Breath analysis device

A portable breath analysis device comprising:

• a primary gas flow pathway for passage of exhaled breath from an inlet to an outlet;
• a secondary gas flow pathway branched from the primary pathway at a branching point between the inlet and the outlet, the secondary pathway also having an outlet;
• a flow sensor (i) positioned between the inlet of the primary pathway and the branching point or between the branching point and the outlet of the primary pathway and (ii) arranged to allow measurement of a gas flow in L/min in the primary pathway;
• an oxygen sensor;
• a carbon dioxide sensor;
• a humidity sensor;
• a temperature sensor;
• and
• a microcontroller;
• wherein:
• the device is an indirect calorimeter;
• the oxygen sensor and the carbon dioxide sensor each have millisecond response rates and are arranged in-line in the secondary pathway to take breath-by-breath measurements of inhaled breath and exhaled breath from a subject in the secondary pathway;
• the humidity sensor is configured to measure humidity of air in the secondary pathway;
• the temperature sensor is configured to measure temperature of air in the secondary pathway;
• the flow sensor, oxygen sensor and carbon dioxide sensor are heated to prevent formation of condensation;
• the microcontroller is configured to:
• receive measurements from the oxygen sensor, carbon dioxide sensor, the humidity sensor, and the temperature sensor;
• and
• compensate for changes in humidity and temperature and accurately determine readings for oxygen and carbon dioxide concentrations;
• the flow sensor is a hot film anemometer or a micro-thermal conductivity detector;
• the portable breath analysis device is wearable or holdable in the hands of the subject;
• the secondary pathway comprises one or more tubes sized of smaller diameter than the primary pathway and configured to regulate flow rate through the secondary pathway;
• and
• the device does not include a pump, a valve system, or a dehumidifying means.