EVALUATION OF THE COSMED K2 PORTABLE TELEMETRIC OXYGEN-UPTAKE ANALYZER

The purpose of this study was to determine the validity and evaluate t he accuracy of a portable telemetric oxygen uptake analyzer (K2). Two experiments were carried out: a) using a mechanical lung, the accuracy of the K2 to measure oxygen fractions and minute ventilation followin g 10 and 60 min of warm-up was determined; and b) two maximal graded e xercise tests (GXT) on 15 subjects, one with the K2 system and the oth er with a standardized breath-by-breath (BBB) system, while heart rate (HR), minute ventilation (V-E) and oxygen uptake (VO2) were compared. Following 10-min warm-up prior to calibration, the K2 underestimated the true oxygen fraction as early as 5 min into the test, and this val ue continued to decrease throughout the 30-min test. After 60 min of w arm-up prior to calibration, the K2 accurately measured the true oxyge n fraction for the first 15 min; at minute 20, and on to minute 30, th e K2 underestimated the oxygen fraction. Ventilation volumes were not affected by warm-up time. Minute ventilation during the K2 GXT was sig nificantly higher than V-E for the BBB test. No significant difference s were found between the HRs obtained with the BBB or K2 systems. No d ifferences in VO2, for any stage of the GXT were identified between th e K2 device, BBB device or when a respiratory exchange ratio (RER) cor rection factor was applied to the K2 derived values. However, the RER correction factor did minimize the VO2 differences between the BBB and K2 systems. Therefore, we conclude that the K2 accurately measures VO 2 during a GXT however, its accuracy can be compromised by limitations inherent to the system.