Sensitivity Analysis of Whole-Room Indirect Calorimeters at the Steady-State Condition

Whole-room indirect calorimeters (WRICs) are accurate tools to precisely measure energy metabolism in humans via calculation of oxygen consumption and carbon dioxide production. Yet, overall accuracy of metabolic measurements relies on the validity of the dynamic model for gas exchange inside the calorimeter volume in addition to experimental and environmental conditions that contribute to the uncertainty of WRIC outcome variables. The aim of this work is to formally study the sensitivity of a WRIC system operated in a push configuration at the steady-state condition to identify the optimal experimental conditions to obtain the best degree of accuracy for outcome metabolic measurements. The results of our sensitivity analysis are then validated with measurements obtained during propane combustion tests performed at the WRIC located at the University Hospital of Pisa. Our results demonstrate that achieving a fractional concentration of carbon dioxide inside the calorimeter $>$ 0.2% leads to relative uncertainty < 5% for the outcome metabolic measurements when assuming an accuracy class of 1% for gas analyzer instruments.