Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
  • A61B17/12—Surgical instruments, devices or methods, e.g. tourniquets for ligaturing or otherwise compressing tubular parts of the body, e.g. blood vessels, umbilical cord
  • A61B17/132—Tourniquets
  • A61B17/135—Tourniquets inflatable
  • A61B17/1355—Automated control means therefor
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61H—PHYSICAL THERAPY APPARATUS, e.g. DEVICES FOR LOCATING OR STIMULATING REFLEX POINTS IN THE BODY; ARTIFICIAL RESPIRATION; MASSAGE; BATHING DEVICES FOR SPECIAL THERAPEUTIC OR HYGIENIC PURPOSES OR SPECIFIC PARTS OF THE BODY
  • A61H2201/00—Characteristics of apparatus not provided for in the preceding codes
  • A61H2201/50—Control means thereof
  • A61H2201/5058—Sensors or detectors
  • A61H2201/5071—Pressure sensors
  • A61H2201/5074—Pressure sensors using electric pressure transducers with proportional output

Definitions

• the present invention relates to tourniquets utilized to provide a bloodless operative field during surgery on the extremities of the body, and more particularly relates to a pressure-responsive, self-adjusting pneumatic tourniquet.
• Measurement of a patient's blood pressure is possible using non—invasive monitoring equipment.
• Such monitoring equipment typically uses one or two pressure cuffs, as shown in U.S. Patents 2,193,945, 3,779,235 and 4,167,181.
• the pressure applied by a tourniquet cuff be automatically adjusted in response to changes in a patient's blood pressure to maintain the tourniquet cuff pressure at the minimum acceptable value above the patient's blood pressure.
• the method of occluding blood flow in a person's limb comprises the steps of applying pressure about the limb with an adjustable tourniquet, monitoring the person's blood pressure, and, responsive to changes in the person's blood pressure, adjusting the tourniquet to maintain application of pressure about the limb at a level greater than the person's blood pressure by a predetermined amount.
• the tourniquet utilized in an apparatus embodying the invention preferably comprises a pneumatic tourniquet operable by inflating a cuff surrounding the person's limb, and the pressure monitoring means preferably comprises a non-invasive cuff means for measuring systolic pressure.
• the means for operating the tourni ⁇ uet in response to changes in blood pressure preferably comprises a means for measuring the pressure applied by the tourni ⁇ uet, comparator means for comparing the pressure applied by the tourniquet with the person's blood pressure, and means responsive to the pressure applied by the tourniquet being greater than the person's blood pressure by more or less than the predetermined amount for lowering or raising, respectively, the pressure applied by. the tourniquet.
• Variations in the person's blood pressure can occur during surgery as a result of reaction to anesthesia or surgical stimulation.
• FIG. 1 is a diagrammatic representation of an automatic tourniquet apparatus embodying the present invention.
• a fluid line 12 leads from a pressure cuff (not shown) of conventional construction to a non-invasive pressure monitor 14.
• the pressure monitor 14 preferably comprises the unit sold by Critikon, Inc. of Tampa, Florida under the trademark "DYNAMAP" Model 845.
• the DYNAMAP monitor measures systolic and diastolic pressure, mean arterial pressure and heart rate using the oscillometric method.
• the circuitry of the pressure monitor 14 causes the cuff to be inflated sufficiently to occlude the artery, and then deflates the cuff incrementally while monitoring pulses introduced into -the cuff by pulsations of the arteries.
• a digital systolic display 15 displays the parameter relevant to operation of the present invention.
• the apparatus shown in the Figure also includes a pneumatic tourniquet 16, elements of which are shown diagrammatically in the figure.
• the pnuematic tourniquet 16 is preferably a Kidde pneumatic tourniquet as shown and described in U.S.
• Patent 3,085,599 issued April 16, 1963 to J.
• the Kidde pneumatic tourniquet includes a conventional pneumatic cuff which surrounds the limb upon which surgery will be performed and a pressure regulator (not shown in the present drawing).
• a fluid line 17 from the tourniquet cuff is connected to a conventional pressure transducer 18.
• the pressure, transducer 18 provides an analog output which is digitized by analog to digital converter 24, the output of which represents the pressure within the tourniquet cuff and is displayed by a digital tourniquet pressure display
• An electr ical l ine 1 9 is connected to the digital systolic pressure output of the pressure monitor 14, and carries such signal to an adder 20.
• An increment signal generator 21 provides another input to the adder 20.
• Increment signal generator 21 may be embodied by any switching arrangement, such as a plurality of thumbwheel switches, which provides an appropriately scaled binary number to adder 20.
• the signal supplied by the increment signal generator 21 can be manually adjusted, and represents the predetermined amount by which the tourniquet pressure about the limb will be maintained above the systolic blood pressure measured by the pressure monitor 14.
• the recommended increment is 100-150 mm Hg.
• the cuff connected to the line 12 for blood pressure measurement can be placed around any limb which will provide an accurate measurement of the person's blood pressure.
• the blood pressure is measured on a limb other than the limb upon which surgery is being performed, so that the tourniquet on the same limb cannot affect the accuracy of the blood pressure readings.
• the output of the analog to digital converter 24 is connected along bus 26 to a magnitude comparator 23, the other input of which is the output signal from the adder 20 which is connected to the comparator 23 along bus 22.
• the comparator 23 is a digital device of well known construction which compares the two input signals and provides one of three output signals depending on the relative magnitudes of the signals being compared. If the signal along bus 22 from the adder 20, representing the sum of the systolic blood pressure and the increment signal, is greater than the signal on bus 26 representing the pressure within the tourniquet cuff, the magnitude comparator 23 provides a ''+" output. If the signal along bus 26 is greater than the signal along bus 22, then the comparator 23 provides a "-" output signal.
• Magnitudinal comparator 23 may be constructed in a known manner by using one or more integrated circuit digital magnitude comparators, for example, the type 4063 CMOS circuit currently manufactured by
• the "+" and “-" outputs of the comparator 23 are input to a selector 28 which is also of conventional construction.
• the selector is activated at regular small intervals by pulses from a pulse generator 29 which is constructed to provide its regular pulses throughout operation of the apparatus
• the selector 28 provides output signals in either a clockwise ("CW") or a counter clockwise (“CCW”) mode to a digital stepping motor 32.
• the stepping motor 32 is connected mechanically by a diagrammatically shown connection 33 to a shaft 35 which is the shaft of the pneumatic tourniquet 16 rotatable to operate the pressure regulator to change the pressure within the tourniquet cuff.
• the clockwise output of the selector 28 activates the motor 32 to rotate the shaft 35 a small amount in the clockwise direction so as to decrease the pressure applied by the tourniquet 16.
• the counter clockwise output of the selector 28 activates the motor 32 to rotate the shaft 35 in the counter clockwise direction so as to increase the pressure applied by the tourniquet 16.
• the shaft 35 is also rotatable manually by a manual pressure set control 36 which is connected mechanically to the shaft 35 by a mechanical connection 37 diagrammatically shown in the Figure.
• the apparatus 10 includes a tourniquet on/off switch 40 which provides power to the components of the apparatus 10 and activates a timer 41 which accumulates the time that the tourniquet has been asserting pressure around the person's limb.
• the output of the timer 41 is connected to a digital display 42 of the duration of tourniquet application, and also to an audible alarm 43 constructed to provide an audible signal at predetermined intervals, such as every fifteen minutes of tourniquet application.
• the monitor cuff and the tourniquet cuff are applied to limbs of the person and the surgical area is prepped, draped and exsanguinated.
• the manual pressure set control 36 is adjusted to a value believed to be near the desired increment above the person's blood pressure, and the increment signal generator 21 is adjusted to provide the desired pressure increment signal to the adder 20.
• the switch 40 is then turned on, initiating operation of the timer 41 and the time display 42.
• Pressure is provided to the pneumatic tourniquet 16, in the conventional manner, and that pressure is measured by the pressure transducer 18 and displayed on the digital display 25. Power is at the same time supplied to the pressure monitor 14, which begins the series of steps required to measure the person's systolic blood pressure and to display the pressure on the digital display 15.
• the pressure monitor 15 measures the systolic blood pressure at selected intervals as often as once per minute.
• the digital systolic pressure signal is added to the increment signal by the adder 20, and the magnitude comparator
• the selector 28 compares the magnitudes of the signal from the adder 20 and the signal representing the tourniquet cuff pressure measured by the transducer 18. If the tourniquet cuff pressure is not greater than the systolic blood pressure by at least the amount of the predetermined increment signal, then the signal along bus 22 will be greater than the signal along bus 26, and the magnitude comparator 23 will provide a "+" output to the selector 28. Upon the next pulse from the pulse generator 29, the selector 28 provides a. counter clockwise output to the stepping motor 32.
• the signal along bus 22 will be less than the signal along bus 26, and the pressure in the tourniquet cuff will be greater than the systolic blood pressure by more than the amount of the increment signal. This will cause the magnitude comparator 23 to provide a "-" output, and the pulse generator 29 will again be enabled to activate the selector 28.
• the selector 28 will provide a clockwise signal output to the stepping motor 32, stepping the shaft of the motor 32 in a clockwise direction and thereby causing the shaft 35 of the pressure regulator of the pneumatic tourniquet 16 to be rotated incrementally so as to slightly decrease the pressure in the tourniquet cuff. This will be repeated automatically until the signals to the comparator 23 along buses 22 and 26 are equalized.
• the compression exerted by the tourniquet cuff about the limb is continually monitored and maintained at a predetermined pressure above the systolic blood pressure of the patient.
• the predetermined amount is determined by the setting of the increment signal which is combined with the systolic blood pressure signal by the adder 20.
• An automatic tourniquet apparatus 10 embodying the present invention thus responds to changes in the patient's blood pressure which may occur during surgery for reasons such as reaction to anesthesia or surgical stimulation.
• the pressure in the tourniquet cuff were to remain at a fixed value, as has been the case in prior pneumatic tourniquet systems, a drop in the patient's blood pressure would unnecessarily increase the differential between the pressure of the tourniquet cuff and the blood pressure.
• the present invention minimizes nerve damage caused by the compression of the tourniquet on nerve tissues.
• the present invention will minimize or eliminate accidents that have occurred from time-to-time as the result of human error by the misreading or misadjustment of manual controls of present pneumatic tourniquets. If the tourniquet cuff pressure is unintentionally set at an extremely high value, the resulting damage to the limb below the tourniquet can result in a need for limb amputation. This would not happen to a patient on which the automatic tourniquet of the present invention is used. Further advantages include a more accurate accounting of actual tourniquet lapsed time, and reductions in hospital and patient costs through the elimination of long rehabilitative processes now necessitated by the slow regeneration of damaged nerve tissue.
• the apparatus 10 can be constructed as a single unit or as a modular unit utilizing commercially available units for the pressure monitor and pneumatic tourniquet components. It is preferable to provide a central control panel including the on/off switch 40, the monitor pressure display 15, the tourniquet pressure display 25, the tourniquet time display 42, the audible alarm 43, and adjustment controls for the increment signal generator 21.

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• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Surgery (AREA)
• Engineering & Computer Science (AREA)
• Heart & Thoracic Surgery (AREA)
• Vascular Medicine (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Hematology (AREA)
• Biophysics (AREA)
• Biomedical Technology (AREA)
• Reproductive Health (AREA)
• Medical Informatics (AREA)
• Molecular Biology (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)

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• 1982
  • 1982-09-24 EP EP19820903123 patent/EP0089369A1/de not_active Withdrawn
  • 1982-09-24 WO PCT/US1982/001317 patent/WO1983000995A1/en unknown

Non-Patent Citations (1)

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