Key result
Nafion-based metabolic carts are linked to ~6% overestimation of maximal oxygen uptake from downscale drift.
Why the study?
Does correcting gas analyzer drift in a Nafion-using metabolic cart alter the determination of maximal oxygen uptake and maximal respiratory exchange ratio in males during incremental maximal exercise?
Observational (n=30)
No
Does correcting gas analyzer drift in a Nafion-using metabolic cart alter the determination of maximal oxygen uptake and maximal respiratory exchange ratio in males during incremental maximal exercise?
p-value: p=<0.001
Gas analyzer drift in Nafion-using metabolic carts causes significant systematic errors in maximal oxygen uptake and respiratory exchange ratio, highlighting the need for post-test verification and correction.
Nafion cart drift requires post-test verification to avoid VO2 max overestimation; leaves open effects on clinical and research interpretations.
The aim was to examine the drift in the measurements of fractional concentration of oxygen (FO2) and carbon dioxide (FCO2) of a Nafion-using metabolic cart during incremental maximal exercise in 18 young and 12 elderly males, and to propose a way in which the drift can be corrected. The drift was verified by comparing the pre-test calibration values with the immediate post-test verification values of the calibration gases. The system demonstrated an average downscale drift (P < 0.001) in FO2 and FCO2 of -0.18% and -0.05%, respectively. Compared with measured values, corrected average maximal oxygen uptakevalues were 5-6% lower (P < 0.001) whereas corrected maximal respiratory exchange ratio values were 8-9% higher (P < 0.001). The drift was not due to an electronic instability in the analyzers because it was reverted after 20 min of recovery from the end of the exercise. The drift may be related to an incomplete removal of water vapor from the expired gas during transit through the Nafion conducting tube. These data demonstrate the importance of checking FO2 and FCO2 values by regular pre-test calibrations and post-test verifications, and also the importance of correcting a possible shift immediately after exercise.
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García-Tabar et al. (2015) conducted an observational in Healthy (Exercise Testing) (n=30). Maximal incremental exercise test vs. Pre-test calibration vs post-test verification was evaluated on Average downscale drift in fractional concentration of oxygen (FO2) (p=<0.001). A Nafion-using metabolic cart demonstrated a significant downscale drift in oxygen and carbon dioxide measurements during maximal exercise, leading to a 5-6% overestimation of maximal oxygen uptake.
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