Abstract: A method of identifying alveolar ventilation (VA) in a subject, the method comprising: (1) using a breathing circuit which, at exhalation, keeps exhaled gas separate from inhaled gas and at inhalation, when a first gas set (FGS) flow is less than the subject's minute ventilation (VE), results in a subject inhaling FGS first and then a second gas set (SGS), for the balance of inhalation; (2) setting the FGS flow at a rate greater that VE; (3) measuring an end tidal CO2 concentration at a steady state; (4) progressively lowering the FGS flow until a time equal to a recirculation time of CO2 in the subject; and (5) deriving VA as the rate of FGS flow at the intersection between an average PETCO2 in a steady state and a line fit to the PETCO2 values after the rise in PETCO2 values begins until the recirculation time.

Abstract: An apparatus to measure pulmonary blood flow and cardiac output ({dot over (Q)}) comprising: a) a breathing circuit which, at exhalation, keeps exhaled gas separate from inhaled gas and at inhalation, when VE is greater than first gas set (FGS) flow, results in a subject inhaling FGS first and then a second gas set (SGS), for the balance of inhalation; b) a gas sensor for monitoring gas concentrations at the patient-circuit interface; c) a gas flow control means for controlling the rate of EGS flow into the breathing circuit; d) machine-intelligence consisting of a computer or logic circuit capable of controlling the gas flow control means which receives the output of the gas sensor means and outputs pulmonary blood flow.

Abstract: A breathing circuit for use with a first gas set (FGS) and a second gas set (SGS), said circuit comprising means for keeping separate the FGS and SGS, and a means for sequentially delivering to a patient, first the FGS, and, on inspiration, when the patient inspires so as to deplete the supply of FGS into the circuit, subsequently delivers substantially SGS for the balance of inspiration.

Abstract: An apparatus to measure pulmonary blood flow and cardiac output (Q) comprising: a) a breathing circuit which, at exhalation, keeps exhaled gas separate from inhaled gas and at inhalation, when VE is greater than first gas set (FGS) flow, results in a subject inhaling FGS first and then a second gas set (SGS), for the balance of inhalation; b) a gas sensor for monitoring gas concentrations at the patient-circuit interface; c) a gas flow control means for controlling the rate of FGS flow into the breathing circuit; d) machine intelligence consisting of a computer or logic circuit capable of controlling the gas flow control means which receives the output of the gas sensor means and outputs pulmonary blood flow.

Abstract: A breathing circuit for sequential gas delivery of a first gas set (FGS) and a second gas set (SGS) employs an arrangement of conduits and active or passive valves to prevent mixing of the FGS and SGS including a valve triggered by depletion of FGS that makes the SGS available for inspiration after the FGS is depleted.

Abstract: In a first aspect, the invention relates to an apparatus for inducing or maintaining a target end tidal concentration of a gas in a subject comprising a breathing circuit, a source of gas flow into the circuit, means for controlling the rate of the source of gas flow into the circuit and means for controlling the concentration of gases in the source gas flow independently from each other. In another aspect, the invention relates to a method of preparing an apparatus for inducing or maintaining a target end tidal concentration of a gas X in a subject comprising selecting a rate of a source gas flow into a breathing circuit, selecting the concentration of at least one constituent gas of a component gas making up the source gas to a level corresponding to the end tidal concentration of the gas X, whereby the apparatus is adapted to administer a source gas having a first gas composition.

Abstract: In a first aspect, the invention relates to an apparatus for inducing or maintaining a target end tidal concentration of a gas in a subject comprising a breathing circuit, a source of gas flow into the circuit, means for controlling the rate of the source of gas flow into the circuit and means for controlling the concentration of gases in the source gas flow independently from each other. In another aspect, the invention relates to a method of preparing an apparatus for inducing or maintaining a target end tidal concentration of a gas X in a subject comprising selecting a rate of a source gas flow into a breathing circuit, selecting the concentration of at least one constituent gas of a component gas making up the source gas to a level corresponding to the end tidal concentration of the gas X, whereby the apparatus is adapted to administer a source gas having a first gas composition.

Abstract: A method of calculating the flux of any gas (x) in a CBC circuit for a ventilated or a spontaneous breathing subject, for example said gas(x) being; a) an anesthetic such as but limited to; i)N2O; ii) sevoflurane; iii) isoflurane; iv) halothane; v) desflurame; or the like b) Oxygen; c) Carbon dioxide; or the like utilizing the following relationships; Flux of gas(x)=SGF (FSX?FEX) wherein SGF=Source of gas flow into the breathing circuit (CBC circuit) in liters/minute as read from the gas flow meter as set by the anesthesiologist; FSX=Fractional concentration of gas X in the source gas (which is set by the anesthesiologist); FEX=Fractional concentration of gas X in the end expired gas as determined by a portable gas analyzer, or the like.

Abstract: An apparatus for inducing hypoxia in a subject is provided. The apparatus includes a breathing port, an inspiratory reservoir, means for introducing oxygen into the apparatus, means for controlling the flow rate of entry of oxygen into the apparatus at a rate below the subject's metabolic requirements, an expiratory reservoir having a vent, Sequential Gas Delivery means, and means for removing CO2 from the circuit.

Abstract: In a first aspect, the invention relates to an apparatus for inducing or maintaining a target end tidal concentration of a gas in a subject comprising a breathing circuit, a source of gas flow into the circuit, means for controlling the rate of the source of gas flow into the circuit and means for controlling the concentration of gases in the source gas flow independently from each other.

Abstract: A process for determining gas(x) consumption, wherein said gas(x) is selected from; a) an anesthetic such as but not limited to; i) N2O; ii) sevoflurane; iii) isoflurane; iv) halothane; v) desflurame; or the like b) Oxygen (O2).

Abstract: A breathing circuit for use with a first gas set (FGS) and a second gas set (SGS), said circuit comprising means for keeping separate the FGS and SGS, and a means for sequentially delivering to a patient, first the FGS, and, on inspiration, when the patient inspires so as to deplete the supply of FGS into the circuit, subsequently delivers substantially SGS for the balance of inspiration.

Abstract: A method of calculating the flux of any gas (x) in a CBC circuit for a ventilated or a spontaneous breathing subject, for example said gas(x) being; a) an anesthetic such as but limited to; i)N2O; ii) sevoflurane; iii) isoflurane; iv) halothane; v) desflurame; or the like b) Oxygen; c) Carbon dioxide; or the like utilizing the following relationships; Flux of gas(x)=SGF (FSX?FEX) wherein SGF=Source of gas flow into the breathing circuit (CBC circuit) in liters/minute as read from the gas flow meter as set by the anesthesiologist; FSX=Fractional concentration of gas X in the source gas (which is set by the anesthesiologist); FEX=Fractional concentration of gas X in the end expired gas as determined by a portable gas analyzer, or the like.

Abstract: A method and device for effective delivery of a gas such as oxygen for inhalation is provided by sequentially diluting room air to the flow of gas during a respiratory cycle. A mask assembly is described that comprises an inspiratory and expiratory limb each containing a very low resistance one-way valve, and a sequential dilution conduit (leading from the atmosphere to the inspiratory limb) with a one-way valve that has a slightly positive cracking pressure. A gas reservoir is also attached to the inspiratory limb. During expiration, the reservoir is filled with oxygen, for example, flowing from the oxygen source. During inspiration, oxygen from the oxygen source and the reservoir are drawn preferentially. If the oxygen flow is equal to or greater than the minute ventilation of the subject, no atmospheric air is entrained into the mask assembly and the subject gets pure oxygen. If the minute ventilation (tidal volume) exceeds the oxygen flow, the reservoir is depleted.