The invention is generally directed at a non-invasive blood pressure measurement system. More particularly, various inventive methods and apparatus disclosed herein relate a detection device for verifying whether an inflatable cuff of the non-invasive blood pressure measurement system is wrapped around a measurement site of a patient and connected to the non-invasive blood pressure measurement system.
High blood pressure is a significant risk factor for heart attack, stroke, kidney disease, and vision loss. It often is referred to as the silent killer because it rarely causes any symptoms until considerable organ damage has occurred. For that reason, obtaining regular, accurate blood pressure readings are important to long-term health. In hospital and ambulatory setting, constant or periodic blood pressure monitoring is essential component of monitoring patient's vital signs.
For many years blood pressure has been measured using an upper arm pressure cuff and auscultation of the brachial artery to identify the appearance and disappearance of Korotkoff sounds. Although the auscultatory method employing mercury sphygmomanometers used to be regarded as the “gold standard” for blood pressure measurement, widespread implementation of the ban in use of mercury sphygmomanometers continues to diminish the role of this technique. When home monitoring was first introduced, most approached relied upon aneroid sphygmomanometers.
Increasingly, automated devices for measuring blood pressure are now used in the clinic, hospitals and by people in their homes. In addition, ambulatory blood pressure measurement devices are available that are programmed to allow blood pressure to be measured repeatedly during the day and night. The standard type of monitor for home or ambulatory use is now an oscillometric device that records pressure from the brachial artery. These have the advantage of being easy to use, because cuff placement is not as critical as with devices that use a Korotkoff sound microphone, and the oscillometric method has in practice been found to be as reliable as the Korotkoff sound method.
Nowadays, automated blood pressure monitoring has rapidly essentially replaced the traditional mercury or aneroid sphygmomanometers and the stethoscope, becoming an essential tool of patient care and home healthcare.
Conventional non-invasive blood pressure (“NIBP”) measurement systems engage the sphygmo-manometric occlusive limb-cuffs that are applied around an extremity of a patient's body, e.g. wrapped around a patient's upper arm. When the NIBP system is used, the blood pressure cuff is placed around a limb of a patient and is inflated to an initial inflation pressure that fully occludes the brachial artery to temporarily prevent blood pressure flow. The cuff is then deflated from the initial inflation pressure and the pressure transducer detects pressure pulses associated with the patient's heartbeat, as blood begins to flow past the pressure cuff. Alternatively, the cuff is inflated slowly until the brachial artery is occluded completely, the pressure transducer detects pressure pulses associated with the patient's heartbeat during inflation and then the cuff is deflated rapidly.
Known NIBP systems support various cuff sizes, from neonatal to extra-large adult cuffs, where the inflation timeout has to be long enough to allow the inflation of the largest supported cuff loosely wrapped around the largest supported limb, because the NIBP system usually does not recognize which size cuff is actually connected. Consequently, the timeout makes it unsuitable for detecting whether or not the cuff is wrapped around a limb for smaller cuffs because a smaller cuff can be inflated to the target pressure faster than the timeout period even though it is not wrapped around a limb.
Not being able to detect whether the cuff is wrapped around a patient's limb (“cuff off” detection) is particularly detrimental to automatic blood pressure monitoring systems capable of programmable measurement sequences, because a clinical staff or a patient may intentionally remove or accidentally dislodge the cuff from the measurement site on the limb or disconnect the cuff from the NIBP monitor without stopping the automatic measurement mode or programmable measurement sequence. As a result, the NIBP system continues to take measurements and may obtain phantom readings due to cuff pressure oscillations caused by stretching of the cuff or movement of the cuff induced by external vibrations, etc.
U.S. Pat. No. 8,808,189B2 discloses a method of detecting the wrapping strength of a cuff that is wrapped around the limb and not detached from it. The detection is made after the pressure-volume relationship according to a change of the cuff pressure detected in the cuff wrapped around the measurement site and, equally, volume change of the cuff detected by the volume detection unit with the change of its pressure whilst it is controlled by pressurization or depressurization by the pressure control unit. However, this approach does not inform whether or not the inflatable cuff is attached to the measurement site of a patient. U.S. Pat. No. 4,669,485A discloses apparatus and related methods for continuous long term non-invasive measurement of the pressure of a pulsatile fluid flowing through a flexible tube, particularly human arterial blood flow, is disclosed. Specifically, the apparatus provides a continuous calibrated pressure measurement by first undertaking a “calibration” phase comprised of determining the pressure at various pre-defined conditions of flow and, in response thereto, ascertaining the values of a plurality of coefficients each of which is associated with a corresponding term in a pre-defined function that characterizes fluid pressure in relation to pulsatile displacement of the wall of the tube; and second, undertaking a “continuous monitoring” phase comprised of determining each subsequently occurring pressure value as the pre-defined function of each corresponding pulsatile wall displacement value, and re-initiating the calibration phase at the expiration of pre-defined time intervals which adaptively change based upon current and prior results.
Generally, it is an object of the present invention to enable cuff-off detection for blood pressure measurement devices. More particularly, in its various embodiments, the invention focuses on a blood pressure measurement system and apparatus capable of detecting improper functioning due to the absence of an inflatable cuff from a patient's measurement site, its improper attachment to the site, or it being disconnected from the blood pressure measurement system.
According to the first aspect of the invention, this object is addressed by a detection device suitable for use in a blood pressure measurement system, wherein said device is coupled to an inflatable cuff attached to a measurement site at a patient's body part. The device is arranged to perform a series of blood pressure measurements, wherein for each measurement of the series, an inflation operation is performed to inflate the cuff. The device includes a determining unit for determining inflation speed-dependent parameter values during inflation operations, and a processor module arranged for receiving the determined inflation speed-dependent parameter values. The processor module is configured to check whether the difference between the cuff inflation parameter value determined during the corresponding inflation operation and the cuff inflation parameter value determined during a preceding inflation operation meets a predetermined criterion. As explained above, it is advantageous to detect whether a cuff is disconnected from a blood pressure measurement system or unattached to the patient's limb to avoid phantom readings during a series of automatic measurements. If the inflation parameter value determined during a preceding inflation operation does not meet a predetermined criterion, the measurements are immediately stopped.
In various embodiments, the corresponding inflation operation and the preceding inflation operation are sequential operations in an automatic measurement series and/or programmable measurement sequences. The “cuff off” detection is particularly important during a series of automatic measurements and programmable measurement sequences.
In various embodiments, the inflation speed-dependent parameter is defined as a period of time required during the inflation operation to bring the pressure of the cuff from the first pressure level to the second pressure level.
In some embodiments, the first pressure level is a pressure of the cuff at the start of the inflation operation. The second pressure level may be any pressure between the first pressure level and the target cuff pressure at the end of the inflation operation. Preferably, the second pressure level is substantially smaller than the target cuff pressure at the end of the inflation operation in order to stop an unnecessary inflation as soon as possible. In many embodiments, the inflation speed-dependent parameter is the first derivative (dP/dt) of the cuff pressure during inflation.
In various embodiments, the device is arranged to stop the inflation process if the difference between the measured inflation speed-dependent parameter and the reference inflation-speed dependent parameter exceeds a predetermined value. All measurements are conducted during the inflation process, which helps to both avoid running the pump for a long time (more than 1 minute) before timeout occurs or deformation of the cuff due to overlong inflation.
According to the second aspect of the invention, the invention focuses on a method for checking whether an inflatable cuff has been disconnected from the device or has been attached to a measurement site of a body part of a patient. The method is performed by a device for using in a blood pressure measurement system, which is coupled to the inflatable cuff attached to a measurement site of a body part of a patient. The device performs a series of blood pressure measurements, whereby for each measurement of the series an inflation operation is performed to inflate the cuff. The method includes the following steps: determining an inflation speed-dependent parameter value during the inflation operation, receiving the inflation speed-dependent parameter values determined, and determining the difference between the cuff inflation parameter value determined during the corresponding inflation operation and the cuff inflation parameter value determined during a preceding inflation operation.
It should be appreciated that all combinations of the previous concepts and the additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive patient matter disclosed herein. In particular, all combinations of the claimed patient matter appearing at the end of this disclosure are contemplated as being part of the inventive patient matter disclosed herein. It should also be appreciated that the terminology explicitly employed herein also appearing in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.
In the drawings, similar reference characters generally refer to the same parts throughout different views. Also, the drawings are not necessarily to scale, with the emphasis instead generally being placed upon illustrating the principles of the invention.
Referring to
The blood pressure cuff 101 is connected by a hose 102 to the housing of system 2 and can be inflated and deflated for occluding the brachial artery of the patient 1 when in the fully inflated condition. As the blood pressure cuff 101 is deflated using deflate valves(s) 104 via an exhaust 110, the arterial occlusion is gradually relieved. The deflation of the blood pressure cuff 101 by the deflate valve(s) 104 is controlled by the central processor module 107 through a control line 111.
A pressure transducer 103 is coupled via the hose 102 to the blood pressure cuff 101 for sensing the pressure within the cuff 101. In accordance with conventional oscillometric techniques, the pressure transducer 103 is used to sense pressure oscillations in the cuff 101 that are generated by pressure changes in the artery under the cuff. The electrical oscillation signals from the pressure transducer 103 are obtained by the central processor module 107, using an analog to digital converter through a connection line 113.
The source of compressed air 106 comprises a pump or gas cylinder filled with compressed air. The compressed air is supplying the pressured air via duct 114 to the inflate valve(s) 105. The operation of the inflate valve(s) 105 or source of pressurized air 106 is controlled by the central processor module 107 through the control line 111. Thus, the inflation and deflation of the blood pressure cuff 101 is controlled by the central processor 107 through the deflate valve(s) 104 and the inflate valve(s) (105) or source of pressurized air 106, respectively.
Furthermore, the verification of whether or not an inflatable cuff is attached to the measurement site of a patient is performed during the inflation process. When performing the verification, the processor 107 checks whether the difference between the cuff inflation parameter value determined during the corresponding inflation operation and the cuff inflation parameter value determined during a preceding inflation operation meets a predetermined criterion. If the predetermined conditions are met, the measurements continue and, if not, the measurements terminate.
Referring again to
The processor 107 receives the inflation speed-dependent parameters and when a blood pressure monitoring system is in the automatic measurement series or programmable measurement series mode, the processor checks the difference between the cuff inflation parameter values determined during corresponding inflation operations in the measurement series. The processor 107 stops the inflation operation if the difference between the inflation speed-dependent parameter of the corresponding and the previous inflation operations exceeds a predetermined criterion.
While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the inventive embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.
It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited. Also, reference numerals appearing in the claims in parentheses pursuant to Rule 6.2(b) of the Patent Cooperation Treaty (“PCT”), are provided merely for convenience and should not be viewed as limiting in any way.
Number | Date | Country | Kind |
---|---|---|---|
15188876.5 | Oct 2015 | EP | regional |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/EP2016/074014 | 10/7/2016 | WO | 00 |