Oscillometric method for determining hemodynamic parameters of the arterial portion of patient's circulatory system and a measuring system for its realization

A method for determining principle hemodynamic parameters of an arterial portion of a circulatory system of a patient using a measuring cuff applied to a major arterial vessel of the patient and a measuring system having a linear conversion characteristic and a flat amplitude-frequency characteristic in a frequency range from approximately 0 to 50 Hz, the method comprising the steps of:

• applying a linearly time-varying pressure to the major arterial vessel with the measuring cuff for a predetermined period of time, the linearly time-varying pressure being in a range from approximately 0 to 300 mm Hg;
• forming a pressure curve representing the linear time-varying pressure applied to the major arterial vessel;
• simultaneously measuring a plurality of amplitude values for a sequence of pulse waves of arterial pressure of the major arterial vessel using the measuring system, the measured amplitude values of the respective pulse waves representing a time-dependent change in a volume of the major arterial vessel and having a flat amplitude-frequency characteristic is a frequency range from approximately 0 to 50 Hz;
• forming an oscillometric curve having a diastolic region and a systolic region based on the measured amplitude values of the sequence of pulse waves;
• determining a plurality of extreme points of the oscillometric curve in the diastolic and systolic regions;
• forming a plurality of lines passing through selected extreme points, the plurality of lines intersecting at points to form a closed contour;
• associating the points at which the plurality of lines intersect with points on the pressure curve;
• determining an absolute value of diastolic arterial pressure of the major arterial vessel based on the measured amplitude values and the associated points on the pressure curve;
• determining an absolute value of a mean dynamic arterial pressure of the major arterial vessel based on the measured amplitude values and the associated points on the pressure curve;
• determining an absolute value of a side systolic arterial pressure of the major arterial vessel based on the measured amplitude values and the associated points on the pressure curve;
• determining an absolute value of a maximum systolic arterial pressure of the major arterial vessel based on the measured amplitude values and the associated points on the pressure curve;
• determining a cross-sectional area of the major arterial vessel in a systolic phase based on the measured amplitude values of the pulse waves and the associated points on the pressure curve;
• and
• determining a cross-sectional area of the major arterial vessel under examination in a diastolic phase based on the measured amplitude values of the pulse waves and the associated points on the pressure curve.

A method for determining principle hemodynamic parameters of an arterial portion of a circulatory system of a patient using a measuring cuff applied to a major arterial vessel of the patient and a measuring system associated with the measuring cuff, the measuring system having a linear conversion characteristic and a flat amplitude-frequency characteristic in a frequency range from approximately 0 to 50 Hz, the method comprising the steps of:

• applying a linearly time-varying pressure to the major arterial vessel with the measuring cuff, the linearly time-varying pressure being in a range approximately from 0 to 300 mm Hg;
• forming a pressure curve representing the linear time-varying pressure applied to the major arterial vessel;
• simultaneously measuring a plurality of amplitude values for a sequence of pulse waves of arterial pressure of the major arterial vessel using the measuring system, the measured amplitude values of the respective pulse waves representing a time-dependent change in a volume of the major arterial vessel and having a flat amplitude-frequency characteristic in a frequency range from approximately 0 to 50 Hz;
• storing the measured amplitude values;
• forming an oscillometric curve having a diastolic region and a systolic region based on the measured amplitude values of the sequence of pulse waves;
• determining a plurality of extreme points of the oscillometric curve in the diastolic and systolic regions;
• determining a plurality of lines passing through selected extreme points, the plurality of lines intersecting at points to form a closed contour;
• associating the points at which the plurality of lines intersect with points on the pressure curve;
• determining an absolute value of diastolic arterial pressure of the major arterial vessel based on the measured amplitude values and the associated points on the pressure curve;
• determining an absolute value of a mean dynamic arterial pressure of the major arterial vessel based on the measured amplitude values and the associated points on the pressure curve;
• determining an absolute value of a side systolic arterial pressure of the major arterial vessel based on the measured amplitude values and the associated points on the pressure curve;
• determining an absolute value of a maximum systolic arterial pressure of the major arterial vessel based on the measured amplitude values and the associated points on the pressure curve;
• and
• subtracting a value of an incremental cross-sectional area of the major arterial vessel in the systolic phase from the total value of the cross-sectional areas of the vessel in the systolic and diastolic phases to obtain the cross-sectional area of the vessel in the diastolic phase.

A measuring system for determining hemodynamic parameters of an arterial portion of a circulatory system of a patient, comprising:

• a pneumatic vessel-constricting pressure cuff which is adapted to be applied to a major arterial vessel of the patient;
• a compression device for generating a pneumatic pressure, the pneumatic pressure generated by the compression device being coupled to the pressure cuff for increasing a pneumatic pressure of the pressure cuff;
• a converter for converting the pneumatic pressure of the pressure cuff to output electrical signals corresponding to a running pneumatic pressure of the pressure cuff and of a pneumatic pressure representing pulse waves of arterial pressure, the converter having a linear conversion characteristic and a flat amplitude-frequency characteristic in a frequency range from approximately 0 to 50 Hz;
• an amplifier for scaling the output electrical signals of the converter, the scaling amplifier having a linear characteristic of conversion and a flat amplitude-frequency characteristic in a frequency range from approximately 0 to 50 Hz;
• a filter for filtering the output electric signal of the converter corresponding to the pulse waves of arterial pulse pressure, the filter having a flat amplitude-frequency characteristic in a frequency range from approximately 0 to 50 Hz, said filter transmitting filtered electrical signals corresponding to volume oscillometric data for said arterial portion derived from the output electric signal;
• and
• a memory for storing the scaled electrical signals corresponding to the running pneumatic pressure of the pressure cuff and the filtered electrical signals corresponding to the volume oscillometric data of the arterial portion of the circulatory system of the patient.

Apparatus for determining a hemodynamic parameter of an arterial portion of the circulatory system of a patient, said apparatus comprising:

• a pressure cuff for applying pressure to a portion of a patient's body and an arterial blood vessel therein responsive to pressurization of said cuff;
• pressurizing apparatus pressurizing said pressure cuff, said pressurizing apparatus being operatively associated with said cuff and varying the pressure applied to said cuff substantially linearly with respect to time;
• a sensor operatively associated with the cuff and generating a pressure signal corresponding to the pressure in said cuff;
• a signal processing system having an input and an output, said input receiving said pressure signal, said signal processing system generating first and second signals and transmitting said first and second signals through said output, said first signal corresponding to the pressure in the cuff, and the second signal corresponding to a volume oscillometric signal for the arterial portion derived from said pressure signal;
• a recording device receiving said first and second signals and recording said signals in a form permitting determination of the amount of pressure applied to the cuff at a point in time identified from the second signal.

Apparatus for determining a hemodynamic parameter of an arterial portion of the circulatory system of a patient, said apparatus comprising:

• a pressure cuff for applying pressure to a portion of a patient's body and an arterial blood vessel therein responsive to pressurization of said cuff;
• pressurizing apparatus pressurizing said pressure cuff, said pressurizing apparatus being operatively associated with said cuff and varying the pressure applied to said cuff substantially linearly with respect to time;
• a sensor operatively associated with the cuff and generating a pressure signal corresponding to the pressure in said cuff;
• a signal processing system receiving said pressure signal and generating first and second signals, and having an output transmitting said first and second signals therefrom, said first signal corresponding to the pressure in the cuff, and the second signal corresponding to a volume oscillometric signal derived from said pressure signal;
• a recording device receiving said first and second signals and recording said signals in a form permitting determination of the amount of pressure applied to the cuff at a point in time identified from the second signal;
• said pressurizing apparatus applying linearly increasing pressure to the cuff;
• and
• said pressurizing apparatus applying said pressure in a range of from approximately 0 mm Hg to a pressure adequate to cause the second signals to have an increase in amplitude relative to the amplitude thereof when the pressurizing apparatus applies pressure to the cuff at approximately the lower limit of said range of pressure.

Apparatus for determining a hemodynamic parameter of an arterial portion of the circulatory system of a patient, said apparatus comprising:

• a pressure cuff for applying pressure to a portion of a patient's body and an arterial blood vessel therein responsive to pressurization of said cuff;
• pressurizing apparatus pressurizing said pressure cuff, said pressurizing apparatus being operatively associated with said cuff and varying the pressure applied to said cuff substantially linearly with respect to time;
• a sensor operatively associated with the cuff and generating a pressure signal corresponding to the pressure in said cuff;
• a signal processing system receiving said pressure signal and generating first and second signals, and having an output transmitting said first and second signals therefrom, said first signal corresponding to the pressure in the cuff, and the second signal corresponding to a volume oscillometric signal derived from said pressure signal;
• a recording device receiving said first and second signals and recording said signals in a form permitting determination of the amount of pressure applied to the cuff at a point in time identified from the volume oscillometric signal;
• and
• said recording device preserving said first and second signals in a form which permits determination of the pressure applied to said cuff approximately at one of the following points in time:
• a) the point in time at which the amplitude of the pulse of the volume oscillometric signal began to increase;
• b) the point in time at which the diastolic minimum of the volume oscillometric signal ceased to decline;
• c) the point in time at which the systolic peaks of the volume oscillometric signal started to decline;
• or
• d) the point in time at which the generally linear rate of decline of the systolic peaks of the volume oscillometric signal changed to a slower linear rate of decline.

A method for determining hemodynamic parameters of a patient's arterial system, said method comprising:

• applying a pressure cuff to said patient;
• applying pressure to said cuff which varies generally linearly with respect to time, said pressure applied being in a range of from about 0 mm Hg to a pressure sufficient to cause said cuff to compress an artery of said patient;
• sensing the pressure in said cuff and generating a pressure signal corresponding to said pressure in said cuff;
• processing said pressure signal, including preparing from said pressure signal a first signal corresponding to the pressure in said cuff at a given point in time and deriving a second signal which corresponds to the oscillometric volume data for said arterial portion at said point in time;
• and
• storing said first and second signals in a form that permits a correlation of a point in time of an event detected from the second signal with the value of the first signal at approximately said point in time.

A method for determining hemodynamic parameters of a patient's arterial system, said method comprising:

• applying a pressure cuff to said patient;
• applying pressure to said cuff which varies generally linearly with respect to time, said pressure applied being in a range of from about 0 mm Hg to a pressure sufficient to cause said cuff to compress an artery of said patient;
• sensing the pressure in said cuff and generating a pressure signal corresponding to said pressure;
• processing said pressure signal, including preparing from said pressure signal a first signal corresponding to the pressure in said cuff at a given point in time and deriving a second signal which represents the value of the oscillometric volume curve at said point in time;
• and
• storing said first and second signals in a form that permits a correlation of an event detected from the second signal with the value of the first at the time of that event;
• and
• determining at least one of the following hemodynamic parameters as the pressure in said cuff at the time of the respective volume oscillometric event:
• a) the diastolic pressure, based on the point in time at which the amplitude of the pulse of the volume oscillometric signal began to increase;
• b) the mean dynamic arterial pressure, based on the point in time at which the diastolic minimum of the volume oscillometric signal ceased to decline;
• c) the side systolic pressure, based on the point in time at which the systolic peaks of the volume oscillometric signal started to decline;
• or
• d) the maximum systolic pressure, based on the point in time at which the generally linear rate of decline of the systolic peaks of the volume oscillometric signal changed to a slower linear rate of decline.