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Gazzetta Medica Italiana - Archivio per le Scienze Mediche 2019 October;178(10):729-35

DOI: 10.23736/S0393-3660.18.03820-2


language: English

An easy method to correct the bias of non-metabolic CO2 release on indirect calorimetry

Steffen LOTZ 1 , Eva HEINEN 1, Fabian STÖCKER 2, Mathias BEYER 3, Edgar HEINEN 3

1 Center for Training and Diagnostics, Injoy Feldkirchen, Feldkirchen, Germany; 2 Center for Teaching and Learning, Technical University of Munich, Munich, Germany; 3 Private Practitioner, Nuremberg, Germany

BACKGROUND: The aim of this study was to define the volume of CO2 during an increasing workload due to bicarbonate buffering of lactate from oxidation at the cellular level, in order to calculate the amount of oxidation of fatty acids and glucose respectively.
METHODS: Eight male soccer players (21-39 years) completed an incremental exercise test (40 W every 4 minutes) to exhaustion on a cycle ergometer. VO2 and the VCO2 were measured for each single workload. Additionally, pCO2, pO2, pH and lactate were measured by blood gas analysis from the hyperemized ear lobe, allowing the calculation of the bicarbonate concentration and of the total volume of CO2 dissolved in one liter of plasma at the end of each workload. Taking into account a CO2 distribution volume of 25% of the bodyweight, the CO2 solved in the extracellular compartment (CO2ECS) of the body could be calculated. Changes of the volume of CO2ECS were subtracted from the VO2. Thus a corrected RER could be obtained.
RESULTS: While RER showed the typical increase when the load was increased, corrected RER did not show any significant change up to maximal load.
CONCLUSIONS: The total amount of fatty acids oxidized increases continuously up to the maximal load. Results from others, who interpret the increased volume of VCO2 seen, when the load is augmented, as a result of a decreased oxidation of fatty acids are due to a neglect of the volume of VCO2, which results from buffering lactate.

KEY WORDS: Respiratory transport; Soccer; Fatty acids; Metabolism; Bicarbonates; Anaerobic threshold

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