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Validity, reliability and stability of the portable Cortex Metamax 3B gas analysis system
1Institute of Human Performance, The University of Hong Kong, Pokfulam, Hong Kong. djmac@hku.hk
European Journal of Applied Physiology
|November 15, 2011
Summary
The portable Cortex Metamax 3B system reliably measures ventilation, oxygen consumption, and carbon dioxide production in adolescents. However, it overestimates oxygen and carbon dioxide during moderate to vigorous exercise, requiring further correction for accurate metabolic assessment.
Area of Science:
- Exercise Physiology
- Sports Science
- Biomedical Engineering
Background:
- Accurate measurement of metabolic gas exchange is crucial for assessing exercise performance and physiological responses.
- Portable automated gas analysis systems offer convenience but require validation against established methods.
- Adolescent populations present unique physiological considerations for exercise testing.
Purpose of the Study:
- To evaluate the reliability and validity of the Cortex Metamax 3B (MM3B) automated gas analysis system.
- To assess MM3B performance in adolescents during simulated and actual exercise.
- To compare MM3B measurements against criterion methods: Douglas bag method (DBM) and Jaeger Oxycon Pro.
Main Methods:
- Systematic validation using a Gas Exchange System Validator (GESV) across simulated metabolic rates.
- Reliability testing over a 3-hour period for stability of gas fraction measurements.
- Validity testing in eight adolescents during rest, moderate, and vigorous cycle ergometry against DBM and Oxycon Pro.
Main Results:
- MM3B demonstrated adequate reliability (<2% error) for expired ventilation (VE), oxygen consumption (VO2), and carbon dioxide production (VCO2) during simulated exercise.
- The system showed acceptable stability (<2% drift) over 3 hours, particularly at moderate to high metabolic rates.
- MM3B significantly overestimated VO2 and VCO2 by 10-17% during moderate and vigorous exercise compared to DBM, and at all exercise intensities compared to Oxycon Pro.
Conclusions:
- The Cortex Metamax 3B system provides acceptably stable and reliable measurements for VE, VO2, and VCO2 in adolescents.
- The system's validity is compromised during moderate and vigorous exercise due to significant overestimation of VO2 and VCO2.
- Further calibration or correction is necessary for the MM3B to be considered adequately valid for assessing metabolic responses during higher intensity exercise in adolescents.
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