Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/44—Detecting, measuring or recording for evaluating the integumentary system, e.g. skin, hair or nails
  • A61B5/441—Skin evaluation, e.g. for skin disorder diagnosis
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
  • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
  • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
  • G01F1/20—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow
  • G01F1/22—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow by variable-area meters, e.g. rotameters
  • G01F1/24—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow by variable-area meters, e.g. rotameters with magnetic or electric coupling to the indicating device
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N25/00—Investigating or analyzing materials by the use of thermal means
  • G01N25/56—Investigating or analyzing materials by the use of thermal means by investigating moisture content
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
  • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
  • G01N33/483—Physical analysis of biological material
  • G01N33/497—Physical analysis of biological material of gaseous biological material, e.g. breath

Definitions

• the present invention relates to a method and a device for measuring vapour flux from a surface, more particularly it relates to a method and a device which can be used to measure the rate of water loss from human skin.
• the transepidermal water loss is important in the evaluation of the efficiency of the skin/water barrier. Damage to the skin resulting from various skin diseases, burns and other damage can affect the TEWL and measurement of the TEWL can indicate such damage and possibly its early onset or response to treatment. It therefore has use in clinical diagnosis.
• TEWL is a measure of the effectiveness of the skin/water barrier its measurement is important in prematurely born infants, when dehydration due to excessive water loss can have serious adverse results.
• the TEWL is also used in testing the effect of pharmaceutical and cosmetic products applied to the skin.
• GB patent 1532419 describes an instrument for measuring the rate of water loss from the skin in which an open cylinder containing two spaced apart relative humidity sensors and two temperature sensors is placed on the skin so that water vapour escaping from the skin diffuses along the cylinder and passes the sensors. The output from these sensors can be used to measure the concentration gradient of water vapour in the cylinder and hence the water vapour flux from, the skin.
• equipment for measuring the water vapour flux from a surface which comprises a cylinder with an opening at one end, which opening is adapted to be placed against the surface of interest, the other end of the cylinder being closed by means of a cooled surface; the cylinder containing sensors, which sensors being able to measure quantities, such as relative humidity and temperature, from which the flux of water vapour from the surface of interest can be calculated.
• the invention also provides a method for measuring the water vapour flux from a surface, which method comprises enclosing a zone adjacent to the surface of interest within a cylinder which is open at one end and closed at the other end, by placing the open end of the cylinder against the surface of interest, cooling the surface closing the closed end of the cylinder and measuring quantities, such as relative humidity and temperature within the cylinder, from which the flux of water vapour from the surface of interest can be calculated.
• the closed surface is preferably cooled to a temperature at which the water vapour in its vicinity condenses to liquid water or ice and steady conditions of water vapour diffusion are established within the cylinder, with the concentration of water vapour in the immediate vicinity of the cold surface being lower than in the immediate vicinity of the surface of interest.
• a water vapour concentration gradient is established along the length of the cylinder.
• the concentration of water vapour at a known distance from the cooled surface is measured and, using the known concentration of water vapour in the immediate vicinity of the cooled surface, the gradient of water vapour concentration along the length of the cylinder can be calculated.
• the concentration of water vapour can be measured by measuring the relative humidity, in which case there is preferably a second sensor which is able to measure the temperature substantially at the location of the sensor which measures the relative humidity. From measurements of the relative humidity and associated temperature, the concentration of water vapour at the sensor location can be determined.
• a suitable and convenient choice of relative humidity sensor includes sensors based on the change in capacitance or change in electrical conductivity etc, which are widely commercially available.
• a suitable and convenient choice of temperature sensor includes the conventional thermocouple and thermistor, which are widely commercially available.
• a composite sensor can be used which simultaneously measures the relative humidity and the temperature so that one such composite sensor can produce the required signals.
• the sensors take their measurements at a point or in a plane substantially parallel to the surface of interest, in order to make the measurement of water vapour flux more accurate.
• An additional temperature sensor is preferably placed in contact with the cold surface in order both to maintain its temperature at a constant value and to provide a temperature reading from which the concentration of water vapour in its immediate vicinity can be calculated.
• the outputs from the sensors are fed to a processing device such as a microprocessor or PC, which is programmed to convert the signals from the sensors to the required type of output or readout.
• a processing device such as a microprocessor or PC, which is programmed to convert the signals from the sensors to the required type of output or readout.
• the closed surface of the cylinder can be cooled by conventional cooling means and preferably uses an electrical cooling means e.g. one based on the Peltier effect. This enables the cooling to be accurately controlled at the requisite level quickly and easily.
• the water which is condensed at the cold surface can be re-evaporated by heating the surface during times when the instrument is not being used for measurement. If the cooler is a Peltier device, then this can conveniently be accomplished by reversing the current flow through it.
• the cylinder is the common geometry of measurement chamber for such instruments, but any convenient shape can be used e.g. rectangular parallelepiped, prism, etc.
• the measurement chamber is preferably made of compact size so that it occupies a small area and can easily be placed on the surface of interest, e.g. the skin at the desired location of a TEWL measurement.
• the measurement chamber can conveniently be constructed in the form of a wand or with a convenient handle etc.
• the equipment and method can be used to measure any vapour flux from a surface although, when the vapour is not water vapour, the sensor and cold plate temperature are chosen accordingly.
• the equipment can be used with any surface and apart from skin the equipment can be used to measure water vapour flux from plants, etc.
• the open end of the cylinder is placed against the skin and the closed end of the cylinder is cooled and readings from the sensors are fed to a processor which converts these readings to the desired water flux measure. After a short period to allow the measurement conditions to stabilise, readings are taken. Alternatively, readings can be taken continuously or periodically in order to record the time change of the signals and the water vapour flux calculated according to suitable criteria.
• the closed cylinder means that neither air movement nor humidity in the air outside the cylinder can affect the measurements taken and so more accurate readings are obtained.
• An alternative means of measuring water vapour flux is to measure the mass of water condensed on the cold surface of the cylinder, the mass of water per unit interval of time being numerically equal to the flux of water vapour emanating from the surface of interest.
• a convenient mass sensor such as a quartz microbalance, can therefore be used in place of the relative humidity sensor(s) in an alternative implementation of the device.
• An alternative means of measuring water vapour concentration in the cylinder includes a sensor based on measuring the absorption of infrared radiation of suitable wavelength by the water vapour.
• a chamber in the from of cylinder (1) is open at end (l a) and is closed at the end (lb) by a surface (2) which is in contact with a Peltier cooling device (3).
• a capacitative relative humidity sensor (4) Inside the cylinder (1) is a capacitative relative humidity sensor (4) and a thermocouple (5) which measures the temperature at the location of the relative humidity sensor (4).
• An additional thermocouple (7) is placed in contact with the cooled surface (2).
• the outputs of (4), (5) and (7) are fed to a computer (not shown).
• the open end (la) is placed against the skin as shown and the surface (2) is cooled down to a sufficiently low temperature to maintain a substantially lower water vapour pressure in its immediate vicinity than in the immediate vicinity of skin at the other end of the cylinder.
• the computer is programmed with a program so that the output from the sensors (4), (5) and (7) are converted to a reading in the desired form, e.g. water vapour flux from the surface.
• the readings are evaluated by the computer.
• readings can be taken continuously or periodically in order to record the time change of the signals and the water vapour flux calculated according to suitable criteria.
• the cold surface After the measurement or periodically, when convenient, the cold surface is heated to re-evaporate condensate, thus preventing a build-up of condensate (liquid water or ice).

Landscapes

• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Chemical & Material Sciences (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Pathology (AREA)
• Molecular Biology (AREA)
• Immunology (AREA)
• Biochemistry (AREA)
• Biophysics (AREA)
• Analytical Chemistry (AREA)
• Dermatology (AREA)
• Urology & Nephrology (AREA)
• Medical Informatics (AREA)
• Fluid Mechanics (AREA)
• Surgery (AREA)
• Animal Behavior & Ethology (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Hematology (AREA)
• Heart & Thoracic Surgery (AREA)
• Food Science & Technology (AREA)
• Medicinal Chemistry (AREA)
• Investigating Or Analyzing Materials Using Thermal Means (AREA)
• Measuring Volume Flow (AREA)
• Measuring And Recording Apparatus For Diagnosis (AREA)
• Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
• Electric Connection Of Electric Components To Printed Circuits (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (9)

Cited By (3)

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Citations (3)

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• 1998
  • 1998-07-10 GB GBGB9814862.0A patent/GB9814862D0/en not_active Ceased
• 1999
  • 1999-07-08 AT AT99929599T patent/ATE243315T1/de not_active IP Right Cessation
  • 1999-07-08 DE DE69908947T patent/DE69908947T2/de not_active Expired - Lifetime
  • 1999-07-08 AU AU46380/99A patent/AU754766B2/en not_active Ceased
  • 1999-07-08 EP EP99929599A patent/EP1097356B1/en not_active Expired - Lifetime
  • 1999-07-08 JP JP2000559399A patent/JP4526707B2/ja not_active Expired - Fee Related
  • 1999-07-08 ES ES99929599T patent/ES2201730T3/es not_active Expired - Lifetime
  • 1999-07-08 US US09/743,619 patent/US6439028B1/en not_active Expired - Lifetime
  • 1999-07-08 WO PCT/GB1999/002183 patent/WO2000003208A1/en not_active Ceased

Patent Citations (3)

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