Abstract:
A method for identifying a non-invasive blood pressure cuff type is disclosed herein. The method includes inflating a cuff and obtaining a first pressure measurement in a non-invasive blood pressure system while inflating the cuff. The method also includes obtaining a second pressure measurement in the non-invasive blood pressure system while inflating the cuff and identifying a cuff type based on the first pressure measurement and the second pressure measurement. A corresponding blood pressure monitoring system is also provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The human heart muscle periodically contracts, forcing blood through the arteries. As a result of this pumping action, pressure pulses exist in these arteries and cause them to cyclically change volume. The minimum pressure for these pulses during a cardiac cycle is known as a diastolic pressure and the peak pressure during a cardiac cycle is known as a systolic pressure. A further pressure value, known as a “mean arterial pressure” (MAP), represents the time-weighted average of the blood pressure. The systolic pressure, MAP and diastolic pressure for a patient are useful in monitoring the cardiovascular state of the patient, and in treating disease. 
         [0002]    A conventional method of measuring blood pressure is referred to as oscillometry. Typically, the measurement of blood pressure by oscillometry requires the inflation of a cuff to a pressure level above the patient&#39;s systolic pressure to fully occlude the artery. The blood pressure is then determined by measuring an oscillation amplitude at multiple cuff pressure levels during the deflation of the cuff. 
         [0003]    In order for oscillometry to provide an accurate estimation of the patient&#39;s blood pressure, it is necessary that the cuff be of an appropriate type for the patient whose blood pressure is being estimated. For example a neonatal cuff is typically smaller in size than an adult cuff, and the neonatal cuff may differ from the adult cuff in other design parameters as well. Due to the differences between cuff types, it is common for a non-invasive blood pressure (NIBP) system to have two or more algorithms in order to accommodate the range of cuff types available. For the purposes of this disclosure, the algorithm is defined to include control of the inflation of the cuff, control of the deflation of the cuff, and the calculation of the patient&#39;s blood pressure parameters. 
         [0000]    In conventional systems, a clinician manually inputs the cuff type being used and this input determines the algorithm used to estimate the patient&#39;s blood pressure. The problem is that if the clinician inputs the wrong cuff type, an incorrect algorithm will be used which could result in patient discomfort. For example, if an adult algorithm is used with a neonatal cuff on an infant, the adult algorithm could result in the inflation of the cuff to a pressure higher than what is comfortable for the infant. Additionally, using the wrong algorithm for a particular cuff type may result in a less accurate blood pressure estimation. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification. 
         [0005]    In an embodiment, a method for identifying a non-invasive blood pressure cuff type includes inflating a cuff, and obtaining a first pressure measurement and a second pressure measurement in the non-invasive blood pressure system while inflating the cuff. The method also includes identifying a cuff type based on the first pressure measurement and the second pressure measurement. 
         [0006]    In an embodiment, a method for identifying a non-invasive blood pressure cuff type includes inflating a cuff and obtaining a first plurality of pressure measurements at a first location upstream relative to the cuff while inflating the cuff. The method also includes obtaining a second plurality of pressure measurements at a second location downstream relative to the cuff while inflating the cuff. The method also includes identifying a cuff type based on the first plurality of pressure measurements and the second plurality of pressure measurements. 
         [0007]    In an embodiment, a blood pressure monitoring system includes a cuff and a first section of hose attached to the cuff. The blood pressure monitoring system also includes a first transducer operatively connected to the first section of hose. The first transducer is configured to obtain a first pressure measurement. The blood pressure monitoring system also includes a second section of hose attached to the cuff and a second transducer operatively connected to the second section of hose. The second transducer is configured to obtain a second pressure measurement. The blood pressure monitoring system also includes a controller operatively connected to the first transducer and the second transducer. The controller is configured to identify a cuff type based on the first pressure measurement and the second pressure measurement. 
         [0008]    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 
         [0009]      FIG. 1  is a schematic diagram illustrating a non-invasive blood pressure system in accordance with an embodiment; 
           [0010]      FIG. 2  is a schematic diagram illustrating an adult non-invasive blood pressure system in accordance with an embodiment; 
           [0011]      FIG. 3  is a schematic diagram illustrating a neonatal non-invasive blood pressure system in accordance with an embodiment; 
           [0012]      FIG. 4  is a flow chart illustrating a method of determining cuff type in accordance with an embodiment; and 
           [0013]      FIG. 5  is a graph of pressure differential versus time illustrating exemplary neonatal cuff data and exemplary adult cuff data. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    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. 
         [0015]    Referring to  FIG. 1 , a schematic representation of a non-invasive blood pressure (NIBP) system  10  is shown in accordance with an embodiment. The NIBP system  10  comprises a monitor  12 , a hose system  14  and a cuff  16 . 
         [0016]    The monitor  12  comprises a generally box-shaped plastic housing (not shown) adapted to retain: a source of pressurized gas  18 ; a first transducer  20 ; a second transducer  22 ; a controller  24 ; and a display  26 . The controller  24  is electronically attached to the source of pressurized gas  18 , the first transducer  20 , the second transducer  22 , and the display  26 . The source of pressurized gas  18 , the first transducer  20 , and the second transducer  22  are all pneumatically connected to the hose system  14 , as will be described in detail hereinafter. The controller  24  comprises a first algorithm  28  and a second algorithm  30 , which will both be described in detail hereinafter. The source of pressurized gas  18  may include a check valve (not shown) biased so as to allow pressurized gas to only flow in the direction away from the source of pressurized gas  18 . 
         [0017]    The hose system  14  is connected to the monitor  12  and to the cuff  16 . The hose system  14  comprises a first section of hose  32  and a second section of hose  34 . The first section of hose  32  and the second section of hose  34  pneumatically connect the monitor  12  to the cuff  16 . The first section of hose  32  is pneumatically connected to the source of pressurized gas  18 , the first transducer  20 , and the cuff  16 . The second section of hose  34  is pneumatically connected to the cuff  16  and the second transducer  22 . The first section of hose  32  is located upstream from the second section of hose  34 . For the purposes of this disclosure, the term “upstream” will be defined to include the direction towards the source of pressurized gas  18  and the term “downstream” will be defined to include the direction away from the source of pressurized gas  18 . According to an embodiment, the first section of hose  32  and the second section of hose  34  may be generally parallel to each other. 
         [0018]    The cuff  16  comprises one or more inflatable bladders (not shown) that can be selectively filled with gas from the source of pressurized gas  18 . Although the cuff  16  is depicted around an arm  36  of a patient  38 , it should be appreciated that the cuff  16  could also be disposed around a leg (not shown) or other limb (not shown). The cuff  16  is attached at the downstream end of the first section of hose  32  and to the upstream end of the second section of hose  34 . 
         [0019]    Referring to  FIG. 2 , a schematic representation of an adult NIBP system  40  is shown in accordance with an embodiment. The adult NIBP system  40  is attached to an adult patient  42 . The adult NIBP system  40  comprises a first section of hose  44 , a second section of hose  46 , and an adult cuff  48 . The first section of hose  44  defines a first internal diameter  50  and the second section of hose  46  defines a second internal diameter  52 . The first section of hose  44  and the second section of hose  46  are connected to the adult cuff  48  which is schematically shown around an adult arm  54  of the adult patient  42 . 
         [0020]    Referring to  FIG. 3 , a schematic representation of a neonatal NIBP system  56  is shown in accordance with an embodiment. The neonatal NIBP system  56  is attached to an infant patient  58 . The neonatal NIBP system  56  comprises a first section of hose  60 , a second section of hose  62 , and a neonatal cuff  64 . The first section of hose  60  defines a first internal diameter  66  and the second section of hose  62  defines a second internal diameter  68 . The first section of hose  60  and the second section of hose  62  are connected to the neonatal cuff  64  which is schematically shown around an infant arm  70  of the infant patient  58 . 
         [0021]    Referring now to both  FIG. 2  and  FIG. 3 , the first internal diameter  50  and the second internal diameter  52  of the adult NIBP system  40  are larger than the first internal diameter  66  and the second internal diameter  68  of the neonatal NIBP system  56 . Because the first internal diameter  66  and the second internal diameter  68  are smaller than the first internal diameter  50  and the second internal diameter  52 , they present a greater resistance to the flow of gas from a source of pressurized gas (not shown). By measuring and/or calculating a variable correlated with the resistance to the flow of gas in an NIBP system (not shown), it may be possible to identify the cuff type of the NIBP system. 
         [0022]    Having described the structure of the NIBP systems  40  and  56 , a method  100  will be described hereinafter.  FIG. 4  is a flow chart illustrating the method  100  in accordance with an embodiment. The individual blocks  102 - 112  of the flow chart represent steps that may be performed in accordance with the method  100 . The technical effect of the method  100  is to determine a cuff type of an NIBP system  10  (shown in  FIG. 1 ). The steps  102 - 112  of the method  100  need not be performed in the order shown. 
         [0023]    Referring to  FIGS. 1 and 4 , at step  102 , the cuff  16  is inflated. As part of step  102 , the controller  24  communicates with the source of pressurized gas  18 , causing gas to travel from the source of pressurized gas  18 , through the first section of hose  32  and into the cuff  16 . At step  104 , the first transducer  20  obtains a pressure measurement within the first section of hose  32 . 
         [0024]    At step  106 , the second transducer  22  obtains a pressure measurement within the second section of hose  34 . According to one embodiment, the pressure measurements obtained during steps  104  and  106  are obtained generally simultaneously. The pressure measurements obtained during steps  104  and  106  are transmitted to the controller  24  prior to step  108 . At step  108 , a pressure differential is calculated by the controller  24 . For the purposes of this disclosure, the pressure differential is defined to include a difference between two pressure measurements. For this disclosure, it should be understood that the implementation of the pressure differential could be replaced by the implementation of alternative methods of comparing pressure measurements. One example of an alternative method of comparing pressure measurements would be calculating a ratio of the pressure measurements obtained at the first transducer  20  and the second transducer  22 . In the embodiment schematically represented by method  100 , the pressure differential comprises the difference between the pressure measurement obtained at the first transducer  20  at step  104  and the pressure measurement obtained at the second transducer  22  at step  106 . 
         [0025]    At step  110 , the controller  24  determines if an additional pressure differential calculation is required to identify cuff type. The controller  24  may make this determination by comparing the number of pressure differentials calculated to a previously determined target number of pressure differentials, or the controller may check to see if the cuff type may be determined based on the pressure differential(s) that have already been collected. If an additional pressure differential is required, the method  100  returns to step  102 , where the source of pressurized gas  18  inflates the cuff  16  with additional gas. Steps  102 - 110  may be iterated as many times as necessary. It should be appreciated that iterations of steps  102 - 110  could be implemented so the pressure within the cuff  16  is increased in either a continuous or in a stepwise fashion. If an additional pressure differential is not required at step  110 , the method  100  proceeds to step  112 . 
         [0026]    According to an alternate embodiment, steps  102 - 110  of the method  100  may be replaced by a generally equivalent sequence of steps wherein a pressure differential similar to that of step  108  is calculated based on a first average pressure measurement and a second average pressure measurement. The first average pressure measurement may, for example, comprise an average of two or more pressure measurements iteratively acquired from the first transducer  20 . Similarly, the second average pressure measurement may comprise an average of two or more pressure measurements iteratively acquired from the second transducer  22 . 
         [0027]    At step  112 , the controller  24  analyzes pressure differential data collected as part of steps  102 - 110 . Based on the pressure differential data collected during the initial inflation of the cuff, the controller  24  determines if the cuff  16  is the adult cuff  48  (shown in  FIG. 2 ) or the neonatal cuff  64  (shown in  FIG. 3 ) as described hereinafter with respect to  FIG. 5 . If the cuff  16  is the adult cuff  48 , the controller  24  will implement the first algorithm  28  to estimate the patient&#39;s  38  blood pressure. If the cuff  16  is the neonatal cuff  64 , the controller  24  will implement the second algorithm  30  to estimate the patient&#39;s  38  blood pressure. By positively identifying if the cuff  16  is the adult cuff  48  or the neonatal cuff  64 , the method  100  ensures that the cuff  16  is inflated in a manner that ensures patient comfort while at the same time providing an accurate estimation of the patient&#39;s  38  blood pressure. While this embodiment is used to identify if the cuff  16  is the neonatal cuff  64  or the adult cuff  48 , it should be understood that other embodiments could be used to identify additional cuff types based on the following nonlimiting list of attributes: size, brand, model, and portion of the anatomy the cuff  16  is designed to fit around. 
         [0028]    Referring to  FIG. 5 , a graph representing pressure differential versus time is shown in accordance with an embodiment. Referring now to  FIGS. 2 ,  3 , and  5 , an exemplary neonatal curve  72  shows the behavior of the neonatal cuff  64  and an exemplary adult curve  74  shows the behavior of the adult cuff  48 . As previously described, the first and second sections of hose  60 ,  62  attached to the neonatal cuff  64  are generally smaller in internal diameter than the first and second sections of hose  44 ,  46  attached to the adult cuff  48 . The generally smaller internal diameters of the first and second sections of hose  60 ,  62  present a greater resistance to the flow of gas, resulting in a relatively larger pressure differential during the initial inflation of the neonatal cuff  64  when compared to the pressure differential calculated during the initial inflation of the adult cuff  48 . Additionally, the size and design of the cuff  48 ,  64  may also affect the pressure differentials measured during the initial inflation of the cuff  48 ,  64 . 
         [0029]    Still referring to  FIG. 5 , from times zero until 0.30 seconds, the pressure differential of the neonatal curve  72  ranges from 17 to 24 mm of Hg while the pressure differential of the adult curve  74  ranges from 5 to 7 mm of Hg over the same time period. By analyzing the pressure differentials collected during the initial inflation and comparing the pressure differentials to known values for a given cuff type, it is possible to identify if the cuff  16  (shown in  FIG. 1 ) is the neonatal cuff  64  or the adult cuff  48 . According to an exemplary embodiment, using a pressure differential from within the first two seconds has been observed to be well-suited to identifying cuff type. However, it should be understood by those skilled in the art that the exact period of time from which the pressure differentials are collected and the range of values used to determine the cuff type may vary depending on specifics of the NIBP system  10  (shown in  FIG. 1 ) being used. 
         [0030]    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.