Monitoring a condition of a patient under anaesthesia or sedation
First Claim
1. A method for monitoring a condition of a patient under anaesthesia or sedation, the method comprising the steps of:
- acquiring a signal representing temporally a cardiovascular activity of the patient;
detecting periodically repeated waveforms in said signal;
calculating at least one parameter selected from;
time intervals between said successive waveforms, pressures from said successive waveforms, temporal rates from said successive waveforms;
forming respectively at least one of the following;
a mathematical time series of said time intervals, or a mathematical pressure series of said pressures, or a mathematical rate series of said temporal rates;
filtering said time series and/or said pressure series and/or said rate series mathematically to provide a plurality of successive average values each over a predetermined first time period; and
detecting a substantial decrease, or increase respectively in said plurality of successive average values.
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Accused Products
Abstract
The invention relates to a method for monitoring a condition of a patient under anaesthesia or sedation. In the method a signal (S) is acquired representing a cardiovascular activity of the patient, and periodically repeated waveforms (P) are detected, followed by calculation of time intervals (Ti) between, and/or pressures (Bi) from, and/or temporal rates (Ri) from successive waveforms. Next at least one of the following—a mathematical time series (T1, T2 . . . Tn, Tn+1 . . . ), or a mathematical pressure series (B1, B2 . . . Bn, Bn+1 . . . ), or a mathematical rate series (R1, R2 . . . Rn, Rn+1 . . . ) is/are formed. Further in the method said time series and/or said pressure series and/or said rate series is mathematically filtered to provide successive average values ({overscore (T)}i; {overscore (B)}i; {overscore (R)}i) over a predetermined first time period (τ), and a substantial decrease, or increase respectively in said average values is detected.
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Citations
42 Claims
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1. A method for monitoring a condition of a patient under anaesthesia or sedation, the method comprising the steps of:
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acquiring a signal representing temporally a cardiovascular activity of the patient;
detecting periodically repeated waveforms in said signal;
calculating at least one parameter selected from;
time intervals between said successive waveforms, pressures from said successive waveforms, temporal rates from said successive waveforms;
forming respectively at least one of the following;
a mathematical time series of said time intervals, or a mathematical pressure series of said pressures, or a mathematical rate series of said temporal rates;
filtering said time series and/or said pressure series and/or said rate series mathematically to provide a plurality of successive average values each over a predetermined first time period; and
detecting a substantial decrease, or increase respectively in said plurality of successive average values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
Firstly, a mathematical derivation of said plurality of successive average values to have temporally variable derivatives thereof.
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3. A method of claim 2, wherein said step of decrease/increase detecting further comprises:
Secondly, emphasizing those values of said derivatives of said plurality of successive average values of said time series decreasing, whereupon said emphasizing is performed by neglecting and/or suppressing those values of said derivatives which are not decreasing.
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4. A method of claim 3, wherein said neglecting and/or suppressing comprises applying a mathematical operator into said temporally variable derivative to have a selection of decreasing accelerations describing the increase of the cardiovascular activity only.
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5. A method of claim 4, wherein said selection of accelerations are compared with one or several predetermined reference values, and only values of the accelerations being below said reference value(s) are reported or forwarded to further calculations.
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6. A method of claim 3, wherein said step of decrease/increase detecting further comprises:
Thirdly, performing said emphasizing over a predetermined second time period.
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7. A method of claim 6, wherein said emphasizing is performed by evaluating said selection of accelerations utilizing a sliding sum of said selected accelerations over said second time period, whereupon said selection provides an acceleration index as a result.
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8. A method of claim 7, wherein at least one of said acceleration indexes is reported.
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9. A method of claim 6, wherein said predetermined second time period is between 20 and 120 beats of heart.
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10. A method of claim 2, wherein said step of decrease/increase detecting further comprises:
Secondly, emphasizing those values of said derivatives of said plurality of successive average values of said pressure series and/or said rate series increasing, whereupon said emphasizing is performed by neglecting and/or suppressing those values of said derivatives which are not increasing.
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11. A method of claim 10, wherein said neglecting and/or suppressing comprises applying a mathematical operator into said temporally variable derivative to have a selection of increasing accelerations describing the increase of the cardiovascular activity only.
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12. A method of claim 11, wherein said selection of accelerations are compared with one or several predetermined reference values, and only values of the accelerations exceeding said reference value(s) are reported or forwarded to further calculations.
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13. A method of claim 10, wherein said step of decrease/increase detecting further comprises:
Thirdly, performing said emphasizing over a predetermined second time period.
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14. A method of claim 13, wherein said emphasizing is performed by evaluating said selection of accelerations utilizing a sliding sum of said selected accelerations over said second time period, whereupon said selection provides an acceleration index as a result.
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15. A method of claim 14, wherein at least one of said acceleration indexes is reported.
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16. A method of claim 13, wherein said predetermined second time period is between 20 and 120 beats of heart.
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17. A method of claim 2, wherein said temporally variable derivatives are compared with one or several predetermined reference values, and only values of the derivatives being below, or exceeding respectively said reference value(s) are reported or forwarded to further calculations.
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18. A method of claim 1, wherein said average value is a sliding even median or a sliding mean value of said time intervals or said pressures or said temporal rates, or a sliding weighted median or a sliding weighted mean value of said time intervals or said pressures or said temporal rates respectively calculated over said first time period.
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19. A method of claim 1, wherein said decrease/increase in the plurality of successive average values is compared with a predetermined threshold change value, whereupon only values of said time series smaller than said threshold value is forwarded for further calculations and/or for reporting and/or for an alarm is given in case said average values are smaller than said threshold value.
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20. A method of claim 1, wherein said decrease/increase in the plurality of successive average values is compared with a predetermined threshold change value, whereupon only values of said pressure series and/or said rate series greater than said threshold value is forwarded for further calculations and/or for reporting and/or for an alarm is given in case said average values are greater than said threshold value.
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21. A method of claim 1, wherein said predetermined first time period for said filtering is between 20 and 60 beats of heart.
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22. A method of claim 1, wherein said step of acquiring signal is performed by measuring electrical manifestations of one of the following:
cardiac actions, or a flow velocity or pressure of blood, or an absorption of electromagnetic radiation by blood, or acoustical manifestations emitted from blood-vascular system.
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23. A method in which:
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a signal representing a cardiovascular activity of a patient is analyzed for detection of periodically repeated waveforms, at least one of the following;
time intervals between successive waveforms, or pressures from successive waveforms, or temporal rates from successive waveforms are calculated to provide at least one of the following;
a mathematical time series of said time intervals, or a mathematical pressure series of said pressures, or a mathematical rate series of said temporal rates, said time series and/or pressure series and/or said rate series are mathematically filtered to provide a plurality of successive average values each over a predetermined first time period, a substantial decrease, or increase respectively in said average values is detected, and data of said detection is forwarded to an operator for monitoring adequacy of analgesia of a patient under anaesthesia or sedation. - View Dependent Claims (24, 25)
said time intervals, decreasing;
orsaid temporal rates, or said pressures respectively, increasing.
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25. A method of claim 23, wherein said data of detection concerning analgesia is forwarded to the operator in form of temporally variable derivatives of acceleration index received from a selection of accelerations by a predetermined mathematical operation.
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26. A method in which:
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a signal representing a cardiovascular activity of a patient is analyzed for detection of periodically repeated waveforms, at least one of the following;
time intervals between successive waveforms, or pressures from successive waveforms, or temporal rates from successive waveforms are calculated to provide at least one of the following;
a mathematical time series of said time intervals, or a mathematical pressure series of said pressures, or a mathematical rate series of said temporal rates, said time series and/or pressure series and/or said rate series are mathematically filtered to provide a plurality of successive average values, a decrease, or an increase respectively in said average values is detected, and data of said detection is forwarded to an operator for monitoring adequacy of analgesia of a patient under anaesthesia or sedation, together with data describing muscle relaxation of said patient and/or data describing loss of consciousness obtained by other means. - View Dependent Claims (27, 28)
said time intervals, decreasing;
orsaid temporal rates, or said pressures respectively, increasing.
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28. A method of claim 26, wherein said data of detection concerning analgesia is forwarded to the operator in form of temporally variable derivatives of acceleration index received from a selection of accelerations by a predetermined mathematical operation.
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29. An apparatus for monitoring a condition of a patient under anaesthesia or sedation, the apparatus comprising:
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detection means for receiving a substantially continuous electrical signal representing a cardiovascular activity of the patient;
a voltage and/or current dependent circuit detecting each predetermined waveform in said signal;
first calculation means providing at least one of the following;
a series of time intervals between successive waveforms, or a series of pressures from successive waveforms, or a series of temporal rates from successive waveforms;
second calculation means providing successive average values of the series of said time intervals and/or said pressures and/or said temporal rates over a predetermined first time period;
third calculation means providing data about a decrease, or increase respectively in said successive average values; and
a display and/or connections into other devices. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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Specification