Abstract: A method and an apparatus for determining an infection condition in an organism by measuring the level of nitrous oxide present in a gas sample taken from the organism. In one embodiment the nitrous oxide content of a gas sample is measured to diagnose systemic inflammatory response in a living organism. In an alternative embodiment, the nitrous oxide level of a gas sample taken from a living organism may be compared the with an expected nitrous oxide level for a healthy organism or with a prior measured nitrous oxide level of the living organism to diagnose the presence or absence of an infection in the living organism. A method and apparatus for determining response to a course of therapy is provided. The method and apparatus compares the nitrous oxide levels of a living organism before and after the administration of a therapy to the living organism to determine a response to the therapy.

Abstract: A method and an apparatus for measuring the concentration of a specific gas component of a gas mixture including another gas whose concentration is independently known using light absorption spectroscopy are provided. A method and an apparatus for assessing human airway inflammation by measuring the concentration of exhaled NO and CO2 present in orally exhaled breath using light absorption spectroscopy are also provided. NO concentration is determined at the time during breath sampling corresponding to a known exhaled CO2 concentration. Methods and apparatus are further provided for measuring NO concentration in orally exhaled human breath that analyze breath emanating from the lower airways and lungs, while excluding breath from the nasal cavity.

Abstract: A method and an apparatus for measuring the concentration of a specific gas component of a gas mixture including another gas whose concentration is independently known using light absorption spectroscopy are provided. A method and an apparatus for assessing human airway inflammation by measuring the concentration of exhaled NO and CO2 present in orally exhaled breath using light absorption spectroscopy are also provided. NO concentration is determined at the time during breath sampling corresponding to a known exhaled CO2 concentration. Methods and apparatus are further provided for measuring NO concentration in orally exhaled human breath that analyze breath emanating from the lower airways and lungs, while excluding breath from the nasal cavity.