Method of continuous measurement of blood pressure in humans

• US 5,237,997 A
• Filed: 11/08/1990
• Issued: 08/24/1993
• Est. Priority Date: 03/09/1988
• Status: Expired due to Fees

• Current Assignee: Vectron Gesellschaft Fur Technologieentwicklung und Systemforschung mbH
• Original Assignee: Vectron Gesellschaft Fur Technologieentwicklung und Systemforschung mbH
• Inventors: von Muller, Albrecht A. C., Greubel, Waldemar, von Stein, Hubertus, Wieczorek, Rudolf
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): PONTIUS, KEVIN LANE
• Application Number:
  US07/576,404
• Time in Patent Office: 1,020 Days
• Field of Search: 128/672, 128/687, 128/691, 128/696, 128/715, 128/713, 128/664, 128/633, 128/689
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/6816 Ear lobe
• CPC Class Codes: A61B 5/7214 using signal cancellation, e.g. based on input of two identical physiological sensors spaced apart, or based on two signals derived from the same sensor, for different optical wavelengths

Abstract

In a process for continuous measurement of blood pressure, the mean blood essure is derived from the measured pulse wave duration. The other blood pressure parameters are obtained by combination with an optoelectrical determination of blood volume density in a typical manner at the ear lobes. An initial individual basic calibration of the blood pressure values is carried out by a conventional method. In addition, a continuous automatic optoelectronic post-calibration is carried out. The measuring sensors are preferably a pair of ear clips and ECG electrodes or a photoelectric sensor. The method can be used to particular advantage in prevention and diagnosis.

Claims

1. A method of continuously measuring blood pressure in humans, and permanently measuring a pulse-wave running time of every pulse wave of a pateint'"'"'s body, comprising the steps of:

determining one of three blood pressure values comprising systolic, diastolic or mean blood pressure by measuring the pulse-wave running time;

fixing an ear pulse measuring instrument to the patient'"'"'s ear lobe and using the ear pulse measuring instrument to measure the pulse-wave running time between the patient'"'"'s heart and the ear lobe;

converting the pulse-wave running time into blood pressure values by using a calibration curve specific of each patient, which indicates the pulse-wave running time as a function method for measuring the blood pressure in order to establish this calibration curve;

continuously determining an arterial blood volume density proportional to the blood pressure by means of an output signal of the ear pulse measuring instrument;

determining the blood pressure using the output signal of the ear pulse measuring instrument after the output signal has been calibrated by comparing it with the blood-pressure measuring process according to Riva-Rocci;

continuously recalibrating the output signal of the ear pulse measuring instrument in order to take into account vasomotoric and other regulations within the body, with the continuous recalibration step performed by electronic means permanently correlating the blood pressure value determined by measuring the pulse-wave running time to the respective output signal of the ear pulse measuring instrument, and thus permanently recalibrating the output signal of the ear pulse measuring instrument as a whole into blood pressure values;

providing the patient'"'"'s other ear lobe with a second ear pulse measuring instrument having an output signal; and

comparing the output signals of the two pulse measuring instruments with each other electronically in order to eliminate disturbances of various kinds.

2. Method according to claim 1, characterised in that recalibration is carried out in that for certain constant blood pressure values the corresponding measurement signals are recorded and the blood pressure values corrected on the basis of alterations of these signals.

3. A method according to claim 1, further including the steps of:

before the beginning of the continuous blood-pressure measurement, measuring the systolic and diastolic blood pressure values according to the Riva-Rocci method;

calculating a pressure difference Δ

p from the measured systolic and diastolic blood pressure values; and

correlating the pressure difference Δ

p to the difference Δ

i of the output signal corresponding to he diastolic value and the output signal corresponding to the systolic value of the ear pulse measuring instrument.

4. A method according to claim 1 further including the step of before the beginning of the continuous blood-pressure measurement, measuring the pulse-wave running time depending on several blood pressure values in order to establish the calibration curve specific of the patient.

5. A method according to claim 1 further including the step of using for measuring the pulse-wave running time a photo-electric sensor, which is placed on an area of the skin at the patient'"'"'s chest or back which is near the heart and is supplied with blood by an intercostal artery close to the heart.

6. A method according to claim 1 further including the step of using ECG electrodes over the heart to measure the pulse-wave running time.

7. A method according to claim 1 further including the step of using for measuring the pulse-wave running time a miniature microphone fixed over the heart to sense a first cardiac sound.

8. A method according to claim 1 wherein the fixing step comprises using a pulsed infra-red light diode to send light through the ear lobe and that the transmission of the ear lobe is measured by a photodiode.

9. A method according to claim 8 further including the step of avoiding influences due to variable oxygen saturation of the blood by choosing a wave length of IR-light near an isometric point for the infra-red light diode.

10. A method according to claim 1, further including the steps of:

receiving the two measurement signals of the two pulse measuring instruments with a coincidence circuit; and

suppressing with the coincidence circuit all signals not measured at both ear lobes at the same time and thus rating them as artefacts.

11. A method according to claim 1 further including the step of continuously taking the body-temperature at the ear lobe.