Abstract:
The present invention relates to a pressure pulse wave transducer for sensing change of the blood pressure within vivo and for converting it into an electrical signal to detect the arterial pressure pulse wave.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to a radial artery pressure pulse wave transducer for sensing change in the pressure of the blood vessels within in vivo and converting the sensed result into an electrical signal to detect a pressure pulse wave. More particularly, the invention relates to a device for equal pressure distribution at given sensing points using a pneumatic system to improve tightness and simultaneous conversion of force transferred through an air medium into an electrical signal to detect the pressure pulse wave.  
         DESCRIPTION OF THE PRIOR ART  
         [0002]    Blood pressure is measured in order to present objective information of a body to a doctor to determine whether there exist diseases in the organ related with cardiovascular system and deciding an individual constitution A conventional technology of measuring the blood pressure employs a method by which an electronic sensor such as a piezoelectric device, etc., directly contacting with a human&#39;s body to measure change in the pressure within the blood vessel. Further, the measurement method differs from a  3 -point measurement method being used as a pulse examination method in an oriental medicine compared with conventional technology detecting and analyzing a signal at one measuring point. Recently, there has been developed several pulse transducers using the 3-point measurement method. However, the device is not reliable due to mechanical failure which comes from an non-uniform measuring condition at 3-point.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention is contrived to solve the above problems and an object of the present invention is to provide a pressure pulse wave transducer that confirms uniform measuring condition on 3-point for the reliability of measured data by using a pneumatic system that applies an uniform pressure at a given sensing point  
           [0004]    In order to accomplish the above object, a pressure pulse wave transducer for detecting pulse waves at three points of the human&#39;s wrist according to the present invention, is characterized in that it comprises a body having a space into which the wrist can be suitably inserted in a longitudinal direction; three depressing frames that are consecutively isolated on an internal upper side of the human&#39;s wrist in the expanding direction, movably installed up and down and contact with the wrist; a pressure means for uniform pressing of the transducers; three measuring cavities for measurement at each point installed at the end of the three air supply lines and filled with compressed air; measuring cavities into which the air supply lines are inserted, for transferring the pressure pulse wave to the measuring cavity for measurement, wherein the contactor is attached to the outside of the measuring cavity for interconnection with measuring point above radial artery of the wrist; three fine differential pressure sensors connected respectively to ports at one end of the measuring cavities for measurement; a reference cavity is connected to the fine differential pressure sensors, for applying a reference pressure to the fine differential pressure sensors, wherein the reference cavity maintains constant pressure; for detecting tiny pressure change inside the measuring cavity, which represents the blood pressure pulse wave, the differential pressure sensor detects the difference of pressure inside measuring cavity with that of reference cavity. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    The aforementioned aspects and other features of the present invention will be explained in the following description, taken in conjunction with the accompanying drawings, wherein:  
         [0006]    [0006]FIG. 1 is a construction of the entire system of a pressure pulse wave transducer according to the present invention;  
         [0007]    [0007]FIG. 2 is a longitudinal cross-sectional view of the pressure pulse wave transducer according to the present invention;  
         [0008]    [0008]FIG. 3 is a horizontal cross-section of the pressure pulse wave transducer,  
         [0009]    [0009]FIG. 4 is a perspective view of an radial artery resulting from a depressing by the pressure inside of the measuring cavity applied to the present invention and its result; and  
         [0010]    [0010]FIG. 5 is a construction of a pressure controller for providing a compressed air according to the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0011]    The present invention will be described in detail by way of a preferred embodiment with reference to accompanying drawings.  
         [0012]    [0012]FIG. 1 is a construction of the entire system of a radial artery pressure pulse wave transducer according to the present invention; FIG. 2 is a longitudinal cross-sectional view of the pressure pulse wave transducer according to the present invention; and FIG. 3 is a horizontal cross-section of the radial artery pressure pulse wave transducer.  
         [0013]    As shown in FIG. 1-FIG. 3, a reference numeral  50  indicates a measurement device body.  
         [0014]    The body  50  has a wrist insertion space  51  into which a wrist  10  is sufficiently inserted in a longitudinal direction, as shown in FIG. 3.  
         [0015]    Three depressing frames  61 ,  62  and  63  are continuously isolated in a longitudinal direction on an internal top of the body  50 . The depressing frames  61 ,  62  and  63  are installed movably up and down and further contact with the skin  12  of the wrist  10 . The depressing frames  61 ,  62  and  63  function to press the skin around the radial artery  11  with a uniform and constant pressure at 3-point based on Pascal&#39;s theory.  
         [0016]    In the present embodiment, the depressing cavities for uniform pressure distribution  71 ,  72  and  73 , are each positioned at an upper side of each of the depressing frames  61 ,  62  and  63  and a lower side of the body  50 . The depressing cavities for uniform pressure distribution  71 ,  72  and  73  communicate via a single air supply line  74 , as shown in FIGS. 2 and 4. Further, the depressing cavities for uniform pressure distribution  71 ,  72  and  73  have same pressure that is set by an air compressor  80  in FIG. 5, which is connected to the air supply line  74 . At this time, it is preferred that the depressing cavities for uniform pressure distribution  71 ,  72  and  73  are made of a thin material having the resilient property.  
         [0017]    A several measuring cavities for measurement  91 ,  92  and  93  within which at first, maintains pressure set by controller and after then are isolated from external supplies by closing the solenoid valves  141 , 142 , 143  during measurement are installed within the plurality of the depressing frames  61 ,  62  and  63 , respectively. Contactors  101 ,  102  and  103  are attached to a bottom of each of the measuring cavities for measurement  91 ,  92  and  93 . At this time, it is preferred that the measuring cavities for measurement  91 ,  92  and  93  are made of a thin and flexible membrane to satisfy the Principle of Tonometry.  
         [0018]    The contactors  101 ,  102  and  103  are located on the radial artery  11  and serve to transfer the force of pulse from the radial artery  11  to the measuring cavities for measurement  91 ,  92  and  93 .  
         [0019]    Therefore, it is preferred that the contactors  101 ,  102  and  103  are made of a very light material considering the high-speed response requirement for measurement. Further, the cross sectional area of the contactors  101 ,  102  and  103  are same.  
         [0020]    The measuring cavities for measurement  91 ,  92  and  93  is connected to ports at one side of fine differential pressure sensors  111 ,  112  and  113  having a high resolution capability, for detecting pressure change varied within the measuring cavities for measurement  91 ,  92  and  93 . Further, a reference cavity  120  having the resilient force of a thin film to apply and maintain a reference pressure, and is connected to ports at the other sides of the fine differential pressure sensors  111 ,  112  and  113 .  
         [0021]    The air compressor  80  in FIG. 5 supplies compressed air in the measuring cavities for measurement  91 ,  92  and  93  and the reference cavity  120 . In the air compressor  80 , the measuring cavities for measurement  91 ,  92  and  93  are connected to a first air supply line  131  and the reference cavity  120  is connected to a second air supply line  132 .  
         [0022]    Solenoid valves  141 ,  142  and  143  are installed in the first air supply line  131 , in order to open and close the first air supply line  131  to isolate the measuring cavities for measurement  91 ,  92  and  93  from each other and maintain the inside the measuring cavity constant before measurement.  
         [0023]    A solenoid  150  for maintaining the pressure exerted by the air compressor  80  between the differential pressure sensors  111 ,  112  and  113  and the reference cavity  120  is installed in the second air supply line  132 , in order to open/close the second tube.  
         [0024]    Meanwhile, a wrist depressing tube  160  supports the wrist from the bottom within the body  50 , allows the depressing frames  61 ,  62  and  63  to be fixedly supported to the tendon  13  of the wrist and the radius bone (not show), and thus allows the contactors  101 ,  102  and  103  to easily contact the radial artery  11  is installed. The wrist depressing tube  160  is connected to the air compressor  80  and is thus filled with compressed air at set pressure by means of a controller  84 . In other words, a solenoid valve (not shown) is installed at the tube side of the wrist depressing tube  160  and can be opened and closed by the command from controller  84 .  
         [0025]    [0025]FIG. 5 shows a state that the air compressor  80  is controlled by a known PWM (pulse width modulation) control method, in which the pressure within an compressed air storage  81  at the air compressor  80  is feedbacked to the controller  84  by means of a gauge pressure sensor  83  and the opening and closing of the solenoid valve  82  is thus controlled to generate a continuous pressure.  
         [0026]    In other words, the air compressed in the air compressor  80  is stored at the air storage  81  and the amount of air exhausted is then controlled by the duty ratio of a square wave to adjust the opening/closing time of the solenoid valve  82  connected to the air storage  81 .  
         [0027]    An operation of the pressure generator is described below.  
         [0028]    As shown in FIG. 3, the wrist  10  is located at the wrist insertion space  51  of the measurement device body  50 . If the air compressor  80  of FIG. 5 is then driven, the air storage  81  is filled with a compressed air. Then, the compressed air is supplied to the measuring cavities for measurement  91 ,  92  and  93  via the solenoid valves  141 ,  142  and  143  that are open and connected to the first air supply line  131 . At the same time, the compressed air is supplied to the reference cavity  120  via the solenoid valve  150  that is open and connected to the second air supply line  132 .  
         [0029]    At this time, the pressure signal sensed by the gauge pressure sensor  83  in FIG. 5 is applied to the controller  84 . The solenoid valves  141 ,  142 ,  143  and  150  is made open by means of the controller  84  until respective containers reach their set pressures.  
         [0030]    At the same time, compressed air is also supplied to depressing cavities  71 ,  72  and  73  for equal pressure distribution and the wrist depressing tube  160  by the air compressor  80 .  
         [0031]    As such, if the compressed air in the measuring cavities for measurement  91 ,  92  and  93 , the reference cavity  120 , the depressing cavities for equal pressure distribution  71 ,  72  and  73 , and the wrist depressing tube  160  reach the pressure set in the controller  84 , the solenoids  141 ,  142 ,  143  and  150  each connected to the containers are closed.  
         [0032]    Therefore, the pressure on the side of the reference cavity  120  communicates the ports at one side of the fine differential pressure sensors  111 ,  112  and  113  and the pressure on the side of the measuring cavities for measurement  91 ,  92  and  93  applied to the ports at the other side of the fine differential pressure sensors  111 ,  112  and  113  are same. Thus, there is no difference in the pressure in the fine differential pressure sensors  111 ,  112  and  113 .  
         [0033]    Meanwhile, the pressure formed in the depressing cavities for equal pressure distribution  71 ,  72  and  73  serves to constantly press the depressing frames  61 ,  62  and  63  downwardly with a constant force. At the same time, the pneumatics applied to the wrist depressing tube  160  supports the wrist from the bottom.  
         [0034]    Thus, the depressing frames  61 ,  62  and  63  apply a uniform force along the radial artery  11 . At the same time, as the contactors  101 ,  102  and  103  each attached to the measuring cavities for measurement  91 ,  92  and  93  are protruded by some degree from a lower center of the depressing frames  61 ,  62  and  62 , so that they press the radial artery  11  with a given pressure. At this time, the fine differential pressure sensors  111 ,  112  and  113  measure the difference in the pressure that is generated in the reference cavity  120  and the measuring cavities for measurement  91 ,  92  and  93  at three points along the radial artery  11 . The measured difference in the pressure is transferred to the display and data storage unit  200 , which then displays it as a waveform. In other words, according to the present invention, the force of the pulse of the radial artery  11  is transferred to the measuring cavities for measurement  91 ,  92  and  93  via respective contactors  101 ,  102  and  103  located at the three points. The pressure change in the measuring cavity for measurement  91 ,  92  and  93  is detected and compared with pressure inside the reference cavity by the differential pressure sensors  111 ,  112  and  113 .  
         [0035]    Therefore, assuming that each of the area of the contactors  101 ,  102  and  103  is “A”, the pressure within the radial artery  11  is “Pa”, the resultant force transferred to each of the contactors  101 ,  102  and  103  by means of the force exerted by pressure change inside the radial artery  11  is “Fa”, the pressure generated within the measuring cavities for measurement  91 ,  92  and  93  by means of the transfer force Fa is “Pm”, and the longitudinal cross section of the contactors is “A”,  
         [0036]    Fa=Pa×A  
         [0037]    Pm=Fa/A,  
         [0038]    As a result, Pa=Pm.  
         [0039]    In other words, the present invention employs a method by which the pressure Pm is obtained using contactors  101 ,  102  and  103  maintaining constant contact area with both measuring cavity and radial artery based on Principle of Tonometry.  
         [0040]    As such, an example of a graph that is displayed through a pulse measurement device of the present invention is shown at Table 1 below. 
         
         
 
         [0041]    As mentioned above, according to the present invention, the pulse pressure of the radial artery at three points varies the pressure within the measuring cavity for measurement via the contactors, which is then measured by means of the precision differential pressure sensors. Therefore, the present invention has an outstanding advantage that it can increase the resolution of the signal by comparing pressure inside of the measuring cavity with reference cavity maintaining constant pressure.  
         [0042]    Further, the tightness compared to a conventional device in which the wrist directly contacts the piezoelectric device in order to measure the blood pressure can be improved much.  
         [0043]    The present invention has been described with reference to a particular embodiment in connection with a particular application. Those having ordinary skill in the art and access to the teachings of the present invention will recognize additional modifications and applications within the scope thereof.  
         [0044]    It is therefore intended by the appended claims to cover any and all such applications, modifications, and embodiments within the scope of the present invention.