Abstract: Embodiments of the invention are generally directed to using breath measurement to identify certain physiological states, conditions and disorders. In one example, breath measurement may be used in producing a non-binary indicator of the likelihood or extent to which a subject is experiencing or approaching ketosis. Other metabolic or respiratory states may be indicated and/or identified.

Abstract: Some embodiments are directed to determining the composition of breath exhaled by a subject. For example, some embodiments are directed to determining a concentration of a gas species in breath exhaled by a human subject, based at least in part upon a measured concentration of the gas species in a chamber which is adapted to hold both breath exhaled by the human subject and ambient air for inhalation by the human subject.

Abstract: Systems and methods are disclosed for temporal sampling of air exhaled by a user. Some embodiments comprise a mask adapted to be worn by a user, a chamber, disposed in or on the mask, the chamber comprising a valve, at least one sensor, disposed in the chamber, for measuring composition of air, an actuator adapted to open the valve, and at least one processor. The at least one processor is programmed to selectively instruct the actuator to open the valve, thereby causing air in the mask to be exposed to the at least one sensor, at a time associated with exhalation by the user, and to selectively instruct the actuator to close the valve, thereby preventing air from entering the chamber, at a time associated with inhalation by the user.

Abstract: Some embodiments are directed to determining the composition of breath exhaled by a subject. For example, some embodiments are directed to determining a concentration of a gas species in breath exhaled by a human subject, based at least in part upon a measured concentration of the gas species in a chamber which is adapted to hold both breath exhaled by the human subject and ambient air for inhalation by the human subject.

Abstract: Some embodiments of the invention are directed to a system configured to support a mask worn on a human head, such as over the human's mouth. The system may comprise a strap having two ends. The strap is adapted to affix to the mask at the ends, and to surround the sides of the head. A headband is adapted to rest approximately over the crown of the head, and comprises one or more features adapted to support the strap on its path around the head so that the strap rests above the human's ears.

Abstract: Some embodiments are directed to a self-contained breathing mask for measuring and monitoring the breath of a human subject. The mask may be lightweight, self-contained, and physically untethered to any test or measurement equipment, providing the subject full mobility, and allowing him/her to perform almost any daily activity during use. The mask may include integrated sensors for measuring properties of the subject's breath, over any length of time, providing respiratory information like breath count, rate and volume, oxygen consumption, and carbon dioxide production, as well as various biometric information.