Apparatus and method for reduction in respiration artifact in pulmonary artery pressure measurement

Claim 1

Apparatus for deriving signals representing the systolic, diastolic and mean pressures of a patient from a signal corresponding to a measured variation in actual pressure, comprising means responsive to said signal for providing signals representing successive maximum pressures, means responsive to said signal for providing signals representing successive minimum pressures, the portion of the signal between successive minimum pressures defining a beat, means responsive to said signal for providing signals representing the mean pressure of each beat, means for deriving a weighting factor for each beat that is a function of the absolute difference between the mean pressure of a current beat and the mean pressure of the adjacent previous beat, recursive means for deriving a weighted value representing the systolic pressure for the current beat equal to the weighted value representing the systolic pressure of the adjacent previous beat plus the difference between the maximum pressures of the current and previous beats divided by the weighting factor, recursive means for deriving a weighted value representing the diastolic pressure for the current beat equal to the weighted value representing the diastolic pressure of the adjacent previous beat plus the difference between the minimum pressures of the current and previous beats divided by the weighting factor, recursive means for deriving a weighted value representing the mean pressure for the current beat equal to the weighted value representing the mean pressure of the adjacent previous beat plus the difference between mean pressues of the current and adjacent previous beats divided by the weighting factor, and means for displaying said weighted values as the systolic, diastolic and mean pressures for the current beat.

Claim 9

A method for determing the systolic, diastolic and mean pressures for each heartbeat, comprising deriving a first signal that varies in amplitude in accordance with blood pressure at a given point in the patient's system, deriving a second signal that successively represents each maximum value of said first signal, deriving a third signal that successively represents each minimum value of said first signal, deriving a fourth signal representing a mean pressures occurring in said first signal between successive values of said third signal, deriving a weighting factor K i equal to F|M i -M i-1 | wherein F is a function, M i is the mean pressure of a given heartbeat, and M i-1 is the mean pressure of the previous heartbeat, recursively deriving a weighted signal SHD i representing the systolic pressure of the given heartbeat which is equal to ##EQU3## wherein S i is the maximum value of the first signal occurring during the given heartbeat; S i-1 is the maximum value of the first signal occurring during the previous heartbeat; and SHD i-1 is the systolic pressure derived for the previous heartbeat, recursively deriving a signal DHD i representing the diastolic pressure of the given heartbeat which is equal to ##EQU4## wherein D i is the minimum value of the first signal occurring during the given heartbeat; D i-1 is the minimum value of the first signal occurring during the previous heartbeat; and DHD i-1 is the diastolic pressure derived for the previous heartbeat, recursively deriving a signal MHD i representing the mean pressure of the given heartbeat which is equal to ##EQU5## wherein M i is the mean pressure of the given heartbeat; M i-1 is the mean pressure of the previous heartbeat; and MHD i-1 is the mean pressure derived for the previous heartbeat, and displaying the values of SHD i, DHD i and MHD i.

Claim 10

A method for determing the systolic, diastolic and mean pressures for each heartbeat, comprising deriving a first signal that varies in amplitude in accordance with blood pressure at a given point in the patient's system, deriving a second signal that successively represents each maximum value of said first signal, deriving a third signal that successively represents each minimum value of said first signal, deriving a fourth signal representing a mean pressures occurring in said first signal between successive values of said third signal, deriving a weighting factor K i equal to F|M i -M i-1 | wherein F is a function, M i is the mean pressure of a given heartbeat, and M i-1 is the mean pressure of the previous heartbeat, recursively deriving a weighted signal SHD i representing the systolic pressure of the given heartbeat which is equal to ##EQU3## wherein S i is the maximum value of the first signal occurring during the given heartbeat; S i-1 is the maximum value of the first signal occurring during the previous heartbeat; and SHD i-1 is the systolic pressure derived for the previous heartbeat, recursively deriving a signal DHD i representing the diastolic pressure of the given heartbeat which is equal to ##EQU4## wherein D i is the minimum value of the first signal occurring during the given heartbeat; D i-1 is the minimum value of the first signal occurring during the previous heartbeat; and DHD i-1 is the diastolic pressure derived for the previous heartbeat, recursively deriving a signal MHD i representing the mean pressure of the given heartbeat which is equal to ##EQU5## wherein M i is the mean pressure of the given heartbeat; M i-1 is the mean pressure of the previous heartbeat; and MHD i-1 is the mean pressure derived for the previous heartbeat, and displaying the values of SHD i, DHD i and MHD i.

Claim 16

A method of deriving a signal representing a selected one of the systolic, diastolic and mean pressures of a patient, comprising deriving an analog signal that varies with the patient's blood pressure at a desired point in his blood circulation system, deriving first signals respectively representing successive maximum values of said analog signal, deriving second signals respectively representing successive minimum values of said analog signal, deriving a third signal respectively representing the mean values of the blood pressure for successive heartbeats, deriving a weighting factor equal to the absolute value of the difference between the value of said third signal for a current heartbeat and the value of said third signal for the adjacent previous heartbeat times a constant, deriving the difference between the value of one of said first, second and third signals for the current heartbeat and its value for the adjacent previous heartbeat, dividing the difference so obtained by the weighting factor, and adding the result of the division to the weighted value of the adjacent previous heartbeat so as to derive the weighted value of said one signal to be displayed for the current heartbeat.

Claim 17

A method of deriving a signal representing a selected one of the systolic, diastolic and mean pressures of a patient, comprising deriving an analog signal that varies with the patient's blood pressure at a desired point in his blood circulation system, deriving first signals respectively representing successive maximum values of said analog signal, deriving second signals respectively representing successive minimum values of said analog signal, deriving a third signal respectively representing the mean values of the blood pressure for successive heartbeats, deriving a weighting factor equal to the absolute value of the difference between the value of said third signal for a current heartbeat and the value of said third signal for the adjacent previous heartbeat times a constant, deriving the difference between the value of one of said first, second and third signals for the current heartbeat and its value for the adjacent previous heartbeat, dividing the difference so obtained by the weighting factor, and adding the result of the division to the weighted value of the adjacent previous heartbeat so as to derive the weighted value of said one signal to be displayed for the current heartbeat.