DE102010014761A1 - Method for determining heart rate, respiration rate, pulse wave running time and medium blood pressure of patient, involves preparing control-and-evaluation unit to determine pressure of patient and output at control-and display unit - Google Patents

Abstract

The method involves arranging a position sensor (10) i.e. acceleration sensor, and a position evaluation unit (24) in a holding element (2) to differentiate an upright layer of an upper body of a patient from a non-upright layer of another upper body of the patient and output as current positional information (56). A control-and-evaluation unit is prepared from current positional information, current pulse wave running time (63) and calibration dataset (44) to determine medium blood pressure of the patient and output at a control-and-display unit (26) via a data interface (18). An independent claim is also included for a device for determining heart rate, respiration rate, pulse wave running time and medium blood pressure of a patient.

Description

The present invention relates to a method and a measuring device for determining the vital parameters respiratory rate, heart rate and the mean blood pressure of a patient by means of electro-impedance plethysmography.

The respiratory rate is a significant indicator of the health of a patient. The recording of the respiratory rate is already carried out with the medical monitors available today as part of a routine monitoring in the field of intensive care. For this purpose, mechanical respirators or respiratory assistive devices are available.

For mobile patients, mobile physiological monitors are available to monitor the cardiovascular function, with which the patient's electrocardiogram (ECG) is recorded, recorded, displayed and in many cases wirelessly transmitted to a monitoring center via radio interface. These monitors are battery-powered, enabling mobile monitoring of mobile patients. This provides the opportunity for ECG monitoring of cardiovascular parameters in a variety of patients without the need for routine full-day hospitalization in a hospital intensive care unit. Such a system for monitoring ECG signals with radio data transmission is in the US 6416471 shown.

For the monitoring of the respiratory activity for patients without airway access via masks or tubes, measurements are carried out by means of thoracic and abdominal ligaments or impedance measurements.

From the DE 10 2007 001 709 A1 For example, a measuring arrangement and method for determining the heart rate on the basis of electro-impedance plethysmography is known. The measuring arrangement consists of a plurality of electrodes arranged on the human body of a patient. The impedance between at least two electrodes is determined by an introduction of alternating electrical current into the human body.

The method is used to determine the respiratory rate from the vessel pressure, taking into account the dependence of the vessel pressure on the chest pressure. The magnitude of the chest pressure depends on the type of breathing, such as a deep or shallow breathing of a patient.

In electro-impedance plethysmography, an AC resistance of a body segment in the environment of a vessel, e.g. B. measured on the collarbone or wrist. The blood in the vessel differs from the surrounding tissue by a significantly lower AC resistance, so that the AC resistance measured in the environment is greatly influenced by the vessel expansion.

From the literature (eg "Apparative vascular diagnostics", Ralf student, ISBN 3-932633-16-4 ) methods for determining cardiac activity by observing vascular dilation as a function of time are known.

Vessel plethysmography generally serves as a diagnostic method for detecting vascular characteristics, such as vascular dilations. The curve shape, amplitude, frequency and course are evaluated as a function of the time of the measurement signal. From this, important information can be obtained for statements about the condition of the vessels, the cardiovascular system.

From the DE 198 295 44 C1 a device for non-invasive blood pressure measurement is known. An upper arm cuff is used to record a blood flow time or a blood flow velocity.

At the upper arm cuff a main unit is arranged, in which an evaluation of sensor signals is carried out in a signal processing unit. The sensors detect a blood flow, a pulse, a blood pressure and the propagation velocity of the pulse wave.

The signal processing unit includes artifact filters, analog-to-digital conversion and units for calculation, calibration, and interfaces for storing and outputting data.

In many cases photoplethysmography is used to determine vascular properties rather than electro-impedance plethysmography, whereby light, preferably different wavelengths, is absorbed with oxygen depending on the degree of saturation of the hemoglobin and can be directly deduced from the detection of this degree of saturation as a function of time , This method is also known as pulse oximetry or very widely used and used as SpO ₂ measurement. However, due to the operation of the light source for photoplethysmography, a continuous sufficient supply of energy is required.

The method of photoplethysmography is particularly suitable for patients whose oxygen saturation must be monitored continuously for physiological, diagnostic or therapeutic reasons anyway.

It must be remembered that to determine the oxygen saturation of the blood only a short duty cycle of a total of a few seconds is required. A quasi-continuous operation for monitoring the oxygen saturation with the help of photoplethysmography is therefore possible in a cyclic manner with short-term switch-on intervals. Thus, the oxygen saturation even with portable devices without large energy storage capacities and thus without significant restrictions on the freedom of movement of a mobile patient possible.

For an exact determination of the respiratory rate, however, a continuous measurement is only possible on the basis of a several minutes lasting on-time with detection of multiple breaths. The disadvantage here is that according to the prior art makes the self-sufficient energy supply comparatively large energy storage capacities, for example in the form of batteries or accumulators required. A continuous operation of a respiratory monitoring by means of photoplethysmography is thus not possible without significant impairment of the freedom of movement of a mobile patient, especially in portable devices.

For non-invasive blood pressure measurement, oscillatory sphygmomanometers with a humeral cuff are known. In cyclic intervals, the cuff is inflated with air until the blood flow through the upper arm is blocked. The pressure that is applied via the cuff from the outside, is measured and provides a measure of the blood pressure in the blocked vessel. About a continuous detection of a heartbeat signal or detection and evaluation of the so-called Korotkow sounds, the flow of blood pressure measurement is controlled.

The Korotkov sounds are used to record various stages of blood flow in the vessels and, based on this, generate different pressure levels in the cuff to record the systolic and diastolic readings.

A disadvantage of this oscillatory measurement by means of the humeral cuff on the one hand, the restriction of freedom of movement of the patient, on the other hand, the vessels are damaged by prolonged use by the compression of the cuff. Continuous use is also not possible, as otherwise the elasticity of the blood vessels would change, which would result in a falsification of the blood pressure readings. It requires a convalescence time, so that the blood vessels after a measurement again have the original elasticity.

It is the object of the present invention to develop an improved measuring arrangement and an improved method for the continuous determination of the vital parameters of a mobile patient.

The object of the method is achieved according to the invention with the features of claim 1.

Advantageous embodiments of the method are listed in the subclaims 2 to 5.

The object of the device method is achieved according to the invention with the features of claim 5.

Advantageous embodiments of the device are listed in the subclaims 6 to 9.

The method according to the invention for determining the respiratory rate by means of electro-impedance plethysmography overcomes in the measurement the dependence of the vessel pressure on the thorax pressure. By using the method according to the invention for the operation of the electro-impedance plethysmography, a low-power, battery-operated operation of a mobile measuring device is made possible.

The magnitude of chest pressure depends on the breathing pattern of the spontaneously breathing patient. In a flat, fast breathing, small pressure changes between the inhalation and exhalation of about ± 5 mbar, with a deep, rapid breathing, a pressure change can reach the value of about ± 20 mbar. An increased airway resistance increases the amplitude of the pressure change with the same breathing pattern. The frequencies of respiration are on average between 0.1 Hz and 1 Hz and are usually free of harmonics, since chest and / or diaphragm movements as stimulating movements themselves are low in harmonics. The pressure changes of the breathing are superimposed with the much stronger pressure change, which is caused by the blood transport in the vessels and fluctuates with the heart rate correlating regularly and alternately.

The amplitude of the pressure change of the blood transport is 100 mbar to 270 mbar, the associated fundamental frequency is in a range between 0.5 Hz and 5 Hz and also has significant harmonics as two- and three-fold harmonics of the fundamental frequency. The blood pressure indication of 100 mbar corresponds approximately to a value of 72 millimeters of mercury (mmHg), 270 mbar corresponds to approximately 200 mmHg. An indication in millimeters of mercury (mmHg) is more common in medical diagnostics than an indication in mbar or hectopascal (HPa). The vascular system even as a low pass reduces further higher frequencies.

In particular short-term changes of the surrounding tissue, such as. B. the muscles on the pressure amplitudes. The altered, external tension has an effect on the distensibility of the vessels and, for example, can cause the vessel pressure to diminish as the external pressure of the muscles increases, without fundamentally changing the pressure conditions in the vessel.

Especially with such disturbances that occur periodically during the measurement period with a frequency in the range of the respiratory rate, a clear distinction from the respiratory associated signal components is difficult. A suitable measuring arrangement for determining the heart rate, the respiratory rate, the pulse wave transit time and the mean blood pressure of a patient by means of electro-impedance plethysmography usually comprises a control and evaluation unit which is connected to the body of the patient via at least two electrodes and through which an alternating current a frequency in the range of 50 kHz to 100 kHz is fed. The injected current is in the range of a few μA with a power of approx. 0.05 μW.

The suitable measuring arrangement further comprises a data memory, a data interface, a position evaluation unit, a power supply unit, a position sensor, and an operating and display unit.

The position evaluation unit is designed in conjunction with the position sensor to detect the horizontal or vertical position of the upper body of the patient and to distinguish the horizontal from the vertical position of the upper body of the patient and to provide as position information of the control and evaluation unit. The position information is used to normalize the pulse wave transit time and / or pulse wave velocity to the upright or non-upright position of the patient's upper body.

The feeding of the alternating current is such that the current direction and the blood flow direction in the current-flowing body environment form an axis. The chosen body environment serves to measure the vessel expansion and should preferably be exposed to little external pressure changes due to muscle movements. A preferred measuring location for this purpose is, for example, in the area of the clavicle or on the shoulder of the patient.

The amplitude of the alternating voltage signal is modulated with the vessel width, wherein a small amplitude corresponds to a narrow vessel state and a widening of the vessel leads to an increase in the signal amplitude.

The frequency range to be detected by the control and evaluation unit reaches up to 10 Hz to the third harmonic of the blood transport.

An evaluation of the second and third harmonic enables the delimitation of the signal components of signals contained in the signal, which are caused by external pressure changes and disturbance variables, associated with the pressure changes of the vascular system and blood transport. From measurement experiments it is known that external disturbances are correlated with steep gradients in the signal curves of the second and third harmonic waves.

In order to be able to perform the harmonic evaluation with sufficient selectivity, an oversampling is preferably used, the at least required sampling rate being 100 Hz or higher.

In a further preferred manner, it is advantageous to select a sampling rate of at least 200 Hz, to also interference from mains electrical voltage fields with a mains frequency of 50 Hz or 60 Hz, as well as disturbances of ballasts and starting elements of fluorescent lamps with twice the mains frequency in conjunction with the harmonics Eliminate evaluation.

The measurement is preferably carried out via an additional measuring electrode pair in a 4-electrode arrangement. Here lies the advantage in an almost currentless measurement of the voltage drop, which can be determined independently of the contact resistance between the electrodes and the skin.

The measured signal consists of an alternating voltage signal as a measure of the impedance of the current-flowing body environment due to the fed alternating current with a carrier frequency of for example 50 kHz. In addition to the input and metrologically detected and the vessel pressure associated AC signals, the superimposed heart activity is detected by the electrodes as an electrocardiogram (ECG) and as a pulse signal.

By contrast to the frequencies of the vessel pressure high carrier frequency of 50 kHz to 100 kHz on the one hand possibilities of further signal processing by means of filtering, smoothing, offset elimination, etc. guaranteed. Furthermore, there is the possibility of using the method according to the invention, both the vessel widening, ie the blood pressure following the pressure change in the blood vessels, as well as the respiration of the To detect patients with a single measuring device and to separate the signals of vascular dilation and respiration from each other. In addition, there is the possibility that the signals associated with the vessel dilation and the respiration-related signals from the pressure influences of the blood transport, the heart rate and muscle-related disturbances, as well as the respiration of the patient from external frequency-selective disturbances, such as by the power frequency of 50 Hz or 60 Hz and their harmonics in the range of 100 Hz to 200 Hz conditional to distinguish interference.

For an evaluation of the signal quality, preferably the signal of the heart rate with respect to amplitude, amplitude profile and signal-to-noise ratio is used.

By convolving the signal with the carrier frequency, the raw signal is demodulated and a useful signal is extracted.

By demodulation, for example by means of rectification, the useful frequencies of respiration in the range 0.1 Hz to 1 Hz, and the useful frequencies of the blood transport in the range 1 Hz to 3 Hz can be distinguished from the carrier signal signal technically.

Various modes of signal processing, such as the Discrete Fourier Transformation (DFT), the Fast Fourier Transformation (FFT), autocorrelation, correlation of the useful signal with a comparison useful signal, correlation with a comparison interference signal, are suitable for the detection of individual frequencies , Correlation with a comparison noise signal, in the frequency range from 0.1 Hz to 200 Hz tunable filters and spectral selection methods based on phase-selective rectification (Lock In method).

In a first advantageous embodiment of the method, a discrete Fourier transformation (DFT) or a fast Fourier transformation (FFT) is used, the signal being transformed as a function of time into a function of the frequency. In this case, longer signal curves must be considered to reduce artifacts.

In a further advantageous embodiment of the method, an autocorrelation is used, wherein a portion of the signal is continuously multiplied and summed with itself and shifted stepwise. This procedure is repeated for all frequencies of interest for the frequency range and the correlation is plotted as a sum against the time offset. This results in a high sum with high coverage with the periodicity of the signal.

In a further advantageous embodiment of the method, a correlation with a comparison signal is used, wherein a portion of the signal is multiplied by a portion of the comparison signal and summed.

This procedure is repeated continuously with a time interval adapted for the frequency range of interest and the resulting correlation function plotted. This results in a high sum with high coverage between the comparison signal and the useful signal.

In a further advantageous embodiment of the method, a lock-in method is used, wherein the useful signal is multiplied by a periodic signal of fixed frequency and amplitude. The result is the course of the amplitude component for this frequency, wherein the phase angle can be determined. This procedure is repeated with the frequencies of interest, and the amplitudes are plotted as a function of frequency, so that the spectral components of the signal show up.

In a further advantageous embodiment of the method, tunable filters are used, the signal being evaluated with a bandpass filter. This evaluation is carried out in the entire interesting frequency range or for individual frequency bands. A parallel connection of several filters can be used to determine an amplitude and phase ratio for several harmonic frequencies.

The five advantageous embodiments of the evaluation of the alternating voltage signal and the superposed ECG signal mentioned above are suitable in connection with the arrangement of at least two electrodes in a holding element arranged in the region of the shoulder in a preferred embodiment and use for determining the vessel expansion of the vessels in the below the holding element and the electrodes lying blood vessels.

In a further preferred embodiment and use, the five advantageous embodiments listed above are suitable for determining the heart rate and an electrocardiogram (ECG).

In a further preferred embodiment and use, the five advantageous embodiments listed above are suitable for determining the respiratory rate, the heart rate and the vascular dilation.

In addition, the five advantageous embodiments mentioned above are suitable Evaluation of the alternating voltage signal and the superimposed ECG signal also for the removal of known and periodically recurring interfering signals in the determination of the vascular dilation, the ECG, the heart rate and the respiratory rate.

The alternating voltage signal to be measured can be evaluated in a further embodiment and use for detecting a pulse transit time. For this purpose, the voltage drop should be measured by means of at least two measuring electrode pairs in addition to the two feed electrodes in a 6-electrode arrangement. Preferably, the two measuring electrode pairs are mounted on the axis between the feed electrodes at a distance of at least a few centimeters to the body.

In this case, one pair of the measurement of the alternating voltage signal is used at a point upstream of the blood flow in the vessel and the other pair of the measurement of the same signal at a point downstream of the blood flow in the vessel. Due to the transit time of the pulse wave in the vessel, the signal from the downstream point is offset by a time offset t relative to the upstream point. Both signals are multiplied by the carrier signal or otherwise filtered and normalized to a mean amplitude normalized. The gain adjustment is performed slowly at a frequency of less than 0.1 Hz compared to the considered pulse wave frequencies in the range of 1 Hz. By comparing the signals by means of subtraction or division, the signal processing is controlled. The pulse wave velocity v is calculated from the time offset t and the spatial offset L with v = L / t, where L is the distance between the pairs of measuring electrodes and either estimated, measured or determined by a common fixed connection.

The pulse wave velocity in this illustrated advantageous embodiment can be determined from the signals associated with the vessel widening with knowledge of the distance between feed electrodes and measuring electrodes from the pulse wave transit time. For this purpose, in this advantageous embodiment, a first pair of electrodes for feeding in the alternating current and at least one further pair of electrodes for measuring and detecting the injected signal is required. In this case, the supply of the alternating current at the first electrode pair is evaluated as a feed start signal for the transit time measurement, the passage of the pulse wave detected by the second pair of electrodes, the vessel-induced modulation of the alternating voltage signal determined therefrom and the demodulated signal contained in the passage as an end signal for the Travel time measurement evaluated. Subsequently, the pulse wave transit time is determined with reference to the feed start signal.

In an alternative advantageous embodiment, the pulse transit time can also be determined by a combination evaluation of the AC signal and the ECG signal by a distinctive and characteristic feature of the ECG signal, preferably the so-called R-wave is used as a heart rate start signal for the pulse wave transit time measurement. The passage of the pulse wave is detected by the electrodes, the vessel-induced modulation of the AC voltage signal determined therefrom and evaluated the run contained in the demodulated signal as an end signal for the transit time measurement. Subsequently, the pulse wave transit time is determined with reference to the heart rate start signal. This alternative advantageous embodiment allows the use of only one pair of electrodes, whereby the arrangement on the body of a patient can be made very comfortable and small in size.

More preferably, the shoulder in the vicinity of the clavicle of the patient is particularly suitable as a location of the electrode assembly, since at this location possible interference by muscle contractions occur only to a small extent.

The electrode arrangement is more preferably held in a flexible holding element. In particular, textile patches which are to be applied with an adhesive adhesive layer on the skin of the patient are suitable for this purpose. In this case, this holding element contains the at least required number of two electrodes for the measurement of respiration, heart rate, ECG and vessel expansion. For detection of the pulse wave transit time in combination of the vessel dilation measurement with the ECG measurement, at least one pair of electrodes is required in the holding element for this purpose. To determine the pulse wave transit time based on the vessel expansion measurement, at least two pairs of electrodes are required for this purpose.

With known blood pressure, the pulse wave velocity is a measure of the elasticity of the vessel or, assuming unchanged vessel elasticity, a measure of the blood pressure.

In this case, the pulse wave velocity represents a measure of an arithmetic mean value of the blood pressure with unchanged vascular elasticity compared with the two values known from the medical-diagnostic blood pressure measurement, namely the systolic blood pressure during cardiac contraction and the diastolic blood pressure during relaxation of the heart muscle.

In a particular embodiment, an absolute measure of the blood pressure can be determined continuously from the pulse wave transit time or pulse wave velocity after a calibration of the pulse wave transit time or pulse wave velocity with an independent blood pressure measurement at the beginning of a blood pressure pulse wave-based monitoring.

As an independent blood pressure measurement for calibration, for example, an oscillatory blood pressure measurement by means of an upper arm cuff can be used by an independent sphygmomanometer. An average value is calculated from the systolic and diastolic blood pressure readings recorded with the independent sphygmomanometer and made available to the control and evaluation unit via the operating and display unit. The advantage in monitoring blood pressure by means of pulse wave transit time or pulse wave velocity, especially in comparison to oscillatory blood pressure measurement by means of the upper arm cuff, is a considerable reduction of the impairments for the patient, in particular with regard to freedom of movement and mobility. As a further advantage of the blood pressure monitoring by means of pulse wave transit time results that compared to an oscillatory blood pressure measurement by means of a humeral cuff a continuous monitoring of the mean blood pressure without vascular damage is possible.

In a preferred embodiment, the calibration of the blood pressure for both an upright upper body position, i. H. a seated or standing position of the patient, as well as made for a lying position of the patient.

Such a calibration relative to the position of the patient is required because the blood pressure for clinical diagnosis is measured at heart level.

On the one hand, in order to be able to continuously indicate the blood pressure and the course of the blood pressure in upright as well as in non-upright position after calibration over a period of several days and during movement of the patient, it is necessary to know the position of the patient during the calibration On the other hand, the current position of the patient is also continuously required as a real-time information in the continuous pulse wave-based blood pressure monitoring. For such a recognition of the position of the patient, a position sensor is used in this preferred embodiment, more preferably, this position sensor is arranged on the shoulder in or on the holding element together with the electrodes.

In this case, for the calibration in a first phase in an upright position of the patient via an independent blood pressure measurement, preferably by means of a cuff on the upper arm of the patient detects a mean blood pressure and stored in a data memory. Subsequently, in the first phase for the upright position and in a second phase for the non-upright position of the patient, a pulse wave transit time over a known or estimated electrode distance is detected and stored in a data memory and the cause pulse velocity determined and stored in a data memory.

Advantageously, the position sensor is interrogated during this calibration. Thus, the inclusion of the position sensor in the calibration allows an assessment of the measurement data in terms of compliance with the necessary calibration conditions. The necessary calibration conditions include that the position sensor over a predetermined period, advantageously over a period of time in the range of 30 seconds to 90 seconds, provides a stable position signal, so that it is ensured by means of a clear status message that the upright position of the not upright position of the patient is distinguishable. Furthermore, it is preferred that during the detection of the electrode signals, the position sensor supplies a stable position signal to ensure that during the calibration no changes in position of the patient have taken place and thus only the measurement data of a correctly expired calibration are stored in the data memory.

This calibration of the pulse wave-based blood pressure monitoring Against an independent blood pressure measurement is necessary depending on the application and medical-diagnostic situation in a daily to weekly time interval.

In a particular embodiment, the calibration is started by the user, for example by the medical staff, by means of the operating and display unit and the phases of the calibration are controlled by the status messages of the position sensor in the sequence.

In a further embodiment, the user is informed of the phases of the calibration and / or the progress of the calibration and / or the end of the calibration and / or the result of the calibration by means of acoustic or optical signaling on the operating unit. If the result of the calibration is incomplete or erroneous, the user is presented with a possibility to repeat the calibration, which can then be restarted by the user by input via the control unit.

In a particularly preferred embodiment, the acoustic signaling can be designed on the basis of different individual tone sequences, as it were a short message, to the user and the patient about the progress, termination or quality of the calibration, or to change from the first phase to the second Phase of calibration.

In a further preferred embodiment, the position sensor is connected to a position evaluation unit for detecting horizontal, vertical positions in real time.

In a further preferred embodiment, the position evaluation unit is connected to the control and evaluation unit to provide status messages on a wired or wireless interface.

In a particular variant of the preferred embodiment, the wireless interface is designed as a telemetric data interface, optical data interface or inductive data interface.

In a further particular embodiment, a measuring arrangement, comprising at least two electrodes, a control and evaluation unit, which are in electrical connection with the at least two electrodes, a position sensor, a position evaluation unit, a data memory, a power supply unit, a data interface, combined as a unit arranged in a holding element. The operating and evaluation unit is connected via the data interface wirelessly or by wire with the measuring arrangement in the holding element.

In this case, the control and evaluation unit makes available via the wired or wireless interface, ECG signals, heart rate, respiratory rate and blood pressure measured values of the operating and display unit.

In a particular variant of the further preferred embodiment, the wireless interface is designed as a telemetric data interface, optical data interface or inductive data interface.

In a further preferred embodiment, the operating unit is connected to the holding element and the control and evaluation unit via the wired or wireless interface.

In a preferred embodiment, the position sensor is designed as an acceleration sensor.

Acceleration sensors evaluate the earth's magnetic field in different ways. This can be done in different ways, for example via 3-axis measuring elements as integrated components. The position in the room is detected by bending beams, strain gauges, inductive or capacitive elements. Other integrated acceleration sensors evaluate thermal effects, and simplest sensors use moving elements, such as spherical bodies in a guide element, to detect changes in position. This is used, for example, in blood pressure monitors, which are intended to detect the blood pressure on the wrist, in order to indicate to the user that he had brought the wrist correctly at heart level into the measuring position or not.

In a preferred embodiment, the position sensor with the position evaluation unit and control and evaluation unit is additionally designed to detect and evaluate sudden changes in position of the patient, as may occur, for example, during a fall.

Further preferably, the control and evaluation unit is designed to provide and output detected sudden changes in position of the patient in the form of an alarm message at the data interface.

In a further preferred embodiment, the control and evaluation unit is designed to take over the data interface ventilation information from a respirator and to compare with the determined by means of electro-impedance plethysmography respiratory rate.

In a particular variant of this further preferred embodiment, the control and evaluation unit is designed to filter the acquired data using the ventilation information of the ventilator in such a way that the respiratory rate associated signal components are removed from the acquired data to heart rate, respiratory rate and pulse transit time to separate from each other with high selectivity.

For filtering and removal of the respiratory rate associated signal portions with the assistance of the ventilation information are the aforementioned embodiments of signal processing: Fourier transform method (DFT, FFT), correlation method (autocorrelation, pattern correlation, noise correlation), lock-in Method and tunable filter advantageously suitable.

The invention is explained in more detail below with reference to an embodiment and with reference to associated figures.

The figures show:

1 a schematic block diagram of a first measuring arrangement for determining the heart rate, the respiratory rate, the pulse wave transit time and the mean blood pressure;

2 a schematic block diagram of a second measuring arrangement for determining the heart rate, the respiratory rate, the pulse wave transit time and the mean blood pressure;

3 : A schematic sequence for the calibration of the first or second measuring arrangement against an independent blood pressure measurement.

In the 1 is a schematic block diagram of a first measuring arrangement 1 and a control and display unit 26 for determining a heart rate, a respiratory rate, a pulse transit time 63 and a mean blood pressure in a holding member 2 in conjunction with a ventilator 28 shown.

The measuring arrangement 1 consists of a control and evaluation unit 4 , a data interface 18 , a data store 22 , a first pair of electrodes 6 , a second pair of electrodes 8th , a position sensor 10 , a position evaluation unit 24 , as well as a power supply unit 20 to supply the control and evaluation unit 4 , the position evaluation unit 24 , the data interface 18 and the position sensor 10 ,

In the control and evaluation unit 4 are an AC source 14 and a signal detection unit 16 arranged. The control and evaluation unit 4 is with the data interface 18 , the energy supply unit 20 , the position evaluation unit 24 and the data store 22 connected.

The AC power source 14 is via electrode leads 12 with the first pair of electrodes 6 connected.

The signal acquisition unit 16 is via electrode leads 12 with the second electrode pair 8th connected.

At the first electrode pair 6 is via the electrode leads 12 an alternating current is injected into the body surface of a patient.

At the second pair of electrodes 8th is via the signal acquisition unit 16 a voltage signal detected and therefrom in the control and evaluation 4 an impedance signal determined.

The impedance signal becomes an actual pulse wave transit time 63 between the time of AC supply to the first pair of electrodes 6 and the signal detection on the second pair of electrodes 8th certainly.

In addition, from the second pair of electrodes 8th detected signal form in the control and evaluation unit 4 a respiratory rate signal and a heart rate signal determined.

The position sensor 10 is from the position evaluation unit 24 queried. In the position evaluation unit 24 becomes a current position information 56 determined and to the control and evaluation unit 4 to hand over.

The current position information 56 contains up-to-date information about whether the upper body of a patient is in an upright or a non-upright position.

In the control and evaluation unit 4 becomes from the current pulse wave runtime 63 , the current position information 56 in combination with one in the data store 22 contained calibration record 44 a mean blood pressure 40 determined by the patient.

The control and evaluation unit 4 represents the mean blood pressure 40 , heart rate and respiratory rate at the data interface 18 to disposal. The data interface 18 is with a control and display unit 26 connected to the the mean blood pressure 40 , the heart rate and the respiratory rate are displayed. Furthermore, the ventilator 28 via the data interface 18 with the control and evaluation unit 4 connected.

The ventilator 28 hands over a ventilation information 29 , such as the respiratory rate, to the control and evaluation unit 4 , With the help of the ventilation information 29 let the respiratory rate associated signal components by filtering the on the second electrode pair 8th remove detected waveform so that a selective separation of pulse wave transit time ( 63 ), Respiratory rate signal and heart rate signal can be made.

In the 2 is a schematic block diagram of a second measuring arrangement 11 and a control and display unit 26 for determining a heart rate, a respiratory rate, a pulse transit time 63 and the mean blood pressure.

The measuring arrangement 11 consists of a control and evaluation unit 4 , a data interface 18 , a data store 22 , a first pair of electrodes 6 , a position sensor 10 , a position evaluation unit 24 , as well as a power supply unit 20 to supply the tax and evaluation unit 4 , the position evaluation unit 24 , the data interface 18 and the position sensor 10 , In the control and evaluation unit 4 are an AC source 14 and a signal detection unit 16 arranged. The control and evaluation unit 4 is with the data interface 18 , the energy supply unit 20 , the position evaluation unit 24 and the data store 22 connected.

The AC power source 14 is via electrode leads 12 with the first pair of electrodes 6 connected.

The signal acquisition unit 16 is within the control and evaluation unit with the AC power source 14 connected.

At the first electrode pair 6 is via the electrode leads 12 an alternating current is injected into the body surface of a patient.

About the electrode leads detects the signal detection unit 16 a voltage signal from the first electrode pair. From the voltage signal is in the control and evaluation 4 an impedance signal determined.

From the first pair of electrodes 6 detected waveform is in the control and evaluation 4 additionally determines a respiratory rate signal and a heart rate signal.

From the heart rate signal, the so-called R wave is used as a distinctive and characteristic feature as a heart rate start signal. The control and evaluation unit 4 determined from the time difference between the heart rate start signal and the passage of the pulse wave at the first pair of electrodes 6 the current pulse wave transit time 63 ,

The position sensor 10 is from the position evaluation unit 24 queried. In the position evaluation unit 24 becomes a current position information 56 determined and to the control and evaluation unit 4 to hand over.

The current position information 56 contains up-to-date information about whether the upper body of a patient is in an upright or a non-upright position.

In the control and evaluation unit 4 becomes from the current pulse wave runtime 63 , the current position information 56 in combination with one in the data store 22 contained calibration record 44 a mean blood pressure 40 of a patient.

The control and evaluation unit 4 represents the mean blood pressure 40 , heart rate and respiratory rate at the data interface 18 to disposal. The data interface 18 is with a control and display unit 26 connected to the the mean blood pressure 40 , the heart rate and the respiratory rate are displayed.

In the 3 schematically is a sequence of calibration of a measuring arrangement 100 on the patient against one by one with an independent sphygmomanometer 30 on the upper arm 60 of the patient 50 determined blood pressure reading 40 shown.

In addition to the actual sequence of calibration is in this 3 the particular situation 54 . 55 of the upper body of the patient 50 indicated schematically for the individual calibration steps.

The measuring arrangement 100 corresponds in structure and contained components of the measuring arrangement 1 to 1 or the measuring arrangement 11 to 2 , The included components of the measuring arrangement 100 are not shown individually and numbered for reasons of clarity.

The data interface 18 ( 1 . 2 ) is in this measuring arrangement 100 as a telemetric data interface 88 wirelessly executed. The operating and display unit 26 is in this measuring arrangement 100 with a telemetric data interface 99 equipped, so the measuring arrangement 100 in a wireless way with the control and display unit 26 Exchanges data.

The independent blood pressure monitor 30 is designed as an oscillatory sphygmomanometer and measures over a cuff 35 on the upper arm 60 the blood pressure of the patient 50 , The cuff 35 is with the sphygmomanometer 30 through an air-bearing blood pressure cuff tube 36 connected. The sphygmomanometer 30 pumps over this blood pressure cuff tube 36 different amounts of air in the cuff 35 and thus achieves different pressure levels on the upper arm 60 of the patient 50 , There are different pressure levels from the sphygmomanometer 30 approached to measure systolic and diastolic blood pressure. The systolic and diastolic blood pressure becomes a blood pressure reading 40 , z. B. by forming an arithmetic mean, determined.

The sequence of calibration of the measuring arrangement 100 takes place in a sequence of four steps 31 . 32 . 33 . 34 ,

In the first and in the second step 31 . 32 the process is the upper body of the patient 50 in an upright position 54 , In the third step 33 is the upper body of the patient 50 in a non-upright position 55 , In the fourth step 34 is the position of the upper body of the patient 50 any.

In a first step 31 will be in an upright position 54 of the patient 50 via the independent blood pressure monitor 30 by means of a cuff 35 on the upper arm 60 of the patient 50 a mean blood pressure reading 40 subsequently measured by the operating and output unit 26 the calibration is started by a first position information 51 through the position sensor ( 1 . 2 ) and the position evaluation unit 24 ( 1 . 2 ), from which the control and evaluation unit 4 ( 1 . 2 ) and then as a first calibration data set 41 in a data store 22 is stored.

In a second step 32 is through the control and output unit 26 the calibration continues in such a way that in an upright position 54 of the patient 50 through the control and evaluation unit 4 ( 1 . 2 ) a first pulse wave transit time 61 is determined and a second position information 52 through the position sensor ( 1 . 2 ) and the position evaluation unit 24 ( 1 . 2 ), from which the control and evaluation unit 4 ( 1 . 2 ) and as a second calibration data set 42 in the data store 22 is stored.

In a third step 33 is through the control and output unit 26 the calibration continues in the expiration that in a non-upright position 55 of the patient 50 through the control and evaluation unit 4 ( 1 . 2 ) a second pulse wave transit time 62 a third position information is determined 53 through the position sensor 10 ( 1 . 2 ) and the position evaluation unit 24 ( 1 . 2 ), from which the control and evaluation unit 4 ( 1 . 2 ) and as a third calibration data set 43 in the data store 22 is stored.

In a fourth step 34 is through the control and output unit 26 The calibration is completed by the control and evaluation unit 4 ( 1 . 2 ) from the first, second and third calibration data sets 41 . 42 . 43 an assignment from the mean blood pressure reading 40 , the position information 51 . 52 . 53 and the first and second pulse wave transit times 61 . 62 and as a fourth calibration record 44 in the data store 22 is filed.

LIST OF REFERENCE NUMBERS

1

first measuring arrangement

2

retaining element

4

Control and evaluation unit

6

first electrode pair

8th

second pair of electrodes

10

position sensor

11

second measuring arrangement

12

electrode leads

14

AC power source

16

Signal detection unit

18

Data Interface

20

Power supply unit

22

data storage

24

Positionsauswerteeinheit

26

Operating and display unit

28

ventilator

29

ventilation information

30

Blood Pressure Monitor

31

first step

32

second step

33

Third step

34

fourth step

35

cuff

36

Blood pressure cuff tubing

40

Blood pressure reading

41

first calibration data set

42

second calibration data set

43

third calibration data set

44

fourth calibration data set

50

patient

51

first position information

52

second position information

53

third position information

54

sitting position of the patient, upright upper body

55

lying position of the patient, not upright upper body

56

current position information

60

Upper arm of the patient

61

first pulse wave transit time

62

second pulse wave transit time

63

current pulse wave transit time

88, 99

telemetric data interfaces

100

Measuring arrangement on the patient

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 6416471 [0003]
• DE 102007001709 A1 [0005]
• DE 19829544 C1 [0010]

Cited non-patent literature

• "Apparative vascular diagnostics", Ralf student, ISBN 3-932633-16-4 [0008]

Claims (9)

Method for determining the heart rate, the respiratory rate, the pulse wave transit time and the mean blood pressure of a patient ( 50 ) by means of electro-impedance plethysmography, with a control and evaluation unit ( 4 ) containing an alternating current source ( 14 ) and a signal evaluation unit ( 16 ), an operating and display unit ( 26 ), a data memory ( 22 ), a data interface ( 18 ) and with a holding element ( 2 ), comprising a power supply unit, at least two electrodes ( 6 ), a position evaluation unit ( 24 ) and a position sensor ( 10 ), wherein the at least two electrodes ( 6 ) with the body surface of the patient ( 50 ), the at least two electrodes ( 6 ) with the control and evaluation unit ( 4 ), the control and evaluation unit ( 4 ) is prepared to conduct an alternating current through the body, whereby the control and evaluation unit ( 4 ) is prepared to provide a measure of electrical impedance between the at least two electrodes ( 6 ), whereby the control and evaluation unit ( 4 ) is prepared to record and evaluate the acquired values for the measure of the impedance as a time curve in order to determine therefrom a chronological waveform of the heart rate and a temporal waveform of the respiratory rate and a current pulse wave transit time ( 63 ) of the patient ( 50 ) in such a way that a characteristic signal component from the chronological waveform of the heart rate is used as a start signal for measuring the pulse transit time (FIG. 63 ), and wherein a position sensor ( 10 ) and a position evaluation unit ( 24 ) in the retaining element ( 2 ) are arranged and formed, an upright position of the upper body ( 54 ) of a patient ( 50 ) from a non-upright position of the upper body ( 55 ) of a patient ( 50 ) and as a current position information ( 56 ), the control and evaluation unit ( 4 ) is prepared from the current position information ( 56 ), the current pulse wave transit time ( 63 ) and a calibration data set ( 44 ) a mean blood pressure of the patient ( 50 ) and via the data interface ( 18 ) to the operating and display unit ( 26 ). Method for determining the heart rate, the respiratory rate, the pulse wave transit time and the mean blood pressure of a patient ( 50 ) by means of electro-impedance plethysmography, with a control and evaluation unit ( 4 ) containing an alternating current source ( 14 ) and a signal evaluation unit ( 16 ), an operating and display unit ( 26 ), a data memory ( 22 ), a data interface ( 18 ) and with a holding element ( 2 ), comprising a power supply unit, at least a first and at least a second pair of electrodes ( 6 . 8th ), a position evaluation unit ( 24 ) and a position sensor ( 10 ), wherein the at least two pairs of electrodes ( 6 . 8th ) with the body surface of the patient ( 50 ), wherein the at least two pairs of electrodes ( 6 . 8th ) with the control and evaluation unit ( 4 ), the control and evaluation unit ( 4 ) is prepared to conduct an alternating current through the body, whereby the control and evaluation unit ( 4 ) is prepared to provide a measure of electrical impedance between the at least two pairs of electrodes ( 6 . 8th ), whereby the control and evaluation unit ( 4 ) is prepared to record and evaluate the acquired values for the measure of the impedance as a time curve in order to determine therefrom a chronological waveform of the heart rate and a temporal waveform of the respiratory rate and a current pulse wave transit time ( 63 ) of the patient ( 50 ) from a time difference from a start signal and an end signal in such a way that the supply of the alternating current to the first electrode pair ( 6 ) as a start signal of the pulse wave transit time ( 63 ) and the detection of the pulse wave at the second electrode pair ( 8th ) as the end signal of the pulse wave transit time ( 63 ) and wherein a position sensor ( 10 ) and a position evaluation unit ( 24 ) in the retaining element ( 2 ) are arranged and formed, an upright position of the upper body ( 54 ) of a patient ( 50 ) from a non-upright position of the upper body ( 55 ) of a patient ( 50 ) and as a current position information ( 56 ), the control and evaluation unit ( 4 ) is prepared from the current position information ( 56 ) and the current pulse wave transit time ( 63 ) and a calibration data set ( 44 ) a mean blood pressure of the patient ( 50 ) and via the data interface ( 18 ) to the operating and display unit ( 26 ). Method according to claim 1 or claim 2, wherein for determining the at least one calibration data record ( 44 ) - in a first step ( 31 ) in an upright position ( 54 ) of the patient ( 50 ) in an upright position of the patient ( 50 ) a mean blood pressure reading ( 40 ) by a sphygmomanometer ( 30 ) and a first position information ( 51 ) by the position sensor ( 10 ) and the position evaluation unit ( 24 ) and as a first calibration data set ( 41 ) in the data memory ( 22 ), - in a second step ( 32 ) in an upright position ( 54 ) of the patient ( 50 ) a first pulse wave transit time ( 61 ) and a second position information ( 52 ) by the position sensor ( 10 ) and the position evaluation unit ( 24 ) and as a second calibration data set ( 42 ) in the data memory ( 22 ), - in a third step ( 33 ) in a non-upright position ( 55 ) of the patient ( 50 ) a second pulse wave transit time ( 62 ) and a third Position information ( 53 ) by the position sensor ( 10 ) and the position evaluation unit ( 24 ) and as a third calibration data set ( 43 ) in the data memory ( 22 ), - in a fourth step ( 34 ) by the control and evaluation unit ( 4 ) from the first, second and third calibration data sets ( 41 . 42 . 43 ) an assignment from the mean blood pressure measured value ( 40 ), the position information ( 51 . 52 . 53 ) and the first and second pulse wave transit times ( 61 . 62 ) and as a fourth calibration data set ( 44 ) in the data memory ( 22 ) is stored. Method according to one of the preceding claims, wherein the control and evaluation unit ( 4 ) is designed, via the data interface ( 18 ) ventilation information ( 29 ) from a ventilator ( 28 ) and compare it with the data obtained by means of the electro-impedance plethysmography and the data determined by means of the electro-impedance plethysmography with the aid of the ventilation information ( 29 ) in such a way that the respiratory rate associated signal components are removed from the acquired data to heart rate, respiratory rate and pulse wave transit time ( 61 . 62 . 63 ) to separate from each other. Device for determining the heart rate, the respiratory rate, the pulse wave transit time and the mean blood pressure of a patient ( 50 ) by means of electro-impedance plethysmography, with one in a holding element ( 2 ) arranged measuring arrangement ( 1 . 11 ) containing a plurality of electrode leads ( 12 ) with the body surface of the patient ( 50 ) connected electrodes ( 6 . 8th ), a control and evaluation unit ( 4 ), an AC power source ( 14 ), a signal evaluation unit ( 16 ), an operating and display unit ( 26 ), a data store ( 22 ), a data interface ( 18 ), a position evaluation unit, a power supply unit ( 20 ), a position sensor ( 10 ), with one with the measuring arrangement ( 1 . 11 ) connected control and display unit ( 26 ), wherein the position evaluation unit ( 24 ) in conjunction with the position sensor ( 10 ) is designed and prepared for the horizontal or vertical position of the upper body of the patient ( 50 ) and the upright ( 54 ) from the non-upright ( 55 ) Position of the upper body of the patient ( 50 ), whereby the control and evaluation unit ( 4 ) is adapted to conduct an alternating current through the body and between at least two electrodes ( 6 . 8th ) to acquire a measure of the impedance, to record and evaluate the detected values for the measure of the impedance as a function of time, in order to derive therefrom the heart rate, the respiration rate, the pulse wave transit time ( 61 . 62 . 63 ) and the mean blood pressure of the patient ( 50 ). Apparatus according to claim 5, wherein the position sensor ( 10 ) is implemented as an acceleration sensor. Device according to one of claims 5 to 6, wherein the measuring arrangement ( 1 . 11 ) via a data interface ( 18 ) with an operating and display unit ( 26 ) and the data interface ( 18 ) and the operating and display unit ( 26 ) are formed, data wireless or wired to the control and evaluation unit ( 4 ) to calibrate the measuring arrangement ( 11 . 1 ) and to determine the mean blood pressure ( 40 ) and / or the respiratory rate and / or the heart rate at the operating and display unit ( 26 ). Device according to one of claims 5 to 7, wherein the position sensor ( 10 ) with the position evaluation unit ( 24 ) and with the control and evaluation unit ( 4 ), sudden changes in the position of the patient ( 50 ) to recognize. Apparatus according to claim 8, wherein the control and evaluation unit ( 4 ), sudden changes in the position of the patient ( 50 ) in the form of an alarm message at the data interface ( 22 ) and spend.

Images