G.d. Searle & Company

Vickers, Inc.

Mcneil Ab

University College London

Novametrix Medical Systems, Inc.

The Medishield Corporation Limited

Dawood Parker

David T Delpy

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

An apparatus is disclosed for monitoring the partial pressure of a gas in the liquid flowing in a line, for example the PO.sub.2 or PCO.sub.2 tension in blood. The apparatus comprises a connector adapted for insertion in the line, the connector having a wall which includes a membrane permeable to the gas but impermeable to the liquid. The membrane has a first face in contact with the liquid in the connector and a second face oppositely disposed to the first face. A sensor, for example, an electrochemical sensor, is located adjacent the second face and is responsive to gas passing through the membrane from the liquid.

Apparatus for monitoring the partial pressure of gases

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

A partially disposable, partially reusable polarographic sensor includes a fixed membrane and gel electrolyte in the disposable portion, and includes all electrical/metallic parts in the reusable portion. The disposable portion comprises a housing having a flow chamber for fluids to be monitored, adjacent to which is the membrane. Behind the membrane is the gel electrolyte, and a screw structure for engaging the reusable part. In turn, the reusable part employs a matable screw portion, and a fixed, coaxial anode-cathode assembly, which when mounted to the disposable portion, engages the membrane.

Disposable polarographic gas sensor system

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.

Transcutaneous probe

This invention relates to an electrochemical sensor system for the simultaneous and continuous measurement of the partial pressure of oxygen PO.sub.2 and carbon dioxide partial pressure PCO.sub.2 in fluids. The electrochemical sensor of the present invention is particularly useful for intra-arterial measuring PCO.sub.2 and PO.sub.2 in blood and is readily adapted to transcutaneous measurement of these blood gases by the addition of a heating element and minor configurational changes.

PO.sub.2 /PCO.sub.2 sensor

A device for the measurement of the partial pressure of blood gases comprising a body having a gas-permeable boundary wall for placement on the skin of the subject, a gas collection chamber in the body connected to an analysis instrument, a heating device to heat the skin area under the boundary wall and an electronic control to control the heating device and monitor the temperature of the skin area.

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London, United Kingdom

Dawood Parker