Method for non-invasive blood pressure cuff identification...

Surgery – Diagnostic testing – Cardiovascular

Reexamination Certificate

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Details

C600S492000, C600S494000

Reexamination Certificate

active

06450966

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to the field of non-invasive blood pressure measurement, and more particularly to a method and apparatus for automatically identifying a given one of a predetermined plurality of non-invasive blood pressure cuffs employable in a sphygmomanometric system.
BACKGROUND OF THE INVENTION
The use of automated sphygmomanometers for the measurement of blood pressure typically entails the placement of an inflatable cuff about an arterial vessel of a body appendage, e.g. the upper arm of a patient. The cuff contains an inflatable bladder which is positioned around the appendage and inflated via an air pump. The inflated bladder provides a constricting pressure against the blood inside the artery. The inflation pressure is generally established to be above a patient's systolic pressure and should serve to partially occlude the artery. After inflation, gas may be slowly bled from the inflated cuff to gradually reduce the pressure acting upon the artery. During deflation, pressure perturbations, or oscillometric pulses, generated by the partially-occluded artery may be transmitted through the cuff gas supply line for sensing. The sensed pulses may then be analyzed to allow for calculation of the systolic, diastolic and/or mean arterial pressure(s) of a patient, as well as the heart rate of a patient.
It should be noted that, if the pressure of the inflated cuff significantly exceeds a patient's systolic pressure, blood flow may be unacceptably impeded for purposes of obtaining meaningful measurements. Additionally, high inflation pressures may cause patient discomfort. On the other hand, if the cuff pressure is insufficient, arterial occlusion may be insufficient to yield oscillometric pulses in a pressure range that allows accurate measurements to be taken.
As will be appreciated, the initial inflation pressure desirable for a given patient (e.g. to achieve the desired arterial occlusion) will depend upon the physical attributes of the patient. Specifically, the desired inflation pressure will normally increase with the size of the patient.
The establishment of the desired cuff pressure is closely correlated to the size of a given cuff (e.g. the circumference thereof). It is important to use a cuff which is large enough to distribute the bladder over a relatively large surface area so that the resulting inflation pressure will be largely uniform. Thus, a properly fitted cuff on an adult will be larger than a properly fitted cuff on a child, and a properly fitted cuff on a child will be larger than a properly fitted cuff on a neonate.
In this regard, it is recognized that medical personnel will generally select the cuff size deemed most appropriate for a given patient. It is also recognized that for the given cuff size selected by medical personnel there will be a corresponding inflation pressure, or range of pressures, desirable for achieving the above-noted partial arterial occlusion appropriate for blood pressure measurement.
SUMMARY OF THE INVENTION
In view of the foregoing, a primary objective of the present invention is to provide a method and apparatus that provides for the automatic identification of a given one of a predetermined plurality of non-invasive blood pressure cuffs employed in a given blood pressure measurement procedure. Such identification facilitates selection of a desirable initial inflation pressure to be utilized in the blood pressure measurement procedure.
An additional objective of the present invention is to provide for automatic cuff identification in a manner that does not compromise the flexibility or application of the blood pressure measurement system.
Yet a further objective of the present invention is to provide for automated cuff identification in a manner that is both convenient and reliable.
One or more of the above objectives and additional advantages are realized in the inventive method and apparatus of the present invention that provide for a cuff identification operation prior to a blood pressure measurement procedure. The inventive method includes the steps of inflating, at least partially, an inflatable cuff in a pneumatic circuit by flowing gas thereinto; and deflating, at least partially, the inflatable cuff by passing at least a portion of the gas out of the inflatable cuff. The method further provides for the obtainment, during the deflating step, of at least one gas pressure measurement in the pneumatic circuit. Such gas pressure measurement may then be utilized to identify the inflatable cuff being utilized. Preferably, the gas pressure measurement is obtained downstream of the inflatable cuff.
In conjunction with the inventive method, a first pressure measurement means may be employed in the pneumatic circuit to obtain the downstream pressure measurement(s), and the deflation step may further provide for the passage of the gas through a gas-flow restriction means (e.g. a member having a shaped orifice therethrough) interconnected with the pneumatic circuit upstream from the first pressure measurement means. More particularly, the gas-flow restricting means may be located downstream from the inflatable cuff, and fixedly interconnected therewith. In the later regard, it should be noted that each of a predetermined plurality of inflatable cuffs employable with the present invention may be provided with a corresponding different one of a predetermined plurality of corresponding gas-flow restrictors, wherein each of the restrictors serves to restrict, or resist, gas flow therethrough to a differing, discernable degree, thereby facilitating automatic cuff identification.
In a related aspect of the inventive method, the deflation step may provide for both the passage of the gas through a first gas-flow restriction means that is located in the pneumatic circuit upstream from the first pressure measurement means and downstream from the inflatable cuff (e.g. fixedly interconnected therewith), and the passage of the gas through a second gas-flow restriction means interconnected with the pneumatic circuit downstream of the first pressure measurement means. The deflation step may also provide for the selective opening of a bleed valve located in the pneumatic circuit downstream of the second gas-flow restricting means, e.g., wherein the bleed valve may be controlled to provide for a gradual, linear release of gas from the pneumatic circuit. In the later regard, it should be noted that second gas-flow restricting means may actually comprise a bleed valve that is operable to provide a desired degree of gas-flow resistance when opened, thereby obviating the need for a separate gas-flow restrictor and release valve.
The inventive method may further provide for conducting at least one gas pressure measurement in the pneumatic circuit upstream of the inflatable cuff (e.g. via the use of a second gas pressure measurement means). Such upstream pressure measurement(s) may then be utilized with the downstream pressure measurement(s) to determine a measurement, e.g. a value corresponding with a ratio therebetween. In turn, such ratio value may be utilized in the cuff identification step.
In another aspect of the inventive method, the inflating step may provide for the inflation of a cuff to a degree corresponding with a first predetermined pressure (e.g. as measured by the first pressure measurement means), and the deflating step may provide for cuff deflation to a degree corresponding with at least a second predetermined pressure. The obtainment of downstream pressure measurement(s) may be terminated upon at least one of two conditions. First, the obtaining step may be terminated when the inflatable cuff has deflated to a degree corresponding with the second predetermined pressure. Alternatively, the obtaining step may be terminated when a predetermined amount of time has lapsed after initiation of the deflating step. Preferably, the obtaining step will be terminated upon the earliest of the two above-noted conditions.
In one arrangement, the inventive method provides for the obtainment of a plurali

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