Stroke volume meter

Claim 2

A stroke volume meter comprising, input means adapted to receive a signal that is proportional to the aorta blood pressure, means for deriving a first signal determined by the instant at which the blood pressure in the aorta reaches a first minimum value corresponding to the end diastolic aorta pressure and determined by the instant at which said blood pressure reaches a second minimum value corresponding to the incision, means responsive to the blood pressure signal for deriving a second signal determined by the value of the end diastolic aorta pressure, integration means responsive to the blood pressure signal and the second signal and adapted to integrate the blood pressure signal indicative exclusively of the part of the blood pressure in the aorta which exceeds the end diastolic aorta pressure from the instant at which this pressure is reached until the instant at which the incision is reached, and means for dividing the signal value obtained by said integration by an adjustable constant.

Claim 3

A volume meter as claimed in claim 1, characterized in that the means for deriving said first signal indicative of the instants at which the end diastolic pressure and the incision are reached comprise first filter circuit means coupled to said input means and adapted to produce a signal pulse each time the second derivative of the blood pressure signal has a maximum value, and second filter circuit means coupled to said input means and adapted to produce a further signal having two levels, the further signal having the first level when the value of the blood pressure signal exceeds the mean value and the further signal having the second level when the blood pressure signal has a value below the mean value, logic circuit means for providing control output signals, and means connecting the outputs of said filter circuits to said logic circuit means.

Claim 4

A volume meter as claimed in claim 2 wherein said logic circuit means includes means for deriving an output pulse signal indicative of the instant of incision, and said means for deriving a second signal determined by the value of the end diastolic aorta pressure comprises a miniMum value detector controlled by said logic circuit means output pulse signal.

Claim 5

A volume meter as claimed in claim 3 wherein said logic circuit means includes means for deriving a control pulse-type signal that is indicative of the time period between said first and second minimum values of aorta blood pressure, and said integration means comprises an integrating circuit means having first and second inputs coupled to said input means and to the output of the minimum value detector, respectively, said integrating circuit means being adapted to integrate the difference between the signals applied to its first and second inputs, and means for coupling said logic circuit means control pulse-type signal to a control input of the integrating means circuit to control the latter circuit means.

Claim 6

A volume meter as claimed in claim 4 wherein said dividing means comprises sample and hold circuit means having an adjustable amplification, and means connecting the input of said sample and hold circuit means to the output of the integrating circuit means.

Claim 9

Apparatus for monitoring blood flow comprising, input means adapted to receive a signal proportional to the aorta blood pressure, means responsive to said blood pressure signal for deriving first and second signals indicative respectively of the time at which the aorta blood pressure corresponds to the end diastolic aorta pressure and the time said blood pressure corresponds to the incision, means responsive to said blood pressure signal for deriving a third signal indicative of the end diastolic aorta pressure, integration means having first and second inputs, a control input and an output, means for applying said blood pressure signal and said third signal to said first and second inputs, respectively, of the integration means, means for coupling said integration means control input to the means for deriving said first and second signals, said integration means including means responsive to the signal at the control input for integrating the difference between the signals at its first and second inputs during the time interval between the occurrence of said first and second signals, and means for modifying the integration signal at the output of the integration means by an adjustable calibration factor.

Claim 10

Apparatus for monitoring blood flow comprising, input means adapted to receive a signal proportional to the aorta blood pressure, means responsive to said blood pressure signal for deriving first and second signals indicative respectively of the time at which the aorta blood pressure corresponds to the end diastolic aorta pressure and the time said blood pressure corresponds to the incision, means responsive to said blood pressure signal for deriving a third signal indicative of the end diastolic aorta pressure, integration means having first and second inputs, a control input and an output, means for applying said blood pressure signal and said third signal to said first and second inputs, respectively, of the integration means, means for coupling said integration means control input to the means for deriving said first and second signals, said integration means including means responsive to the signal at the control input for integrating the difference between the signals at its first and second inputs during the time interval between the occurrence of said first and second signals, and means for modifying the integration signal at the output of the integration means by an adjustable calibration factor.

Claim 11

Monitoring apparatus as claimed in claim 7 wherein the means for deriving said first and second signals comprises, first and second filter means with their inputs coupled to said input means and their outputs coupled to first and second inputs of logic circuit means, said logic circuit means including means responsive to the signals received from said first and second filter means for deriving a squarewave type signal having a pulse width equal to the time interval corresponding to the time between the occurrence of said first and second signals, and said coupling means couples said squarewave type signal to the control input of the integration means.

Claim 12

Monitoring apparatus as claimed in claim 8 wherein said logic circuit means includes means for deriving an output pulse signal synchronized to the incision time, and the means for deriving said third signal includes a minimum vlaue detector controlled by the logic circuic means output pulse signal.

Claim 13

Monitoring apparatus as claimed in claim 9 wherein said modIfying means comprises sample and hold circuit means with its input coupled to the output of the integration means and a control input coupled to the logic circuit means to receive said synchronized output pulse signal.

Claim 14

Monitoring apparatus as claimed in claim 8 wherein said first filter means includes first and second signal differentiating circuit means in cascade with a peak detector and comparator and said second filter means includes a band-pass filter in cascade with a zero-passage detector.