Abstract: A method or device for assaying physiological gas levels in a human, comprising: repeatedly measuring a gas in samples of breath or blood, or continuously measuring the gas through the skin or fingernail, while he or she holds his or her breath for a specified time interval (BHt) before each measurement, wherein these time intervals are selected from the group consisting of BHt=0, 4-6, 20-25 and 35-40 seconds, and recording the results to form a series of values including at least one measurement at BHt=35-40 which is treated as representing the average gas level in all the tissues of the body (T) at that time, to determine if the individual is net inhaling, net exhaling or in equilibrium with the gas.

Abstract: A method of rebreathing for a human, comprising: breathing through a rebreathing device for up to 20 minutes at a time, repeated as needed; wherein said rebreathing device has a form of a) cylindrical form made by rolling a sheet of paper, and able to fit snugly over either the mouth or the nose of a human in need of rebreathing; b) cylindrical form made with a cardboard tube from a toilet paper roll; c) cylindrical form made with a cardboard tube from a paper towel roll; d) cylindrical form made from a washable, re-useable, solid tube and able to fit snugly over either the mouth or the nose; e) rectilinear form made from a paper bag made of absorbent paper, at least 5 inches long [=12.7 cm] for adults, that is modified by i) cutting or tearing horizontally to shorten the bag so the remaining bag is approximately 5 to 7 inches [12.7 to 17.8, cm] tall, and ii) folding over one corner of the rectangular bottom approximately 1 inch [=2.5 cm] and cutting or tearing it off to make a hole approximately 1.

Abstract: A method or device for assaying physiological gas levels in a human, comprising: repeatedly measuring a gas in samples of breath or blood, or continuously measuring the gas through the skin or fingernail, while he or she holds his or her breath for a specified time interval (BHt) before each measurement, wherein these time intervals are selected from the group consisting of BHt=0, 4-6, 20-25 and 35-40 seconds, and recording the results to form a series of values including at least one measurement at BHt=35-40 which is treated as representing the average gas level in all the tissues of the body (T) at that time, to determine if the individual is net inhaling, net exhaling or in equilibrium with the gas.