A Smart System for the Contactless Measurement of Energy Expenditure.

Energy Expenditure (EE) (kcal/day), a key element to guide obesity treatment, is measured from CO ₂ production, VCO ₂ (mL/min), and/or O ₂ consumption, VO ₂ (mL/min). Current technologies are limited due to the requirement of wearable facial accessories. A novel system, the Smart Pad, which measures EE via VCO ₂ from a room's ambient CO ₂ concentration transients was evaluated. Resting EE (REE) and exercise VCO ₂ measurements were recorded using Smart Pad and a reference instrument to study measurement duration's influence on accuracy. The Smart Pad displayed 90% accuracy (±1 SD) for 14-19 min of REE measurement and for 4.8-7.0 min of exercise, using known room's air exchange rate. Additionally, the Smart Pad was validated measuring subjects with a wide range of body mass indexes (BMI = 18.8 to 31.4 kg/m ² ), successfully validating the system accuracy across REE's measures of ~1200 to ~3000 kcal/day. Furthermore, high correlation between subjects' VCO ₂ and λ for CO ₂ accumulation was observed ( p < 0.00001, R = 0.785) in a 14.0 m ³ sized room. This finding led to development of a new model for REE measurement from ambient CO ₂ without λ calibration using a reference instrument. The model correlated in nearly 100% agreement with reference instrument measures ( y = 1.06 x , R = 0.937) using an independent dataset (N = 56).