Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
  • A61B5/021—Measuring pressure in heart or blood vessels
  • A61B5/022—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
  • A61B5/021—Measuring pressure in heart or blood vessels
  • A61B5/022—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
  • A61B5/02233—Occluders specially adapted therefor
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
  • A61B5/021—Measuring pressure in heart or blood vessels
  • A61B5/022—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
  • A61B5/02208—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers using the Korotkoff method
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2560/00—Constructional details of operational features of apparatus; Accessories for medical measuring apparatus
  • A61B2560/02—Operational features
  • A61B2560/0242—Operational features adapted to measure environmental factors, e.g. temperature, pollution
  • A61B2560/0247—Operational features adapted to measure environmental factors, e.g. temperature, pollution for compensation or correction of the measured physiological value
  • A61B2560/0261—Operational features adapted to measure environmental factors, e.g. temperature, pollution for compensation or correction of the measured physiological value using hydrostatic pressure
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
  • A61B5/021—Measuring pressure in heart or blood vessels
  • A61B5/022—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
  • A61B5/02225—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers using the oscillometric method

Definitions

• This invention relates generally to methods and medical apparatuses for non-invasive monitoring of arterial blood pressure, and specifically to the devices and methods that use inflatable cuffs.
• Blood pressure monitoring has rapidly become an accepted and, in many cases, essential aspect of human and veterinary treatment. Blood pressure monitors are now a conventional part of the patient environment in emergency rooms, intensive and critical care units, in the operating theater, and in homes.
• auscultation, oscillometry, tonometry and flowmetry Several well known techniques have been used to non-invasively monitor a subject's arterial blood pressure waveform, namely: auscultation, oscillometry, tonometry and flowmetry.
• the auscultation, oscillometry and flowmetry techniques use a standard inflatable cuff that occludes an artery (for example, the subject's brachial artery).
• the auscultatory technique determines the subject's systolic and diastolic pressures by monitoring certain Korotkoff sounds that occur as the cuff is slowly deflated or inflated.
• the oscillometric technique determines these pressures, as well as the subject's mean pressure, by measuring the small pressure oscillations that occur in the cuff as me cuff is deflated or inflated.
• the flowmetric technique relies on detecting variations in blood flow downstream from the cuff.
• the oscillometric method of measuring blood pressure is currently the most popular method in commercially available automatic systems. This method relies on measuring changes in arterial counter pressure, such as imposed by an inflatable cuff, which is controllably relaxed or inflated. In some cases, the cuff pressure change is continuous, and in others it is incremental.
• a transducer pressure sensor
• processing electronics convert selected parameters of these oscillations as represented by signals produced by the transducer into blood pressure data.
• the mean blood pressure value is the mean of the cuff pressure values that correspond in time to a peak of the envelope of the pressure oscillations.
• Systolic blood pressure is generally estimated as the pressure of a decaying pressure slope prior to the peak of the pressure oscillations envelope, corresponding to a point in time where the amplitude of the envelope is equal to a fraction of the peak amplitude.
• systolic blood pressure is the pressure on the decaying pressure of the cuff prior to the peak of the envelope where the amplitude of the envelope is 0.57 to 0.45 of the peak amplitude.
• diastolic blood pressure is the pressure on the decaying pressure of the cuff after the peak of the envelope that corresponds to a point in time to where the amplitude of the envelope is equal to a different fraction of die peak amplitude.
• diastolic blood pressure may be conventionally estimated as the pressure on the decaying pressure of the cuff after the peak where the amplitude of the envelope is equal to 0.82 to 0.74 of the peak amplitude.
• Other algorithms are also well known in die art.
• the auscultatory method also involves inflation of a cuff placed around a cooperating artery of the patient.
• Systolic pressure is indicated when the Korotkoff sounds disappear as the cuff is inflated above the highest pressures exerted by the heart onto the arterial walls.
• Diastolic pressure is indicated when d e Korotkoff sounds first appear as the cuff pressure is elevated above the atmospheric pressure.
• the auscultatory method can only be used to determine systolic and diastolic pressures, and it does not determine mean pressure.
• an oscillatory signal of sufficient quality must be obtained from the artery.
• the signal quality (for example, as determined by pulse shape distortion and noise level) is greatly influenced by a matching between the inflatable cuff and the patient limb geometry.
• the cuff size should correspond to the length and circumference of the limb.
• a fluid bladder positioned inside the cuff should be wrapped around at least a portion of the limb in such a manner as to fully envelop the arterial path, and to effect a gradual and full compression of the artery when pressure in the bladder reaches the systolic pressure inside the artery.
• the pressure generated by the cuff should not be affected by a gravitational force exerted by die weight of the limb.
• the bladder should not be compressed by any external forces except the fluid pump and the arterial blood pressure.
• the wrist should be elevated approximately at the aorta level, otherwise a hydrostatic pressure of blood will cause additional errors.
• prior art pressurizing cuffs have had the following deficiencies: a need for a manual adjustment of the cuff size to match the limb size, and deleterious effects caused by hydrostatic pressure and the limb weight on the accuracy of die pressure measurement.
• U.S. Patent No. 3,527,204 to Lem which is incorporated by reference herein in its entirety, discloses a dual cuff having a liquid-filled chamber positioned on the top of an air- filled chamber, configured so that the pressure exerted over a patient's limb is developed by applying pressure to both air and liquid.
• a dual-cuff design with side-by-side bladders is described in U.S. Patent No. 3,752,148 to Schmalzbach, which is incorporated by reference herein in its entirety.
• a dual air chamber cuff design with two chambers positioned in layers is disclosed in U.S. Patent No.
• the present invention is directed to a cuff for a sphygmomanometer mat can be used to measure arterial blood pressure from a patient's limb (for example, at a patient's wrist, upper arm or lower arm) while the limb is positioned in a gravitational field.
• the cuff includes interconnected first and second sections, where die first section is configured to position a pressurizing device (for example, an air bladder) against an arterial side of the patient's limb, while the second section is mechanically coupled to a support.
• the pressurizing device is coupled with a pressure sensor for monitoring pressure oscillations in the pressurizing device mat are indicative of an arterial blood pressure.
• the second section and the support are mutually arranged within the gravitational field to direct a vector of the gravitational field in away from the arterial side and toward a rear side of the patient's limb, such that substantially no gravitational force is applied to the pressurizing device.
• the pressurizing device is disposed away from the second section.
• the force generated by the limb within the gravitational field is instead absorbed by the second section and the support.
• the cuff has a variable geometry that allows the patient's limb to be easily inserted and then fixedly gripped so that it may be supported by the second section.
• Fig. 1 provides a perspective view of a sphygmomanometer including a measurement cuff according to the present invention
• Fig. 2 provides a cross-sectional view of the sphygmomanometer of Fig. 1 ;
• FIG. 3 provides a side view of another sphygmomanometer including a measurement cuff according to the present invention
• FIG. 4 provides a front view of the sphygmomanometer of Fig. 3;
• FIG. 5 provides a front view of another sphygmomanometer including a measurement cuff according to the present invention
• FIG. 6 provides a perspective view of a variant to the sphygmomanometer of FIG. 4 including a measurement cuff according to the present invention
• FIG. 7 provides a perspective view of another sphygmomanometer including a measurement cuff according to the present invention.
• Fig. 8 is a cross-sectional view of the sphygmomanometer of Fig. 7;
• FIG. 9 provides a perspective view of another sphygmomanometer including a measurement cuff according to the present invention.
• Fig. 10 a cross-sectional view sphygmomanometer of Fig. 9.
• the present invention relates to non-invasive arterial blood pressure measurement methods using pressurizing cuffs with suitable pressurizing devices (for example, inflatable bladders).
• Pressure inside the bladder may be generated by a compressed fluid.
• the compressed fluid may be selected to be air that is compressed and provided to the bladder by a conventional air pump and released from the bladder by a conventional decompression valve).
• the pressure generated by the bladder is preferably monitored using a pressure sensor coupled to the bladder.
• the oscilloroetric method described above is performed by analyzing oscillations in cuff pressure measurements caused by blood surges passing through a pliant artery that transmit pressure pulses to the bladder.
• the auscultatory method described above is performed by analyzing the characteristics of acoustic waves (Korotkofif sounds) produced inside the compressed artery.
• the method relies on accurate detection of the mechanical oscillations or vibrations of the artery that are of arteries that are transmitted to the bladder.
• oscillations and vibrations may be detected by a corresponding sensor coupled to the bladder.
• One source of error operating when a conventional cuff is wrapped around a patient's wrist and positioned on a tabletop is the weight of the arm and hand. Even small variations in the gravitational force can result in spurious oscillations and vibrations inside the cuff, and thereby contaminate the signals indicating oscillations and vibrations from the arteries. For example, such pressure variations may be caused by the patient motions or external vibrations (generated, for example, when the patient is being transported).
• the present invention relies on a combination of two design features: a decoupling of the inflatable cuff from the support structure, and a cuff geometry that is adjusted for the size and shape of the patient limb.
• a key idea behind the invention is decoupling the gravitational force from the arterial side of the limb, and directing it toward a back side of the cuff mat is adjacent to the rear side of the limb.
• Fig. 1 illustrates a sphygmomanometer according to the present invention that includes a cuff 16 divided into two sections.
• a first section 101 contains a bladder 11, and a second section 102 comprises a back support 10 supported by a stem 4 (see also Fig. 2).
• the cuff 16 is wrapped around a patient's limb 1, and locked in place with a suitable locking device such as a locking tape 13, 14 (for example, a hook and loop fastener such as a VELCRO fastener).
• An inflatable bladder 11 is positioned on the inner side of the cuff 16 (within the boundaries of the first section 101) to face an inner side of a wrist of the patient's limb 1.
• the first section 101 is configured to face the arterial side of the patient's limb.
• the bladder is preferably formed from an elastic material, such as latex, synthetic or natural, or any elastomeric material, such as polyurethane.
• the sphygmomanometer of Fig. 1 further includes an electronic module mat is incorporated inside a base 3, a display 19 and at least one control button 17.
• the back support 10 preferably includes a cushion 12 to comfortably support the patient's limb 1 against the back support 10.
• the bladder 1 1 is inflatable to compress arteries inside the limb I, causing a restriction of the blood flow inside the arteries. The restriction generates arterial oscillations which can be detected by a conventional pressure sensor or accelerometer coupled to the bladder 1 1.
• the back support 10 is attached to a base 3 by a stem 4.
• the base 3 is preferably placed on a platform such as a tabletop.
• two armrests 7, 8 are coupled to the base 3 by corresponding stand-offs 5 and 6.
• the armrests 7, 8 support the patient limb 1 at positions away from the first section 101.
• the armrests 7, 8 relieve die cuff 16 from supporting the full weight of the limb 1 and assist in reducing the effect of the weight of the limb 1 on signal noised generated at the pressurizing device.
• base 3 may contain other components, such as a power supply, other sensors, electronic circuitry, an internal pump, valves, and die like.
• a hose assembly for connecting the bladder 11 to the internal pump, pressure sensors and valves may preferably be hidden inside the base 3 and stem 4.
• a liquid-filled bag 31 as shown in Fig. 2 may preferably be provided at a position between the bladder 11 and limb 1 to improve pressure compliance with the arterial blood flow.
• the sphygmomanometer of Figs. I and 2 may be operated as follows. Initially, as locking tape 13, 14 is unlocked, the first section 101 of the cuff 16 is released from the back plate 10, and the limb 1 (a patient's arm, as illustrated in Fig. 1) is placed on the cushion 12 in a manner such that a wrist 30 faces outwardly to position an inner surface (arterial side) of the limb 1 outwardly such that arteries 22 are positioned away from the cushion 12. The cuff 16 is men wrapped around the limb 1, and the locking tape 13, 14 is secured. In this configuration, the bladder 11 and liquid-filled bag 31 (if provided) face the arteries 22.
• An operator proceeds to press a switch 17, which initiates a measurement cycle of the sphygmomanometer.
• the internal pump pressurizes die bladder 11 to compress the arteries 22 against supporting bones 23 inside the limb 1.
• an axis 21 of the back plate 10 is tilted by an angle a with respect to a vertical direction 20 of the sphygmomanometer.
• the base 3 of the sphygmomanometer is preferably positioned so that the vertical direction 20 is parallel to a gravity vector 24. Because the limb 1 in this configuration is primarily supported by the cushion 12 and back 10, the gravitational force vector 24 is directed toward the support 5, and away from bladder 11 and the arterial side of the limb 1.
• the angle ⁇ should preferably be set between 20° and 60° (see also Fig. 3).
• the bladder 1 1 receives arterial oscillations from the arterial side of the limb 1, and transmits the oscillations to the internal pressure sensor.
• the internal pressure sensor transmits a signal to the electronic circuit, and the electronic circuit translates the signal to determine a pressure inside die bladder 1 1, to compute systolic and diastolic pressure values, and to transmit signals to the display 19 for displaying the systolic and diastolic pressure values.
• the gravity vector 24 is directed away from the bladder 11, distortions in the arterial pressure arising from variations in the weight vector 24 (for example, as would arise from movements by the patient of the limb 1) are reduced.
• the stem 4 may preferably incorporate a pivot and/or spring 18 configured to further absorb variations in the gravity vector 24 due to patient movement of the limb 1 while it supported by armrests 7, 8.
• the stem 4 is configured to tilt die cuff 16 with respect to a horizon 34 to form an angle ⁇ between the horizon 34 and a cuff axis 35.
• a horizontal plane defined by the horizon 34 is perpendicular to the direction of the gravity vector.
• a guide 33 is preferably provided.
• the guide 33 is configured to rest at the base 32 of the patient's thumb, thereby setting a longitudinal position of the cuff 16 relative to the patient's wrist 30. In this manner, the guide 33 positions the cuff 16 consistently, thereby improving repeatability of successive blood pressure measurements.
• a pillow 85 is preferably provided on the base 3 for supporting an elbow S3 of the limb 1 in a comfortable and stable manner.
• Figs. 5 and 6 Alternate configurations for tilting and supporting the limb 1 to relieve the bladder 11 from the gravity vector 24 are illustrated in Figs. 5 and 6. Both configurations employ one or more legs 52 that may be positioned to rest on and against a tabletop 50 to support the sphygmomanorneter and the limb.
• the effect of the gravity vector 24 can be further isolated from the bladder 11 by providing links 54 and a hand rest 55 being attached to second section 102 for further stabilizing the position die wrist 30 of the limb 1 in relation to the cuff 16.
• the links 54 preferably comprise a flexible material (for example, nylon or another suitable plastic) to further absorb variations in the gravity vector 24 due to patient movement of the limb 1.
• an axis 51 of the limb I is tilted with respect to a horizon 34 by an angle ⁇ mat is preferably set between 20 and 45°.
• this positioning helps to keep the level of the cuff 16 approximately at the level of the aorta, and away from tabletop 50 by a distance 56 to safely ensure that the first section 101 and the cuff 16 make no contact with the tabletop 50 during use to negatively affect measurement accuracy.
• an inner part 58 of the limb 1 (artery side) and the bladder 1 1 are accordingly not affected by the weight of the limb 1.
• the cuff 16 In addition to relieving the bladder 11 from effects of the gravity vector 24, the cuff 16 must be sized to provide good compliance in gripping the limb 1. In other words, the limb I should be well-supported by the cuff 16, while at the same time decoupling the weight of the cuff 16 from the bladder 11. Thus, a rear side of the limb I (away from the arteries) should not be mechanically coupled to the bladder 11 , but should be coupled to a weight-supporting part of the cuff. This is illustrated for example in Fig. 7, which illustrates a sphygmomanometer according to another embodiment of the present invention.
• the sphygmomanometer of Fig. 7 contains a base 65 that supports the bladder 11, and is coupled with a retractable belt 60 that is soft and pliant (for example, a rubberized woven fabric).
• the belt 60 may preferably be retractably rolled onto a spool 63 rotatably provided within a holding cylinder 62.
• the spool 63 is preferably spring-loaded to retract the belt 60 within the spool 63 under die control of a grip 67 positioned inside a handle 66.
• the handle 66 serves as a support for the sphygmomanometer, and is in effect a functional equivalent to the support 4 of Figs 1 and 2. During operation, it is held by an operator in order to support the weight of the limb 1 against the belt 60.
• one end of the retractable belt 60 is fixed to a pin 64, while the opposite end is attached to the spool 63 so that the belt 60 is movable in a direction 61 into the cylinder 62 until die retractable belt 60 fully embraces the limb I.
• the operator squeezes the grip 67 which, via links 68, operates the spool 63 to release and allow the retractable belt 60 to expand outwardly from the cylinder 62.
• the limb 1 (for example, beginning with the patient's hand as illustrated in Fig. 7) can be inserted through the expanded retractable belt 60.
• the bladder 11 is deflated and the pressure sensor coupled to the bladder 11 is "zeroed” with respect to atmospheric pressure.
• the operator releases the grip 67, and the spool 63 rotates under spring force to pull the retractable belt 60 in the direction 61 until it tightly encircles the limb 1.
• the spool 63 preferably includes a ratchet or other conventional "one-way” mechanism, causing the tightened belt 60 to become locked such that it can no longer be tightened or expanded without further squeezing the grip 67.
• An air pump preferably provided within the base 65 inflates the bladder 11, and arterial pressure is measured by one of the previously-described, known methods known in art
• the weight of the limb 1 is supported by the back side 2 of the tightened belt 60 and, subsequently, by handle 66, while the arterial side of the arm is exposed only to pressure exerted by the bladder 1 1 and not exerted by the weight of the limb 1.
• the weight of the limb 1 may be further supported by testing the limb 1 on a side of the tabletop 50, or by using one of the supporting structures shown in Figs. 1-6.
• FIG. 9 and 10 An alternative embodiment of the cuff 16 of Figs. 7 and 8 is shown in Figs. 9 and 10.
• retractable belt is replaced by an articulated, three-part jaw including a base 78 and clamps 73, 77 which are rotatably coupled to the base 78 by pivots 75 and 57, respectively.
• the bladder 1 1 is configured so mat it does not protrude beyond open ends of the clamps 73 and 77.
• the clamps 73 and 77 close, they support the limb 1 at lips 74 and 76, respectively, so that the bladder 11 is relieved from supporting the arm's weight once the cuff 16 is rotated counter-clockwise to its position as shown in Figs. 9 and 10.
• the clamps 73 and 77 can be opened by squeezing the grip 67 to move in a direction 80.
• the clamps 73 and 77 open so that the bladder 1 1 may be positioned against the arterial side of the limb 1 in proximity to an interior surface 86 of the base 78.
• the artery 22 can be compressed by the bladder 1 1 against the bone 23.
• the grip 67 is released, the clamps 73, 77 are rotated to close and tightly encircle the limb 1.
• the clamps 73, 77 are preferably provided with conventional spring-return mechanisms.
• an internal pump 81 controlled by an electronic control circuit is housed within an internal cavity 84 of the base 78 of the sphygmomanometer, and inflates the bladder via an inflation tube 83.
• a pressure sensor 82 in communication with the bladder 11 via the inflation tube 83 senses a bladder pressure, and transmits a signal indicating the bladder pressure to the electronic control circuit for processing.
• the electronic control circuit is preferably housed behind a control panel 72 of the sphygmomanometer.
• the control panel 72 preferably includes one or more control buttons 17, 79 for activating the electronic circuit, pump 81, pressure sensor 82 and electronic control circuit.
• the control panel 72 is also preferably equipped with indicator lamps 9 for providing an indication of a current status of the arterial blood pressure measurement.

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• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Cardiology (AREA)
• Vascular Medicine (AREA)
• Engineering & Computer Science (AREA)
• Medical Informatics (AREA)
• Physics & Mathematics (AREA)
• Ophthalmology & Optometry (AREA)
• Biophysics (AREA)
• Pathology (AREA)
• Veterinary Medicine (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Physiology (AREA)
• Molecular Biology (AREA)
• Surgery (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Dentistry (AREA)
• Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)

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Citations (17)

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• 2009
  • 2009-11-11 WO PCT/US2009/063972 patent/WO2011059429A1/en active Application Filing
  • 2009-11-11 MX MX2012005515A patent/MX2012005515A/es not_active Application Discontinuation
  • 2009-11-11 JP JP2012538799A patent/JP2013510642A/ja active Pending
  • 2009-11-11 KR KR1020127015052A patent/KR20120119908A/ko not_active IP Right Cessation
  • 2009-11-11 EP EP09851332.8A patent/EP2498674A4/en not_active Withdrawn
  • 2009-11-11 CN CN2009801624194A patent/CN102665537A/zh active Pending
  • 2009-11-11 CA CA2779602A patent/CA2779602A1/en not_active Abandoned

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