WO2005074809A1

WO2005074809A1 - Device for measuring the function of a lung

Info

Publication number: WO2005074809A1
Application number: PCT/EP2005/001145
Authority: WO
Inventors: Dirk Rüter
Original assignee: Rueter Dirk
Priority date: 2004-02-05
Filing date: 2005-02-04
Publication date: 2005-08-18

Abstract

The invention relates to a device for measuring the function of a lung, especially in a human body. Said device comprises an ultrasound emitter that can be brought into sound-conducting contact with the body, an ultrasound signal being generated by the contact point in such a way that it is radiated into the body; an ultrasound receiver that can be brought into sound-conducting contact with the body, an ultrasound signal being generated by the contact point in a receiving manner; and an evaluation and control device that is embodied in such a way as to control the ultrasound emitter and to receive and evaluate a signal produced by the ultrasound receiver. The invention is characterised in that the device is embodied in such a way as to be operated within a frequency range of between 5 and 1000 kHz or part thereof.

Description

Device for measuring the function of a lung

The invention relates to a device according to the preamble of claim 1.

In the case of serious illnesses, acute or chronic breathing difficulties, especially in cases of lung failure, after accidents or after surgery, further artificial ventilation in an intensive care unit is necessary for some of the patients. The periods in which patients rely on artificial ventilation can extend from days to weeks.

It can be a lung complication such. B. come to a so-called atelectasis. This is a section of the lung that is not filled with air, usually caused by a local collapse of the lungs. The alveoli here have collapsed or are filled with fluid. The affected area of the lungs no longer participates in gas exchange in the lungs, respiration. In addition to the reduced and changed lung function, there is still a significantly increased risk of pneumonia (pneumonia) with local atelectasis. Pneumonia is a significant life threatening for a weakened patient. For these and other reasons, correct and individual adaptation of the ventilation parameters such as pressure, volume, etc. is important to avoid such less ventilated lung areas. The pressure or volume load on the ventilated lungs must not be set too low or too high. Excessive ventilation also significantly damages the lungs and the circulation of the ventilation patient. An atelectasis is characterized in the X-ray image by shadowing the affected lung segment because the material composition of the atelectasis is different, namely denser than that of the intact lung areas. In Fig. La and Fig. Lb, frontal X-rays of an intact lung (Fig. La) and a lung with an atelectasis in the lower right lung (Fig. Lb) are compared. Most of the time, postoperative respiratory patients are unilaterally affected by a lower section of the lung (somewhat less often a middle section).

For this reason, chest radiographs are taken daily in many clinics with appropriate high-risk patients who are connected to artificial ventilation. In addition to the radiation exposure for the patient, the x-ray images also have the disadvantage that they are associated with a high outlay in terms of apparatus and personnel (mobile x-ray device, development of the films). In addition, with unfavorable constellations, this method can leave a local lung complication undetected for 24 or more hours, which can lead to further complications.

It would therefore be desirable to have a device which enables reliable, continuous, spatially resolving and automatable measurements of lung ventilation, which can be implemented with little equipment, and which impairs the patient as little as possible. Approaches for such a device can be found in the prior art, but none of the approaches has particularly distinguished itself in practice.

For example, so-called impedance tomography is known. In this technique, which is described, for example, in Hahn G, Sipinkova I, Baisch F, et al. "Changes in thoracic impedance distribution under different ventilatory conditions.", Physiol. Meas. 1995, 16, A161-A173, several electrodes are applied to the patient's body. A sequence of current patterns is fed in via these electrodes. For example, a current is fed into the body via one electrode and out of the body via another electrode. All other electrodes are used as measuring electrodes and the voltage applied to them is measured. The positive thing about impedance tomography is that the currents used are largely harmless for the patient. It is also positive that the measurement method can be carried out over a longer period of time and allows a spatial resolution. Cross-sectional images of the lungs can be generated almost continuously. Disadvantages of this method, however, are the low stability against disturbances and the great computational effort to infer physiological parameters from the measurement results, for example the lung density. One of the reasons for this is that the currents flow undirected in the body. Another reason is the low dynamics of the useful signal, ie the low signal contrast, for example, between the inspiratory and the expiratory state of the lungs. Another reason is the difficulty in adequately describing the running processes mathematically. The mathematical evaluation is not very stable and only leads to a result if certain previous expectations are included. Furthermore, as typically 2-dimensional measuring method, impedance tomography has a considerable blurring in the direction of the longitudinal axis of the body. The reconstruction of lung properties in the direction of the longitudinal axis of the body is only possible with considerable additional effort. In addition, with the help of impedance tomography, which measures the specific electrical resistance, only an indirect conclusion is drawn about the air content of the tissue, and from here again only an indirect conclusion about the alveolar ventilation. Furthermore, the attachment of many high-quality electrical contacts around the chest of an intensive care patient involves considerable effort in terms of electrical safety and quality of the measurement technology. So far, impedance tomography has been a relatively prone to failure and very process that is to be carried out is not yet practical, especially not in the fast and time-critical environment of an intensive care unit.

Other known devices for measuring the lung function are the X-ray based computed tomographs and the magnetic resonance tomographs, both of which, however, are technically very complex and expensive to operate. Furthermore, with both non-mobile devices, the patient has to endure loads caused by transport, etc. A permanent monitoring or continuous measurement over the breathing cycles or at least a regular measurement is not practical with these devices. Here, too, only the general density or the mean air filling of the lung tissue is determined. The computer tomographs mentioned do not react specifically to the alveoli.

According to a traditional method, the lungs are checked with manual percussion. The procedure is based on a thorax tapping by a doctor. The lung condition is then deduced from the knocking noises (frequencies below 1 kHz) that are more or less "dull" or "damped". This method is very dependent on the experience of the performing doctor. Percussion is therefore a subjective manual method, not exactly reproducible and in particular not suitable as a continuous, spatially resolving continuous monitoring. The sound of the percussion changes somewhat with the mean air content of the lung tissue, although in particular not directly, but only on the basis of further previous knowledge and assumptions of the doctor to infer the structure (pulmonary alveoli, bronchi, emphysema, pneumothorax ...) of the lung tissue is.

A generic device for measuring lung function is known from Technischen Messen 69 (2002) 4, page 194 ff "Acoustic Diagnostics of the Lung". The procedure represents an objective-technical implementation of the manual Percussion. Acoustic audible sound in the frequency range from below 100 Hz to 1 kHz is radiated into the body via a sound transmitter attached to the chest. The sound signal is then picked up by a sound receiver arranged on the opposite side of the body. The method is technically simple and basically suitable for a regular or permanent functional test of the lungs. Due to the technical design - as with percussion - the sound in this process spreads at a low speed of 30 - 300 m / s in the lung tissue. The method is designed in such a way that sound transmission in the lungs is preferably carried out through the air-filled lung areas (bronchioles, bronchi, ...). In particular, the closing of such a tubular sound channel results in a high signal change. Overall, the method reacts to a change in the general air content of the lungs, but is not specific or selective with regard to alveolar ventilation or the filling and emptying of the alveoli. Due to the measurement methodology, the local resolution is very limited because only relatively low frequencies are used. In fact, practically only frequencies below about 1 kHz can be used. Above about 1 kHz, this method results in such strong sound attenuation in the lung tissue that meaningful signal evaluation is no longer possible. There are also considerable problems with sound coupling. The transmitters and receivers using this method are designed for low frequencies (typically a few hundred Hz) and are correspondingly voluminous and bulky in design. In addition, in this method, care must be taken to ensure that the sound is introduced or removed between the ribs, because the ribs represent mechanical stiffening and thus an obstacle to sound.

US Pat. No. 6,443,907 discloses a diagnostic method of a non-generic type in which sound audible via the airway is radiated into the lungs. Also Here, due to the characteristic design features, the sound propagates at low speed (typically less than 300 m / s) in the lung tissue and preferably in the trachea. A sound receiver arranged on the chest records a transmitted sound signal. It works with sound with frequencies up to a maximum of 2 kHz. Likewise, only the lower frequency range around a few hundred Hz is preferred and practically usable according to this method. Again, attenuations in the lung tissue are so strong for frequencies from approximately 1 kHz that useful signal evaluation is no longer possible. A sound supply line must be routed to the patient via the respiratory tract, which is a disturbing burden. This device also lacks selectivity with regard to alveolar ventilation.

On the other hand, with common ultrasound ultrasound devices (see, for example, "Der Radiologe", Springer-Verlag Heidelberg, Issue Volume 38, Number 5, May 1998, pages: 364-369, 'Diagnostics of Pulmonary Diseases with Transthoracic Sonography') meaningful local information about the lungs can be obtained by placing and aligning an approximately 1 cm ² ultrasound sonography head with the use of ultrasound gel on an intermediate rib position, with the echo sound field or echo field of view reaching up to a few cm into the lungs and allows very good additional diagnoses to lung diseases at this position. Sonography devices work with ultrasound frequencies of typically greater than 1? MHz. At these frequencies, the lung tissue shows a strong reflectivity or scattering power, the attenuation of the lung tissue is almost independent of ventilation with this methodology is only a very local and superficial part visible in the lungs, and only with careful positioning and alignment of the transducer between the highly absorbent ribs. Finally, from US 5,485,841 a non-imaging diagnostic method is known, which also works at frequencies above 1 MHz. The strongly scattering or backscattering property of the lung tissue is also exploited here. The ultrasound signal also has a limited depth of penetration into the lungs. Spectral changes in the backscatter signal or reflection signal of 1-10 MHz are measured, which result depending on whether the patient has inhaled more or less. The spectral changes are not very strong, however, they depend very much on the positioning and orientation of the transmitter, which must be arranged in the spaces between the ribs.

In the latter two methods, high frequencies greater than 1 MHz are used, so that high sound velocities greater than 300 ms are measured in the lungs. The strong scatter or reflectivity (not the direct absorption) of the blistered lung structure is the limiting factor with regard to the depth of penetration of the ultrasound radiation into the lung tissue. At these high sound frequencies, the lungs are more reactive (scattering) than resistive (absorbing). The damping (resistive property) depends only weakly on the ventilation at frequencies above 1 MHz.

On the other hand, the lung tissue behaves at low acoustic frequencies, e.g. B. at 1 kHz, very resistive (highly absorbent, non-scattering or reflective) with a low overall sound speed of only 30 - 300 m / s.

It is the object of the present invention to provide a device which enables a continuous and spatially resolving measurement of the pulmonary function, a low outlay in terms of apparatus and personnel in operation, e.g. B. requires in the intensive care unit and affects the patient as little as possible. adversely. The device should preferably also allow the measurement of the alveolar ventilation.

This object is achieved by a device according to claim 1. Further advantageous refinements of the invention are specified in the subclaims.

The device according to the invention works with ultrasonic sound signals in the low-frequency ultrasonic range between 5 and 1000 kHz, in particular with frequencies between 10 and 1000 kHz. For the measurement, an ultrasound transmitter, which emits ultrasound into the body, is arranged on the patient's body, preferably on the thorax or on the back. An ultrasound receiver, which is also on the body, e.g. arranged on the chest, receives the ultrasound signal after passing through the body and through an area of the lungs. The received signal contains the desired information about the lungs, since the ultrasound interacts with the lungs on its way through the body, e.g. by being dampened, reflected, slowed down, accelerated or absorbed in the lung tissue.

It has now been found that in the frequency range according to the invention intact lung areas and damaged lung areas interact very differently with the ultrasound. It can be seen, for example, that the rhythm of breathing is impressed on the received ultrasound signal at suitable frequencies. At these frequencies, the sound signal received is characteristically modulated by ventilation of the lungs. However, areas of the lungs that do not participate in breathing cause little or no modulation. Due to the different behavior, e.g. the different modulation behavior, the different damping or phase shift, a different transit time behavior (the speed of sound increases with colla- lung tissue significantly), a distinction is made between intact and damaged lung areas.

The device according to the invention also includes an evaluation and control device which receives an electrical signal from the ultrasound receiver. It evaluates e.g. the signal intensities, transit times, phase shifts or the like. The desired information can e.g. are extracted from the absolute signal intensities or the spectral curve, as well as their relative shift in the rhythm of breathing.

For a reliable measurement of lung function, measurements should be taken over several breathing cycles. Continuous monitoring is possible, but the measurement can also be carried out at suitable time intervals, e.g. hourly, e.g. each for a period of a few breathing cycles.

The outstanding suitability of ultrasound with a frequency according to the invention for measuring the function of the lungs can be explained if it is assumed that a particularly high, almost specific interaction with the alveoli occurs at these frequencies. It is the low ultrasonic frequencies used, for. B. at 10 kHz, presumably around frequencies that just above the very strong dispersion of the lung tissue from low speed of sound (z. B. 30 m / s at 1 kHz) to high speed of sound (z. B. more than 350 m / s 10 kHz). It can be determined experimentally that typically only around 1 kHz and above 5 to 10 kHz up to MHz can substantial sound transmission in the lung tissue be achieved. The geometric mean of these two cutoff frequencies is around 3.5 kHz. Around here, a maximum of dispersion and also damping due to resonance or relaxation with practically disappearing sound propagation would be expected. The pulmonary alveoli are organized in grapes about 1 mm in size, which can be understood as acoustically uniform air bubbles in an aqueous tissue. According to the Minneart ^' see formula, air bubbles in water have specific resonance frequencies at which the cross-section of interaction with sound increases very strongly (very strong absorption or scattering). For bubbles with a diameter of 1 mm at 100 kPa pressure in water, the calculated maximum frequency of absorption or scattering is about 3.5 kHz. The very high dispersion of the lung tissue between 1 and 10 kHz can therefore be understood as a specific effect of the numerous pulmonary alveoli.

The working frequency selected in accordance with the invention and capable of spreading in the lungs in the low ultrasound range from typically 5-10 kHz is just above the strong dispersion and is therefore very effective. At these low ultrasonic frequencies, the resistive part of the scatter is still present, i.e. the sound absorption variable with ventilation, and not just the strong reactive component known at MHz frequencies. Therefore, with the device according to the invention, ventilation-dependent attenuations (sound absorption) in the lung tissue can also be measured very well and very dynamically, and not only the known ultrasound effects of reflection and scattering.

There are also methodological advantages. At the frequencies according to the invention, the device is relatively insensitive to the ribs. The received signal of the receiver - unlike in the prior art - is not significantly impeded or disturbed by ribs. Smaller transmitters and receivers can also be used. This enables compact, soft and flat transmitter reception systems that can be used particularly well in intensive care settings. Finally, the use of ultrasound gel can be dispensed with at the low ultrasound frequencies.

Since there are no further significant acoustic inhomogeneities in the lungs below the dimensions of the alveoli, significant acoustic dispersion can no longer be expected and observed even above a few 10 kHz. The dispersion maximum around 3.5 kHz results in a lower limit of 5 to 10 kHz. If you want to get even closer to the dispersion maximum with the ultrasound frequencies, suitable technical measures have to be taken to obtain reliable measurements with the weaker signal intensities. Such measures are available in the prior art. There is no significant discontinuity up to 1 MHz, the speed of sound slowly increases to even higher values. The ultrasound according to the invention differs fundamentally in its physical properties - for example high speed of sound - and in its specific interaction with the lungs from the acoustic sound phenomena at even lower frequencies - here, for example, significantly lower speed of sound - according to the prior art discussed above.

In the device according to the invention, e.g. can be measured in reflection. In particular, a single ultrasound transducer can also be used simultaneously as an ultrasound transmitter and receiver, e.g. intermittently.

Previous investigations have shown that the frequency range in which the device operates can be restricted to 100-500 kHz or a subrange thereof. Intact and damaged lung areas behave differently in this area, and these differences can be read out well in an ultrasound signal of the frequency mentioned. However, surrender Problems due to scattering of the measurement signal on the lungs, which occurs less strongly at lower frequencies.

Alternatively, the device according to claim 3 can also operate in a frequency range from 10 to 200 kHz or a sub-range thereof, advantageously according to claim 4 in a frequency range from 10 to 50 kHz or a sub-range thereof, and according to claim 5 in a frequency range from 10 - 30 kHz.

At the lower ultrasonic frequencies from about 5 or 10 kHz and ending at about 100 kHz, the strong resistive effects (damping depending on ventilation) can be favorably reduced. B. measured in transmission. The damping of the lung tissue varies greatly with the local ventilation or the alveolar ventilation. Furthermore, the transit time and the speed of sound can be measured here. At frequencies from around 50 kHz, the runtime effects (speed of sound) can be measured more sharply and more reactive effects have the upper hand (reflectivity, echo signal for depth profiles, scattering of the lung tissue). Because of the shorter wavelengths, higher-resolution tomography is possible here.

At even higher frequencies (200 kHz, 500 kHz, 1 IVIHz) there are increasingly disturbing effects due to the strongly absorbing and scattering bone structures (ribs, sternum, spine) and the increasingly required ultrasound gel. The individual transducers are becoming increasingly sensitive to position and orientation, the depth of penetration of the ultrasound radiation decreases sharply due to scattering, the effort required to obtain in-depth and spatially resolving information about the lungs increases.

The device can measure, for example, in the transmission position. It can also measure in reflection. Advantageously, however, the features of claim 6 are provided, because this enables a good spatial allocation to a lung nano- malie succeeds. Bent transmission is understood to mean that the signal travels from the transmitter through the body to a receiver on a curved path. In an arrangement according to claim 6, the ultrasonic signal changes its direction by almost 180 °.

The features of claim 7 are advantageously provided. The transmitter and receiver must be arranged so that the ultrasound can penetrate the lung to be examined. It is therefore preferred to mount both the transmitter and the receiver on the patient's upper body in the immediate vicinity of the lungs. It has proven to be advantageous to utilize the property of the heart as a good conductor for ultrasound of the abovementioned frequencies in that the transmitter or receiver is arranged on the body near the heart. In this way, a simple, radial and location-specific transmission of the respective lung section can be achieved. Even when arranged on the spine, there is good access to the heart. In this geometry, the heart can act as a radially radiating ultrasound center and a measurement can be carried out particularly well in a transmission arrangement in which the transmitter and receiver are arranged on different, in particular opposite sides of the body. However, it could also be radiated in through the abdominal cavity as a sound conductor.

In principle, the device can also work with only one ultrasonic transducer. It can also work with an ultrasound transmitter and an ultrasound receiver. However, the features of claim 8 are advantageously provided. With a suitable distribution of the receivers, there is an improved spatial resolution because each receiver receives an ultrasound signal that has passed through different lung areas. In this way, it can be localized more precisely, for example, at which point, for example, an atelectasis is present. The ultrasound signal could, for example, be a sine, sweep, or a noise signal, it could be narrow-band, for example. However, the features of claim 9 are advantageously provided. A noise signal in the weakly audible foothills, for example, is perceived by the patient as less acoustically disturbing than, for example, a sweep signal. In contrast, pulse signals are advantageous in the evaluation, for example, according to transit times, in particular if sequential switching is carried out between several transmitters or receivers. Broadband radiation is preferable to narrowband signals, since there is a risk of narrowband radiation that there is no or only a slight difference between intact and damaged lungs at this frequency. It can only be roughly predicted at which frequency differences can advantageously be identified, because this is patient-specific. It can be seen that optimal frequencies can vary, for example in adults and children, in men and women, in the trained and untrained. When using broadband noise or broadband pulses, it is reliably ensured that a suitable frequency range is recorded for the evaluation for each patient.

The transmitters and receivers can e.g. individually attached to the patient's body. The features of claim 10 are advantageous for faster attachment. Only one or a few carriers then have to be attached instead of the multiple receivers. When arranged on a carrier, the receivers are also constantly positioned relative to one another, while a location assignment with individual fastening is more difficult to achieve and prone to errors. The wiring can also be simplified.

The carrier can be fastened, for example, by gluing or another method known in the prior art. However, the features of claim 1 1 are advantageously realized. A belt can be put on the patient quickly and can be worn comfortably for a long time. After the belt is put on, the receivers distributed on the belt are distributed around the body in the intended and defined manner, for example around the thorax. The belt can be elastic, for example.

To reduce mutual interference between the receivers, the features of claim 12 are provided. The belt that lies against the body between the receivers reduces possible mutual interference. A suitable material according to claim 13 is e.g. a polymer foam.

Since the belt is used in the medical and clinical fields, the merlαnale of claim 14 are advantageously provided. As an alternative to this, the belt could also be manufactured as a disposable item or covered with an exchangeable sterile film.

The carrier and the transmitter and / or receiver arranged thereon can e.g. be firmly connected. With the features of claim 15 it is advantageously achieved that the ultrasonic transducers e.g. can be attached to different belts, e.g. selected according to patient size. Furthermore, individual converters can be replaced in the event of malfunction or damage. Finally, the belt and receiver can also be disinfected or sterilized separately. The belt could also be designed as a disposable item.

If the device has several receivers, the features of claim 16 can advantageously be provided. Such an arrangement enables a particularly good spatial limitation of possible lung damage and can be used for a visual representation of the measurement results, for example by suitable temporal and spatial control of the transmitter and receiver. The features of claim 17 are advantageously provided. As a result, the receivers fit better against the body and with higher contact pressure.

For example, the evaluation and control device can operate according to the features of claim 18. It then receives information on different lung areas in quick succession, and can e.g. calculate an overall lung image and show it on a display provided for this purpose.

With the features of claim 19, sectional views of the lungs can advantageously be generated. The section level in the views corresponds to the level of the recipient. The spatial resolution can thereby advantageously be increased.

In principle, the function of the transmitter and receiver can also be interchanged. If, therefore, a particular arrangement of the receivers and a single transmitter was previously discussed, a plurality of transmitters can also be used instead, e.g. in the same arrangement as described above for the receiver, and a single receiver.

Advantageously, the merlαnale of claim 20 are provided, the plurality of ultrasound transmitters transmitting simultaneously and acting like a transmitter. The advantage is that possible contact or attenuation problems at the ultrasound coupling point are reduced if, for example, three ultrasound transmitters operated in parallel are used simultaneously in close proximity to one another. This promotes large-scale, safe and reproducible sound coupling. Analogously, receivers operated in parallel and spatially densely arranged can also be combined to form a reception channel in order, for. B. interference occurring at higher frequencies due to ribs in any system position. The multiple transmitters are preferred designed as a structural unit and arranged in the immediate vicinity of the heart or on the spine.

The electronic or physical coupling or phase-adapted parallel connection of several transmitters and receivers can be used via diffraction effects for directional control or depth resolution of the sound field. A so-called Ultrasc all tomography can be implemented with the aid of numerical and phase-accurate calculation of several transmitter or receiver signals.

Preferably, the Merlαnale are provided according to claim 21, in order to ensure good ultrasound introduction into the body. Because an air gap e.g. between the ultrasound transmitter and the body represents an impedance boundary layer with an impedance jump, which leads to loss of intensity due to reflection, x

The coupling of the ultrasound into the body can be further improved with the features of claim 22, because the acoustic transition from a hard transducer into the thorax is significantly influenced by the contact pressure and the moisture of the interface. Corresponding effects are known from ultrasound imaging technology. Ultrasound gel is used there as standard to ensure reproducible and low-reflection sound transmission. The use of ultrasound gel would be very cumbersome, in particular with several transducers. In addition, the gel dries out, making it difficult for long-term use. Although the proposed coupling layer, for example in the form of a soft-elastic coating, causes a certain signal damping of the ultrasound, it very much reduces the influence of contact pressure and moisture on the transfer function of the interface. The layer can only be applied to the transducers or also to the entire contact surface of the belt. It could also use transmitters or receivers a hard surface profile, in which the protruding structures as sound bridges have the necessary contact pressure on the body for good sound-conducting contact, because the local contact pressure near the protruding structures is often greater than with a smooth and flat support. Therefore, there is less dependence on contact pressure and moisture for sound transmission. In the long run, however, the patient could experience these structures as uncomfortable or even painful.

The features of claim 23 effect a further advantageous improvement of the system of the ultrasound transducers designed in this way.

Since the device is to be used in the medical, and in some cases even in the intensive medical field, it must also meet sterility requirements. The parts of the device that come into contact with the body could therefore e.g. be trained as a disposable item, which is disadvantageous for cost reasons. Features of claim 24 are therefore advantageously provided. The Merlαnale of claim 25 represent an alternative.

In principle, any of the types of ultrasonic transducers known in the prior art can be used. With regard to reliability and costs, however, the merlαnale of claim 26 are advantageously provided.

The device advantageously has the features of claim 27 in order to be able to save results of the measurements, for example after evaluation and conversion into an intuitively interpretable representation. In this way, for example, temporal developments in the lungs can be tracked and archived. The storage can be permanent, for example, in order to be able to edit, view or use the stored data later for comparison purposes. The features of claim 31 are preferably also provided. The saved For example, data can also be transferred to memory outside the device, for example a hospital memory, in order to be stored in the patient file. The memory used can be, for example, a removable memory or a computer memory which is connected to the device by means of a data cable.

The device advantageously has the merits of claim 28, ixm when a defined situation is determined, e.g. a dangerous situation to attract the attention of medical personnel or the user of the device in general. Then e.g. further examinations can be arranged or a doctor called. However, the alarm signal can e.g. a malfunction, a power supply that is only secured for a short time, or the like are also displayed.

With the advantageous Merlαnalen of claim 29, the device can be easily transported, e.g. carried by patients or by emergency physicians. The device can then e.g. are carried by the patient during ongoing measurements, in particular with the advantageous features of claim 30, with which independence from power grids is achieved. The power supply can take place via any current storage or generator known in the art, e.g. Batteries, accumulators, solar cells, fuel cells etc.

The measurement results can be displayed in any way. In order to enable an intuitive and easy reading, the features of claim 32 are provided. This representation is similar to the usual representation in computer tomography. The invention will be explained in more detail below by describing some exemplary embodiments. The invention is shown by way of example and schematically in the drawings. Show it:

Fig. La, lb: X-rays of an intact lung (la) and a lung with partial atelectasis,

2: a first embodiment of a device according to the invention, the receivers and transmitters are preferably attached in the side and back area,

Fig. 3: a second embodiment of a device according to the invention, here too the receivers and transmitters are preferably mounted in the side and back area

4: a third embodiment of a device according to the invention,

5: a sectional view through the device according to FIG. 4,

6a-f: spectral representations of transmission and reflection measurements between different transmitters and receivers of the device according to FIG. 4,

7: an example of a pictorial representation of measurements carried out with the device according to FIG. 4,

8: a sectional view through a hand-held device according to a further exemplary embodiment of the invention, and

9 a-c show a basic illustration to explain the measured spectra.

A ventral x-ray image of an intact lung 1, 2 of an adult person is shown in FIG. 1b shows a damaged lung 3, 4 in a similar ventral image. In the lower left lung 3 an atelectasis 5 is shown as a light spot, because this lung area is another, namely has a denser tissue structure than the intact areas of the lungs, which appear as dark shadows from the surrounding tissue and skeleton.

Figure 2 shows a first embodiment of a device for measuring the lung function. Four ultrasound transducers 21 are arranged above the lower area of the left lung 1 and two above the lower area of the right lung 2 of a patient 22 shown on the chest 23, e.g. glued. The electro-acoustic transmitters and receivers 21 (only collectively referred to as transducers), which are only a few cm in size, are designed on the outside to be similar to common EKG electrodes, that is to say they are of flat design and lie well on the body 22.

Via control and signal lines 24, the transducers 21 are connected to a control and evaluation unit 25, which can control each of the transducers 21 and receives an electrical signal from the transducers 21 that corresponds to an ultrasound signal picked up by the transducer 21. For the measurement of the lung function, one, several or all of the transducers 21 are controlled to send an ultrasound signal. The signal penetrates through the skin into the body 22 and into the lungs 1, 2, and is partially reflected on its way through the body 22 by the various tissue structures. The reflected signal is picked up again by the same transducers 21 that have emitted the ultrasound signal, and an electrical signal is transmitted to the control and evaluation device 25. The evaluation device 25 calculates from the electrical signals obtained whether and which of the lung areas 1, 2 below one of the transducers 21 shows an abnormal interaction with the irradiated ultrasound signal, for example by an unusually high proportion of ultrasound of a certain frequency or within a certain frequency window has been transmitted or reflected. If no abnormality is found, the examined lungs 1, 2 can be considered intact. Becomes If an abnormality is found, it can be assigned to one of the transducers 21 and the location of the lung anomaly can thus be narrowed further. This measurement can be continued for many hours, for example. However, the control and evaluation device 25 can also carry out a measurement automatically or triggered by an operator at defined time intervals, which, for example, extends over several breathing cycles.

The exemplary embodiment shown in FIG. 3 of a further device for measuring the lung function differs from the previous example in that two transducers are arranged on a common carrier 31 and form a compact and flat functional group. The transducers are arranged on the side of the carrier facing the patient's body 22; they can otherwise correspond identically to those shown in FIG. 2. The carrier 31 is wired to the control and evaluation device 25 via lines 24 which run further inside the carrier 31 to the converters (not shown). Compared to the measuring process explained in connection with FIG. 2, there are no differences in this second measuring device. However, the carrier 31, which also rests on the thorax 23 between the transducers and has sound-insulating properties in the spectral range emitted by the transducers, has the effect that adjacent transducers interfere less less, that is to say, for example, neighboring transducers do not also each measure the ultrasound signal emitted by the neighbor, which is reflected on the body surface, for example, without penetrating deeper into the body 22. The transducers can be based on piezo technology, for example, and can operate in a frequency range of 10-50 kHz. For example, you can emit a broadband signal. Structure-borne noise frequencies above 10 kHz are generally not perceivable by humans, so that the patient and also the medical staff are not disturbed by the measurement signal. In FIG. 4, the device for measuring the lung function has a belt 41, on the side facing the body of which, in an array arrangement, a plurality of ultrasound receivers 21 are arranged in three rows around the body 22 and in several columns. These receivers 21 are predominantly located on the back and the lateral thoracic area of the patient 22 and are indicated by white circular areas. A central ultrasound transmitter 42 is located in the immediate vicinity of the heart 43. It emits an ultrasound signal in the direction of the heart 43. From the heart 43, the ultrasound signal penetrates the two lungs 1, 2 and finally reaches the receivers 21, at which the incoming signal is measured, converted into electrical signals and passed on to the evaluation and control device 25 via a control and data line 24. The signals are processed there and displayed if necessary. The central transmitter 42 is accommodated in the belt 41 in this exemplary embodiment. However, it can also be arranged separately, for example on its own carrier. This can be advantageous, for example, for the separate positioning of the transmitter 42 and the receiver 41, the transmitter also being able to be designed as a transmitter unit with a plurality of individual transmitters which, together or independently, generate an ultrasonic signal and radiate it into the body.

FIG. 5 shows a horizontal section through a device according to FIG. 4, the section running through the lower of the rows of receivers 21 in FIG. 4. The belt 41 carries ultrasound receivers 21 on its inside, which can be detachably attached, for example, and which rest on the patient's body 22 in good sound-conducting contact. The central ultrasound transmitter 42 is also attached to the inside of the belt. All transducers 21, 42 lie flat or somewhat raised on the body surface and transmit / receive essentially vertically through the body surface. The two dark crescent-shaped areas 1 and 2 correspond to the left and right air-filled lungs genflügel. The path of the ultrasound signal leads from the transmitter 42 via the heart 43 through one of the lungs 1, 2 to one of the receivers 21.

Alternatively, the central point of entry or entry can also be provided on the dorsal spine or on the abdomen.

In a manner not shown, the belt 41 can rest on the body between the transducers 21 and thereby suppress parasitic ultrasound, especially when measured in reflection. This is understood to mean the proportion of sound that does not penetrate the body and is then reflected to the receiver, but e.g. directly from the sender to the receiver.

In Figures 4 and 5, the device has a transmitter and a plurality of receivers. However, the device can also work with one receiver and several transmitters, or with several transmitters and several receivers.

FIGS. 6a-6f show ultrasound signal profiles measured between different transmitters and receivers of the device shown in FIG. A broadband noise signal was always used. The signal intensity is plotted in the spectra, coded by the brightness, whereby dark areas indicate a low signal intensity (corresponds to a strong beam attenuation when passing through the lungs) and bright areas indicate a high signal intensity, depending on the measuring time x-axis) and the frequency (y-axis).

FIG. 6a shows the signal curve as it was measured between the central transmitter 42 and the ultrasound receiver 52, FIG. 6b when measured at the receiver 56, FIG. 6c when measured at the receiver 51, and FIG. 6d recorded with the receiver 55. FIG. 6e shows a spectrum that was measured in arcuate ger transmission, wherein the converter 52 works as a transmitter and the converter 54 as a receiver. Finally, spectrum 6f also shows an arcuate transmission measurement with transducer 51 as transmitter and transducer 53 as receiver. During the different measurements, the ultrasound passed through different areas of the lungs.

It can be clearly seen that in the frequency range shown up to 22 kHz with light breathing activity (i.e. normal and even breathing at rest in a lying position) the received ultrasound signal is clearly modulated in time with the breathing frequency. When you exhale, the attenuation decreases (light areas 61), when you inhale, the receiver only reaches a very weak signal (dark areas 62). The signal modulation or useful signal dynamics is very large compared to the prior art and definitely reaches values of 30 dB.

Below approximately 8 kHz, approximately constant blackening can be seen in all spectra, which corresponds to a consistently low signal intensity. The sound of this frequency is largely attenuated as it passes through the lungs, regardless of the breathing movement. At very low frequencies, that is to say at the lower end of the spectra, areas 61 of lower attenuation can be identified, which are presumably attributable to tracheal sound or immediate airborne sound with low sound speed in accordance with the prior art for knocking sound. Below 5 kHz one speaks of audible sound.

In a certain frequency window, however, which varies slightly from spectrum to spectrum and is approximately between 10 and 20 kHz, an influence of respiratory activity on the attenuation of the ultrasound signal can be seen. Dark 62 and light areas 63 alternate with the rhythm of breathing. The modulation in time with the breath is also simple, that is, not frequency-resolved. th intensity representation 64 of the signal can be seen in each case at the upper edge of the spectra.

The frequencies used in FIG. 6 are low-frequency ultrasound with high speed of sound. Here - close to the strong dispersion - strong resistive effects are observed, which vary greatly with the local ventilation. A sound reflection in the classic sense does not occur dominantly here.

With these signals, the transit time or the change in the speed of sound can be measured in a manner not shown here. The high speed of sound in this frequency range varies significantly with ventilation due to its proximity to the maximum dispersion.

Below about 10 kHz, the attenuation increases sharply and the sound conduction in the lung tissue decreases. By increasing the measurement sensitivity and sound level, measurements could also be made below 10 kHz. However, the subjective noise pollution of patient and staff would increase, which is why only frequencies above 10 kHz were used here.

The spectra shown are not yet optimally suitable for immediate display. Therefore, the evaluation and control unit 25 can evaluate the measurements obtained, save them and display them on a display, e.g. in the representation shown in FIGS. 7a and 7b and familiar from computer tomography.

By activating certain transducers 21, a specific area of the lungs can be irradiated in a targeted manner, specifically by means of a belt 41 in FIG. Through an automatic, fast and sequential query and evaluation of the transducers 21, 42 of the belt 41, a quasi 3-dimensional ventilation state of the lungs can be determined and dynamized in several sectional images corresponding to the three horizontal planes in which the transducers 21 are arranged from breath to breath.

An advantageous form of representation is shown in FIG. 7. Fig. 7a shows the lungs in the empty, Fig. 7b in the filled state. In each case corresponding to one of the three horizontal rows of transducers 21 of the belt 41, the lungs are shown in three horizontal sectional planes 71, 72, 73. Within each section plane 71, 72, 73, in turn, variable display segments 74, 75, 76, 77, 78, 79 are each assigned to one of the sound paths to the receivers 51 to 56. Display segment 74 e.g. corresponds to the sound path from transmitter 42 to receiver 51.

The display segments follow the breathing rhythm by changing their color or brightness, which corresponds to the measured sound attenuation, ie scaled with the measured sound intensity in a predetermined frequency range. This representation is similar to the usual representation in computer tomography and allows the clinic staff or another operator to read the lung function intuitively. In the case of local atelectasis or a lung malfunction, the sound signal will typically no longer vary significantly in the breathing cycle and at the same time show a significantly different basic level. Such an endangered lung segment would be easy to find using this type of representation.

A real tomography can be achieved with the inclusion of phase-locked calculation of several receiver or transmitter signals. In a manner not shown here, the display according to FIG. received profile. This would result in a completely 3-dimensional reconstruction of the lungs. As an alternative to tomography, real echo signals can also be used at a somewhat increased frequency of e.g. B. 50 - 150 kHz can be used for depth information and thus completely 3-dimensional reconstruction.

Fig. 8 shows a device for measuring lung function in training as a handheld device 81. This embodiment is based on the same measuring principles already described above. The handheld device can be used on an outpatient basis for short-term local examination of the lung. The ultrasound transmitter 82 with a transmitter 42 is connected by a control and data line 83 to the main device 84, in which the control and evaluation means are accommodated. The support device 85 formed on the side of the main device 84 accommodates an array of four receivers 21, only two of which are shown in the side view. The support device 85 is made of a sound-absorbing material and is typically up to 20 cm in diameter. A soft coupling coating 86 is provided on its contact side. A display 87, which can be read from the outside, is arranged on the main device 84 for displaying the measurement results. Without the additional ultrasonic transmitter 82, e.g. also in reflection or - e.g. at lower frequency - can be measured in arcuate transmission.

The principle representations shown in FIGS. 9a to 9c are used to describe below how the empirically determined rhythmic changes in an ultrasound signal of the frequency according to the invention can be explained. Horizontal sections through a human torso are shown. The dark gray arrows represent the path of an ultrasound signal, the arrow thickness indicating the intensity of the ultrasound signal. The ultrasound signal propagating in the body is indicated by dark gray arrows, the signal emerging from the body with black arrows. The transmitters or receivers which rest on the outer circumferential surface of the body are omitted here for the sake of simplicity, for example they could be arranged exactly as shown in FIG. 5.

9a, an ultrasound signal is radiated into the heart of a patient. From there the signal spreads radially outwards with decreasing intensity and also penetrates into the patient's two lungs. After passing through the lungs, a signal emerges from the body and can be measured by appropriate ultrasound receivers.

In the lungs, the alveolar grapes are indicated by white circles. 9a shows the lungs in the exhaled state, that is to say the alveoli have a somewhat smaller diameter (exaggerated here). In practice you will have a distribution of alveolar diameters. However, the basic principle applies to all alveoli.

In Fig. 9b the lung is shown in the inhaled state. As a result, the diameter of the alveoli has increased, and with this change in size, the interaction cross section with the ultrasound signal. Compared to FIG. 9a, a larger part of the irradiated signal is attenuated, for example by absorption, that is to say the signal leaving the body in FIG. 9b is of a lower intensity than in the situation outlined in FIG. 9a. The above explanation applies to frequency ranges in which the interaction with filled alveoli can be found. Other frequencies, at which such an interaction with the alveoli hardly takes place, show hardly any changes when inhaling and exhaling. Changes can then result, for example, from a breath-modulated lung density. 9c shows the lungs according to FIG. 9b, that is to say in the inhaled state, with a lung abnormality present in the left lung (viewed ventrally in the body direction), for example an atelectasis, which is shown as a dark gray circular area with smaller light gray circular areas arranged therein, which schematically indicate the alveoli in this area of the lungs. The abnormality of this area of the lungs manifests itself by the fact that the alveoli inside are not aerated when inhaled and therefore do not change their diameter. The area remains static during breathing cycles. For the signal emerging from the body, this means that the portion of ultrasound signals that passes through the damaged lung area modulates less or not at all with the rhythm of breathing, indicated by the arrows emerging from the body in the area of the anomaly, compared to those away from the anomaly arrows emerging from the body are more intense. Receivers resting on the body will therefore notice little or no signal modulation in the vicinity of the anomaly, while receivers located away from it will measure a greater depth of modulation. This also applies to the transit time behavior of the ultrasound signal or other parameters that are influenced by the type of lung tissue and its change during breathing. These parameters can also be used to evaluate the measurements.

In the examples shown, transmitters could also be arranged where receivers are arranged, and vice versa where receivers are shown, receivers could also be arranged. The measuring arrangement is reversible in principle.

Claims

PATENT CLAIMS:

1. Device for measuring the function of a lung (1, 2, 3, 4), in particular a human body (22), with an ultrasonic transmitter (21, 31, 42, 51, 53, 52, 54) that is in sound-conducting contact with can be brought to the body (22) and an ultrasound signal is emitted into the body (22) via the contact point, with an ultrasound receiver (21, 31, 51, 52, 53, 54, 55, 56) which is in sound-conducting contact with the body (22) can be brought and is designed to receive an ultrasound signal via the contact point, and with an evaluation and control device (25, 84) which controls the ultrasound transmitter (21, 31, 42, 51, 53, 52, 54) and for reception and for evaluating a signal generated by the ultrasound receiver (21, 31, 51, 52, 53, 54, 55, 56), characterized in that the device is designed to work in an ultrasound frequency range from 5 to 1000 kHz or a sub-range thereof ,

2. Device according to claim 1, characterized in that the device is designed to work in a frequency range of 100-500 kHz or a partial range thereof.

3. Device according to claim 1, characterized in that the device is designed to work in a frequency range from 10 to 200 kHz or a partial range thereof.

4. The device according to claim 3, characterized in that the device is designed to work in a frequency range of 10 - 50 kHz or a partial range thereof.

5. The device according to claim 4, characterized in that the device is designed to work in a frequency range of 10 - 30 kHz or a partial range thereof.

6. Device according to one of the preceding claims, characterized in that the ultrasonic transmitter (21, 31, 51, 52, 53, 54) and the ultrasonic receiver (21, 31, 51, 52, 53, 54, 55, 56) for measurement a curved transmission are arranged in spatial proximity to one another, in particular on essentially the same sides of the body.

7. Device according to one of the preceding claims, characterized in that the ultrasonic transmitter (42) or the ultrasonic receiver (21, 31, 51, 52, 53, 54, 55, 56) is arranged near the heart (43) on the body (22) ,

8. Device according to one of the preceding claims, characterized in that the device has a plurality of ultrasonic receivers (21, 31, 51, 52, 53, 54, 55, 56) which are arranged at a distance from one another on the body (22).

9. Device according to one of the preceding claims, characterized in that the transmitted ultrasound signal is a pulse signal.

10. The device according to claim 8, characterized in that the ultrasonic receiver (21, 51, 52, 53, 54, 55, 56) are arranged in groups or in total on a common carrier (31, 41).

1 1. Device according to claim 10, characterized in that the carrier is designed as a belt (41).

12. The apparatus of claim 10 or 11, characterized in that the carrier (31, 41) or the belt (41) is made of an ultrasound insulating material such that it between the ultrasound receivers (21, 51, 52, 53, 54th , 55, 56) is in good contact with the body (22).

13. Device according to one of claims 10 to 12, characterized in that the carrier (31, 41) or the belt (41) is made of a polymer foam.

14. Device according to one of claims 10 to 13, characterized in that the carrier (31, 41) or the belt (41) is disinfectable, in particular sterilizable.

15. Device according to one of claims 10 to 14, characterized in that the ultrasound receivers (21, 51, 52, 53, 54, 55, 56) are removably arranged on the carrier (31, 41) or belt (41).

16. The device according to one of claims 8 to 15, characterized in that the ultrasonic receiver (21, 51, 52, 53, 54, 55, 56) in an array in rows around the body (22) and arranged in columns in the longitudinal direction of the body are.

17. The device according to one of claims 8 to 16, characterized in that the ultrasonic receiver (21, 51, 52, 53, 54, 55, 56) protrude from the belt surface to be applied to the body (22).

18. Device according to one of claims 8 to 17, characterized in that the evaluation and control device (25, 84) automatically and in rapid succession alternately individual or groups of ultrasonic receivers (21, 51, 52, 53, 54, 55, 56 ) evaluates.

19. The apparatus according to claim 18, characterized in that the evaluation and control device (25, 84) automatically and in rapid succession alternating in a plane perpendicular to the longitudinal axis of the body ultrasound receiver (21, 51, 52, 53, 54, 55, 56 ) evaluates.

20. Device according to one of the preceding claims, characterized in that a plurality of ultrasonic transmitters (21, 42, 51, 52, 53, 54) are provided, which are combined in particular to form a structural unit, and in particular near the heart (43) or on the spine arranged on the body (22) and directed towards the heart (43).

21. Device according to one of the preceding claims, characterized in that the or the ultrasonic transmitter (21, 42, 51, 52, 53, 54) and the or the ultrasonic transducer (21, 51, 52, 53, 54, 55, 56) are designed in a flat shape that can be easily placed on the thorax.

22. Device according to one of the preceding claims, characterized in that the or the ultrasonic transmitter (21, 42, 51, 52, 53, 54) and / or the or the ultrasonic receiver (21, 51, 52, 53, 54, 55, 56) on their ultrasound transmitting or receiving side are provided with an ultrasound-conducting coupling layer 86.

23. Device according to one of the preceding claims, characterized in that the surfaces of the ultrasonic transmitter (21, 42, 51, 52, 53, 54) and / or receiver (21, 51, 52, 53, 54, 55, 56) are made of a soft plastic.

24. Device according to one of the preceding claims, characterized in that the ultrasonic transmitter (s) (21, 42, 51, 52, 53, 54) and / or receiver (21, 51, 52, 53, 54, 55, 56) disinfectable, in particular sterilizable, are formed.

25. Device according to one of the preceding claims, characterized in that the ultrasonic transmitter (21, 42, 51, 52, 53, 54) and ultrasonic receiver (21, 51, 52, 53, 54, 55, 56) on their transmitter or Interchangeably have a sterile, sound-conducting cover film.

26. Device according to one of the preceding claims, characterized in that the ultrasonic transmitter (s) (21, 42, 51, 52, 53, 54) and / or receiver (21, 51, 52, 53, 54, 55, 56) have a piezoelectric vibrator.

27. Device according to one of the preceding claims, characterized in that the device has a storage device in which measurements can be stored.

28. Device according to one of the preceding claims, characterized in that the device has an Alann device, and the evaluation and control device (25, 84) is designed to trigger an alarm signal in the presence of predetermined conditions.

29. Device according to one of the preceding claims, characterized in that the evaluation and control device (25, 84) is arranged in a portable hand-held device (81).

30. The device according to claim 29, characterized in that the device has a power supply independent of the mains supply, and in particular is battery-operated.

31. Device according to one of the preceding claims, characterized in that reference measurements are stored in the storage device, and the evaluation and control device (25, 84) uses the reference measurements for evaluating the measurement results.

32. Device according to one of the preceding claims, characterized in that the evaluation and control device (25, 84) carries out a phase-accurate calculation of several transmitter or receiver signals, a depth profile of the lung is determined and from this a 3-dimensional image of a lung is generated, which can be shown on a display.