Abstract:
The present invention is directed to a method and apparatus for obtaining blood pressure measurements employing a user releasable and adjustable blood pressure cuff. In one aspect of the invention, the blood pressure cuff apparatus consists of a first cuff member connected to a mounting surface and rotatable about a first axis of rotation substantially perpendicular to the mounting surface. The first cuff member is connected to a second cuff member that is rotatable about a second axis of rotation that is substantially perpendicular to the first. A blood pressure cuff comprised of a loop adapted to receive the arm of a test subject is connected to the second cuff member. In another aspect of the invention, the elongated flexible band has a first end and a second end. The first end is connected to the second member of the cuff housing, and the second end is connected to a cuff retainer. The cuff retainer is releasibly latchable from the second member so that the elongated flexible band forms a loop to snugly fit the arm of the test subject with a first circumferential length when the cuff retainer is latched. When the cuff retainer is unlatched, the elongated flexible band forms a loop with a second circumferential length, which allows the arm of the test subject to be easily withdrawn.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to blood pressure measurements, and more particularly to a blood pressure cuff that may be easily installed around the arm and released.  
         BACKGROUND OF THE INVENTION  
         [0002]    Hypertension in adults is regarded as a significant health risk since the symptoms of the disease are not apparent to the individual. The presence of the disease in the individual may therefore remain hidden until a catastrophic health event, such as a heart attack, or a stroke occurs. Fortunately, initial diagnosis of the condition is easily accomplished by a simple blood pressure measurement. Consequently, automatic blood pressure monitoring stations have become widely available to the general public that allow blood pressure measurements to be self-administered. An example of one such system is the VITA-STAT™ blood pressure monitoring station manufactured by Spacelabs Medical, Inc. of Redmond, Wash., which is shown in U.S. Pat. No. D-371,844 to Sadritabrizi, et al. Briefly, the VITA-STAT™ station consists of a kiosk, in which a test subject can be accommodated in a sitting position. The test subject then places an upper arm into a blood pressure cuff apparatus that constricts the flow of blood in an artery to obtain blood pressure measurements at systole and diastole. A processor accepts and processes blood pressure signals obtained from the cuff apparatus during the examination, and subsequently displays the processed information to the test subject on a monitoring device.  
           [0003]    A significant difficulty encountered in self-administered blood pressure measurements is the application of the blood pressure cuff to the test subject. The flat, flexible cuff commonly associated with the sphygmomanometer is particularly unsuited for use in automatic blood pressure monitoring stations, since the application of the flexible cuff around the arm of the test subject is difficult to accomplish without assistance. Moreover, once properly positioned, it must be secured into place by hooks, elastic bands, or specialized fasteners such as VELCRO™. As a consequence, a number of automatic cuff devices have been developed for use with automatic blood pressure monitoring stations. An example of a self-installing cuff apparatus is described in U.S. Pat. No. 4,109,646 to Keller, which uses a motor-driven rotating drum to continuously wrap a blood pressure band onto a limb of a test subject that is placed within the drum. Removal of the blood pressure band from the test subject is accomplished by reversing the motor. A similar technique is described in U.S. Pat. No. 4,206,765 to Huber, which uses a motor driven tensioning drum to tension the blood pressure band around the limb of a test subject. A slip clutch is provided to prevent over tensioning of the blood pressure band during the application of the band to the test subject. U.S. Pat. No. 3,935,984 to Lichowsky, et al., uses a mechanical cable wrapped around the blood pressure band to snug the band tightly about the arm of the test subject. Release of the test subject&#39;s arm is similarly accomplished by reversing the direction of the motor.  
           [0004]    A significant shortcoming of these prior art devices is that they rely on a blood pressure band tensioning means that requires a blood pressure band tensioning drive motor and mechanism, which adds to the cost and complexity of the blood pressure monitoring station. Further, since the tensioning means is motor driven, some means must be provided to allow the test subject to release the blood pressure cuff in the event of a power failure, or to protect the test subject from over-tensioning the band due to system malfunctions. The release mechanisms employed in prior art devices have not, in general, adequately addressed these abnormal operating conditions. Additionally, a particular shortcoming present in the prior art devices is that there is no provision for a release mechanism that allows the band tension and the pneumatic pressure in the band to be released simultaneously through a user actuated release.  
           [0005]    The self-installing cuff used with the VITA-STAT™ blood pressure monitoring station mentioned previously does not rely on a motor driven tensioning means to snug the blood pressure band about the arm. Instead, the arm is tightly confined within a fixedly mounted cylindrical housing that retains the inflatable blood pressure band. The use of a cylindrical, non-resilient member to retain the inflatable band also has some drawbacks. A limit on the maximum cylinder diameter exists because the blood pressure band must achieve adequate snugness prior to inflation. Since the cylinder diameter is generally sized according to median estimates of upper arm diameter, some individuals may find that the cylindrical cuff apparatus simply cannot accommodate them. In other cases, some individuals may damage the flexible blood pressure band inside the cylinder by unsuccessfully attempting to insert their upper arms into the cylinder, which may render the blood pressure cuff apparatus unusable, or cause it to yield inaccurate measurements. Still other individuals may misalign the upper arm with the cylindrical housing so that a successful inflation of the blood pressure band is impeded, resulting in an erroneous blood pressure reading. Finally, some individuals may find the insertion of the arm into a closed cylindrical member that subjects the arm to a constriction too psychologically intimidating to use.  
           [0006]    A further drawback present in all prior art cuff devices is that they lack an ergonomic adjustment feature. Typically, automatic blood pressure devices, such as the VITA-STAT™ blood pressure monitoring station, accommodate the test subject in a seated position while undergoing a blood pressure test. Since the orientation of the cuff assembly cannot be adjusted, the test subject must make suitable adjustments in body position to properly align the arm in the cuff assembly prior to inflation of the internal band, and maintain the arm in the aligned position until the blood pressure evaluation is complete. As a consequence, individuals whose bodily dimensions significantly differ from median estimates cannot be accommodated by the blood pressure cuff in a comfortable manner.  
           [0007]    Accordingly, there is a need in the art for a cuff assembly that does not use a motor driven band tensioning devices to tension the band prior to inflation, and that provides a cuff release capability to a greater degree than present in prior art devices. Further, there is also a need in the art for a cuff apparatus that does not rely on a confining cylindrical member to retain the inflatable band. Finally, the cuff assembly should provide an ergonomic adjustment capability that will permit the proper alignment of the blood pressure cuff with the arm to be conveniently attained during a blood pressure measurement, which, at the same time, enhances the comfort of the test subject.  
           [0008]    Other advantages of the invention will become apparent based upon the description of the invention provided below when read with reference to the drawing figures.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention is directed to a method and apparatus for obtaining blood pressure measurements employing a user releasable and adjustable blood pressure cuff. In one aspect of the invention, the blood pressure cuff apparatus consists of a first cuff member connected to a mounting surface and rotatable about a first axis of rotation substantially perpendicular to the mounting surface. The first cuff member is connected to a second cuff member that is rotatable about a second axis of rotation that is substantially perpendicular to the first. A blood pressure cuff comprised of a loop adapted to receive the arm of a test subject is connected to the second cuff member. In another aspect of the invention, the elongated flexible band has a first end and a second end. The first end is connected to the second member of the cuff housing, and the second end is connected to a cuff retainer. The cuff retainer is releasibly latchable from the second member so that the elongated flexible band forms a loop to snugly fit the arm of the test subject with a first circumferential length when the cuff retainer is latched. When the cuff retainer is unlatched, the elongated flexible band forms a loop with a second circumferential length, which allows the arm of the test subject to be easily withdrawn. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a frontal isometric view of one embodiment of the user releasable and adjustable automatic cuff apparatus.  
         [0011]    [0011]FIG. 2 is a frontal isometric view the embodiment of the user releasable and adjustable automatic cuff apparatus shown in FIG. 1 with the release mechanism shown in the open position.  
         [0012]    [0012]FIG. 3 is a rear isometric view the embodiment of the user releasable and adjustable automatic cuff apparatus shown in FIG. 1.  
         [0013]    [0013]FIG. 4 is a rear isometric view the embodiment of the user releasable and adjustable automatic cuff apparatus shown in FIG. 1 with the release mechanism shown in the open position and the inner housing removed to show internal details.  
         [0014]    [0014]FIG. 5 is an isometric view of the embodiment of the user releasable and adjustable automatic cuff apparatus in FIG. 1 shown receiving an upper arm for a blood pressure determination.  
         [0015]    [0015]FIG. 6 is a rear isometric view of an alternative embodiment of the user releasable and adjustable automatic cuff apparatus.  
         [0016]    [0016]FIG. 7 is a frontal isometric view of an alternative embodiment of the user releasable and adjustable automatic cuff apparatus.  
         [0017]    In the drawings, like reference numbers identify similar elements or steps. For ease in identifying the discussion of any particular element, the most significant digit in a reference number refers to the Figure number in which the element is first introduced (e.g., element  24  is first introduced and discussed with respect to FIG. 2). 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    For purposes of the following description, the terms “upper”, “lower”, “front” and “back” and relative terms of similar reference shall refer to the orientation of the invention a shown in FIGS. 1 through 7, except where expressly specified to the contrary. Specific dimensions and other physical characteristics related to different embodiments are not to be considered as limiting unless the claims expressly state otherwise.  
         [0019]    [0019]FIG. 1 illustrates an embodiment of the user releasable and adjustable blood pressure cuff according to the invention. The blood pressure cuff  10  includes an elongated flexible band  11  with inner and outer surface layers. The band  11  also has a plurality of air-impermeable compartments (not shown) between the inner and outer surface layers that can be connected to a pressurization source to allow the band  11  to be inflated prior to a blood pressure measurement. The elongated flexible band  11  is preferably formed of layers of a durable woven fabric such as nylon, and the air impermeable compartments located between the inner and outer layers are preferably retained in position by stitching. Alternatively, other structures could be used to form the band  11 , such as fabricating the band  11  from rubber-impregnated fabrics, or from entirely non-woven resilient materials such as elastomers. The band  11  may also be fabricated as a single structure, with the air impermeable compartments formed within the band.  
         [0020]    Still referring to FIG. 1, the blood pressure cuff  10  further includes an outer housing  13 , and an inner housing  14  that are rotationally connected to allow ergonomic adjustment to the test subject. A swivel plate  15 , which is rotationally connected to the inner housing  14 , provides additional rotational flexibility. The rotational relationship between the outer cuff housing  13 , the inner cuff housing  14  and the swivel plate  15  will subsequently be described in greater detail in connection with other figures. The outer cuff housing  13  is a box like structure having top and bottom sides, and having a back side, which is preferably open. The back side of the outer cuff housing  13  is adapted to receive an inner cuff housing  14 , so that inner cuff housing  14  can be at least partially recessed within the outer cuff housing  13 . The inner cuff housing  14  is similarly a boxlike structure with top and bottom sides, an open front side (not shown) and a back side. When inner cuff housing  14  is recessed within outer cuff housing  13 , an enclosure is formed which contains internal elements of the apparatus, that will be discussed more fully in connection with a subsequent figure.  
         [0021]    With reference now to FIG. 2, a first end of the band  11  is attached to the outer cuff housing  13  by metal retainer strips  23  which are held in place by screws. The other end of the band  11  is similarly attached by metal retainer strips  46  (as best seen in FIG. 4) to the cuff retainer  12 , to form the loop  19 . Although the retainer strips  23  and  46  securely hold the ends of the band to the outer cuff housing  13  and the cuff retainer  12  by clamping means, other means for attaching the band  11  to the outer cuff housing  13  and to the cuff retainer  12  are possible.  
         [0022]    Still referring to FIGS. 1 and 2, the cuff retainer  12  is located on the top side of the outer cuff housing  13  and is held in a position adjoining outer housing  13  by a latching mechanism (not shown). When the cuff retainer  12  is latched to the top side of the outer cuff housing  13 , the loop  19  has a minimum circumferential length so that the band  11  forms a snug fit about the arm of the test subject. As shown in FIG. 2, where the elongated flexible band  11  has been partially cut away, the cuff retainer  12  is free to translate away from the top of the outer cuff housing  13  when the cuff retainer  12  is released. As a result, the circumferential length of the loop  19  increases when the cuff retainer  12  is in the released state, which allows the test subject additional freedom of movement during withdrawal of the limb.  
         [0023]    Referring now to FIGS. 2 and 4, where the cuff retainer  12  is shown in the unlatched state, the cuff retainer is supported by a pair of support rods  22  securely attached to the under side of cuff retainer  12 . The support rods  22  slide through access holes  27  and through linear bearings  40  to restrict the cuff retainer  12  to vertical movement relative to the outer cuff housing  13 . The cuff retainer  12  further includes a release knob  17 , which allows manual release of the cuff retainer  12  from a latched condition when actuated. The release mechanism will be described in more detail in connection with subsequent figures.  
         [0024]    Although the support rods  22  as shown in FIG. 2 are securely attached to the cuff retainer  12 , other support rod configurations are possible. For example, the cuff retainer  12  may be supported by a single support rod, which has a longitudinal surface groove that engages a key in the outer cuff housing  13  to prevent rotation of the cuff retainer  12  relative to the outer cuff housing  13  when the cuff retainer  12  is released. Alternatively, more than two support rods may also be used. Still another configuration may be obtained when the support rods are securely attached to the outer cuff housing, with the cuff retainer  12  sliding along the stationary support rods when the cuff retainer is released.  
         [0025]    Turning now to FIG. 3, the rotational relationship between the outer cuff housing  13  and the inner cuff housing  14  and the swivel plate  15  will now be discussed. With the inner cuff housing  14  recessed into the outer cuff housing  13 , the inner cuff housing  14  and the outer cuff housing  13  are preferably connected by a pair of pivot screws  31  which are inserted through the top and bottom sides of the outer cuff housing  13  to engage threads in adjacent holes in the inner cuff housing  14 . Rotational movement between the outer cuff housing  13  and inner cuff housing  14  about an axis  33  that projects through the centerline of the pivot screws  31  is thus attained. Since the rotational axis  33  is shown at an intermediate position along the length of the outer cuff housing  13 , a clearance bevel  35  is formed in the outer cuff housing  13  to permit rotation of the outer cuff housing  13  about the axis  33 . The back side of the inner cuff housing  14  is connected to swivel base  15  by a screw  32  (not shown). The swivel plate  15  is a thin, flat member with attachment holes  35  to permit secure attachment to a fixed support. An access hole  30  is provided in the swivel base  15  to allow routing of electrical wiring and pneumatic tubing from an external monitoring device (not shown) into the interior of the enclosure formed by the outer cuff housing  13  and inner cuff housing  14 . The screw  32  permits rotational movement of the inner cuff housing  14  relative to the swivel plate  15  about an axis  34 , which is substantially perpendicular to the axis  33 . Accordingly, rotational motion of the blood pressure cuff  10  about the mutually perpendicular axes  33  and  34  provides the blood pressure cuff  10  with an ergonomic adjustment feature that allows the blood pressure cuff  10  to be conveniently adjusted to the test subject&#39;s body position when the upper arm of the test subject is inserted into the loop  19 .  
         [0026]    Although the present embodiment preferably uses pivot screws  31  and a swivel plate  15  to attain rotational movement about the mutually perpendicular axes  33  and  34 , other equally feasible means are available for establishing these rotational relationships. For example, a hinge pin could be substituted for the pivot screws  31  to allow rotation of the outer cuff housing  13  about axis  33 . Rotation of the inner cuff housing about axis  34  may also be obtained when the screw  32  is also used to in mount the blood pressure cuff  10  to a fixed support, thus eliminating the swivel plate  15 .  
         [0027]    Internal components of the blood pressure apparatus  10  will now be described with reference to FIG. 4. In order to view these internal components, FIG. 4 shows the blood pressure apparatus  10  with the inner cuff housing  14  and swivel plate  15  removed, and also shows the cuff retainer  12  in the unlatched state for clarity. FIG. 4 shows pneumatic pressure relief components located within the blood pressure cuff  10  which allow pressurized air contained within the band  11  to be exhausted to the surroundings when the cuff retainer  12  is moved from the latched state to the released state. An electrical switch  26 , located within the housing  39  is connected by a wire  44  to an electrically actuated valve  41 , which is, in turn, connected to a source of electrical energy through wire  46 . When the cuff retainer  12  is moved from the latched state to the released state, the electrical switch  26  located in the housing  39  is moved to a relaxed state, which causes the electrically actuated valve  41  to open. Pressurized air held within the band  11  is thus released from the band  11  through the flexible tube  42 , where it is exhausted to the surroundings through the valve  41 . Actuation of the switch  26  may additionally be used to provide an indication to the monitoring station that the band  11  is snug about the arm of the test subject, and flexible band is ready to be inflated.  
         [0028]    Alternative approaches may be used to release pressurized air within the band  11  when the cuff retainer  12  is unlatched. For example, a mechanical valve which is opened by a mechanical linkage attached to cuff retainer  12  may be substituted for the electrical components described above, thus eliminating the need for a source of electrical energy. Further, where electrical components are used, alternative circuit designs are possible. For example, the electrical switch  26  may be of the normally closed, or normally open type. Similarly, the electrically actuated valve  41  may be in the open state when electrical energy is applied, or when it is removed, depending on the configuration of the electric circuit.  
         [0029]    Still referring to FIG. 4, the latching mechanism will now be described. Attached to cuff retainer  12  is a latching mechanism  45  with a spring-loaded pawl  47 . When the cuff retainer  12  is moved to the latched position (as shown in FIG. 1), the pawl  47  engages an aperture  25  to latch the cuff retainer  12  securely to the outer cuff housing  13 . When the pawl  47  is engaged with the aperture  25 , the latching mechanism  45  is concealed within a recess  24  (best seen in FIG. 2) in the linear bearing assembly  40 . When the latching mechanism  45  is concealed in the recess  24 , the latching mechanism  45  also engages and actuates the electrical switch  26 .  
         [0030]    Alternatives to the mechanical latching mechanism  45  are available, and may be substituted for the mechanical device shown. For example, an electrically actuated latching device, such as a spring-loaded solenoid latch, may replace the mechanical latching mechanism  45 . Still other means, such as pneumatic latching mechanisms, may also be used.  
         [0031]    FIGS.  5 ( a ) and ( b ) illustrate the operation of the blood pressure cuff  10  during a blood pressure measurement. As shown in FIG. 5( a ), an upper arm  50  of a test subject is inserted into the circumferential loop formed by the band  11 , while the remainder of the arm rests on a supporting surface  52 . The cuff retainer  12  is also shown in the released state, with the support rods  22  fully extended from the outer cuff housing  13 . When the cuff retainer  12  is in the released state, the circumferential length of the loop  19  formed by the band  11  is increased by approximately a length  51 , which affords the test subject additional freedom of movement within the loop  19 . In preparation for the blood pressure determination, the test subject may adjust the orientation of the band  11  through manual manipulations about the two independent axes of rotation  33  and  34  to accommodate his body position. Before a measurement can be made, the cuff retainer  12  must be moved to the latched condition, as shown in FIG. 5( b ). At this point, the band  11  is held snugly about the upper arm  50 , and the electrical switch  26  (not shown in FIG. 5) has been actuated by the latching mechanism  45  (also not shown in FIG. 5) causing the electrically actuated valve  41  to close. Upon commencement of the blood pressure measurement, the band  11  is inflated by a pneumatic source, which causes constriction of the blood flow in an artery within the upper arm  50 . When the flow is fully constricted, air is bled from the band  11  at a controlled rate, whereupon systolic and diastolic determinations are made by conventional means. At the conclusion of the measurement, the test subject actuates the release knob  17  to allow the cuff retainer  12  to move to the released state. Since the electrical switch  26  is moved to the deactivated state when the cuff retainer  12  is released, the electrical switch  26  causes the electrically actuated valve  41  (not shown in FIG. 5) to depressurize the band  11 . If it is desired to terminate the blood pressure evaluation prior to completion, the test subject may actuate the release knob  17  at any time to simultaneously release the cuff retainer  12  and depressurize the band  11 .  
         [0032]    [0032]FIG. 6 illustrates an alternative embodiment of the invention. In this embodiment, the cuff retainer  12  is allowed to translate along guide surfaces  51  in a direction  52  when cuff retainer  12  is in the released state in order to permit the test subject to remove his arm. The released state affords the test subject additional freedom of movement by increasing the circumferential length of the loop by a length  53 . As in the previous embodiment, release of the cuff retainer  12  will simultaneously deactivate an electrical switch (not shown in FIG. 6), or other similar means, to depressurize the band  11 .  
         [0033]    [0033]FIG. 7 illustrates still another alternative embodiment of the invention. In this embodiment, the cuff retainer  12  coincides with the top surface of outer cuff housing  13 . Actuation of release knob  17  allows a slidable member  71  to translate along guide surfaces  72  in a direction  73  in order to increase the circumferential length of the loop by a length  74 . As in the previous embodiments, actuation of the release knob  17  will simultaneously deactivate an electrical switch (not shown in FIG. 7), or other similar means, to depressurize the band  11 .  
         [0034]    The above description of illustrated embodiments of the invention is not intended to be exhaustive or to limit the invention to the precise form disclosed. While specific embodiments of, and examples of, the invention are described in the foregoing for illustrative purposes, various equivalent modifications are possible within the scope the invention, as those skilled in the relevant art will recognize. Moreover, the various embodiments described above can be combined to provide further embodiments. Accordingly, the invention is not limited by the disclosure, but instead the scope of the invention is to be determined entirely by the following claims.