Abstract:
A cuff of a wrist-mount blood pressure monitor capable of oppressing an artery of the wrist securely without having effects of muscle, tendon or bone existing in the wrist area is presented. This cuff  10  of a wrist-mount blood pressure monitor comprises a first air bag  14 A as a first inflatable portion, and a second air bag  16 A as a second inflatable region disposed between the first inflatable portion  14 A and the wrist, being made of a material of a higher stretchability than the material for the first air bag  14 A.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a cuff of a blood pressure monitor for measuring the blood pressure as being mounted on the body of a subject, and more particularly relates to a structure of the cuff of a wrist-mount blood pressure monitor used in a wrist-mount blood pressure monitor for measuring the blood pressure on the wrist.  
           [0003]    2. Description of the Related Art  
           [0004]    Recently, importance of self-control of blood pressure has recognized, and the wrist-mount blood pressure monitor capable of measuring more easily than the brachial type is widely used at home as a household blood pressure monitor. A schematic configuration of a conventional wrist-mount blood pressure monitor  100  is explained by referring to FIG. 12 and FIG. 13. FIG. 12 is a general perspective view showing the appearance of the wrist-mount blood pressure monitor  100 , and FIG. 13 is a block diagram showing an internal structure of the wrist-mount blood pressure monitor  100 . Referring to both diagrams, the wrist-mount blood pressure monitor  100  comprises a main body  101  incorporating a control device for measuring the blood pressure, and a cuff  102  of a wrist-mount blood pressure monitor which the main body  101  is attached.  
           [0005]    A display  103  and a start switch  104  are provided on the outer surface of the main body  101 , and a pressure sensor  105 , a pressurizing pump  106 , an exhaust valve  107 , and a CPU  108  for controlling these devices are provided in its inside.  
           [0006]    The cuff  102  of wrist-mount blood pressure monitor comprises an air bag  109  for collecting the air sent out from the pressurizing pump  106  and oppressing an artery of the wrist, a band  110  having the air bag  109  disposed at its inner side for mounting on the wrist, and a fastener  111  for winding and fixing the band  110  on the wrist.  
           [0007]    Measurement of blood pressure by using the wrist-mount blood pressure monitor  100  having such configuration is explained by referring to FIG. 14 to FIG. 16. In FIG. 14 to FIG. 16, for the sake of convenience, only the cuff  102  of the wrist-mount blood pressure monitor is shown, and the main body  101  is not shown. FIG. 14 is a schematic sectional view of the cuff  102  of the wrist-mount blood pressure monitor along the longitudinal direction before mounting on the wrist, and air is not supplied into the air bag  109  yet. FIG. 15 is a sectional diagram showing a deflated state of the cuff  102  of the wrist-mount blood pressure monitor mounted on the wrist  1 . FIG. 16 is a sectional view showing an inflated state of the cuff  102  of the wrist-mount blood pressure monitor mounted on the wrist  1 .  
           [0008]    The cuff  102  of the wrist-mount blood pressure monitor shown in FIG. 14 is fixed by using the band  110  so that the air bag  109  comes to a position confronting the radial artery  5  and ulnar artery  7  of the wrist  1 . Herein, the principal constituents of the wrist  1  include, as shown in FIG. 15,the radius  2  positioned at the thumb side, the ulna  3  positioned as the little finger side, the deep flexor digital tendon  4   a  and palmar long flexor tendon  4   b  positioned near the radius  2 , the radial artery  5 , the superficial flexor digital tendon  6   a  and ulnar carpal tendon  6   b  positioned near the ulna  3 , and the ulnar artery  7 .  
           [0009]    When the cuff  102  of the wrist-mount blood pressure monitor is completely mounted on the wrist  1 , by supplying air from the pressurizing pump  106  into the air bag  109  as shown in FIG. 16, the radial artery  5  or the ulnar artery  7  (or both) of the wrist  1  is oppressed, and the exhaust valve  107  is released, and in the process of discharging air from the air bag  109 , the pressure in the air bag  109  is measured by the blood pressure sensor  105 , and the blood pressure measurement data is obtained.  
           [0010]    The wrist-mount blood pressure monitor is said to be inferior in precision to the brachial type blood pressure monitor. One of the causes is lack of oppression force on the artery of the wrist. Lack of oppression force on the artery means that the pressure of the vascular inner wall to be measure (hereinafter called vascular inner wall pressure) is smaller as compared with the air bag inner pressure. When the vascular inner wall pressure and air bag inner pressure are equal, by measuring the air bag inner pressure, an accurate vascular inner wall pressure is obtained, so that an accurate blood pressure can be measured.  
           [0011]    However, when the oppression force is insufficient, the air bag inner pressure becomes higher than the vascular inner wall pressure, and the air bag inner pressure is directly measured as the blood pressure, so that a higher blood pressure than the actual pressure is measured. One of the causes of such lack of oppression force is lack of oppression width (hereinafter cuff width) in the wrist by the air bag.  
           [0012]    The guideline of cuff width of brachial type blood pressure monitor is specified by AHA (American Heart Association), but there is no guideline for the cuff width of wrist-mount blood pressure monitor. Accordingly, the definition of cuff width of the brachial type blood pressure monitor (width of specific multiple of diameter of applicable brachial girth) is directly applied to the wrist. At the present, the cuff width of wrist-mount blood pressure monitor is set at about 50 to 60 mm. If the cuff width of the wrist-mount blood pressure monitor is determined according to this definition, lack of oppression force occurs. One of the causes is that the wrist contains many muscles and tendons not existing in the brachium, and the bones are present relatively near the cuticle, and the oppression of artery by the air bag is impeded.  
           [0013]    As shown in a sectional view in FIG. 16, a sufficient air is supplied in the air bag  109 , and the air bag  109  is inflated toward the wrist  1  side. However, due to the presence of the radius  2  and palmar long flexor tendon  4   b , the inflation of the air bag  109  is impeded, and the radial artery  5  is not oppressed sufficiently, and also the inflation of the air bag  109  is impeded by the presence of the superficial flexor digital tendon  6   a  and ulnar carpal tendon  6   b , and the ulnar artery  7  is not sufficiently oppressed.  
           [0014]    If the oppression of artery by the air bag  109  is not impeded at all, as schematically shown in FIG. 17, a specified cuff width W 1  can be obtained by sufficiently inflating the air bag  109 , but in the presence of the radius  2 , palmar long flexor tendon  4   b , and others, as schematically shown in FIG. 18, inflation of the air bag  109  is impeded by the presence of the radius  2 , palmar long flexor tendon  4   b , and others, and hence the cuff width W 2  is insufficient.  
           [0015]    It is hence a primary object of the invention to present a cuff of wrist-mount blood pressure monitor capable of oppressing the artery positioned at the wrist securely without having effects of muscle, tendon and bone existing in the wrist area.  
         SUMMARY OF THE INVENTION  
         [0016]    The cuff of a wrist-mount blood pressure monitor according to the invention comprises an inflatable bag receiving a predetermined amount of a fluid for pressurizing an artery of the wrist, and mounting means for mounting the inflatable bag on the wrist, in which the inflatable bag includes a first inflatable portion, and a second inflatable portion disposed between the first inflatable portion and the wrist, being made of a material having a higher stretchability than the material of the first inflatable portion.  
           [0017]    In this configuration, when a fluid is supplied into the inflatable bag, both the first inflatable portion and second inflatable portion are inflated by the supply of the fluid. Since the second inflatable portion is made of a material having a higher stretchability than the material of the first inflatable portion, a specified pressure to the wrist side is assured by inflation of the first inflatable portion. Moreover, the second inflatable portion is inflated in a state of tight contact with the wrist, the second inflatable portion flexibly intrudes into the tendons and bones, so that the second inflatable portion may intrude into the spaces between a tendon and a tendon, between a tendon and a bone, or between a bone and a bone.  
           [0018]    Accordingly, regardless of the presence of muscle, tendon or bone in the wrist, it is possible to sufficiently apply a pressure to the artery of the wrist since the pressure from the first inflatable portion is applied to the wrist with which the second inflatable portion comes into contact. As a result, insufficient pressurizing force can be improved, so that it is possible to measure the blood pressure with good accuracy even in a wrist-mount blood pressure monitor.  
           [0019]    Owing to these features, as mentioned above, by inflation of the first inflatable portion, a specified pressure to the wrist side is assured, and the second inflatable portion is inflated in a state of tight contact with the wrist, so that the second inflatable portion may flexible intrude into the muscles, tendons and bones.  
           [0020]    Further preferably, the shape of the second inflatable portion at the wrist side is formed of extruding portions and dent portions. By the shape of extruding portions and dent portions, a higher expanding and contracting property may be obtained, and intrusion of the second inflatable portion into the muscles, tendons and tone when inflated can be realized more securely. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    [0021]FIG. 1 is a schematic view of a sectional structure of a cuff  10  of a wrist-mount blood pressure monitor along the longitudinal direction before mounting on the wrist in a preferred embodiment of the invention.  
         [0022]    [0022]FIG. 2 is a sectional view showing the cuff  10  of a wrist-mount blood pressure monitor being mounted on the wrist  1 .  
         [0023]    [0023]FIG. 3 is a sectional view showing a state of pressing the wrist  1  by the cuff  10  of a wrist-mount blood pressure monitor.  
         [0024]    [0024]FIG. 4 is a schematic view showing the principle of oppression of the wrist by using the cuff  10  of a wrist-mount blood pressure monitor.  
         [0025]    [0025]FIG. 5 is a sectional view showing a structure at the time of deflation of first air bag  14 B and second air bag  16 B in embodiment 1.  
         [0026]    [0026]FIG. 6 is a sectional view showing a structure at the time of inflation of first air bag  14 B and second air bag  16 B in embodiment 1.  
         [0027]    [0027]FIG. 7 is a sectional view showing a structure at the time of deflation of first air bag  14 C and second air bag  16 C in embodiment 2.  
         [0028]    [0028]FIG. 8 is a sectional view showing a structure at the time of inflation of first air bag  14 C and second air bag  16 C in embodiment 2.  
         [0029]    [0029]FIG. 9 is a general perspective view (a), a sectional arrow view of X-X (b), and a sectional view in inflated state (c), showing a first undulated shape at the wrist  1  side of the second air bag  16 C.  
         [0030]    [0030]FIG. 10 is a general perspective view showing a second undulated shape at the wrist  1  side of the second air bag  16 C.  
         [0031]    [0031]FIG. 11 is a sectional view when the cuff  10  of a wrist-mount blood pressure monitor is applied in a structure for oppressing only the vicinity of the radial pedicular process.  
         [0032]    [0032]FIG. 12 is a general perspective view showing a structure of conventional wrist-mount blood pressure monitor  100 .  
         [0033]    [0033]FIG. 13 is a block diagram showing an internal structure of conventional wrist-mount blood pressure monitor  100 .  
         [0034]    [0034]FIG. 14 is a sectional structural view of cuff  102  of a wrist-mount blood pressure monitor along the longitudinal direction before mounting on the wrist.  
         [0035]    [0035]FIG. 15 is a sectional view in deflated state showing a state of cuff  102  of a wrist-mount blood pressure monitor mounted on the wrist  1 .  
         [0036]    [0036]FIG. 16 is a sectional view in inflated state showing a state of cuff  102  of a wrist-mount blood pressure monitor mounted on the wrist  1 .  
         [0037]    [0037]FIG. 17 is a schematic diagram showing an ideal state of oppression of the wrist by using the cuff of a wrist-mount blood pressure monitor.  
         [0038]    [0038]FIG. 18 is a schematic diagram showing problems of oppression of the wrist by using the cuff of a wrist-mount blood pressure monitor. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0039]    Referring to the drawings, preferred embodiments of the invention of the cuff of a wrist-mount blood pressure monitor are explained. The basic structure of the wrist-mount blood pressure monitor using the cuff of wrist-mount blood pressure monitor in the embodiments is same as that of the conventional wrist-mount blood pressure monitor  100  explained in FIG. 12, and the detailed description is omitted, and only the features of the structure of the cuff of wrist-mount blood pressure monitor of the invention are explained below.  
         [0040]    First, the structure of the cuff of wrist-mount blood pressure monitor based on the invention and its principle of oppressing the wrist are explained below while referring to FIG. 1 to FIG. 4. FIG. 1 is a schematic view of a sectional structure of a cuff  10  of a wrist-mount blood pressure monitor along the longitudinal direction before mounting on the wrist in a preferred embodiment of the invention, FIG. 2 is a sectional view showing the cuff  10  of a wrist-mount blood pressure monitor being mounted on the wrist  1 , FIG. 3 is a sectional view showing a state of pressing the wrist  1  by the cuff  10  of a wrist-mount blood pressure monitor, and FIG. 4 is a schematic view showing the principle of oppression of the wrist by using the cuff  10  of a wrist-mount blood pressure monitor.  
         [0041]    (Configuration)  
         [0042]    First, referring to FIG. 1, the configuration of the cuff of a wrist-mount blood pressure monitor is explained. This cuff  10  of a wrist-mount blood pressure monitor comprises a first air bag  14 A as a first inflatable portion used for collecting the air sent out from a pressurizing pump and oppressing an artery of the wrist, and a second air bag  16 A as a second inflatable portion disposed between the first air bag  14 A and the wrist, being made of a material of a higher stretchability than the material of the first air bag  14 A. A band  11  is mounting means for mounting the first air bag  14 A and second air bag  16 A on the wrist, and a fastener  15  is used for winding around and fixing the band  11  on the wrist. In FIG. 1, air is not supplied into the air bags yet.  
         [0043]    (Principle of Oppression on Wrist)  
         [0044]    Secondly, the principle of oppression on the wrist by using the cuff  10  of a wrist-mount blood pressure monitor is explained by referring to FIG. 2 to FIG. 4. Referring to FIG. 2, by using the band  11 , the first air bag  14 A and second air bag  16 A are fixed to the positions confronting the radial artery  5  and ulnar artery  7  of the wrist  1 . The constituents of the wrist  1  are same as explained in FIG. 15, and same reference numerals are given and detailed description is omitted.  
         [0045]    Next, referring to FIG. 3, when air is supplied, the first air bag  14 A is inflated toward the wrist  1  side, and further the second air bag  16 A, when air is supplied, is inflated to intrude mainly into the tendons or bones of the wrist  1 .  
         [0046]    Explaining in further detail, by inflation of the second air bag  16 A, the second air bag  16 A intrudes into the radius  2  and palmar long flexor tendon  4   b . As a result, the second air bag  16 A gets into the space between the radius  2  and palmar long flexor tendon  4   b , and the radial artery  5  is sufficiently oppressed by the second air bag  16 A. Also by inflation of the second air bag  16 A, the second air bag  16 A intrudes into the superficial flexor digital tendon  6   a  and ulnar carpal tendon  6   b . As a result, the second air bag  16 A gets into the space between the superficial flexor digital tendon  6   a  and ulnar carpal tendon  6   b , so that the ulnar artery  7  is sufficiently oppressed by the second air bag  16 A.  
         [0047]    As shown in FIG. 4, when air is supplied into the first air bag  14 A and second air bag  16 A, both the first air bag  14 A and second air bag  16 A are inflated by supply of fluid, but since the second air bag  16 A is made of a material of a higher stretchability than the material of the first air bag  14 A, by inflation of the first air bag  14 A, a specified pressure to the wrist  1  side is maintained. In a state in tight contact with the wrist  1 , the second air bag  16 A is inflated, and the second air bag  16 A flexibly intrudes into the tendons or bones, so that the second air bag  16 A gets into the space between the radius  2  and palmar long flexor tendon  4   b , and hence the pressure from the first air bag  14 A is applied to the wrist  1  which is kept in contact with the second air bag  16 A regardless of the presence of the radius  2  and palmar long flexor tendon  4   b  of the wrist  1 . Similarly, the second air bag  16 A gets into the space between the superficial flexor digital tendon  6   a  and ulnar carpal tendon  6   b . As a result, a sufficient cuff width W 3  can be obtained.  
         [0048]    From the viewpoint of intrusion of the air bags into the tendons and bones, the air bags may be made of stretchable materials only. However, in the case of using air bags made of stretchable materials only, sufficient pressure is not applied in the direction for oppressing the wrist, but the air bags are largely inflated in the lateral direction, and the wrist cannot be oppressed sufficiently. Therefore, as mentioned above, it is important to combine the first air bag  14 A as the first inflatable portion, and the second air bag  16 A as the second inflatable portion made of a material of higher stretchability than the first air bag  14 A.  
         [0049]    (Embodiment 1)  
         [0050]    A configuration of exemplary embodiment  1  on the basis of the above principle of oppression is explained by referring to FIG. 5 and FIG. 6. FIG. 5 shows only the air bags of the cuff  10  of wrist-mount blood pressure monitor in a deflated state before supply of air, and FIG. 6 shows an inflated state after supply of air.  
         [0051]    As shown in FIG. 5, the structure comprises a first air bag  14 B as a first inflatable portion, and a second air bag  16 B as a second inflatable portion positioned between the first air bag  14 B and the wrist, being made of a material of a higher stretchability than the material of the first air bag  14 B. A specific material of the first air bag  14 B is vinyl chloride (a film thickness of about 0.3 mm). Other material usable for the first airbag  14 B includes EVA (vinyl acetate; a film thickness of about 0.3 mm), and urethane (a film thickness of about 0.3 mm).  
         [0052]    To encourage inflation to the wrist side, a taper is formed of side walls  14   a ,  14   b  (accordion structure). When deflated, the thickness of the first air bag  14 B is about 1.2 mm.  
         [0053]    Specific materials for the second air bag  16 B include thin films of silicone and latex, and the film thickness is about 0.3 mm. Other materials for the second air bag  16 B include silicone and latex.  
         [0054]    In the first air bag  14 B and second air bag  16 B, air feed pipes  14   c ,  16   c  are provided, and a common air feed tube  17  is coupled to equalize the air pressure between the first air bag  14 B and second air bag  16 B.  
         [0055]    In the configuration above, when air is fed into the first air bag  14 B and second air bag  16 B, as shown in FIG. 6, since a taper is formed in the first air bag  14 B, it is inflated mainly in a direction of oppressing the wrist. On the other hand, the second air bag  16 B is inflated in all directions. As a result, as mentioned above, the artery of the wrist can be oppressed sufficiently.  
         [0056]    (Embodiment 2)  
         [0057]    A configuration of exemplary embodiment 2 on the basis of the above principle of oppression is explained by referring to FIG. 7 and FIG. 8. FIG. 7 shows only the air bags in a state before supply of air, and FIG. 8 shows a state after supply of air.  
         [0058]    As shown in FIG. 7, the structure comprises a first air bag  14 C as a first inflatable portion, and a second air bag  16 C as a second inflatable portion positioned between the first air bag  14 C and the wrist, being made of a material of a higher stretchability than the material of the first air bag  14 C. Specific materials and thickness of the first air bag  14   c  are same as in embodiment 1. In structure, similarly, a taper is formed of side walls  14   a ,  14   b  for encouraging inflation to the wrist side. Specific materials for the second air bag  16 C are also same as in embodiment  1 , but the structural feature of this embodiment is that the shape of the second air bag  16 C at the wrist side is an undulated shape  18 .  
         [0059]    By this undulated structure  18 , as shown in FIG. 8, when air is supplied into the first air bag  14 C and second air bag  16 C, a higher stretchability than in embodiment 1 is obtained at the wrist side of the second air bag  16 C, and when inflated, the second air bag  16 C can intrude more securely into the tendons or bones. Or if the required size of the second air bag  16 C in inflated state is same as in embodiment 1, in deflated state, the size of the second air bag  16 C is smaller than in embodiment 1, so that the size of the air bag can be reduced.  
         [0060]    [0060]FIG. 9 and FIG. 10 perspective development views showing the specific shape of the undulated shape  18  at the wrist  1  side of the second air bag  16 C. FIG. 9 shows a first undulated shape  18 A, in which (a) is a general perspective view, (b) is a sectional arrow view of X-X of (a), and (c) is a sectional view in inflated state. FIG. 10 is a general perspective view showing a second undulated shape  18 B at the wrist  1  side of the second air bag  16 C.  
         [0061]    The undulated shape  18 A in FIG. 9( a ) comprises extruding portions  18   a  and dent portions  18   b  disposed alternately like waves along the longitudinal direction (see sectional view in FIG. 9( b )), and in inflated state, as shown in FIG. 9( c ), all parts corresponding to the extruding portions  18   a  and dent portions  18   b  come to the outer side, so as to be inflated largely. The length of the extruding portions  18   a  is about 30 mm, the width is about 7.5 mm, and the height is about 2 mm.  
         [0062]    On the other hand, the undulated shape  18 B shown in FIG. 10 comprises block-shaped extruding portions  18   a  disposed in a matrix, and dent portions  18   b  disposed between the extruding portions  18   a  like a lattice. The size of one extruding portion  18   a  is about 7.5 mm×7.5 mm, and the height is about 2 mm. In the case of this undulated shape  18 B, too, same as in the undulated shape  18 A, when inflated, all parts corresponding to the extruding portions  18   a  and dent portions  18   b  come to the outer side, so as to be inflated largely.  
         [0063]    In embodiments 1 and 2, the first air bags  14 A,  14 B,  14 C, and second air bags  16 A,  16 B,  16 C are provided in order to oppress both the radial artery  5  and ulnar artery  7  of the wrist, but a method of oppressing only the vicinity of the radial pedicular process is proposed by S. Mutsu et al. in “Analysis by finite element method about fitting position and size of cuff for local oppression in measurement of blood pressure by the wrist” (11th fall general meeting of Japan Society of ME). This paper, however shows or, teaches nothing about the technology of using first air bag and second air bag.  
         [0064]    Therefore, the structure of these embodiments can be also applied in a structure for oppressing only the vicinity of the radial pedicular process. FIG. 11 shows the structure of the cuff  10  of a wrist-mount blood pressure monitor being applied for oppressing only the vicinity of the radial pedicular process. In this case, too, by inflation of the first air bag  14 A, a specified pressure to the wrist  1  side is assured, and the second air bag  16 A is inflated in a state of tight contact with the wrist  1 , and the second air bag  16 A intrudes flexibly into the tendons or bones, so that the second air bag  16 A gets into the space between the radius  2  and palmar long flexor tendon  4   b , so that the radial artery  5  can be sufficiently oppressed.  
         [0065]    In the foregoing embodiments, the first air bag and second air bag are composed as independent air bags, but they may be made of a single air bag as far as the region of the first air bag is inflated mainly toward the wrist  1  side when air is supplied and the region of the second air bag is inflated to intrude mainly into the tendons or bones of the wrist  1  when air is supplied.  
         [0066]    In the embodiments, air is used as the fluid, but not limited to air, but other gas having similar properties may be used (for example, oxygen, carbon dioxide, helium). Not limited to gas, water or other liquid may be also used. When liquid is used, an airtight structure must be employed in the fluid passage so as to avoid liquid leak.  
         [0067]    Therefore, the present embodiments are illustrative and not restrictive, since the scope of the invention is defined by the appended claims rather than by the description preceding them, and all changes that fall within metes and bounds of the claims, or equivalence of such metes and bounds thereof are therefore intended to be embraced by the claims.  
         [0068]    According to the cuff of a wrist-mount blood pressure monitor according to the invention, the pressure from the first inflatable portion is applied to the wrist which is kept in contact with the second inflatable portion regardless of the presence of tendons and bones of the wrist, and the artery of the wrist can be oppressed sufficiently. As a result, the problem of lack of oppression force of the artery is eliminated, and the blood pressure can be measured precisely by using a wrist-mount blood pressure monitor.