Measurement of Energy Expenditure on a Smartphone Using a Hand-held Breath Analyser

An indirect calorimeter is presented for measurement of Energy Expenditure (EE) in the free-living environment. A 1 minute breath sample is sufficient for EE calculation. A smartphone or laptop can display the EE data. The calorific energy required by the body is vital to healthcare (e.g. to ensure adequate feeding during physical exertion), and can provide dietary guidance for the general population. The availability of accurate calorimeters is limited, particularly for in- and out-patients. The novel analyser has been trialled against respiratory chambers. On average, resting EE was calculated to within 2.4% for 9 subjects. The prototype uses an innovative NDIR sensor and an electrochemical sensor to calculate the volumes of CO2 produced and O2 consumed, with errors of 5.4% and 3.4% found respectively compared to the chambers. Further work includes investigating the energy cost of food digestion.