Method and apparatus for calculating blood pressure of an artery

Abstract

The present invention is a method for calculating blood pressure of an artery having a pulse. The method includes applying a varying pressure to the artery. Pressure waveforms are sensed to produce pressure waveform data. Waveform parameters are derived from the sensed pressure waveform data. Blood pressure is then determined using the derived parameters.

1 . An apparatus for non-invasively sensing a pressure pulse waveform in an artery of a patient underlying body tissue, comprising: 
 a pressure transmission medium comprising an active surface for placement upon the body tissue with a first dimension generally parallel to the artery;    a force application body comprising a rigid section and a damping section, the rigid section and the damping section having portions coupled to one another for transferring force from the rigid section to the body tissue to offset forces perpendicular to the artery, and the damping section being disposed adjacent to the pressure transmission medium at least along the first dimension for attenuating forces parallel to the artery, the pressure transmission medium being disposed within the force application body for being urged against the body tissue; and    a pressure transducer having a pressure-sensitive port isolated from the force application body and coupled to the pressure transmission medium.    
   
   
       2 . The apparatus of  claim 1  wherein the active surface has a second dimension generally perpendicular to the artery that is greater than a diameter of the artery.  
   
   
       3 . The apparatus of  claim 1  wherein the damping section comprises a compressible foam material.  
   
   
       4 . The apparatus of  claim 1  wherein: 
 the force application body comprises an expansion cavity; and    the pressure transmission medium comprises a deformable portion for operationally deforming into the expansion cavity upon an operational application of force to the tissue by the force application body.    
   
   
       5 . The apparatus of  claim 1  wherein the force application body comprises a deformable section disposed between the rigid section and the damping section, for conforming to an anatomy of the patient.  
   
   
       6 . The apparatus of  claim 1  wherein for conforming to an anatomy of the patient: 
 the force application body comprises a deformable section disposed between the rigid section and the damping section for operationally deforming upon an operational application of force to the tissue by the force application body; and    the pressure transmission medium comprises a deformable portion for operationally deforming upon an operational application of force to the tissue by the force application body.    
   
   
       7 . The apparatus of  claim 6  wherein: 
 the deformable section of the force application body comprises a chamber having flexible solid walls and containing a fluid; and    the pressure transmission medium comprises a chamber having flexible force-transmitting solid walls and containing a fluid.    
   
   
       8 . The apparatus of  claim 1  wherein: 
 the damping section comprises a compressible foam body; and    the pressure transmission medium is encircled by the foam body.    
   
   
       9 . The apparatus of  claim 8  wherein: 
 the force application body further comprises a chamber partially filled with a fluid and mounted to the rigid section;    the foam body being mounted to the chamber; and    the pressure transmission medium being encircled by the foam body and by the chamber.    
   
   
       10 . The apparatus of  claim 1  wherein: 
 the force application body further comprises an annular chamber partially filled with a fluid and mounted to the rigid section;    the damping section comprises an annular compressible foam body mounted to the chamber; and    the pressure transmission medium comprises a fluid-filled chamber encircled by the annular foam body and by the annular chamber.    
   
   
       11 . The apparatus of  claim 10  wherein: 
 the fluid-filled chamber is operationally deformable; and    the force application body includes an expansion cavity for operationally receiving a portion of the fluid-filled chamber upon deformation thereof.    
   
   
       12 . The apparatus of  claim 11  wherein the fluid-filled chamber comprises: 
 a generally disk-like body comprising a first diaphragm and a second diaphragm bonded along peripheral portions thereof to form the chamber; the first    diaphragm being operationally deformable into the expansion cavity, and the active surface being on the second diaphragm;    the first diaphragm being bonded to the annular foam body.    
   
   
       13 . The apparatus of  claim 12  wherein: 
 the annular foam body has a generally constant width; and    the active surface of the second diaphragm has a diameter that is greater than the width of the annular foam body.    
   
   
       14 . A sensor for sensing blood pressure pulses within an underlying artery surrounded by tissue as the underlying artery is compressed, the sensor comprising: 
 a pressure transducer;    an active area having a dimension greater than a diameter of the artery for compressively contacting tissue over the artery;    a pressure transmission path for transmitting pressure operationally present upon the active area to the pressure transducer; and    a compressible member for compressing tissue over the artery, the compressible member being distinct from the pressure transmission path and the pressure transducer, and at least partially surrounding and in proximity to the pressure transmission path for attenuating forces parallel to the artery.    
   
   
       15 . The sensor of  claim 14  wherein: 
 the compressible member is annular; and    the active area is circular and encircled by the annular compressible member.    
   
   
       16 . The sensor of  claim 15  wherein the annular compressible member comprises a foam material.  
   
   
       17 . The sensor of  claim 14  further comprising: 
 an annular deformable member;    the compressible member being annular and bonded to the annular deformable member; and    the active area being circular and encircled by the annular compressible member and the annular deformable member.    
   
   
       18 . The sensor of  claim 14  wherein: 
 the compressible member comprises a foam material; and    the active area is circular and encircled by the compressible member.    
   
   
       19 . A method for non-invasively sensing a pressure pulse waveform in an artery of a patient at a measurement site through overlying body tissue, comprising: 
 applying pressure to the overlying body tissue at least on both sides of the measurement site along the artery with a compressible material, to neutralize forces exerted by the overlying body tissue and to attenuate forces parallel to the artery;    urging a pressure transmission medium upon the overlying body tissue at the measurement site, the pressure transmission medium being distinct from the compressible material; and    detecting a pressure pulse waveform through the pressure transmission medium.    
   
   
       20 . The method of  claim 19  wherein the pressure applying step further comprises applying pressure to the compressible material through a deformable material.