MEASURING DEVICE AND METHOD FOR DETERMINING AT LEAST ONE RESPIRATORY PARAMETER

Abstract

The invention relates to a measuring device and to a method for determining at least one respiratory parameter, wherein an electromagnetic field is irradiated into a body and is received on an opposite side of the body, then a phase of the received alternating field is compared in a time-dependent manner to a phase of the irradiated alternating field, and the at least one respiratory parameter is determined from a result of the comparison.

Claims

1-26. (canceled)

27. A measuring device for determining at least one respiratory parameter, comprising: at least one transmitting structure and at least one receiving structure; a signal generator, which is coupled to the at least one transmitting structure and with which an AC voltage can be generated that can be applied to the at least one transmitting structure; a comparison unit, with which a phase of a signal supplied from the receiving structure can be compared to a phase of the AC voltage as a function of time; and an evaluation unit, with which at least one respiratory parameter can be determined from a result of the comparison of the phase of the signal supplied by the receiving structure to the phase of the AC voltage.

28. The measuring device according to claim 27, wherein a phase difference between the phase of the signal supplied by the receiving structure and the phase of the AC voltage can be determined with the comparison unit as a function of time.

29. The measuring device according to claim 27, wherein the AC voltage can be generated with variable and/or varying frequency.

30. The measuring device according to claim 27, wherein the at least one transmitting structure is connected to the signal generator via a first cable having a predefined wave impedance and is fed via a first resistance, the value of which is equal to the wave impedance of the first cable, and wherein the receiving structure is connected to the comparison unit via a second cable having a predefined wave impedance and is terminated via a second resistance, the value of which is equal to the wave impedance of the second cable, and optionally, the first and second resistances as well as the wave impedance of the first and second cables are 50 ohms.

31. The measuring device according to claim 27, wherein the signal generator is configured to generate the AC voltage with a frequency of greater than or equal to 10 MHz.

32. The measuring device according to claim 27, wherein the measuring device comprises three, four or more than four of the transmitting structures and/or three, four or more than four of the receiving structures.

33. The measuring device according to claim 27, wherein the at least one transmitting structure is an antenna or an electrode, and/or wherein the at least one receiving structure is an antenna or an electrode.

34. The measuring device according to claim 33, wherein at least one of the antennas of the receiving structure is arranged in the near field of at least one antenna of the transmitting structure.

35. The measuring device according to claim 33, wherein the at least one transmitting and/or receiving antenna has a meander-shaped structure, and optionally, the at least one transmitting and/or receiving antenna is applied to a substrate having increased permittivity.

36. A method for determining at least one respiratory parameter, wherein: an alternating electromagnetic field is irradiated, via at least one transmitting structure, into a body by generating an AC voltage with a signal generator, which AC voltage is applied to the at least one transmitting structure; the alternating field irradiated into the body is received by at least one receiving structure after having passed through the body; in a comparison step, a phase of a signal supplied from the at least one receiving structure is compared to a phase of the AC voltage as a function of time; and at least one respiratory parameter is determined from a result of the comparison step.

37. The method according to claim 36, wherein, in the comparison step, a phase difference between the phase of the signal supplied by the receiving structure and the phase of the AC voltage is determined as a function of time.

38. A method for determining at least one respiratory parameter, wherein: an alternating electromagnetic field is irradiated, via at least one transmitting structure, into a body by generating an AC voltage with a signal generator, which AC voltage is applied to the at least one transmitting structure; a change in a resonance of the transmitting structure during the irradiation of the alternating electromagnetic field is determined as a function of time, and a respiratory parameter is determined therefrom.

39. The method according to claim 36, wherein the at least one transmitting structure is arranged on a thorax and/or an abdomen of the body, and the at least one receiving structure is attached to the thorax and/or the abdomen.

40. The method according to claim 39, wherein the transmitting structure and the receiving structure are attached laterally at the abdomen and/or at the thorax.

41. The method according to claim 36, wherein a maximum phase deviation is determined from the comparison of the phase of the signal supplied by the at least one receiving structure to the phase of the AC voltage, and a volume of a breath of air is determined as the at least one respiratory parameter from the maximum phase deviation.

42. The method according to claim 36, wherein a derivative of the difference between the phase of the signal supplied by the at least one receiving structure to the phase of the AC voltage is determined, and whether inspiration or expiration is taking place is determined as the respiratory parameter from the derivative.

43. The method according to claim 36, wherein the AC voltage is generated, having a plurality of different frequencies, and the at least one respiratory parameter is determined from a comparison of the phase of the signal supplied by the at least one receiving structure to the phase of the AC voltage at one of the frequencies at which, among all of the plurality of frequencies, the coupling between the transmitting structure and the receiving structure is maximal, or an amplitude of the signal supplied by the receiving structure is maximal, or a maximum change in the difference between the phase of the signal supplied by the receiving structure and the phase of the AC voltage results over the course of a breathing cycle.

44. The method according to claim 36, wherein the AC voltage is generated, utilizing a plurality of different frequencies, and the at least one respiratory parameter is determined from a comparison of the phase of the signal supplied by the receiving structure to the phase of the AC voltage at least two of the applied frequencies.

45. The method according to claim 36, wherein a temporal beginning and/or a progression of an inspiration and/or expiration, a blockage of the respiratory tract and/or labored breathing against mechanical ventilation is determined as the at least one respiratory parameter.

46. The method according to claim 36, wherein a temporal change in a difference between the phase of the signal supplied by the receiving structure and the phase of the AC voltage is represented as a function of time.

47. The method according to claim 36, wherein at least one further electrode and/or at least one further measuring frequency is evaluated so as to remove at least one disturbance variable from the computation.

48. The method according to claim 36, wherein at least one disturbance variable is removed from the computation of a respiratory parameter determined in the method.

49. The method according to claim 36, which is a non-diagnostic method.

50. A respiratory apparatus, wherein the respiratory apparatus is configured to carry out a method according to claim 36, and to control the respiration based on the at least one respiratory parameter.

51. A device for injecting a contrast agent for imaging processes, which is configured to carry out a method according to claim 36 so as to carry out the injection of the contrast agent as a function of the respiratory parameter.

52. A device for imaging, which is configured to carry out a method according to claim 36 so as to only record images at defined respiratory parameters and/or so as to only use collected image data at defined respiratory parameters and/or so as to offset collected image data in the computation as a function of the respiratory parameters.

Description

[0056] The invention will be described hereafter by way of example based on several figures. Identical reference numerals denote identical or corresponding features. The features described in the examples can also be implemented independently of the specific example and be combined between the examples.

[0057] In the drawings:

[0058] FIG. 1 shows a basic design of a measuring device according to the invention in the form of a block diagram;

[0059] FIG. 2 shows a curve of a phase of a received signal at different measuring frequencies;

[0060] FIG. 3 shows a phase deviation for different breathing volumes;

[0061] FIG. 4 shows, by way of example, the determination of a phase difference between an irradiated signal and a received signal as well as an exemplary determination of respiratory parameters;

[0062] FIG. 5 shows a phase difference over the time with unobstructed and obstructed breathing;

[0063] FIG. 6 shows a meander-shaped antenna structure;

[0064] FIG. 7 shows the antenna structure shown in FIG. 6 in a side view;

[0065] FIG. 8 shows an embodiment of the transmitting and receiving structures in the form of circumferential conductors; and

[0066] FIG. 9 shows an embodiment of the transmitting and receiving structures arranged at a distance from the patient.

[0067] FIG. 1 shows an exemplary design of a measuring device according to the invention in the form of a block diagram. A respiratory parameter is determined in the process by irradiating an alternating electromagnetic field through a body 1. The alternating electromagnetic field is irradiated into the body 1 by a transmitting structure 2, which can be an antenna or an electrode, for example, and is received by a receiving structure 3, which likewise can be an antenna or an electrode. So as to generate the signal to be irradiated, an AC voltage, which is supplied via a cable here, for example a coaxial cable, is applied to the transmitting electrode 2. Such a cable can have a defined wave impedance. The AC voltage is amplified in the process by a transmitting amplifier 4 having a terminating resistance, wherein the value of the terminating resistance is preferably equal to the wave impedance of the cable via which the transmitting electrode 2 is connected to the transmitting amplifier 4.

[0068] The AC voltage is supplied to the transmitting amplifier 4 via an oscillator 5, which generates the AC voltage with a given frequency and a certain phase. For this purpose, the oscillator 5 is controlled by a control unit 6, which can be controlled by a suitable interface, for example a human-machine interface or a machine-to-machine interface.

[0069] The alternating field irradiated into the body 1 from the transmitting electrode 2 is received by a receiving structure 3, which is connected, for example via a coaxial cable, to a receiving amplifier 8 having a terminating resistance. The absolute value of the terminating resistance is preferably equal to a wave impedance of the cable via which the receiving amplifier 8 is connected to the receiving electrode 3. The receiving amplifier 8 is connected to a phase detector 9, which is able to measure a phase of the signal received by the receiving structure 3 and amplified by the receiving amplifier 8. The phase detector 9 is furthermore connected to the oscillator 5, which generates the transmission signal. The phase detector 9 receives information about the phase of the irradiated signal from the oscillator 5. The phase detector 9 can thus carry out a comparison of the phase of the irradiated signal to the phase of the detected signal and, for example, determine a phase difference between these signals. This phase difference is particularly preferably determined as a function of time, that is, for at least two or more points in time. The phase detector can then send the, preferably time-dependent, phase difference to an evaluation unit 10, which determines the at least one respiratory parameter from the phase difference. The evaluation unit 10 can carry out suitable computing or correction steps for this purpose, such as averaging, differentiation, determination of minima and maxima, adaptive filtering, correlation filtering, frequency filtering, and the like. The evaluation unit 10 can then pass the ascertained result, that is, the respiratory parameter, on to the interface 7, where it is accessible for a person or a machine, such as a respiratory apparatus.

[0070] FIG. 2 shows the curve of the phase over time during natural breathing at three different measuring frequencies, which are represented as dotted, dashed and solid lines. The dashed line shows a measurement at double the frequency of the dotted line, and the solid line shows a measurement at triple the frequency of the dotted line. It is apparent that the measurement at triple the frequency of the dotted line shows the greatest phase deviation and is therefore suited best as the measuring frequency.

[0071] FIG. 3 shows the phase deviation for different breathing volumes. The phase deviation is plotted on the vertical axis, and the breathing volumes are plotted relative to a reference volume on the horizontal axis. It is apparent that an approximately proportional relationship exists between the breathing volume and the phase shift. The greater the breathing volume, the greater is the phase shift.

[0072] FIG. 4, by way of example, shows how a progression of the breathing volume can be determined from a sent and a received signal. The time curves of the transmitted signal (larger amplitude) and of the received signal (smaller amplitude) are plotted in partial FIG. 4A. A phase offset Phi exists between the transmitted signal and the received signal, which is the temporal difference between identical phases, such as the maximum or the minimum, of the transmitted signal and the received signal, multiplied by the angular frequency.

[0073] This phase offset Phi, also referred to as phase difference, is plotted against the time in seconds in partial FIG. 4B. A progression of the phase offset as shown by the dotted line is obtained. Shown by way of example here, the phase offset increases during inspiration. The phase offset decreases during expiration. The inverse of the distance with adjoining maximum or minima is the respiratory frequency.

[0074] FIG. 4C shows a chronological progression of the phase offset or the phase difference in relation to the time. Here, ΔPhi is plotted, which is the difference between the maximum phase offset Phi and the minimum phase offset Phi, as is plotted in FIG. 4B. Since the breathing volume increases over time, ΔPhi increases over time.

[0075] FIG. 5 shows the curves of a phase measured in the method according to the invention over time, with sections of unobstructed and obstructed breathing. An obstructed phase string is apparent in the sections denoted by reference numeral 51. The phase deviation, that is, the difference between the maximum phase difference and the minimum phase difference, is considerably smaller here during a breath than in the case of unobstructed breathing. In this way, the method according to the invention can be used to identify an obstruction. Furthermore, labored breathing during the obstruction is also apparent, which can be used, for example, for controlling mechanical ventilation.

[0076] FIG. 6 shows an example of an antenna structure 2 arranged on a substrate 61. The substrate 61 can have high permittivity here, whereby an electrical length of the antenna is increased compared to the geometric length thereof. The antenna here is designed as a dipole antenna, the mechanical width of which is shortened in relation to the electrical length thereof (that is, the length of the conductors 2a and 2b), by placing the dipole arms 2a and 2b in a meander-shaped manner.

[0077] FIG. 7 shows the embodiment of the antenna shown in FIG. 6 in the side view, viewed in the direction parallel to the surface of the substrate 61. In this example, the antenna 2 is arranged on a substrate 2 which, on the side thereof facing away from the antenna 2, is arranged on a ground plane 72. The ground plane can shield the antenna against rear-side disturbances.

[0078] FIG. 8 shows an exemplary embodiment in which two insulated conductors 81a, 81b, serving as antennas, are placed around the thorax of the patient 82. In the process, one conductor 81a is guided ventrally, for example across the chest region, and one conductor 81b is guided dorsally, for example across the back region.

[0079] A transmitting structure 83, here serving as a differential interpretation comprising a terminal A and a terminal B which can be activated in phase opposition, the receiving structure 84 (likewise differential), as well as the ventrally guided conductor 81a and the dorsally guided conductor 81b are shown here. The voltage can be applied here between the terminals A and B. If, for example, the impedance is then measured, changes in the body of the person 82 can then be inferred therefrom.

[0080] FIG. 9 shows an arrangement in which the transmitting and receiving antennas 2, 3 are arranged at a distance from the body of the person 91. An alternating field 92 is emitted here from the transmitting structure 83, and a field 93 modulated by respiration is received by the receiving structure 84. The antennas are arranged at a distance from the body of the person 91. The alternating fields 92, 93 thus pass through a region in the air.

[0081] The method according to the invention is advantageous compared to conventional methods since the measurement can take place directly, and no adjustment of the signal for a cardiac component is required. The cardiac components, however, can be taken into consideration so as to increase the signal quality. Furthermore, it is possible to minimize artefacts and a drift of the measurement signal as a result of a change in the electrical conductivity of the electrodes or the skin, since this does not involve a determination of the conductivity. Moreover, the method according to the invention is very low in movement artefacts, which would occur if amplitudes were considered alone. Compared to the bands around the chest, the wearing comfort for the user is considerably higher due to a low number of attached electrodes and/or antennas. It is also possible to use existing ECG electrodes.

[0082] The described transmission measurement of the invention allows the measured volume to be clearly defined, which is advantageous over reflecting measurements in which the volume is less clearly defined since the penetration depth is dependent on the dielectric properties, and thus on the structure of the measured tissue. The method according to the invention allows spontaneous breathing during mechanical ventilation to be identified. The measurements are intrinsically low in movement artefacts, whereby little post-processing and no additional sensor system are required, but may be used to enhance the signal quality. Compared to other measurements, the user is less restricted.