Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
  • A61B5/087—Measuring breath flow

Definitions

• the present invention relates to an arrangement for measuring two-way or bidirectional respiration gas flows w ithout increasing the dead space.
• Such an arrangement includes a hose which is connected to the breathing passages of a patient and which , via a Y-piece , is connected to a tube for inspiration gas and a tube for -
• a hose 1 is connected to the breating passages of the patient. 5 That end of the hose 1 which extends away from the patient is connected to a Y-piece 2, to which is connected two tubes 3 and 4. Unidirectional flow for alternating inspiration gas is effected through the one tube 3 and for expiration gas through the other tube 4.
• the tubes are, in turn, connected to a respirator or breathing 0 apparatus not shown.
• the known technique employs various kinds of flow meter, for example: 1 ) Respiration flow meters according to Fleisch, incorporating inserts having narrow, mutually parallel channels. The pressure drop across the inserts is proportional to the flow. The flow meter is symmetrical, and measures in both directions.
• Vortex meters in which a rod is placed perpendicular to the gas flow, so as to generate vortices.
• the vortices move as swiftly as the gas and can be detected with the aid of ultrasonic devices.
• the vortex meter is intended for flow in one direction only.
• Venturi tubes which are provided with a constriction, such that the gas moves at a faster rate and the lateral pressure falls. Downstream of the constriction there is an elongate gradual transition to the "general" diameter of the gas tube.
• the difference is lateral pressure between a location immediately upstream of the constriction to the narrowest location thereof is proportional to the square of the flow.
• the total drop in pressure over the whole of the venturi tube is much lower than the pressure difference measured in the first instance.
• the lateral pressure in the constricted area of the tube is lower than the lateral pressure upstream and downstream of the constriction. Consequently, the flow can be measured by determining the difference is lateral pressure between the narrowest part of the constriction and the lateral pressure downstream of the venturi tube.
• the differential pressure thus measured is 20-30% lower than the difference in pressure which prevails simultaneously between an upstream location and the narrowest location of the constriction.
• the venturi tube is intended for flow in one direction.
• Routines for setting the arrangement to zero are necessary in all methods, except for the vortex method.
• the object of the present invention is to improve the aforementioned techniques for measuring the bidi rectional respiration f lows of anaesthetized patients or patients under intensive care.
• the invention is mainly characterized in that a pressure-differential meter having two inlets or inputs is connected to the inlet of each venturi 's device, that a magnet valve is arranged to connect the two inlets together periodically; and that an electronic means is arranged to ca lculate the measured value and to control setting of the arrangement to zero, said electronic means to this end being electrical ly connected to the pressure- differential meter and to the magnet values.
• a pressure-differential meter having two inlets or inputs is connected to the inlet of each venturi 's device, that a magnet valve is arranged to connect the two inlets together periodically; and that an electronic means is arranged to ca lculate the measured value and to control setting of the arrangement to zero, said electronic means to this end being electrical ly connected to the pressure- differential meter and to the magnet values.
• the invention is illustrated schematically in Figure 2 and relates to a venturi-tube meter, which offers many advantages when used as a respi ration flow meter, as will be gathered from the resume above.
• a tube 1 connected to the breathing passages of a patient is connected to an inspiration tube 3 and an expiration tube 4, via a Y-piece 2.
• a venturi means In each of these tubes there is arranged a venturi means, the latter being arranged to co-act with a common transducer means in the form of a pressure differential meter 8 and to indicate the flow electrically.
• the meter 8 is connected to the venturi means in the tube 3 via a first line 5, and to the venturi means in the tube 4 via a second line 6.
• An annular chamber 5 'and 6* connects the lateral orifices together at the narrowest location of the venturi means.
• Connected across the two inputs of the meter 8 is a short line 10.
• Zero-setting of the transducer is essential for obtaining a correct measurement.
• simple zero-balancing' of the pressure differential meter 8 is effected by intermittently (e.g. each hour) connecting both inlets of the meter to the same pressure, by means of a magnet valvue 7 (by rotating the valve body 90 , as shown by the arrow in Figure 2).
• An electronic means 9 for calculating the measured value and for controlling the zero-setting of the transducers is arranged to control the setting of the valve 7 and to lineate the measured pressure-differential signal, so that it can be presented as a calibrated flow signal. Flow will be present alternately in either the inspiration tubes 3 or the expiration tube 4. The pressure signal will have different characteristics, depending upon which of the two tubes 3 , 4 is through-passed by gas.

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• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Biomedical Technology (AREA)
• Molecular Biology (AREA)
• Pulmonology (AREA)
• Biophysics (AREA)
• Pathology (AREA)
• Engineering & Computer Science (AREA)
• Physiology (AREA)
• Heart & Thoracic Surgery (AREA)
• Medical Informatics (AREA)
• Physics & Mathematics (AREA)
• Surgery (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
• Measuring Volume Flow (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20348429

Family Applications (1)

Country Status (3)

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• 1982
  • 1982-11-02 SE SE8206211A patent/SE8206211L/ not_active Application Discontinuation
• 1983
  • 1983-10-28 EP EP19830903599 patent/EP0125274A1/de not_active Withdrawn
  • 1983-10-28 WO PCT/SE1983/000370 patent/WO1984001704A1/en unknown

Non-Patent Citations (1)

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