Closed-loop control of air supply to whole-room indirect calorimeters to improve accuracy and standardize measurements during 24-hour dynamic metabolic studies.
Obesity (Silver Spring)
; 31(3): 780-788, 2023 03.
Article
em En
| MEDLINE
| ID: mdl-36788466
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 Ì O 2 ) and carbon dioxide (CO2 ) production ( V Ì 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 Ì O 2 and V Ì 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 Ì O 2 , V Ì 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 Ì 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 Ì 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 Ì 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.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Oxigênio
/
Dióxido de Carbono
Idioma:
En
Ano de publicação:
2023
Tipo de documento:
Article