DE19645579A1 - Heart and blood circulation system function evaluation device - Google Patents

Abstract

The function evaluation device uses non-invasive optical and/or electrical measurement of physical parameters related to the heart operation, with auto-and/or cross-correlation of the measured values to provide functions which are stored and compared with normal values and/or characteristic curves. A dual wavelength NIR-ROT remission photoplethymographic measurement of the blood oxygen content can be obtained for each heart cycle, together with the relative microvascular filling volume, with storage of the functions obtained by auto-, or cross- correlation.

Description

The invention relates to a device and a Arbeitsver drive to operate the device for determining and off evaluate functional states in the cardiovascular system.

From Steinmann, J. et al .: "In vivo measurement of blood oxygen saturation with quartz light guides and an optical multi-channel analyzer", Biomed. Technik 31 (1986), 246-251, it is known to measure by means of NIR red remission photoplethysmography as follows:

• - With the wavelength of 840 nm, the relative amount of blood or erythrocytes in the illuminated tissue, regardless of its degree of oxygenation, since the so-called Hb / HbO ₂ isobestic wavelength range at 840 for remission measurement in vivo. . . 850 nm. That wavelength range of radiation or light, in which different chemical substances, eg. B. hemoglobin and oxyhemoglobin, weaken the light passing through these substances equally, ie their extinction or attenuation coefficient is the same. The NIR wavelength 840 nm thus measures the amount of blood or erythrocytes relative to the illuminated total tissue, which passes through the microvessels according to the Fåhraeus effect in the form of blood volume pulse waves.
• - With the wavelength 640 nm, on the other hand, the relative blood or erythrocyte quantity detected by 840 nm with regard to their degree of oxygenation by changing the measurable light intensity ratio between 640 nm and 840 nm during the microvascular or capillary passage due to deoxygenation. From the change in intensity of the backscatter signal of both wavelengths, both the general change in the blood flow to the illuminated tissue and the relative amount of the erythrocytes passing through the deoxygenating capillaries can be determined quantitatively, ie oxymetrically, as is realized in conventional oximeters. The oxygen saturation SaO _{2 of} the arterial blood is defined as the ratio of oxygen-enriched hemoglobin (HbO ₂ ) and total hemaglobin (HbO ₂ + Hb + other forms, such as carbosyhemoglobin, methemoglobin, sulfhemoglobin):
  [according to the Ohmeda Biox 3740 Pulse manual].

On the other hand, oxygen saturation is generally defined as the ratio of O ₂ content (in% by volume) to O ₂ capacity (in% by volume) (Netter, FH: Color Atlas of Medicine, Vol. 1: Heart, 3. revised and expanded edition, The Ciba Collection of Medical Illustrations, 1993):
A normal value of 97% degree of saturation of the blood in the capillary bed is obtained with an O ₂ content of 20.4% by volume and an O ₂ capacity of 21% by volume.

An arteriovenous difference avDO _{2 of} the O ₂ contents is also introduced (Schmidt, RF; Thews, G .: Physiologie des Menschen. 23rd ed., Springer publishers Berlin / Heidelberg / New York / London / Paris / Tokyo 1987), by using the values for arterial O ₂ saturation (SaO ₂ = 97%) and venous O ₂ saturation (SaO ₂ = 73%) to have a chemically bound oxygen content in the arterial and venous blood of about 0.2 and 0.15 l O ₂ / l blood was found to be invasive and thus approximately avDO ₂ = 0.05 l O ₂ / l blood normally results. Accordingly, only about 25% of the total O ₂ binding capacity of the blood is normally used up when it passes through the tissue capillaries:

 d. H.

avDO ₂ = 20.4% by volume - 15.3% by volume ≈ 5% by volume ≘ 0.05 l O ₂ / l blood.

The relative arteriovenous O ₂ difference is therefore found

SaO _{2 arterial} - SaO _{2 venous} = 0.24

respectively.

Based on the prior art, it is therefore an object of the invention a more advanced device and a more meaningful one Working method for operating the device for determination and evaluating functional states in the cardiovascular system specify.

The task is solved with the characteristics of the independent pending claims, the sub-claims at least include expedient refinements and developments.

The invention is based on the basic idea that with the in the tissue irradiated wavelength of 640 nm with 840 nm measured relative amount of blood or erythrocytes with regard  their degree of oxygenation is detected and thus for each Heart action or respiratory period the time functions received

x ₁ (t) = x _NIR (t),

x ₂ (t) = x _RED (t)

are similar. The correlation factor r (n) = OX (n), ie per cardiac action or respiratory period n, should be defined and derived as a corresponding measure of similarity and thus as a "degree of oxygenation" (OX degree) or degree of saturation analogous to SaO ₂ . The arteriovenous difference of the O ₂ contents should also be determined non-invasively.

They represent:

x ₁ (t) = x _NIR (t): reference signal, setpoint (100% oxygenation)

x ₂ (t) = x _RED (t): actual value.

To determine the (linear) correlation between these signals, the mean square deviation ε ² (t) is formed as follows with a compensation factor a:

ie with an optimal compensation factor a _opt "maximum similarity" must be reached, the mean square difference then becomes minimal so that the correlation factor can be determined from it. You get

By differentiation follows

or is obtained for the optimal compensation factor

By inserting and reshaping it follows for the minimum mean square difference

or in standardized form

Transferred to the ratios of oxygen saturation in the arterial and venous area and in the non-invasive determination of the arteriovenous difference in the O ₂ contents, it was surprisingly recognized that:

the correlation factor

corresponds to the arterial saturation SaO ₂ . This value is called "degree of oxygenation" [OX degree] below. It can be determined in the presence of corresponding volume pulsations per heart action n:

The following applies as the average OX degree for a certain measurement duration (presence of N volume pulses or N cardiac actions):

If there is an extreme arterial circulatory disorder or (generally speaking) it is no longer possible to speak of a periodic volume pulsation of the microcirculation, then the correlation factor can be taken as the mean

 determined within the specified measuring time (e.g. 60 s) will.

If this 2-wavelength remission method is applied to the conditions in the lungs by attaching the sensor "close to the lungs" to the body, then "arterial saturation in the lungs" (corresponds to the pulmonary venous blood) can be obtained for each breathing period n * ) determine

or as an arithmetic mean for N * breathing periods

From the determined and represented courses r (n) [with the Mean r (n)], r (n *) [with the mean r (n *)] according to the invention the absolute and relative standard deviation as well as the average in the courses Periods in the corresponding autocorrelation functions as quasi-quality measures can be determined in the cardiovascular system.  

_Taking the standard deviation (scatter) S _ΔOX

to the mean OX (n), an "oxygenation variability" OXV should be introduced:

Such a parameter is also determined for the lungs.

The minimum mean square difference

or in standardized form

can be determined per heart action n and corresponds to the square of the absolute and relative arteriovenous difference of the O ₂ contents:

As a relative arteriovenous Different follows

It is defined as an approximation

The invention is based on exemplary embodiments and Figures are explained in more detail.

Here show:

Fig. 1 is a derived from a model relationship between the absolute and relative arteriovenous O ₂ -difference and the absolute and relative arterial O ₂ content,

Fig. 2 shows the oxygenation before [a)] and after an infusion of Prostavasin at a patient lying with PAD (measurement location big toe), and tidal breathing,

Fig. 3 (re measurement location 2. finger.) The oxygenation in a 79-year olds lying patients with left heart failure and tidal breathing,

Fig. 4, the integral microcirculation, measured with NIR-ROT remission photoplethysmography, right at the measuring point big toe. in an 85 year old patient with PAD,

Fig. 5 remission photoplethysmography signals at lungs breathable with superimposed Volumenpulsationen at the measuring point Waist / lung area,

FIG. 6a shows the section of a measured time to a fingertip NIR-labeled Blutvolumenpulsation including heart period durations [T _H (n) for n-th volume pulse belonging etc.];

Fig. 6b is a tachogram the heart period T _H in Depending ness of the respective volume pulse n as an example,

Fig. 7 is a tachogram T _H = f (n) subjects for a 40-year Normal,

Fig. 8 belonging to Fig. 7 auto-correlation function Φ _ΔTH (m) including identification and normal values,

Fig. 9 is a derived from Fig. 7 histogram of heart period durations including defined boundaries and any percentage details of occurrence of periods in the corresponding regions,

Fig. 10 is a tachogram T _H = f (n) at a 35 year old diabetic (type I WHO),

Fig. 11 belonging to Fig. 10 AKF Φ _ΔTH (m),

Figure 12 is a tachogram T _H = f (n) incidence. At a 72 year old female patient lying on tidal breathing with coronary 3-Gefäßer, arterial hypertension and posterior myocardial infarction,

Fig. 13 to 12 is associated. AKF Φ _ΔTH (m),

Fig. 14 th n-The Blutvolumenpulsation and the (n + 1) -th pulse with the corresponding surfaces of F _n and F _{n + 1} as a measure of microvascular perfusion at the measuring point, a micro-vessel region,

Fig. 15 (measuring site 2. fingertip re.) The course of the relative filling volume is at from normal volunteers after Fig. 9,

Fig. 16 shows the course of the relative filling volume (measuring site 2. fingertip re.) Wherein the diabetic to Fig. 10, and

Fig. 17 shows the course of the Oxygenierungsgrades OX = f (n) in the normal subjects according to Fig. 15.

Fig. 1 shows the graphical representation of the abilities mentioned. It can be seen that with degrees of oxygenation (degrees of saturation) of approximately one, the arteriovenous difference runs to zero, ie the arterial blood is then not desaturated. The invasive normal values

SaO 2 _artery = 0.97,

SaO 2 _arterial - SaO _{2 venous} = 0.24

lie directly on the theoretically determined curve.

The scales given in FIG. 1 for the absolute values for _arterial O ₂ content and avDO ₂ in [l O ₂ / l blood] are based on an O ₂ capacity of 21% by volume [according to Rein, H .; Schneider, M .: Human Physiology, 11th ed., Springer Berlin / Göttingen / Heidelberg 1955, p. 39].

Fig. 2 shows the course of the degrees of oxygenation at the measuring site big toe before [a)] and after [b)] infusions of prostavasin in a 72-year-old patient with peripheral arterial occlusive disease (PAD). In addition to an increase in the mean oxygenation wheel by this infusion, the reduction in the oxygenation variability is evident, e.g. Sometimes breath-dominant periods of 4 to 5 heartbeats occur.

From Fig. 3, the oxygenation ratios with z. T. emerges from dominant respiratory dominant periods in a 79-year-old lying patient with left heart failure and resting breathing (measurement site 2. Fi.li).

FIG. 4 shows the courses of the integral microcirculation measured with NIR-ROT remission photo plethysmography at the measurement site of the big toe in an 85-year-old patient with PAD. Since it is hardly possible to speak of periodic volume pulsations, only the mean value of the degree of oxygenation (correlation factor) is used for such courses of the time functions.

 certainly.

In FIG. 5, which provides detected in a normal subjects remission photoplethysmography signals at pulmonary respiration with superimposed Volumenpulsationen at the measurement site (lung nearby) Darge. The degree of oxygenation OX (n *) in the _lungs occurring during a breathing period T _breathing is determined analogously to OX (n). To suppress the higher-frequency volume pulsations in the NIR and ROT signals, the same low-pass filter with a cut-off frequency of approx. 0.6 Hz is connected downstream of these signals in order to subsequently determine the degree of oxygenation OX (n *) _lung .

With near infrared remission photoplethysmography leaves as known from DE 42 38 641, non-invasively on one corresponding peripheral location (e.g. fingertip) the relative Amount of blood per heartbeat for a selected measuring time capture that the microvasculature in the form of volume pulse waves happen.  

As the volume pulsation is measured at an "end point" of the arterial vascular system, it is known that it contains all the essential parameters that characterize the interaction of the "central", the heart, with the vascular system in between:

• - Cardiac period T _H and its change per heart pulsation during the measuring time (e.g. 60 s). In "Perfusion" 7/96, 9th year, pages 268 to 279, it is stated that in the normal case (no pAD on the "transmission line", no stenoses) the pulse period measured there equates with the cardiac period T _H with sufficient approximation can be. In general, therefore, the fingertip should be selected as the measurement site if there are no circulatory disorders (Cave: lower blood pressure on the measurement side),
• - Parameters of the micro and arterial macrovascular area, such as the relative filling volume FV or the degree of oxygenation or the arteriovenous difference in the O ₂ contents.

Please refer to the publications "Perfusion" 7/96, 9. Vintage, pages 268 to 279, "Perfusion" 8/96, 9th year, Pages 300 to 310, as well as "European Journal of Medical Research ", Vol. 1, February 22, 1996, pages 237 to 244 referenced to explain the counter presented here can be considered as belonging.

FIG. 6a shows the time segment of an NIR blood volume pulsation measured on a fingertip, including marked cardiac periods [T _H (n) belonging to the nth volume pulse, etc.], and FIG. 6b the tachogram T _H (n) derived therefrom as an example. The occurrence of cardiac periods can be seen as permanent deviations ΔT _H (n) from the mean

FIG. 7 shows the tachogram T _H = f (n) in a 40-year-old normal subject, where the respiratory sinus rhythm becomes clear, while FIG. 8 shows the autocorrelation function Φ _ΔTH (m) associated with the cardiac period deviation ΔT _H (n) as the mean function including normal range as well as characteristic values occurring in Φ _ΔTH (m) (including respiratory sinus arrhythmia with 8 heartbeats on average).

FIG. 9 shows the histogram of the cardiac cycle duration resulting for the normal test subject according to FIG. 7, including defined limits with percentages of the occurrence of the periods in the corresponding areas.

FIGS. 10 and 11 enter the cardiovascular characteristic features at a 35 year old diabetic (type I WHO) again. The occurrence of abnormally long basic periods as an expression of an increased sympathetic tone or a changed cardiac microcirculation is clear.

FIGS. 12 and 13 show the courses in a 72-year-old lying patient with resting breathing with coronary 3-vessel disease, arterial hypertension and posterior wall infarction. The differences from the normal test subject according to FIGS. 7, 8 become as clear as from the type I diabetic according to FIGS. 10, 11. Characteristic of the course according to FIG. 13 is the low heart rate variability, in particular the occurrence of periods of 2 or 3 heartbeats.

The area of each volume pulse, based on the average area of all pulsations in a measurement file (e.g. 80 volume pulses), is determined as "relative (microvascular) filling volume" at a corresponding measuring point (a microvessel area), as shown in FIG. 14.

Fig. 15 shows the course of such a relative filling volume (measuring point 2nd finger pad right) in the normal band according to Fig. 7, Fig. 16 for the diabetic according to Fig. 10 (measuring point 2nd finger pad right)

According to the invention, it was recognized that a tachogram of the relative filling volume FV (n) can be determined analogously to the tachogram T _H = f (n) and an autocorrelation function of the deviation of the relative filling _volume from the mean value FV1 = 1 can be determined analogously to Φ _ΔTH (m) can:

ΔFV (n) = FV (n) - FV (n)

= FV (n) - 1This means that _{folgt ΔTH} (m):

Φ _ΔFV (m) = FV (n) .FV (nm) -1.

At m = 0, the "filling volume variability" FVV is obtained

while Φ _ΔFV (m) shows the middle filling periods (e.g. _{breathing dominance} in the normal case).

According to the invention it was further recognized that an autocorrelation function of the deviation of the degree of oxygenation from the mean value OX (n) can also be derived from the tachogram of the degree of oxygenation OX = f (n), as is shown in FIG. 17 for the normal test subject according to FIG. 15 .

It follows with

ΔOX (n) = OX (n) - OX (n)

for the autocorrelation function analog Φ _ΔTH (m):

Φ _ΔOX (m) = OX (n) .OX (nm) - [OX (m)] ² .

Also from Φ _ΔOX (m = 0) follows the "oxygenation degree variability" OXV

from the course Φ _ΔOX (m) the occurring middle periods (e.g. respiratory dominance in the normal case and if perfusion equilibrium is present, see Fig. 17).

In a further embodiment of the invention, the introduced state functions T _H = f (n), FV = f (n), OX = f (n) and

cross-correlated with each other, ie correlation factors and periods m _period according to the educational algorithm

Φxy (m) = x (n) .y (n-m)

certainly:

A comparison is also made with normal courses and -characteristics.

Claims (18)

1. Device for determining and evaluating functional states in the cardiovascular system, in particular the blood vessels including the heart in cooperation with the autonomous nervous system, characterized by

• Means for acquiring the state functions by means of optical and / or electrical measurement which is not vasive,
• - Description of the state of each heart action and the auto- and / or cross-correlation functions derived therefrom as generalized mean value functions or associated amplitude spectra as state functions,
• - Means for storing and displaying the status functions and
• - Means for comparing the state functions obtained with normal values and courses.

2. Device according to claim 1, characterized in that means for determining the degree of oxygenation of the blood are provided on the basis of a two-wavelength NIR-RED remission photoplethysmography measurement, the time functions x ₁ (t) = x _NIR (t) andx ₂ (t) = x _RED (t) per cardiac action
and the similarity measure of the time functions and the correlation factor is determined, the correlation factor being derived from one another
results and is defined as the degree of oxygenation. 3. Working method for operating the device according to claim 1 or 2, characterized in that from the undisturbed volume pulsations of the NIR signal in transmission or remission photoplethysmography and in electronic oscillography at a predetermined measuring time the cardiac cycle tachogram T _H = f (n ), ie for each heart action n, is derived and represented by periods and deviations from the mean
to determine. 4. Working method according to claim 2, characterized in that from the deviation of the cardiac period from the linear mean per cardiac action n
their autocorrelation function
is formed to represent the mean periods m occurring in the time series T _H = f (n) as a multiple of the heart rate, and the standard deviation S _TH occurring at m = 0 as the mean quadratic deviation of the cardiac period or by reference to the linear one Average
the heart rate variability VHF
5. Working _method according to claim 4, characterized in that in the formation _algorithm of Φ _ΔTH (m) in the tachogram T _H = f (n) occurring extrasystoles by the mean
be replaced. 6. Working _method according to claim 4, characterized in that in the presence of perfusion _equilibrium , the course obtained Φ _ΔTH (m) with normal _courses (m _{period normal} = 4 _... 14 heartbeats) is compared. 7. Working _method according to claims 4 or 6, characterized in that in Φ _ΔTH (m) occurring periods (m _period = 2; 3; <14 heartbeats) represent non- _{normal courses} . 8. Working method according to one of claims 4, 6 or 7, characterized in that for the characterization of the cardiovascular state in addition to the state function Φ _ΔTH (m) the further characteristic values or functions systolic and diastolic blood pressure, degree of oxyge nation including its autocorrelation function Φ _ΔOX ( m) and / or relative filling _volume FV including its autocorrelation function Φ _ΔFV (m) are used. 9. Working method according to claims 1, 3 or 4, characterized in that as related function tests of the cardiovascular system deep breathing to increase the delivery capacity of the heart and the reflex vasoconstriction by sympathetic stimulation are used and thereby changes in the characteristic functions T normally _H = f (n), Φ _ΔTH (m), which can be used for the evaluation. 10. Working _method according to claim 4, characterized in that the autocorrelation function Φ _ΔTH (m) is formed from the RR distance in the EKG. 11. Working _method according to claims 3 or 4, characterized in that the equivalent power spectrum of the heart rate variability is formed by Fourier transformation of Φ _ΔTH (m) and is used as a comparison value for evaluation. 12. Working method according to one of the preceding claims, characterized in that from the tachogram of the relative filling _volume FV (n), the autocorrelation function is determined as a status function _{Φ ΔFV} (m) = FV (n) .FV (nm) - 1, from which at m = 0 the "filling volume variability" FVV and _{mittleren ΔFV} (m) the occurring middle periods can be derived. 13. Working _method according to claim 12, characterized in that when perfusion _{equilibrium is present,} the obtained curve Φ _ΔFV (m) is compared with normal _curves and used for evaluation. 14. Working method according to claim 12, characterized in that the increased delivery of the heart resulting from deep breathing causes changes in FV (n) and in Φ _ΔFV (m), which is determined quantitatively with the characteristic values of Φ _ΔFV (m) and for Evaluation can be used. 15. Working method according to claim 1, 2, 4, characterized in that from the tachogram of the degree of oxygenation OX (n), the autocorrelation function as a state function _{Φ ΔOX} (m) = OX (n) .OX (nm) - [OX (n)] ² it is determined from which an oxygenation degree variability OXV at m = 0 and the occurring mean periods are derived from Φ _ΔOX (m) and used for evaluation. 16. Working _method according to claim 15, characterized in that when the perfusion _{equilibrium is present,} the obtained curve Φ _ΔOX (m) is compared with normal curves and used for evaluation. 17. Working method according to claim 1, characterized in that from the tachogram
the autocorrelation function
as a status function of the periphery of the cardiovascular system is determined according to:
from which at m = 0 a heart-periphery variability as well
the occurring mean periods are determined and compared with normal courses for evaluation. 18. Procedure for determining the effects of pharmaceuticals or drugs, as well as to derive sizes from the patient monitoring using the status and evaluation parameters obtained according to one or more of claims 1 to 17.