Apparatus and method for non-invasively monitoring a subject's arterial blood pressure

Apparatus for non-invasively monitoring the pressure within a subject's blood vessel, comprising:

• a base having an open cavity;
• a flexible diaphragm extending across the open cavity of the base to define a closed, fluid-filled chamber;
• a coupling device configured to urge the diaphragm into compressive engagement with tissue overlying a subject's blood vessel, to compress the vessel and ensure that pressure variations within the vessel are coupled through the tissue to the diaphragm;
• a fluid volume controller that supplies a fluid to and from the closed chamber in accordance with a modulation signal, such that the flexible diaphragm oscillates about an actual mean position;
• a pressure sensor that senses the pressure of the fluid within the closed chamber and produces a corresponding pressure signal;
• an analyzer, responsive to the pressure signal, for sensing any deviation of the flexible diaphragm's actual position from a prescribed position and to produce a corresponding error signal that is coupled to the fluid volume controller, to cause the volume controller to supply fluid to or from the closed chamber, to move the flexible diaphragm toward the prescribed position;
• a filter that filters the pressure signal to produce a filtered pressure signal indicative of the pressure within the subject's blood vessel.

Apparatus for non-invasively monitoring the pressure within a subject's blood vessel, comprising:

• a base having an open cavity;
• a flexible diaphragm extending across the open cavity of the base to define a fluid-filled chamber;
• a coupling device configured to urge the diaphragm into compressive engagement with tissue overlying a subject's blood vessel, to compress the vessel and ensure that pressure variations within the vessel are coupled through the tissue to the diaphragm;
• a first control system that supplies fluid to and from the fluid-filled chamber such that the portion of the flexible diaphragm overlying the subject's blood vessel has a prescribed position that optimally compresses the blood vessel;
• a second control system that supplies fluid to and from the fluid-filled chamber so as to servo control the position of the flexible diaphragm and maintain the diaphragm in its prescribed position despite pressure variations within the subject's blood vessel;
• and
• a pressure sensor that senses the pressure of the fluid within the fluid-filled chamber and produces a corresponding pressure signal indicative of the pressure within the subject's blood vessel.

An apparatus for non-invasively monitoring the pressure within a subject's blood vessel, comprising:

• a base having an open cavity;
• a flexible diaphragm extending across the open cavity of the base to define a closed, fluid-filled chamber;
• a coupling device configured to urge the diaphragm into compressive engagement with tissue overlying a subject's blood vessel, to compress the vessel and ensure that pressure variations within the vessel are coupled through the tissue to provide a variable force against the diaphragm;
• a fluid volume controller that controllably supplies fluid to and from the closed chamber, to substantially balance the variable force applied to the diaphragm by any pressure variations in the subject's blood vessel;
• a sensor that senses the pressure of the fluid within the closed chamber and produces a corresponding pressure signal indicative of the pressure within the subject's blood vessel;
• and
• a filter that filters the pressure signal to produce a filtered pressure signal indicative of the pressure within the subject's blood vessel;
• wherein the fluid volume controller includes
• a fluid source that applies fluid to and from the closed chamber in accordance with a modulation signal, such that the flexible diaphragm oscillates about an actual position, wherein this oscillation induces a corresponding oscillation in the pressure signal produced by the sensor, and
• an analyzer, responsive to the pressure signal, for sensing any deviation of the flexible diaphragm's actual position from a prescribed position and to produce a corresponding error signal that is coupled to the fluid source, to cause the fluid source to supply fluid to or from the closed chamber to move the diaphragm toward the prescribed position.

An apparatus for non-invasively monitoring the pressure within a subject's blood vessel, comprising:

• a base having an open cavity;
• a flexible diaphragm extending across the open cavity of the base to define a closed, fluid-filled chamber;
• a coupling device configured to urge the diaphragm into compressive engagement with tissue overlying a subject's blood vessel, to compress the vessel and ensure that pressure variations within the vessel are coupled through the tissue to provide a variable force against the diaphragm;
• a fluid volume controller that controllably supplies fluid to and from the closed chamber, to substantially balance the variable force applied to the diaphragm by any pressure variations in the subject's blood vessel, wherein the fluid volume controller is configured to maintain the subject's blood vessel optimally compressed continuously, without the need for separate calibration;
• and
• a sensor that senses the pressure of the fluid within the closed chamber and produces a corresponding pressure signal indicative of the pressure within the subject's blood vessel.

A method for non-invasively monitoring the pressure within a subject's blood vessel, comprising:

• providing a pressure sensor assembly that produces a pressure signal indicative of the pressure applied against it;
• urging the pressure sensor assembly into compressive engagement with tissue overlying a subject's blood vessel, to compress the vessel and ensure that pressure variations within the vessel are coupled through the tissue to the pressure sensor assembly;
• and
• controllably modulating the position of the pressure sensor assembly relative to the subject's blood vessel and monitoring the resulting effect on the pressure signal, to produce a control signal that controllably positions the pressure sensor assembly relative to the subject's blood vessel such that the vessel is compressed by a prescribed amount.