Sensor for measuring the concentration of a gaseous component in a fluid by absorption

Analytical apparatus comprising:

• a catheter body having a distal end positionable in vivo,
• waveguide means carried by the catheter body and defining an axially-elongated energy path having an inlet aperture for receiving an incident energy signal within a predetermined wavelength range and an emission aperture for emitting an emitted energy signal, said waveguide means allowing passage of and being substantially transparent to energy within the predetermined wavelength range;
• an axial segment of said waveguide means comprising a block of fixed axial length of a solid material which is substantially transparent to energy within the predetermined wavelength range and permeable to a gaseous component that has an energy absorption peak in the predetermined wavelength range, the remainder of said waveguide means being substantially impermeable to the gaseous component;
• wherein, when said axial segment is exposed along said fixed length to a body fluid containing the gaseous component, the gaseous component permeates said segment and absorbs the incident energy signal along said fixed length to thereby reduce the intensity of the emitted energy signal in proportion to the concentration of the gaseous component in the segment, whereby differences between the intensities of the incident and emitted energy signals may provide an indication of the concentration of the gaseous component in the patient's body fluid.

A system for measuring the concentration of a gaseous component in a fluid by absorption, the gaseous component having an energy absorption peak lying within a predetermined wavelength range, said system comprising:

• waveguide means defining an axially-elongated energy path having an inlet aperture receptive to an incident energy signal within the predetermined wavelength range and an emission aperture for emitting an emitted energy signal, said waveguide means for allowing passage of and being substantially transparent to energy within the predetermined wavelength range;
• an axial segment of said waveguide means comprising a block of fixed axial length of a solid material which is substantially transparent to energy within the predetermined wavelength range and permeable to a gaseous component to be measured, the remainder of said waveguide means being substantially impermeable to the gaseous component;
• wherein, when said axial segment is exposed along said fixed length to a fluid the gaseous component to be measured will permeate said segment and absorb an incident energy signal along said fixed length to thereby reduce the intensity of an emitted energy signal in proportion to the concentration of the gaseous component in the segment;
• energy source means for directing to said inlet aperture the incident energy signal;
• a detection means and means for directing the emitted energy signal from said emission aperture to said detection means, said detection means being constructed and arranged to provide an indication of the concentration of the gaseous component in the fluid as a function of the intensity of the emitted every signal.

A fiber optic sensor for measuring the concentration of a gaseous component in a fluid by absorption, the gaseous component having an energy absorption peak lying within a predetermined wavelength range, said sensor comprising:

• an optical fiber which is substantially impermeable to the gaseous component and substantially transparent to the predetermined wavelength range, said fiber being axially-elongated and having a proximal end and a distal end, the proximal end being coupled to means for inputting an incident energy signal within the predetermined wavelength range and being further arranged to emit an emitted energy signal;
• a block of fixed axial length disposed at the distal end of said fiber, said block being made of a solid material which is substantially transparent to the predetermined wavelength range and permeable to the gaseous component, said block having a first end coupled to said distal end of said fiber and a second end having an inwardly reflective surface, wherein, when said block is exposed to the fluid along said fixed length the gaseous component permeates said block and absorbs the incident energy signal as it travels along said fixed length to thereby reduce the intensity of the emitted energy signal in proportion to the concentration of the gaseous component in the block, and
• means for detecting the emitted signal for measuring differences between the intensities of the incident and emitted signals and for providing an indication of the concentration of the gaseous component in the fluid based on said differences.

A method for detecting a gaseous component in a fluid by absorption, the gaseous component having an energy absorption peak lying within a predetermined wavelength range, said method comprising the steps of:

• directing an incident energy signal within said predetermined wavelength range to an inlet aperture of an axial waveguide means, the waveguide means allowing passage of and being substantially transparent to energy in the predetermined wavelength range and being substantially impermeable to the gaseous component except for a fixed-length axial segment thereof comprising a block of solid material which is permeable to the gaseous component;
• exposing said axial segment along the fixed length thereof to a fluid containing the gaseous component, wherein the gaseous component permeates the segment;
• passing the incident energy signal through said waveguide means, wherein the incident energy signal is absorbed by the gaseous component along the fixed length of the axial segment to thereby reduce the intensity of the emitted energy signal in proportion to the concentration of the gaseous component in the segment;
• detecting the emitted energy signal from an emission aperture of said waveguide means;
• and determining the concentration of the gaseous component from the detected emitted energy signal.