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A validation study of the Q-Plex I cardiopulmonary exercise system

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Davey, William G
Butts, N. K.
MS, Adult Fitness/Cardiac Rehabilitation
May 1991
Pulmonary function tests - Validity; Treadmill exercise tests - Validity; Pulmonary gas exchange; Q-Plex I Cardiopulmonary Exercise System
A total of 27 Ss from the University of Wisconsin-La Crosse, ages 19-34 yrs, volunteered to participate in the validation study of the Q-Plex I Cardiopulmonary Exercise System developed by the Quinton Instrument Company. Each S performed a constant speed, grade incremented treadmill test to volitional exhaustion. Simultaneous measurements of expired air ware performed with the Q-Plex and a meteorological balloon gas collection system to determine the validity of the Q-lex. Respiratory and metabolic assessments were made during at least 3 different levels of exercise; low steady state, medium steady state, and at maximal exertion. A total of 93 gas samples were collected and analyzed by the 2 methods. The means for FeO2 and FeCO2 were significantly (p0.85) different. However, the absolute mean differences were only 0.5% for FeO2 and 0.3% for FeCO2 which are within the accuracy of the reported error for the analyzers. These results indicated that the Q-Plex gas analyzers are as accurate as the micro-Scholander technique. Correlation coefficients between the 2 systems were .9735 for FeO2 and .9729 for FeCO2. After all the validation data were collected a final comparison was mule between a series of volumes obtained with the Parkinson-Cowan meter and the Tissot spirometer. These results indicated there was a much larger discrepancy in volumes obtained between these methods than those initially reported. These differences were of sufficient manitude to question the accuracy of using this meter to validate the volumes obtained with the Q-Plex. Since it was impossible to determine the cause of this error, or at what point in the study it occurred, the VE volumes of the Q-Plex could not be legitimately validated using the Parkinson-Cowan meter. Unfortunately, since the accuracy of measuring VO2 and VCO2 is dependent upon VE volumes, neither of these volumes could be compared. Within the limitations of the present study, it was concluded that the gas analyzers in the Q-Plex demonstrate accuracy comparable to that of the micro-Scholander technique.
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