DE102006026126A1 - Fractional oxygen saturation monitoring and pathological changes detection method for patient`s cardiovascular circulation system, involves evaluating photoplethysmogram signals, and deriving parameters interpreted for doctor from signals - Google Patents

Abstract

The method involves evaluating photoplethysmogram (PPG) signals by a signal-connected computing unit with photoplethysmogram sensors, which are designed as transmission sensors and reflection sensors. Diagnostic parameters interpretable for a doctor are derived from the PPG signals by the computing unit. A continuous blood pressure measurement is also carried out in a patient (2) by using a blood pressure sensor (4). An independent claim is also included for a multi-sensor for non invasive monitoring of fractional oxygen saturation and detection of pathological changes in a cardiovascular circulation system by simultaneous detection of different optical Photoplethysmogram signal using Photoplethysmography sensors.

Description

The The invention relates to a method and a multisensor for non-invasive monitoring fractional oxygen saturation and detection of pathological changes in the cardiovascular system.

In the industrialized countries diseases of the cardiovascular system are sometimes the most common Cause of death. A lack of oxygenation can, among other things in case of emergency due to various causes occur quickly and already in a short time cause death among other brain cells. Therefore, the rapid detection of disturbances in oxygen uptake and the oxygen distribution in the body especially in the emergency and Intensive care of great Importance.

A general reduction in hemoglobin concentration can cause anemia to lead. General Fatigue, limited physical ability, Shortness of breath and palpitations occur under stress, headache and difficulty concentrating doing so as symptoms. The hemoglobin concentration can be used to diagnose anemia To date, only invasively measured, what with a high load for the patients and the staff is connected. There are also results such a measurement always only with a time delay, so that a continuous monitoring is not possible so far.

By small disturbances like the warming the light sources used and by computational approximations The results quickly become unusable.

Pulse oximeters are usually used to determine the blood oxygen, which also allow monitoring of the oxygen saturation of hemoglobin. According to the Lambert-Beer law, the transmitted light falls through a sample irradiated with the light intensity I ₀ , exponentially with the sample thickness d and the absorptivity of the sample μ _a , which results from the concentration of the sample c and its extinction coefficient ε as follows: I = I 0 · 10 -ε · c · d

With the pulse oximeter the functional oxygen saturation is calculated, ie only the oxygenated and reduced hemoglobins are taken into account. The fractional oxygen saturation, which represents the ratio of the concentration of oxygenated hemoglobin to the total concentration of all hemoglobin components, namely oxygenated hemoglobin O ₂ Hb, reduced hemoglobin Hb, carboxyhemoglobin COHb and methemoglobin Met-Hb, can not be determined with the pulse oximeter. The carboxyhemoglobin produced by carbon monoxide poisoning or methaemoglobin resulting from the action of oxidants on hemoglobin is not considered. However, these two forms of hemoglobin are no longer capable of transporting oxygen and thus falsify the determined value for the oxygen saturation. In particular, this can have serious health consequences for carboxyhemoglobin.

Furthermore Pulse oximeters are not other devices for monitoring oxygen saturation known. In the developed methods for non-invasive measurements Many simplifications are used to make the measurements for monitoring to be used. At the same time, however, this means that one simple Use of the detected signals in the calculations to a falsified approach leads. The error caused thereby leaves to a later Do not fix the time.

There the oxygen saturation and the hemoglobin concentration as well as other blood contents play a significant role, they should in the analysis of the other physical parameters such as Plethysmogram and heart rate variability in cardiovascular diagnosis considered become. In the previous developments, measurements of a each of these sizes performed only at a certain place. The dependence the measurements of the location and of the other sizes are not considered, what a mistake Assessment of physiological changes may result.

Of the Invention is therefore based on the object, a device for Noninvasive detection of pathological changes in the cardiovascular system as well as circulatory disorders to provide, which allows a monitoring of the patient and for this as little as possible during the examination Unpleasant.

Is solved this object by the method according to the features of the main claim as well as by the multisensor according to the sibling Claim 8. Further useful embodiments can be taken from the subclaims become.

According to the invention, a multisensor is used for the detection of pathological changes in the cardiovascular system as well as circulatory disorders, by means of which a plurality of photoplethysmogram (PPG) signals can be recorded simultaneously. Their evaluation is carried out via a signal-connected Re with the sensors unit, which processes the signals of the sensors into diagnostic parameters, as they are read by doctors. Since human physiological parameters are not independent of one another, it is important to measure as many parameters as possible at the same time in order to ensure effective and accurate diagnosis. Not only heart rate, oxygen saturation or ECG recordings are important to investigate heart and blood tissue status, but also measurement of blood pressure, determination of blood constituents and the function of controlling the cardiovascular system via the sympathetic and parasympathetic nerves. A simple, non-invasive method of measuring these nerve activities can be achieved by measuring heart rate and blood pressure variability by performing a visible or near-infrared light diagnosis. The focus of these measurements is the monitoring of fractional oxygen saturation and hemoglobin concentrations as well as heart rate, blood pressure, temperature and heart rate variability for the detection of pathologies. The measurements are non-invasive due to the optical sensors and can be used for a long time without any side effects for monitoring.

With Advantage is a measurement of the body parameters mentioned at the same time at several parts of the body of a patient. For this purpose, a multi-sensor has a plurality of sensors, so that different body parts simultaneously with a body sensor can be applied.

flanking becomes the acquisition of measured values, for example during the Patient monitors, the body temperature of the patient continuously recorded and the multisensor as a parameter supplied so that too in this regard and more dependent on it Parameter a constant monitoring can take place. For the same reason is by means of a mechanical Pressure sensor or over a photoplethysmographic sensor (PPG sensor) a continuous blood pressure measurement performed.

Around a surveillance also perform visually to be able to it is advantageous if the measured values are not only determined but also processed and / or issued for inspection become. Especially due to partly longer time frames of surveillance It is advisable to print the measured values, for example in the form of a curve.

With particular advantage is both the blood pressure and the temperature continuously determined so that a determination of the cardiac output via temperature and blood pressure variability is possible.

One important factor in the accuracy of the detection method the signal-to-noise ratio. Especially with underperfusions leads to a small signal-to-noise ratio poor results or it may even be the measurements not possible. However, there are many sources of noise that can be minimized. at very small perfusions, the useful signals are very weak. As she caused by interaction between pulsating blood and light, you can increase the perfusion, for example by heat. A reaction to this but can be too slow. An increase in the number of photons which may interact with the tissue may improve the signal but also contribute.

The PPG sensors are transmission sensors, reflection sensors or Transflexionssensoren. As far as transmission sensors are concerned, is the light source of the optical sensor on one side of the test to be tested Tissue and the detector on the other side. A reflection sensor has on the same side light source and receiver and a Transflexionssensor is on both sides with a receiver fitted. Depending on which tissue parts are to be examined, Different sensors are better or worse for it.

In advantageous embodiment, it is used Light sources around LEDs, because of their large light output, their low power consumption and their small size especially suitable. In addition, a very slight warming is observed here, what else a falsification would mean the measurement results. Alternatively, however, is an application of laser diodes or lamps possible with filters.

Corresponding are also used with advantage photodiodes as a receiver, and also here alternatives in the form of phototransistors or CCD detectors ready.

By promote their low design the components mentioned also the possibility of the multi-sensor to run in a particularly small design, so that the sensor too can be inserted into hollow organs is. In particular, it is thus suitable for use on unborn Child and for monitoring from mother and fetus while of birth.

If the sensor is applied to the site of measurement on the patient's body, the pressure used to hold the sensor on the measuring point is set so large that there is no relative movement between sensor and sample, but at the same time so small that the volume change caused by the pulse wave with the sensor not ver may be prevented.

With Advantage is the multi-sensor also multi-patient capable, so able to do more as a patient to monitor at the same time. These are the multisensor associated with multiple sensor groups, each group being a patient is created and this supervised so can be. For example, this can be helpful in disaster response if only in limited Dimensions of material is available.

It is also advantageous if those determined by the multi-sensor Data can be provided in a file system. For this Provide an interface through which an infeed the measured values in a computer system, such as a hospital data system and there preferably directly into the relevant electronic patient file, insertable is.

With the multi-sensor is associated with particular sensors, which are regularly used by clinics and medical practices in everyday life such as venous oxygen saturation sensors, for the creation of ECG or EEG, a skin impedance sensor, respiratory gas sensors, a sensor for detecting caries and other pathological changes in dentistry and / or chemical sensors for tear, gas and sweat analyzes.

Especially when used with multiple patients, creating a heavier load the computing capacity the arithmetic unit is generated, it may be useful if the Processing of the measurement data does not necessarily have to be done online, but also to a later one Time can be made offline.

The The invention described above will be described below with reference to a explained in detail in the drawing embodiment.

It demonstrate

1 a measuring setup in which a patient is connected to a multisensor,

2a a sensor constructed as a reflection sensor PPG sensor with central photodiode,

2 B a built-in as a reflection sensor PPG sensor with central LED and

3 a flow chart of a measurement with a multi-sensor.

1 shows a measurement setup with a patient 2 which is connected to a multisensor 1 connected. The multisensor is used in emergency and intensive care medicine, in the operating room, in patient transfers, in (premature) births, in fetal monitoring during pregnancy and childbirth, in home care and in sleep medicine. The device can also be used in doctors' offices, hospitals, in sleep medicine, in sports, in the homecare sector, in sleep apnea and for biofeedback measurement.

In the present case is the patient 2 via three PPG sensors 3 . 4 . 5 connected to the multisensor. Blood pressure is recorded and recorded using multiple PPG sensors. At the same time, other parameters, such as the ECG, the temperature or in particular the oxygen saturation and the hemoglobin concentration in the blood of the patient 2 determined and converted into readable by a physician diagnostic values.

In hospitals can also be a device for monitoring used by several patients at the same time.

there with a mode the results of the oxygen saturation, Heart rate and PPG signals shown. There is also the possibility to measure other parameters, such as concentrations of the calculated Hemoglobin components (HbO2, RHb, COHb, Met-Hb, sulf-Hb) and the total hemoglobin concentration as well the oxygen saturation display.

Next In addition to these functions, the multisensor can also Sensors for the determination of venous Oxygen saturation, for the creation of ECG or EEG, a skin impedance sensor, respiratory gas sensors, a sensor for detecting caries and other pathological changes in dentistry and / or chemical sensors for tear, gas and sweat analyzes so that a comprehensive diagnosis of the patient is possible.

In 2 are two variants of a PPG sensor 6 shown in which a central photodiode 8th of distributed light emitting diodes 7 is surrounded (or vice versa). With this sensor 6 it is an optical reflection sensor which irradiates the skin section to be examined with light. Light reflected from the skin is from the photodiode 8th detected and evaluated the corresponding signal. The sensor 6 is planar, allowing a flat application to the skin of the patient 2 is possible.

3 shows a flowchart of a measurement with the multi-sensor described above 1 , After the start 9 the measurement takes place at the same time tiges reading of the various sensors, namely a readout of a finger sensor 10 , a universal sensor 11 , a reflection sensor 12 and an ECG 13 , Other sensors can be used with the multisensor 1 also be assigned. The read signals are in a signal processing step 14 compiled and evaluated. Below, the multi-sensor compares 1 in step 15 taking into account all measured values, the results obtained with the multisensor 1 provided empirical values and derives therefrom information and recommendations that are made available to the diagnosing physician for diagnostic support. This is done in the last step 16 an edition of the above notes and recommendations, and if desired also the measured values, on a display or a printer. The evaluation can also be used for permanent monitoring as an alternative to the one-time execution, in which case a continuous interrogation of the sensor system takes place.

1

multisensor

2

patient

3

finger sensor

4

Blood Pressure Sensor

5

Universal sensor

6

Plethysmography sensor

7

led

8th

photodiode

9

begin

10

select of the finger sensor

11

select of the universal sensor

12

select of the reflection sensor

13

select of the ECG

19

signal processing

15

derivation of hints and recommendations

16

output on a display or printer

Claims (17)

Method for noninvasive monitoring of fractional oxygen saturation and detection of pathological changes in the cardiovascular system by simultaneous acquisition of various optical photoplethysmogram (PPG) signals using photoplethysmographic (PPG) sensors ( 6 ), wherein an evaluation of the PPG signals by one with the PPG sensors ( 6 ) signal-connected arithmetic unit takes place and be derived using the arithmetic unit from the PPG signals for a physician interpretable diagnostic parameters. A method according to claim 1, characterized in that a measurement simultaneously on a plurality of body parts of a patient ( 2 ) is made. Method according to one of claims 1 or 2, characterized in that a simultaneous detection of several parameters by means of the PPG sensors ( 6 ) is carried out. Method according to one of the preceding claims, characterized in that a continuous temperature measurement is made. Method according to one of the preceding claims, characterized in that a continuous blood pressure measurement using the PPG sensor. Method according to one the claims 4 or 5, characterized in that the measured parameters, for example on a printer and / or oscilloscope screen continuously be issued. Method according to claim 5, characterized in that the cardiac output determined thereby is that from the continuously detected blood pressure signal the Blood pressure variability is determined while the temperature variability determined from also continuously recorded temperature values becomes. Multi-sensor for the noninvasive monitoring of fractional oxygen saturation and detection of pathological changes in the cardiovascular system by simultaneous acquisition of various optical photoplethysmogram (PPG) signals using photoplethysmography (PPG) sensors ( 6 ), is connected to the evaluation of the PPG signals with a computing unit and can be derived by means of the arithmetic unit from the PPG signals for a physician interpretable diagnostic parameters. Multi-sensor according to claim 8, characterized in that the PPG sensors ( 6 ) Are transmission, reflection and / or transflectance sensors. Multi-sensor according to one of claims 8 or 9, characterized in that the PPG sensors ( 6 ) as light sources LEDs ( 7 ), LDs or a lamp are associated with optical filters for selecting specific wavelengths. Multi-sensor according to one of claims 8 to 10, characterized in that the PPG sensors ( 6 ) as detectors photodiodes ( 8th ), Phototransistors, CCD detectors are assigned. Multi-sensor according to one of claims 8 to 11, characterized in that for the multi-sensor ( 1 ) a small design, preferably in the form of a probe, is selected. Multi-sensor according to one of claims 8 to 12, characterized in that the contact pressure of the PPG sensor ( 6 ) is automatically dynamically adjustable to the measuring site so that it is smaller than the diastolic blood pressure of the patient, but so large that a movement is prevented at the measuring location. Multi-sensor according to one of claims 8 to 13, characterized in that from the existing sensors a plurality of sensor groups are formed such that in each case one sensor group for each one patient ( 2 ) can be used. Multi-sensor according to claim 14, characterized in that data determined via a Data interface of the arithmetic unit in a data system readable are. Multi-sensor according to one the claims 8 to 15, characterized in that the multisensor further additional Sensors, for example for the determination of venous oxygen saturation, for the creation of ECG or EEG, a skin impedance sensor, respiratory gas sensors, a sensor for detecting caries and other pathological changes in dentistry and / or chemical sensors for tear, gas and sweat analyzes, assigned. Multi-sensor according to one the claims 8 to 16, characterized in that the evaluation of the sensor data by the arithmetic unit online or offline feasible.