Closed‐loop control of air supply to whole‐room indirect calorimeters to improve accuracy and standardize measurements during 24‐hour dynamic metabolic studies. Issue 3 (14th February 2023)

• Record Type: Journal Article
• Authors: Piaggi, Paolo; Rodzevik, Theresa L.; Wohlers, Erica; Ruud, Katherine; Moon, Jon; Krakoff, Jonathan; Chang, Douglas C.
• Is Part Of: Obesity. Volume 31:Issue 3(2023)
• Page Start: 780
• Page End: 788
• Publication Date: 2023-02-14
• Subjects: Obesity -- Periodicals; 616.398005
• DOI: 10.1002/oby.23683
• Languages: English
• ISSNs: 1930-7381

Abstract

Abstract: Objective: The aim of this study was to test proportional‐integral‐derivative (PID) control of air inflow rate in a whole‐room indirect calorimeter to improve accuracy in measuring oxygen (O2 ) consumption ( V ̇ O 2 ) and carbon dioxide (CO2 ) production ( V ̇ CO 2 ). Methods: A precision gas blender infused nitrogen (N2 ) and CO2 into the calorimeter over 24 hours based on static and dynamic infusion profiles mimicking V ̇ O 2 and V ̇ CO 2 patterns during resting and non‐resting conditions. Constant (60 L/min) versus time‐variant flow set by a PID controller based on the CO2 concentration was compared based on errors between measured versus expected values for V ̇ O 2, V ̇ CO 2, respiratory exchange ratio, and metabolic rate. Results: Compared with constant inflow, the PID controller allowed both a faster rise time and long‐term maintenance of a stable CO2 concentration inside the calorimeter, resulting in more accurate V ̇ CO 2 estimates (mean hourly error, PID: −0.9%, 60 L/min = −2.3%, p < 0.05) during static infusions. During dynamic infusions mimicking exercise sessions, the PID controller achieved smaller errors for V ̇ CO 2 (mean: −0.6% vs. −2.7%, p = 0.02) and respiratory exchange ratio (mean: 0.5% vs. −3.1%, p = 0.02) compared with constant inflow conditions, with similar V ̇ O 2 ( p = 0.97) and metabolic rate ( p = 0.76) errors. Conclusions: PID control in a whole‐room indirect calorimeter system leads to more accurate measurements of substrate oxidation during dynamic metabolic studies.