Understanding respirometry chambers: what goes in must come out.

An examination of the compartmental dilution washout in metabolic chambers was conducted and new equations for the calculation of "instantaneous" VO2 were derived. Using appropriate compartmental models, an evaluation was carried out on systems used in previous estimates of this parameter. Effects of chamber mixing and sampling times on calculated VO2 values were also examined. Alternatives to resolving "instantaneous" VO2 are presented with emphasis on system design rather than on mathematical manipulation.