Validation of the COSMED K4 b² Portable Metabolic System

The purpose of this investigation was to assess the accuracy of the COSMED K4 b² portable metabolic measurement system against the criterion Douglas bag (DB) method. During cycle ergometry on consecutive days, oxygen consumption (V˙O₂), carbon dioxide production (V˙CO₂), minute ventilation (V˙_E), and respiratory exchange ratio (R) were measured at rest and during power outputs of 50, 100, 150, 200, and 250W. No significant differences (P > 0.05) were observed in V˙O₂ between the K4 b² and DB at rest and at 250 W. Though the K4 b² values were significantly higher (P < 0.05) than DB values at 50, 100, 150, and 200 W, the magnitude of these differences was small (0.088, 0.092, 0.096, and 0.088 L × min^-1, respectively). V˙CO₂ and V˙_E values from the K4 b² were significantly lower than the DB at 200 and 250 W, while no significant differences were observed from rest through 150 W. The slight overestimation of V˙O₂ (50 - 200 W) combined with the underestimation of V˙CO₂ (200 and 250 W) by the K4 b² resulted in significantly lower R values at every stage. These findings suggest the COSMED K4 b² portable metabolic measurement system is acceptable for measuring oxygen uptake over a fairly wide range of exercise intensities.

Key words:

Assessment, oxygen consumption, indirect calorimetry, portable, exercise.

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