal is an indication of the intensity of the venous bloodstream. This may be the signal which is picked up via one of the sensors 38' or 40' and is an indication of the venous bloodstream from the legs or from the arms/the head, but it can also be a signal which is possibly combined. For the purpose of further discussion, however, it is assumed that it is the signal which is indicative of the venous bloodstream from the legs. This signal is fed to the unit 43 which contains a threshold-value detector which allows through only the peaks in the signal, corresponding to the bloodstream surges, in particular at the beginning of the inspiration and expiration phases, and therefore suppresses noise signals. Depending on the strength of these peaks a signal can now be transmitted via a connection 44 (possibly after assessment by an operator) to a unit 45 which will be discussed in more detail below.

Figure 6 shows an exemplary embodiment of the unit referred to in Figure 5 in its generality by 45. The unit

45 is provided with a number of inflatable cuffs 53, 54, 5 which are attached in a row with (little or) no spacing, for example, around the calves of a patient. These cuffs are of a known type which, for example, are also used in sphygmomanometers. Although three cuffs are shown in the figure, other numbers can also be used. It should further be noted that such a unit 45 can be attached around each of the calves, in which case both units must be operated synchronously.

Each of the cuffs 53, 54, 55 is connected via a respective tubular lead 52, 51, 50 to a pump unit 49, 48,

47. These pump units are in their turn activated by signals originating from the control unit 46. This control unit 46 receives an input signal via the connection lead 44 in Figure 5 already mentioned from the unit 43. The input signal from the line 44 is used to start a clock pulse generator 56 which delivers clock pulses to a counter 57. The counter 57 steps from one state to the subsequent state under the control of these clock pulses and in doing this, delivers control signals to the pump units 47, 48, 49 depending on the state reached in a manner such that these pump units are sequentially switched on in a manner such that first of all the cuff 55 is placed under a predetermined pressure, a short time later the cuff 54 and again a short time later the cuff 53. Instead of separate pumps various valves can of course be connected to a single pump to inflate or ventilate the various cuffs. Once a subsequent cuff has been brought up to pressure, the previous cuff can, if required, be deflated again. It is, however, also possible to deflate all the cuffs simultaneously at the end of a sequence.

The result is that a propulsive action is exerted on the blood which is located in the veins within the thigh 59 and, indeed, in the direction of the arrow 58. The arrow 58 indicates the return direction of the venous blood flow and the propulsive action produced by means of this row of cuffs thus results in a forced increase in the venous return blood flow to the heart.

It will be clear that the control can be such that surges are emitted in each case at the correct instant in time (to intensify excessively weak naturally occurring surges). On the other hand, however, a continuous series of sligjit, surges can also be produced (venous massage) if this is desirable from a medical point of view. It should be further noted that such an apparatus can also be used for venous massage around the arms of a patient, albeit with less effect in view of the fact that the legs form as it were a much larger reservoir from which the blood can be pumped in the direction of the heart by the massage apparatus.

It should in addition be noted that by preference the normal venous bloodstream must, if possible, be measured beforehand so that the measurements then obtained can be used to control the intensity of the massage action. In the above it is indicated that the cuffs are placed under a predetermined pressure. Depending on this pressure and depending on the rate at which this pressure is reached or depending on the rate at which the subsequent cuffs are activated, the intensity of the surges produced in the bloodstream can be varied as required.

For this purpose the unit 45, for example, can contain a detector circuit 66 which determines the strength of the incoming signals and which ensures, by means of a signal via the conductor 67, that the pump pressure is reduced to the extent the signal strength increases.

The apparatus of Figures 5 and 6 can in particular be used in cases in which a patient has to be artificially respirated. As already indicated in the introduction, it is certainly not fictitious that under artificial respiration conditions the venous return blood flow decreases sharply because of the totally modified pressure conditions within the body. If the intensity of the return blood flow now falls below a certain value, the apparatus in Figure 6 is put into action to increase the venous blood flow in a forced manner. Figure 7 shows a further embodiment of the invention which only differs in a few points from the embodiment in Figure 5. The parts corresponding to Figure 5 are indicated by the same reference numbers.

A unit 69 has been added which is a monitoring unit for the venous bloodstream from the arms, which bloodstream in its turn is an indication of the venous bloodstream from the head. During artificial respiration it may happen that during the inspiration phase the venous bloodstream from the arms stops, which is an indication that the venous bloodstream from the head also stops. That is then due to an excessively large expansion of the higher lung sections, as a result of which the head veins affected are pressed shut. In such a case the unit 69 can give a warning which can be reacted to by switching the artificial respiration apparatus directly or, if necessary, after an acceptable, very short period to expiration. The unit 69 may, if required, deliver a signal for this purpose directly to the artificial respiration apparatus via the lead 70. In the artificial respiration apparatus the still outstanding period for pumping in air can be regulated between 0 and some very short period after receipt of the warning signal via the lead 70.

It should be noted that the embodiments of the apparatus have only been described di agrammatically and that it has been assumed that various components of the apparatus are normally available as standard components or can be constructed by an expert in this field without any difficulty, for which there are then various options. A detailed description of the various components in the various figures is therefore considered superfluous.

Figure 8 shows a further embodiment of an apparatus according to the invention. This apparatus is again provided with the heart beat sensor 134 which is connected via the lead 135 to the heart beat meter 136, the bloodstream sensors 138 and 140 which are coupled to the associated bloodstream flowmeter 132, which by preference operates on the Doppler principle, via the leads 137 and 138, the cage construction indicated in its generality by 100 on the bed 104 with the sensor elements 109 and 110 for the determination of the respiratory movements, which construction can be the same as the construction which is shown in Figure 1, and the processor 133 which receives input signals from the respiratory movement detectors 109 and 110, the heart beat meter 136 and the bloodstream flowmeter 132 and which delivers output signals via the connection 141 to the display unit 130 and possibly to the recording unit 131. The processor 133 further delivers control signals via the connection 142 to the massage unit 145 which can be of the type shown in Figure 6, either directly or via a further signal-processing unit 143, which is shown in the figure by a dotted line.

This apparatus is now used for a patient, who is lying on the bed 104, in combination with an artificial respiration apparatus 150, which may be of a per se known type. The artificial respiration apparatus delivers pulses via the lead 146 to the processor 133 in a chosen artificial respiration rhythm if the patient no longer has any natural respiration. If the patient does have natural respiration which has to be supported with the apparatus 150, then the processor 133 delivers control pulses to the apparatus 150 in the measured spontaneous respiration rhythm. The patient is further provided with means by which the movement of the high chest respiration (the uppermost inspiration muscles) can by choice be limited to a greater or lesser degree. In Figure 8 these means are indicated in general by 151, possibly connected via a control lead 147 to the processor 131. In Figure 9a an embodiment of these means 151 is shown consisting of one or more expandable or inflatable tapes 154 which are stretched round the upper part of the chest and which are connected via air or liquid lines to the control unit 160. Furthermore, similar shoulder top tapes are present which run round the shoulder tops and terminate at the front and back in the centre of tape 154 in a manner such that the bloodstream through the arm and head veins is not hampered by these tapes even in the stretched condition. These shoulder top tapes 155, 156 are connected via liquid or air lines 1 58 , 1 59 t o t h e c o n t r o l u n i t 1 60. T h i s u n i t 1 60 i s c o n t r o l l e d via the connection 147 by the processor 133.

The apparatus 151 must function in a manner such that the high chest respiration is limited in a desired manner to a greater or lesser extent in favour of a lower inspiration. The detectors 109, 110 at the same time provide information on the instantaneous condition, and on the basis of this information the processor 133 can react in a satisfactory manner by delivering the correct control signals inter alia to the unit 151. In addition, the apparatus 151 must by preference function in a manner such that during a respiration cycle the expiration muscles are supported at a chosen point in time or points in time during the expiration by the tapes 154, 155, 156 being tensioned and released in a pulsating manner. The tensioning pulses produced in these tapes can have an adjustable duration and amplitude, both under the control of the processor 133.

The apparatus shown in Figure 8 operates as follows. The artificial respiration apparatus ensures that air is first pumped into the lungs of the patient in a desired respiration rhythm, after which the pump pressure is reduced so that the lungs empty again (classical artificial respiration). The processor now determines in each case the instant in time in which the massage apparatus 145 has to be brought into operation. By preference this takes place just before the inspiration because the conditions are then favourable for increasing the perfusion because of the low transmural pressures in the air passages (and in the pulmonary alveoli). The result of this is that blood is fed to the lungs immediately before the inspiration.

As already noted, when air is pumped into the lungs, a movement of the chest occurs which is similar to the movement which occurs in costal respiration. Through this the higher parts of the lungs are filled with air to a much greater degree than is the case for an efficient natural (abdominal) respiration, as a result of which the higher lung sections press shut, to a greater or lesser degree, the veins which cater for the return of blood from the arms and from the head so that the return of blood from these parts of the body is hampered. To overcome this drawback aids are attached, within the scope of the invention, to the body of the patient which ensure that this respiratory movement of that high part of the chest is restrained or at least considerably limited. These aids can, for example, consist of a tape which is stretched around the body at the height of the uppermost lung sections. This tape can, for example, consist of a tightening strap which is stretched around the body of the patient. with a predetermined force. It is also possible (as shown in Figure 9a) to include in this tape 154 one or more inflatable or expandable cavities running around the bod of the patient, of the type shown in the tapes which are illustrated in Figure 6 so that by controlled pumping up or expansion of these tapes the pressure which is exerted on the chest can be regulated.

In a further embodiment shoulder top tapes 155, 156 are also present which run over the shoulder tops of the patient from the front to the back and ensure that these shoulders can move up as Little as. possible (in the direction of the head of the patient), as a result of which the costal respiratory movement is also limited.

This small harness made up of the various said taps caters for the controlled limiting of the higher respiratory movement without pressure being exerted on those parts of the body which cater for the lower respiratory movement and without pressure being exerted on the flow mechanism of the venous and arterial circulation system. Any pressure from the outside on the veins which run from the arm and the head is also prevented by this. The circulation through these veins can be correctly stimulated.

By preference the processor 133 will control the unit 151 in a manner such that at the end of the expiration movement until just before the inspiration movement the harness is detensioned to a greater or lesser extent as required to give the blood, which is supplied venously (by abdominal respiration and/or by the action of the massage apparatus 145), the chance of flowing to the top of the Lungs. During the actual inspiration movement the harness is tensioned so as to guide the air flowing in to the lowermost parts of the lungs.

Towards the end of the inspiration movement the pressure in the harness may be reduced. During the expiration the harness can be (now and again) stretched more tightly or more loosely through pulse control by the unit 151 via suitable control signals from the processor 133. As a result of the tensioning of the harness the tops of the lungs are as it were squeezed out, as a result of which the venous return stream from the lung to the left heart is intensified and space is made for new blood to the tops of the lungs. The venous return flow from the arms and head is also intensified by this. As is shown in Figure 9b, the harness can also consist of tapes which are tensioned by the person under treatment on the basis of the signals which are made visible on the display screen 130. In this case the harness is only an aid to correcting high costal respiration. The harness shown in Figure 9b consists of the tape 170 stretched around the uppermost part of the chest and the two shoulder top tapes 171 and 172 which at the front and the back are attached approximately in the centre of the body to the first-named ring 170 and which run over the shoulder tops of the patient. Both tapes 171 and 172 are provided with shoulder top pieces which ensure that these tapes remain in their correct position.

Hitherto the classical artificial respiration model has been assumed. However, according to choice, high-frequency artificial respiration or a combination of classical and high-frequency artificial respiration can also be used (in which cases, of course, a modified apparatus 150 must be used), combined with the natural respiration (provided the patient has natural respiration).

There are advantages in designing the apparatus 150 in a manner such that it is capable of reducing the pressure in the artificial respiration connection to the patient at a chosen moment in the expiration phase in such a manner that air is sucked out of the lungs to a greater or lesser degree. This reduces the transmural pressures in the air passages (temporarily) in favour of the perfusion. This intensifies the described action of the harness during the expiration phase.

The apparatus in Figure 8 can be further extended with a separate blood flow detector which measures the b l o od s t r e a m through the carotid artery. This blood flow gives a clear indication of the quantity of blood which is circulating through the brain and is therefore an indication of the effectiveness of the apparatus shown in Figure 8. A good blood circulation through the brain results in an efficient removal of metabolites and gases (including CO₂) from the brain. A poor blood circulation causes metabolic changes, changes in the acidity and build-up of PCO₂ and/or pO₂ in the brain, which is revealed, for example, in a patient under anaesthetic in a deeper anaesthetisation of the patient than was desired. This additional blood flow detector can of course be coupled to the processor 133 via a suitable bloodstream meter in the same way as the detectors 138 and 140.

The apparatus according to the invention can furthermore be used to advantage in combination with per se known instruments for determining the so-called "cardiac output", the arterial blood pressure, venous pressures, plethysmography, etc. Regardless of the method which is used with such instruments to arrive via further calculations at values which are of importance especially for the "cardiac output" starting, for example, from pressure measurements or thermodilution, it is precisely of importance for the said calculations to have available an accurate reference for the point in time in the respiration cycle (artificial respiration cycle) and the behaviour of the venous return. In this connection the instruments must either be calibrated beforehand or continuously provided with reference values, in particular values which relate to the respiratory movements and the blood flow. The apparatus according to the invention can therefore with advantage provide these reference signals which indicate at which favourably chosen moment the calibration or the calculation must be carried out. Through this combination of the apparatus according to the invention with known means for the determination of the "cardiac output" the accuracy of this determination is found to be considerably increased.

In Figure 8 the above-named instruments are diagrammatically indicated by 152 which, for the reception of the said reference signals are coupled to the processor 133 via a line 153 which via inputs 154 is coupled to one or more measured value recorders (e.g. pressure sensors, etc.).

In addition, the unit 152, on the basis of the experimental or calculated values, can send signals back to the processor- 133 which can be used to influence the massage unit 145, the harness 151 and, if required, the artificial respiration unit 150. These signals can, of course, also be made visible on the monitor.

In general it should further be noted that influence can be exerted on the various parts of the apparatus in Figure 8 not only by the processor; often values can also be fed in or adjustments made manually.

By preference the unit 152 includes a recorder for recording an ECG. This supplies information to the processor regarding the instance of inter alia the diastole and systole. Together with the peripheral (continuous) pressure and/or flow measurements and/or further non-blood observations, the processor is in a position to determine the delay, pulse strength and/or pulse differences between heart pulses and peripheral pulses, which is a measure of the so-called "resistance" (the resistance of the arterial vessel system) and/or the cardiac output. The use in addition of a finger plethysmograph under these circumstances provides information on the peripheral circulation and the peripheral resistance (vasoconstriction and vasodilatation).

Claims

C LA I M S

1. Apparatus for determining the respiratory behaviour of a patient, characterised by a first and a second measuring element for determining the rhythm and the amplitude of the abdominal respiration and the costal respiration respectively, and a third measuring element for determining the behaviour of the heart rate, and means for simultaneously making observable and/or recording the output signals from these three measuring elements with the same time base.

2. Apparatus according to claim 1, characterised in that further means are provided for determining the flow rate of the blood from the legs and/or from the arms and/or from the head of the patient.

3. Apparatus according to claim 2, characterised in that the apparatus is coupled to means with which the intensity of the venous return blood flow, in particular from the legs, is increased, which means are activated if the means determining the bloodstream flow rate deliver a signal below a predetermined threshold level.

4. Apparatus according to claims 1-3, characterised in that the first and the second measuring elements each consist of a sensor which can be placed against the abdomen or the chest of a patient respectively, which is movably suspended on a bearing frame and which is connected to an electrical element which reacts to the displacement of the sensor.

5. Apparatus according to claim 4, characterised in that each sensor is borne by a sprung element to which a strain gauge is attached.

6. Apparatus according to claim 4 or 5, characterised in that the bearing frame is provided with two parallel brackets (which can be placed over the recumbent patient, which are connected by a connecting rod of adjustable length and on which the sensors are secured.

7. Apparatus according to one of claims 1-3, characterised in that the first and the second measuring elements each consist of an elastic tape which incorporates a mercury wire and which can be attached around the body of the patient at the height of the abdomen or the chest respectively, which mercury wire is connected to a circuit which delivers an output signal varying depending on the change in resistance of the wire caused by change in length of the mercury wire.

8. Apparatus according to claims 1-3, characterised in that the first and the second measuring elements each consist of a flexible tape or wire which can be placed around the body under slight spring pressure, the ends of which are connected to an electrical signal generator, which reacts to the relative movements of these ends occurring during respiration.

9. Apparatus according to one of the preceding claims, characterised in that the measuring appliance for the heart rate includes two hand electrodes to be grasped by the patient which are connected to a heart rate meter.

10. Apparatus according to one of claims 1-8, characterised in that the measuring appliance for the heart rate includes electrodes or a finger or ear plethysmograph attached at a suitable place on the body of the patient and connected at a circuit for delivering output signals corresponding to the heart rate.

11. Apparatus according to one of claims 2-10, characterised in that the means for determining the bloodstream flow rate consist o f at least one probe to be used at a suitable point on the body of the patient which probe is coupled to a measuring circuit based on the Doppler principle.

12. Apparatus according to one of the preceding claims, characterised in that the output signals of the measuring elements are transmitted to a monitor via an electronic processing unit and reproduced in a suitable form on the display screen of the monitor.

13. Apparatus according to claim 12, characterised in that the signals are reproduced on the display screen of the monitor as a number of wavy-line curves situated above each other, the common time base being indicated along the abscissa of the graph and the amplitude of the abdominal and costal respiration, the rate of the heart beat, and if applicable the intensity of the bloodstream flow rate being plotted along the ordinate of the graph.

14. Apparatus according to claim 12, characterised in that the output signals on the display screen of the monitor are reproduced in the form of so-called bar diagrams, the length of the respective bar corresponding to the amplitude of the abdominal and costal respiration, the rate of the heart beat and, if applicable, the rate of the venous return blood flow.

15. Apparatus according to one of claims 3-14, characterised in that the means by which the venous return blood flow is stimulated consist of a series of expandable cuffs attached directly one behind the other by preference around a leg or the legs of the patient, the expandable section of which is coupled via hoses to a pump mechanism, which pump mechanism functions in a manner such that the expandable cuffs can in each case be put under a chosen pressure in sequence after a predetermined time interval and at a predetermined rate.

16. Apparatus according to claim 15, characterised in that the hoses of the various expandable cuffs are coupled to a series of valves which are controlled by means of a processor.

17. Apparatus according to claim 15 or 16, characterised in that the pump mechanism or the valves respectively are controlled by a counting mechanism to which counting pulses are supplied by a clock pulse unit, which clock pulse unit is started as a function of an externally generated signal.

18. Apparatus according to claim 17, characterised by a comparator circuit in which the intensity of the peaks in the signal corresponding to the surges in the venous bloodstream are assessed and which can deliver an output signal, which may or may not be dependent on the said intensity, to the means for stimulating the venous bloodstream.

19. Apparatus according to one of claims 2-18, characterised in that the appliance is used in combinationwith an artificial respiration apparatus and that the means for determining the bloodstream flow rate, in particular of the venous bloodstream from the arms, deliver a signal to a monitoring unit, which delivers a signal if this bloodstream (virtually) stops, which signal can be fed with or without a very short delay period to the artificial respiration apparatus in order to stop the pumping in of air.

20. Apparatus according to one of the preceding claims, characterised in that the apparatus is used in combination with an artificial respiration apparatus, signals being transmitted via a connection between the two pieces of apparatus which are a representation of the desired respiration rhythm in order to synchronise both pieces of apparatus with each other.

21. Apparatus according to claim 20 intended for use with patients still having an at least partially natural respiration, characterised in that the processor transmits synchronisation signals on the basis of the measured costal and/or abdominal respiratory movements via the said connection to the artificial respiration apparatus.

22. Apparatus according to one of the preceding claims, characterised in that the apparatus is further provided with a garment or harness constructed of tapes which is placed around the uppermost parts of the chest and, if required, around the shoulder tops and with which at least the uppermost sections of the chest, which move during costal respiration, are restricted in their movement to a lesser or greater degree.

23. Apparatus according to claim 22, characterised in that the tapes of the garment or harness are made of expandable or inflatable parts which can swell up as a result of the supply of liquid or gas to a greater or lesser extent, which parts are connected by lines to a liquid- or gas-supplying unit, which unit is controlled via a connecting lead by control signals generated in the processor.

24. Apparatus according to one of the preceding claims, characterised in that a bloodstream flow rate probe for measuring the blood flow through the carotid artery is coupled to the processor.

25. Apparatus according to one of the preceding claims, characterised in that the apparatus, dependent on the respiratory movements detected and dependent on the venous blood flow detected, supplies signals to the control means or to the processing unit respectively from instruments known per se for determining the so-called "cardiac output"