Hamamatsu-photonics K.k.

University College London

National Research Development Corporation

Vickers, Inc.

Novametrix Medical Systems, Inc.

The Medishield Corporation Limited

David T Delpy

Dawood Parker

Timothy Noel Mills

Paul Beard

Mark Cope

Stephen John Matcher

A probe comprises an excitation source and a double-core optical fiber. A pulsed laser signal () of the excitation sources supplied to the outer core () at one end of the optical fiber. The other end is provided with an interferometer film (). An excitation signal () produced in the sample () modulates the thickness of the film (). This provides an interferometer signal () detected from the inner core ().

Optical fibre probe for photoacoustic material analysis

A method of forming an interferometer film for an interferometer sensor comprises forming a parylene polymer layer ( ) of substantially uniform thickness directly on an interferometer substrate ( ), the layer forming the interferometer film. Since the interferometer film ( ) formed directly onto the surface of the interferometer substrate, there is improved conformity between the two surfaces at the interface between the polymer layer and the substrate and improved uniformity in the thickness of the film.

Fabrication of fabry-perot polymer film sensing interferometers

A spectrometric technique is described for quantitatively determining the change in concentration of a substance which is contained in a medium which both absorbs and scatters spectroscopically interrogated radiation, and in particular to the specific case in which the change in concentration of the substance occurs in one spatially distinct region of the medium. The medium includes a plurality of such regions displaying potentially different absorption and scattering properties to the radiation. Specific applications are disclosed involving the noninvasive determination of changes in concentration of the substances oxyhemoglobin and deoxyhemoglobin and/or changes in the redox state of the substance cytochrome oxidase within the brain or skeletal muscle, and in cases where the brain or skeletal muscle is interrogated by radiation in the near-infrared part of the electromagnetic spectrum through intervening surface tissues, i.e., cortical bone or adipose tissue, where it may be assumed that no changes of concentration of said substances occur within said surface tissues.

Spectroscopic method for quantitatively determining the change of

A diagnostic apparatus includes light sources which emit near infrared light rays of different wavelengths. The light rays are introduced into human brain to be subjected to diagnosis and the light rays transmitted through the brain are picked up. There are provided a first detector which detects occurrences of respirations of the subject and outputs a respiration signal, and a second detector which detects occurrences of heartbeats of the subject and outputs a heartbeat signal. The light transmitted through the brain is derived in synchronism with both the respiration signal and the heartbeat signal and first and second modulated light transmission signals are produced which are respectively modulated by the respiration signal and the heartbeat signal. The first and second modulated light transmission signals are separately analyzed to provide variations in concentration of oxygenated media .DELTA.X.sub.02 and disoxygenated media .DELTA.X contained in venous and arterial blood of the brain, respectively. Based thereon, oxygen saturations of both venous and arterial blood flowing in the brain are separately computed and displayed in a monitor screen.

Diagnostic apparatus for measuring changes of arterial and venous blood

A tissue oxygen measuring system enabling the automatic and continuous measurement of diagnosing items including cerebral blood flow, cerebral blood volume, and response of cerebral blood volume in arterial carbon dioxide tension uses an oxygen measuring system based on near infrared spectroscopy, a pulse oximeter, and an arterial carbon dioxide tension measuring unit. A gas blending unit is employed before a ventilator or face mask to control the ventilator so that a rate of a quantity of oxygen and/or a quantity of carbon dioxide to be blended in the air is changed at predetermined intervals. Trigger signals are produced in synchronism with the changes of the gaseous contents of the air, and parameters for computing information regarding the diagnosing items are measured in response to the trigger signals. With the repetitive measurements of the parameters, a signal-to-noise ratio can be improved by averaging the data and erroneous data can easily be identified.

Tissue oxygen measuring system

The calibration of a polarographic oxygen sensor (20) at zero oxygen concentration is accomplished by providing an oxygen-free liquid environment at the sensor active surface. This is accomplished electrolytically by depleting a thin film of electrolyte (24) of oxygen to zero concentration with an oxygen-reducing cathode (6), and complementary anode (4), connected via a battery (10) and switch (12). The sensor (20) is placed into close proximity with the electrodes (4,6) and the oxygen in the electrolyte (24) reduced while its concentration is measured by the sensor (20). A low steady-state signal for the sensor provides the zero oxygen concentration calibration point.

Method and apparatus for zero calibration of oxygen-sensing

The determination of the concentration of compounds such as CO.sub.2 having an influence on the pH of a medium during polarography is described. Characteristics of polarograms when obtained in unbuffered electrolytes (the polarogram plateau slope position of the upper knee and half-wave potential thereof) are pH-sensitive. These can be detected electronically and signals processed to provide a measure of such concentrations. In one preferred embodiment (FIG. 2) a miniature pO.sub.2 polarographic sensor has cathode channels (A) and (B) biased respecitvely at -750 mV and -950 mV. The output of channel (A) provides pO.sub.2 as in normal polarography. The output of (B) is divided (6) and further corrected for pO.sub.2 (8,10) to provide pCO.sub.2. The apparatus is especially useful for simultaneous pO.sub.2, pCO.sub.2 monitoring in physiological fluids without the need for a separate pCO.sub.2 sensor.

Process and apparatus for polarographic determination of oxygen and

A transcutaneous gas sensor for application to the body surface of a patient is provided. The sensor includes a sensing electrode having an exposed surface region which, in use, is applied to the body surface of the patient with an electrolyte layer between the electrode and the patient's body. Gas which has diffused through the patient's body from his blood to the body surface results in an electrochemical reaction taking place at the exposed surface region of the electrode. This exposed surface region can consist of an individual surface area, or several such surface areas. In one embodiment, the surface area or areas are arranged and are of a configuration such as to have associated therewith an imaginary envelope of greater area than the total area occupied by the individual surface area or areas; with such an arrangement, the surface area or areas have the same or similar widths. In a second embodiment, the or each exposed surface area(s) of the electrode has a sufficiently small width dimension and is shaped and arranged so that the depletion zone set up in the electrolyte layer when the sensor is in use is confined to a depth not exceeding about 1 mm. The flow of gas from the patient's blood to his body surface can be encouraged by local heating of the area under investigation. Detection of the current flowing through the electrode as a result of the electrochemical reaction in the electrolyte layer provides a measure of the gas partial pressure in the patient's blood.

Transcutaneous gas sensor

An instrument for use in the measurement of gases in body fluids comprises a flexible catheter having an inner tube within an outer tube, the tubes being of such diameters that there is a substantially cylindrical passage between the tubes which can be evacuated or flushed with a non-interfering gas. Spacers can be provided in the passage, such as radial webs or a single or double helix filament.

Instruments for use in the measurement of gases in body fluids

A transcutaneous probe for causing oxygen and other gases or vapors carried in the bloodstream of a mammal to be extracted from the blood through the skin and passed to a device, such as a mass spectrometer, for analyzing the extracted gas. The probe has a boundary wall intended to be placed in contact with the skin comprising a first layer of gas permeable material and a second layer of perforate or porous gas-impermeable material in intimate contact with the first, the size and distribution of the perforations or pores in the second layer being such that the wall has a substantially uniform extrinsic macropermeability which is significantly lower than the inherent permeability of the first layer alone and such that in use, gas passes into the perforations or pores of the second layer from respective volumes of tissue which do not substantially overlap.

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London, United Kingdom

David T Delpy