Method and apparatus for automatic blood pressure monitoring

Claim 2

Method for automatic non-invasive monitoring of a patient's blood pressure, comprising the steps of: (1.1) applying a cuff (5) around a limb of the patient, (1.2) inflating said cuff (5) to a predetermined pressure, (1.3) step-wise reducing the pressure applied to said cuff (5), (1.4) holding the applied pressure constant at each step until (1.4.1) at least one superimposed oscillation caused by a heartbeat has occurred, or until (1.4.2) a predetermined time period (t max ) has expired, (1.5) measuring the amplitudes of said superimposed oscillations and processing them in order to determine the systolic, the diastolic or/and the mean blood pressure, characterized by the steps of (1.6) determining the time interval between the heart beats, or the heart rate, of the patient, (1.7) calculating and/or varying said predetermined time period (t max ) in dependence of said time interval, or in dependence of the inverse of said heart rate, such that the duration of said predetermined time period (t max ) is increased when said time interval increases, or when said heart rate decreases.

Claim 3

Method according to claim 1, characterized in that said predetermined time period (t max ) is substantially proportional to said time interval, or inversely proportional to said heart rate.

Claim 4

Method according to claim 2, characterized by adding an offset (A) to said predetermined time period (t max ), said offset (A) being either constant or a variable which depends on said time interval or said heart rate.

Claim 5

Method according to at least one of the preceding claims, characterized in that said predetermined time period (t max ) is compared with a lower and/or an upper limit, and that it is set to said lower/upper limit when it falls below said lower limit and/or exceeds said upper limit.

Claim 6

Method according to at least one of the preceding claims, characterized in that said predetermined time period (t max ) is determined via a look-up table.

Claim 7

Apparatus for non-invasive measuring of a patient's blood pressure comprising: (6.1) cuff inflation means, in particular a pump (3), (6.2) cuff deflation means, in particular a valve (5a), (6.3) at least a pressure sensor (6), (6.4) wherein said cuff inflation means, said cuff deflation means and said pressure sensor (6) are set up for pneumatic connection with a cuff (5) for appliance around a patient's limb, (6.5) control means operatively connected with said cuff inflation means, said cuff deflation means and said pressure sensor (6), said control means being set up to inflate the cuff (5) to a predetermined pressure and to step-wise reduce the applied pressure, said control means further being set up to hold the applied pressure constant at each step until at least one superimposed oscillation has been observed or until a predetermined time period (t max ) has expired, (6.6) blood pressure calculation means, particularly a microprocessor (2), for calculating the systolic, the diastolic and/or the mean blood pressure from the amplitudes of the superimposed oscillations recorded by said pressure sensor (6), characterized by (6.7) heart rate determination means (7) or interval measuring means for measuring the time interval between the heart beats, (6.8) time period calculation means set up to calculate said predetermined time period (t max ) in dependence of the heart rate indicated by said heart rate determination means (7) or in dependence of the time interval between the heart beats indicated by said interval measuring means.

Claim 8

Apparatus for non-invasive measuring of a patient's blood pressure comprising: (6.1) cuff inflation means, in particular a pump (3), (6.2) cuff deflation means, in particular a valve (5a), (6.3) at least a pressure sensor (6), (6.4) wherein said cuff inflation means, said cuff deflation means and said pressure sensor (6) are set up for pneumatic connection with a cuff (5) for appliance around a patient's limb, (6.5) control means operatively connected with said cuff inflation means, said cuff deflation means and said pressure sensor (6), said control means being set up to inflate the cuff (5) to a predetermined pressure and to step-wise reduce the applied pressure, said control means further being set up to hold the applied pressure constant at each step until at least one superimposed oscillation has been observed or until a predetermined time period (t max ) has expired, (6.6) blood pressure calculation means, particularly a microprocessor (2), for calculating the systolic, the diastolic and/or the mean blood pressure from the amplitudes of the superimposed oscillations recorded by said pressure sensor (6), characterized by (6.7) heart rate determination means (7) or interval measuring means for measuring the time interval between the heart beats, (6.8) time period calculation means set up to calculate said predetermined time period (t max ) in dependence of the heart rate indicated by said heart rate determination means (7) or in dependence of the time interval between the heart beats indicated by said interval measuring means.

Claim 9

Apparatus according to claim 6, characterized in that said time period calculation means comprises a look-up table which holds values or ranges of the heart rate and the corresponding values of said predetermined time period.

Claim 10

Apparatus according to claim 6 or 7, characterized in that said heart rate determination means or said interval measuring means comprises electrocardiogram recording means and peak trigger means, said electrocardiogram recording means being set up for connection with electrocardiogram electrodes.

Claim 11

Apparatus according to claim 6 or 7, characterized in that said heart rate determination means or said interval measuring means comprises plethysmogram recording means and peak trigger means, said plethysmogram recording means being set up for connection with a plethysmogram transducer or an oxygen saturation transducer.

Claim 12

Apparatus according to claim 6 or 7, characterized in that said heart rate determination means or said interval measuring means comprises invasive or non-invasive blood pressure recording means and peak trigger means.