Noninvasive blood pressure determination method and apparatus
The method and the apparatus serve for non-invasively determining the blood pressure of a patient. An electrical cardiac potential measurement signal and a pulse-pressure-wave measurement signal are detected which, starting from the heart, propagate within the blood vessels as far as to a pulse-feeling location. A pulse-pressure-wave propagating time between the heart and the pulse-feeling location is determined, based on the electrical measurement signal and the pulse measurement signal. The blood pressure is determined by the aid of a function interrelationship on the basis of the propagating time, with the function interrelationship comprising a first portion that specifies the active elasticity behaviour of the blood vessels, and a second portion that specifies the passive electricity behaviour of the blood vessels. In this way, especially accurate blood pressure determination is rendered possible.
1. A method of noninvasively determining a blood pressure (P) of a patient ( 2 ), in which
a) an electrical cardiac potential measurement signal (EM) is detected;
b) a pulse measurement signal (PM) of a pulse pressure wave which, starting from a patient's heart, propagates within blood vessels is detected at a pulse-feeling location ( 15 );
c) a propagating time (T) of the pulse pressure wave between the heart and the pulse-feeling location ( 15 ) is determined, based on the electrical measurement signal (EM) and the pulse measurement signal (PM);
d) wherein the blood pressure (P) is determined from the propagating time (T) by means of a function interrelationship that comprises a first portion specifying an active elasticity behaviour of the blood vessels and a second portion specifying a passive elasticity behaviour of the blood vessels.
2. A method according to claim 1 , wherein, in determining the blood pressure, an additional calibration portion is considered in the function interrelationship.
3. A method according to claim 1 , wherein a body height of the patient ( 2 ) is considered in determining the blood pressure.
4. A method according to claim 1 , wherein the electrical measurement signal (EM) and the pulse measurement signal (PM) are detected virtually at the same location.
5. A method according to claim 1 , wherein in the function interrelationship the blood pressure determination is based on, use is made of an equation
P
=
C
1
·
D
T
·
ⅇ
C
2
·
D
T
+
C
3
·
(
D
T
)
C
4
+
(
P
c
al
-
P
0
)
with P being a to-be-determined blood pressure in [mmHg]; with D being an approximate distance in [cm] which the pulse pressure wave covers between the heart and the pulse-feeling location ( 15 ); with T being the propagating time of the pulse pressure wave in [ms]; with C 1 , C 2 , C 3 , C 4 being a given or selectable parameter; with P 0 being a determined, uncalibrated blood pressure value in [mmHg]; and with P cal being a calibration blood pressure value in [mmHg].
6. An apparatus for noninvasively determining of a blood pressure (P) of a patient ( 2 ), comprising
a) an ECG sensor ( 3 ; 18 ) for detecting an electrical cardiac potential measurement signal (EM);
b) a pulse sensor ( 4 ; 19 ) for detecting a pulse measurement signal (PM) of a pulse pressure wave which, starting from the heart, propagates within the blood vessels as far as to a pulse-feeling location ( 15 ) where the pulse sensor ( 4 ; 19 ) is disposed;
c) an evaluation unit ( 6 ) for determining a propagation time (T) of the pulse pressure wave between the heart and the pulse-feeling location ( 15 ) on the basis of the electrical measurement signal (EM) and the pulse measurement signal (PM);
d) wherein the evaluation unit ( 6 ) is designed for determining the blood pressure (P) from the propagating time (T) by means of a function interrelationship which comprises a first portion that specifies the active elasticity behaviour of the blood vessels, and a second portion that specifies the passive elasticity behaviour of the blood vessels.
7. An apparatus according to claim 6 , wherein the evaluation unit ( 6 ) is designed for consideration of an additional calibration portion, obtained from a calibration measurement, in the blood pressure determination by the function interrelationship.
8. An apparatus according to claim 6 , wherein means ( 11 ) are provided for input or detection of the body height (H) of the patient ( 2 ).
9. An apparatus according to claim 6 , wherein the ECG sensor ( 18 ) and the pulse sensor ( 19 ) are accommodated in a joint detection module ( 16 ).
10. An apparatus according to claim 6 , wherein an equation for the blood pressure determination function interrelationship is deposited in the evaluation unit ( 6 ), according to which
P
=
C
1
·
D
T
·
ⅇ
C
2
·
D
T
+
C
3
·
(
D
T
)
C
4
+
(
P
c
al
-
P
0
)
with P being the to-be-determined blood pressure in [mmHg]; with D being an approximate distance in [cm] which the pulse pressure wave covers between the heart and the pulse-feeling location ( 15 ); with T being the propagating time of the pulse pressure wave in [ms]; with C 1 , C 2 , C 3 , C 4 being a given or selectable parameter; with P 0 being a determined, uncalibrated blood pressure value in [mmHg]; and with P cal being a calibration blood pressure value in [mmHg].