Abstract: Oxygen dispensing apparatus (10) is provided which includes a relatively large, primary oxygen chamber (12) operably coupled to a cup-like passenger mask (14), along with a flexible inflatable apertured indicator element (18) positioned within the confines of the chamber (12) and operably coupled with the oxygen supply conduit (16) for the apparatus (10). In use, oxygen flows through the conduit (36) and inflates the element (18) to give a visual indication of proper oxygen flow to the user; the oxygen then flows from the aperture (42) of the element (18) into the primary chamber (12), where it is available for consumption by the passenger. Placement of the element (18) within the confines of primary chamber (12) assures that oxygen flow is maintained to the passenger, even in the event of failure of the indicator element (18).

Abstract: The movements of an exhalation valve are damped at a variable rate to control pressure oscillations within a ventilation system. The exhalation valve is damped as a function of its velocity at a rate that is a function of a variable linked to the pneumatic state of the system, to provide a feedback signal to the valve driver.

Abstract: The calibration cuvette apparatus for storing and calibrating a chemical sensor in a tonometered solution includes an upper cuvette section and a lower cylindrical valve section for alternately sealing the cuvette section and admitting a gas mixture to the cuvette section. The upper cuvette section has relatively narrow diameter upper and lower ends on either side of a wide diameter middle portion. The cuvette section is adapted to receive the sensor and retain the sensor in a fluid bath in the cuvette section so that the chemical sensor portion is disposed approximately in the center of the wide middle portion of the cuvette section. The chamber formed within the cuvette section is thus shaped so as to maintain the sensor in a position in the fluid bath so that any gas bubbles within the chamber will not dry the sensor. A lower end portion of the cuvette section includes a gas communication inlet for introducing gas into said chamber to equilibrate the tonometered buffer solution.

Abstract: An improved chemical oxygen generator (10) includes an oxygen generating candle (12) having an oxygen source, which upon decomposition will yield oxygen, and a nontoxic additive to smooth decomposition and suppress formation of toxic free chlorine gas. The nontoxic additive may be taken from the group consisting of: (1) the oxides, hydroxides and carbonates of calcium and the rare earth elements; (2) the hydroxides and carbonates of magnesium; and (3) mixtures of the foregoing. A complete chemical oxygen generator utilizes the candle (12) of the invention. The oxygen generator preferably includes a canister (14), oxygen-generating candle (12), and an ignition device (16). Triggering of the ignition device ignites an ignition pellet (52) which initiates decomposition of the candle body (50). Once initiated, the candle will sustain decomposition to release breathable oxygen until the candle is completely reacted.

Abstract: A sensor element includes an analyte-permeable matrix which supports and maintains an emulsion of a sensing solution containing an analyte-sensitive indicator substance in a plurality of tiny vesicles. The sensing solution is immiscible with the matrix material, and contains a dye indicator which dissociates into two different species. The sensing solution is initially mixed with an agent which modifies the equilibrium of dissociation of the dye indicator for optimal sensitivity. The liquid matrix preferably includes a curing inhibitor to allow the matrix to remain liquid until applied to a sensing surface, such as the tip of an optical fiber. The sensing solution remains suspended in these homogeneously dispersed vesicles after the matrix solidifies.

Abstract: The method for making an optical fiber microsensor involves applying an uncured analyte sensing matrix to an optical fiber and crosslinking the sensing matrix in situ on the optical fiber to yield an ion permeable microsensor which can be used intravascularly to monitor pH, or partial pressures of oxygen or carbon dioxide in blood. The liquid form of the sensing matrix contains a crosslinking agent and a crosslinking inhibitor which can be removed by exposure to elevated temperatures to allow the sensing matrix to crosslink and cure as desired, in situ, on the surface of the optical fiber. A liquid crosslinking overcoat layer containing a crosslinking agent and a crosslinking inhibitor which can be removed by exposure to heat can also be applied over the cured sensing matrix.

Abstract: In measuring a selected parameter of a test gas in isolation from gas pressure fluctuations, a pump draws the test gas through a storage capacitor into a sensor, storing the gas in the storage capacitor. A valve closes a fluid flow path which admits the test gas to the storage capacitor and opens a fluid flow path between the storage capacitor and a constant pressure alternate gas source, isolating the storage capacitor and the sensor from pressure fluctuations in the test gas. The storage capacitor prevents any mixing of the test gas with the alternate gas until measurement of the selected parameter has been accomplished.

Abstract: The carbon dioxide sensor includes a CO.sub.2 sensing matrix formed from a hydrophilic, gas permeable, cross-linked polyurethane. The polyurethane matrix is formed from a polyurethane pre-polymer mixture which cross links when mixed with an aqueous carbon dioxide buffer solution. The dye-buffer solution is physically entrapped as a homogeneous dispersion in the polymer matrix. The matrix is applied to the exposed glass core of an optical fiber, which may first be coated with a primer to allow the polyurethane matrix to bond firmly to the tip of the optical fiber. The hydrophilic polymeric matrix is preferably coated with a hydrophobic material to help avoid leaching of the dye from the matrix, and to prevent diffusion of hydronium ions into the sensing matrix. The hydrophobic polymer overcoat may thereafter be cured by heat treatment. The hydrophobic coating may also contain a light reflective material such as TiO.sub.2.

Abstract: The present invention provides a system and method for providing a correction to a flow control signal to a flow control valve in a ventilator system. The correction component sums the errors in the flow rate actually delivered as compared with the desired flow rate for each control interval in a breath with the sum of past errors corresponding to control intervals in past breaths to generate a corrected command flow signal to the flow control valve.

Abstract: An ultrasonic gas measuring device including a housing, end walls for the housing, the end walls having a gas inlet and a gas outlet provided therethrough, ultrasonic detecting means provided within the housing means, the ultrasonic means having a transmitter, operatively mounted on one end wall, and a receiver, operatively mounted on the other end wall, arranged at spaced locations within the housing, the housing incorporating gas processing means for dividing the gas flow at least at some instance during its flow through the housing, electronic circuitry functioning to detect and generate a signal in cooperation with the ultrasonic detecting means representative of the concentration of gas passing through the housing, the electronic means also generating a reference signal corresponding to the electronic signal delivered to the ultrasonic means, a phase shift provided within the electronic circuitry and effecting a shift of one of said signals to furnish an aligned phased relationship between the two signal

Abstract: The microphone of a breathing mask such as an aircraft flight crew oxygen mask is disabled during inhalation to prevent transmission of air flow sounds. In the preferred embodiments, selected mechanisms determine when breathable gas has been delivered to the mask and in response, disable the microphone by disconnecting it during this time. In another embodiment, a cover shifts into position over the microphone to prevent or reduce reception of sounds thereby during delivery of gas to the mask.

Abstract: The ventilator control method for delivery of respiratory gas to a patient involves an apparatus which includes a pressure sensor for measuring the pressure within a gas containment vessel, the control of the flow of respiratory gas into the containment vessel responsive to pressure within the containment vessel, and the control of the outflow of respiratory gas responsive to changes in pressure in the containment vessel. Both the inflow of gas to a receiver tank and outflow of respiratory gas are responsive to modes of breathing being provided to a patient.

Abstract: An oxygen-generating candle composition is disclosed of the type that includes an amount of an alkali metal chlorate or perchlorate oxygen source and which upon initiation and decomposition yields oxygen and residual chlorine, wherein the improvement comprises a non-toxic additive in the candle composition for suppression of the residual chlorine and to enhance uniform oxygen generation and evolution. The additive is selected from the group consisting of from about 0.05% to about 10% by weight of lithium aluminate, metaborate, tetraborate, phosphate or pyrophosphate, metasilicate or orthsilicate, or carbonate, calcium phosphate or pyrophosphate, strontium carbonate or phosphate, or sodium metasilicate or orthosilicate. A metal oxide catalyst, a metal powder fuel, and a binder or filler are also included in the composition.

Abstract: An oxygen-generating candle composition is disclosed of the type that includes an amount of an alkali metal chlorate or perchlorate oxygen source and which upon initiation and decomposition yields oxygen and residual chlorine, wherein the improvement comprises a non-toxic additive in the candle composition for suppression of the residual chlorine and to enhance uniform oxygen generation and evolution. The additive comprises from about 0.1% to about 1.0% by weight of lithium peroxide. The composition also includes a cobalt oxide catalyst, an iron powder fuel and a binder or filler.

Abstract: The optical fiber pH microsensor includes an optical fiber having a portion of the surface of a light conducting core covered with a layer of a pH sensitive dye material. The dye material is covalently bonded to a polymeric matrix which is in turn covalently bonded to the optical fiber core to prevent leaching of the indicator dye material during extended use. The dye material is crosslinked in situ over the tip of the optical fiber to yield a hydrophilic, ion permeable pH sensor which can be used intravascularly to monitor blood pH.

Abstract: The present invention provides a system and method for providing an improved correction to an input flow control signal to a flow control valve in a ventilator system. The correction as derived from a sum of the error in the flow rate actually delivered as compared with the desired flow rate for each control interval in a breath with the sum of past errors corresponding to control intervals in past breaths to generate a cumulative error signal for application in the control interval in a next breath. The cumulative error signal is stored as the sum of previous sustained errors arising periodically in the system for each control interval of previous breaths, and is integrated with the current error signal for each control interval to generate an integrated correction component signal. The input flow control signal is summed with the integrated correction component to generate a corrected command flow signal to the flow control valve.

Abstract: The optical fiber sensor is formed from an optical fiber having a light conducting optical fiber core, and a coating of cladding material, with a length of a sensing material matrix applied to the distal portion of the optical fiber core. The method involves removing a length of the cladding material from the distal portion of the optical fiber to expose a distal tip of the optical fiber core, applying a sensing material matrix to the exposed distal portion of the optical fiber core, and applying a coating of reflective material over the sensing material matrix.

Abstract: The optical fiber microsensor includes an optical fiber having a portion of the surface of a light conducting core covered with a layer containing an analyte sensitive dye material. The dye indicator material is covalently bonded to a copolymer which is covalently bonded to a blocked polyether polyisocyanate. The resulting polymer is covalently bonded to the optical fiber core to prevent leaching of the indicator dye material during extended use.

Abstract: A lightweight, easily maintainable passenger oxygen mask is provided with a face mask sized to cover the mouth and nose of a passenger and a reservoir bag in communication with the face mask. Oxygen is permitted to flow through the bag into the mask, while being prevented from flowing back into the bag. A bag connector is positionable within the bag for holding the bag against the face mask, and cooperative structure is provided on the connector and the mask for providing snap-fit connection between the connector and the face mask to permit the bag connector to be selectively, manually attached to and removed from the face mask.

Abstract: The method for making an optical fiber microsensor involves applying an uncured analyte sensing matrix to an optical fiber and crosslinking the sensing matrix in situ on the optical fiber to yield an ion permeable microsensor which can be used intravascularly to monitor pH, or partial pressures of oxygen or carbon dioxide in blood. The liquid form of the sensing matrix contains a crosslinking agent and a crosslinking inhibitor which can be removed by exposure to elevated temperatures to allow the sensing matrix to crosslink and cure as desired, in situ, on the surface of the optical fiber. A liquid crosslinking overcoat layer containing a crosslinking agent and a crosslinking inhibitor which can be removed by exposure to heat can also be applied over the cured sensing matrix.