Patent Publication Number: US-2015088010-A1

Title: Blood pressure cuff apparatus and system

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to a blood pressure cuff apparatus configured to minimize cuff migration or slip during a blood pressure measurement. 
     Conventional non-invasive blood pressure (NIBP) monitoring systems generally inflate a pressure cuff above the patient&#39;s systolic pressure and measure oscillations in the cuff as the cuff is deflated. The pressure cuff is wrapped around the patient&#39;s arm and secured thereto with a fastening mechanism such as, for example, a hook and loop fastening mechanism. After wrapping and securing the pressure cuff, a cuff bladder is inflated with air to apply a variable amount of pressure. 
     In order to maximize the precision with which a NIBP monitoring system measures a given patient&#39;s blood pressure, the cuff bladder should be centered over a predetermined target region. One problem is that the pressure cuff and cuff bladder can migrate or slip during the course of the blood pressure measurement. Such motion is particularly common with automated monitoring systems, and with NIBP measurements taken on a tapered limb. As an example, NIBP measurements taken on the upper arm of obese patients or muscular patients, and forearm NIPB measurements are all particularly prone to cuff migration. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification. 
     In an embodiment, a blood pressure cuff includes a sleeve, a cuff bladder retained by the sleeve, and a retention feature secured to the sleeve. The retention feature is adapted to apply a force securing the blood pressure cuff to a patient. 
     In another embodiment, a forearm blood pressure cuff includes an arcuate shaped sleeve, an arcuate shaped cuff bladder retained by the sleeve, and a retention feature secured to the sleeve. The retention feature is adapted to compress as the forearm blood pressure cuff is applied to a patient. This compression is adapted to generate a force securing the forearm blood pressure cuff to the patient and to thereby minimize migration of the forearm blood pressure cuff during a blood pressure measurement. 
     In another embodiment, a system for determining blood pressure includes a blood pressure monitor, and a blood pressure cuff pneumatically coupled with the blood pressure monitor. The blood pressure cuff includes a sleeve, a cuff bladder retained by the sleeve, and a retention feature secured to the sleeve. The retention feature is adapted to passively apply a force securing the blood pressure cuff to a patient and to thereby minimize migration of the blood pressure cuff during a blood pressure measurement. 
     Various other features, objects, and advantages of the invention will be made apparent to those skilled in the art from the accompanying drawings and detailed description thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a non-invasive blood pressure monitoring system attached to a patient in accordance with an embodiment; 
         FIG. 2  is a schematic diagram of a pressure cuff in accordance with an embodiment; 
         FIG. 3  is an isometric diagram of the pressure cuff show in  FIG. 2  in accordance with an embodiment; 
         FIG. 4  is a schematic diagram of a pressure cuff in accordance with another embodiment; and 
         FIG. 5  is a schematic diagram of a pressure cuff in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken as limiting the scope of the invention. 
     Referring to  FIG. 1 , a non-invasive blood pressure (NIBP) monitoring system  10  attached to a patient  12  is schematically shown in accordance with an embodiment. The NIBP monitoring system  10  includes a pressure cuff  14  pneumatically coupled with a NIBP monitor  16  via the flexible tubes  18 ,  20 . The pressure cuff  14  includes a cuff bladder  22  and a retention feature  23 . For purposes of this disclosure, the term bladder should be defined to include an inflatable pocket or chamber. The NIBP monitor  16  includes a pump  24  adapted to inflate the cuff bladder  22 , and one or more valves  26  adapted to deflate the cuff bladder  22 . The NIBP monitor  16  also includes a pressure transducer  30  operable to sense or identify pressure pulses at the portion of the limb to which the pressure cuff  14  is attached. A controller  32  converts the pressure pulse data from the pressure transducer  30  into blood pressure data in a known manner. 
     It is well known to those skilled in the art that optimal NIBP monitoring precision generally requires that cuff bladder  22  remain centered over a predetermined target region of interest, typically an artery. Accordingly, the retention feature  23  is adapted to minimize pressure cuff  14  migration or slip away from the target region of interest during the course of NIBP measurement, and to thereby optimize NIBP monitoring system  10  precision. 
     The NIBP monitor  16  is configured to measure mean arterial pressure (MAP), systolic blood pressure (SYS), and/or diastolic blood pressure (DIA) by inflating the pressure cuff  14  to a supra-systolic pressure level and measuring oscillations under the pressure cuff  14  as the pressure cuff  14  is deflated. For purposes of this disclosure, the term “oscillation” refers to a measurable pressure level pulse produced by a change in volume of an artery under the pressure cuff  14 . 
     Referring to  FIG. 2 , a schematic illustration of the pressure cuff  14  is shown in accordance with an embodiment. Common reference numbers from  FIG. 1  will be used to identify common components. 
     The pressure cuff  14  comprises a flexible, non-distensible sleeve  34  and the cuff bladder  22 . The sleeve  34  is flexible such that it may be conveniently wrapped around a patient&#39;s limb, and non-distensible such that it generally does not expand or swell in response to pressure. According to one embodiment, the sleeve  34  comprises two or more layers that are impermeable to air and are fused together near their peripheral edges in a manner adapted to form the cuff bladder  22 . According to another embodiment, the cuff bladder  22  is a separate component retained by the sleeve  34 . The sleeve  34  is generally rectangular defining a sleeve end  36  and a generally opposite sleeve end  38 . A cuff length L1 is defined between sleeve ends  34  and  36 , and a cuff width W1 is defined in a direction perpendicular thereto. The cuff bladder  22  is also generally rectangular. 
     The sleeve  34  is preferably long enough to be wrapped around a patient&#39;s limb such that the sleeve ends  36 ,  38  overlap each other by an amount necessary to secure the pressure cuff  14 . According to one embodiment, the sleeve  34  comprises complementary hook and loop type fastening portions  40 ,  42  adapted to retain the pressure cuff  14  on the patient. 
     The retention feature  23  is shown in accordance with an embodiment as comprising a rectangular pad  50 . The pad  50  is preferably composed of a compressible material having a memory (e.g., foam or elastomer) such that it generally returns to its original shape after deformation. This material compression applies a retention force adapted to resist migration or slip of the pressure cuff  14  during an NIBP measurement. By minimizing slip, the cuff bladder  22  remains more precisely centered over a target region of interest to thereby optimize measurement precision. 
     The stiffness of the pad  50  may be selected to allow for a measured or selectable retention force when exposed to forces typically encountered during the process of applying the pressure cuff  14  to the target limb. Advantageously, the retention force applied in this manner is passive meaning a user can produce it without any taking additional steps in the process of applying the pressure cuff  14 . In other words, the act of wrapping and securing the pressure cuff  14  in the traditional manner has the added effect of generating the retention force. It should also be appreciated that the pressure cuff  14  with the pad  50  is generally inexpensive to manufacture and assemble. 
     The pad  50  is preferably secured to the sleeve  34  between ends  36 ,  38  at a position away from the cuff bladder  22 ; however other positions can be envisioned. It should be appreciated that NIBP analysis involves the measurement of oscillations under the cuff bladder  22  during deflation, and that anything positioned between the cuff bladder  22  and the patient could interfere with such measurement. Accordingly, by positioning the pad  50  away from the cuff bladder  22 , system interference is minimized. According to an alternate embodiment (not shown), the pad  50  may be positioned on the cuff bladder  22 . For this embodiment, pad  50  composition is preferably selected to minimize pressure measurement interference and may include, for example, open-cell foam. 
     The pad  50  may be oriented to extend in a direction along the cuff width W1 in order to axially align with a target limb when secured thereto; however other orientations can be envisioned. A pad  50  positioned in this manner advantageously applies a generally uniform force across the entire width of the pressure cuff  14  when applied to a patient. A force applied in this manner is well suited to securing the pressure cuff  14  in place and thereby minimizing slip. 
     Referring to  FIG. 3 , an isometric illustration of the pressure cuff  14  is shown in accordance with an embodiment. The depicted embodiment of the pad  50  defines a thickness protruding away from the surface of the sleeve  34 . This thickness may define a semi-cylindrical geometry such that the pad  50  is thickest near its centerline. It should be appreciated that other pad  50  geometries may be envisioned. 
     Referring to  FIG. 4 , a schematic illustration of a pressure cuff  60  is shown in accordance with an embodiment. The pressure cuff  60  comprises a sleeve  62  and a cuff bladder  64 . The sleeve  62  and cuff bladder  64  are similar in composition and operation to the sleeve  34  and cuff bladder  22  (shown in  FIG. 2 ), respectively. The pressure cuff  60  also comprises a retention feature  23  shown in accordance with an embodiment as comprising one or more flexible inserts  66 . 
     The sleeve  62  is generally rectangular defining a sleeve end  68  and a generally opposite sleeve end  70 . A cuff length L2 is defined between sleeve ends  68  and  70 , and a cuff width W2 is defined in a direction perpendicular thereto. The cuff bladder  64  is also generally rectangular. 
     The flexible inserts  66  are preferably composed of a material having a memory (e.g., plastic) such that they generally return to their original shape after deformation. The flexible inserts  66  are preferably elongated members oriented to extend along the cuff length L2 of the pressure cuff  60  such that the flexible inserts  66  elastically deform and coil around a target limb as the pressure cuff  60  is applied to a patient. As the flexible inserts  66  coil, they apply an outward retention force tending to uncoil the pressure cuff  60  thereby effectively tightening the cuff wrap and further securing the pressure cuff  60  to the target limb. This retention force helps minimize migration or slip of the pressure cuff  60  during an NIBP measurement. By minimizing slip, the cuff bladder  64  remains more precisely centered over a target region of interest to thereby optimize measurement precision. 
     The stiffness of the flexible inserts  66  may be selected to allow for a measured or selectable retention force when exposed to forces typically encountered during the process of applying the pressure cuff  60  to the target limb. As described previously with respect to the pad  50  (shown in  FIG. 2 ), the retention force produced by the flexible inserts  66  is passive. It should also be appreciated that the pressure cuff  60  with the flexible inserts  66  is generally inexpensive to manufacture and assemble. 
     According to the depicted embodiment, there are two flexible inserts  66  retained at a position away from the cuff bladder  22  in order to minimize NIBP measurement interference; however other quantities and positions can be envisioned. The two flexible inserts  66  may be disposed such that one is positioned near the top of the non-bladder side of the sleeve  62 , oriented to extend along the length of the cuff bladder  64 . The other flexible insert  66  may be positioned near the bottom of the non-bladder side of the sleeve  62 , oriented to extend along the length of the cuff bladder  64 . In this manner, when the pressure cuff  60  is wrapped around a target limb, the two flexible inserts  66  may apply a securing force at opposing ends of the pressure cuff  60  to retain the cuff bladder  64  therebetween. 
     Referring to  FIG. 5 , a schematic illustration of a pressure cuff  80  is shown in accordance with an embodiment. The pressure cuff  80  comprises a sleeve  82  and a cuff bladder  84 . The sleeve  82  and cuff bladder  84  function similarly to the sleeve  34  and cuff bladder  22  (shown in  FIG. 2 ), but differ in their shape. The pressure cuff  80  also comprises a retention feature  23  shown in accordance with an embodiment as comprising a pad  86 . 
     The sleeve  82  is generally arcuate shaped defining a sleeve end  88  and a generally opposite sleeve end  90 . A cuff length L3 is defined between sleeve ends  88  and  90 , and a cuff width W3 is defined in a direction generally perpendicular thereto. The cuff bladder  84  is also generally arcuate shaped. 
     The arcuate shape of the sleeve  82  forms a generally conical shape when the sleeve ends  88  and  90  are engaged in the manner described hereinabove with respect to the pressure cuff  14  (shown in  FIG. 2 ). This conical shape is intended to conform with and thereby accommodate a patient&#39;s forearm. Applying the pressure cuff  80  to the forearm is particularly advantageous for obese patients and muscular patients for whom more traditional rectangular NIBP cuffs may not fit well. 
     It should be appreciated that the potential for NIBP cuff migration or slip away from the clinically appropriate location is increased for tapered limbs. In other words, a pressure cuff is more likely to slip when applied to a tapered limb such as a patient&#39;s forearm. The pad  86  is therefore particularly well suited for use with forearm cuffs. 
     The pad  86  is similar in composition (e.g., a compressible material having a memory) and operation to the pad  50  (shown in  FIG. 2 ). This material compression applies a retention force adapted to resist migration or slip of the pressure cuff  80  during an NIBP measurement. 
     The stiffness of the pad  86  may be selected to allow for a measured or selectable retention force when exposed to forces typically encountered during the process of applying the pressure cuff  14  to the target limb. As described previously with respect to the pad  50  (shown in  FIG. 2 ), the retention force produced by the pad  86  is passive. It should also be appreciated that the pressure cuff  80  with the pad  86  is generally inexpensive to manufacture and assemble. 
     The pad  86  is preferably secured to the sleeve  82  between ends  88 ,  90  at a position away from the cuff bladder  84  in order to minimize measurement interference. The pad  86  may be oriented to extend in a direction along the width of the sleeve  82  in order to axially align with a patient&#39;s forearm, and to thereby apply a generally uniform force across the entire width W3 of the pressure cuff  80 . 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.