System of automated gas-exchange analysis for the investigation of metabolic processes

Abstract

Conventional gas-exchange instruments are confined to the measurement of O(2) consumption (VO(2)) and CO(2) production (VCO(2)) and are subject to a variety of errors. This handicaps the performance of these devices at inspired O(2) fraction (FI(O(2))) > 0.40 and limits their applicability to indirect calorimetry only. We describe a device based on the automation of the Douglas bag technique that is capable of making continuous gas-exchange measurements of multiple species over a broad range of experimental conditions. This system is validated by using a quantitative methanol-burning lung model modified to provide reproducible (13)CO(2) production. The average error for VO(2) and VCO(2) over the FI(O(2)) range of 0.21-0.8. is 2.4 and 0.8%, respectively. The instrument is capable of determining the differential atom% volume of known references of (13)CO(2) to within 3.4%. This device reduces the sources of error that thwart other instruments at FI(O(2)) > 0. 40 and demonstrates the capacity to explore other expressions of metabolic activity in exhaled gases related to the excretion of (13)CO(2).

Validity and reliability of selected commercially available metabolic analyzer systems

“…The Deltatrac and CPX devices both exhibited increasing . VO 2 errors as F I O 2 was elevated (Midownik et al, 2000). There was no significant difference in .…”

“…The Med Graphics CPX average V̇O 2 and V̇CO 2 error was 2.6% and 1.7%, respectively. The Deltatrac and CPX devices both exhibited increasing V̇O 2 errors as F I O 2 was elevated (Midownik et al, 2000). There was no significant difference in V̇CO 2 measurements for all devices.…”

“…. Midownik et al (2000) developed a semi-automated gas exchange measurement system based on a Douglas bag design. This system was validated using a modified version of the quantitative funnel burner lung model (Miodownik et al, 1998) and standard water volume displacement.…”

“…In order to verify the preciseness of this important parameter, a number of studies have examined the biological variability of day-to-day measures and have reported good reliability values (Katch et al, 1982;Kuipers et al, 1985). Several studies make comparisons of the measurement agreement between different automated systems and between automated systems and a criterion method (Kannagi et al, 1983;Versteeg & Kipperluis, 1989;La Mere et al, 1993;Miles et al, 1994;Unnithan et al, 1994;Babineau et al, 1999;Jacobs, 1999;Midownik et al, 2000;Bassett et al, 2001). Furthermore, many new portable metabolic measuring devices are being validated against a standard reference value (Melansen et al, 1996;Wideman et al, 1996;Midownik et al, 2000), that most consider to be accurate and assume, without hesitation, that it represents the gold standard.…”

VO2 and VCO2 variabilities through indirect calorimetry instrumentation

“…It is clear that the canopy in the Delta Track II performs as an open circuit MC technique with the capability to reject high frequency variabilities. Deltra Track’s hardware can be modelled as a time average filter so that the VO 2 and VCO 2 variabilities from unstable patients produce minimum inter-individual variations in the REE estimation (Severine et al 2013; Miodownik et al 2000). …”