Validity of the Lumen^® hand-held metabolic device to measure fuel utilization in healthy young adults

Objective To evaluate the validity of a novel hand-held device (Lumen^®) for measuring metabolic fuel utilization in healthy young adults.

Background Metabolic carts measure the carbon dioxide produced and oxygen consumed from the breath in order to assess metabolic fuel usage (carbohydrates vs. fats). However, these systems are expensive, time-consuming, and only available in the clinic. A small hand-held device capable of measuring metabolic fuel via CO₂ was developed.

Approach Metabolic fuel usage was assessed in healthy participants (n = 33; age: 23.1 ± 3.9 y) via respiratory exchange ratio (RER) values from the “gold-standard” metabolic cart as well as %CO₂ from the Lumen device. Measurements were performed at rest in two conditions, fasting, and after consuming 150 grams of glucose in order to determine changes in metabolic fuel. Major axis regression was performed as well as Bland-Altman plots and linear regressions to test for agreement between RER and Lumen %CO₂.

Main results Both RER and Lumen %CO₂ significantly increased after glucose intake compared with fasting conditions (p < 0.0001). Regression analyses and Bland-Altman plots revealed an agreement between the two measurements (mean bias = 3.505; limits of agreement = 2.784 - 4.226) with a fixed bias resulting from the nature of the different units.

Significance This study shows the validity of Lumen^® to estimate metabolic fuel utilization in a comparable manner with the “gold-standard” metabolic cart, conveniently providing real-time metabolic information for users anywhere.