Source: Annual Congress 2002 - Assessment of lung function, telemonitoring and quality of life
Disease area: Airway diseases

Abstract

Introduction
Oxygen consumption V_O2 and carbon dioxide production V_CO2 during exercise are the main outcome parameters in clinical exercise testing. These values may be of crucial importance for patients as to decide whether surgery is feasible. Since these patients exercise at a much lower workload than normal subjects (typically V_O2 at 1 l/min), it is necessary to know the precision of the measurements in that range rather than at high workloads.The question therefore is to find an estimate of precision and to calculate a Confidence Interval (C.I.).
Methods
Five healthy volunteers (median age 27 yr, range 22-31 yr) performed a submaximal test on a cycle ergometer (Oxycon Champion). Minute ventilation V_E, V_O2 and V_CO2 were measured when a steady state was reached. This procedure was repeated every week during 5 weeks. Data were analyzed by repeated measurements Analysis of Variance(ANOVA) with as factors the differences between and within the subjects. The remaining variance is determined by uncontrolled sources as instrument uncertainty, slight protocol deviations etc. From this the residual standard deviation (RSD) can be calculated which is an estimate of the precision of the measurement and from which a C.I. can be calculated.
Results:

parameter	Mean	RSD	90 % C.I.
VE	25.1 l/min	2.05	21.5 - 28.7
VO2	1075 ml/min	66	959 - 1191
VCO2	1018 ml/min	84	871 - 1165

Conclusion
The precision in clinical exercise parameters at low workloads can be assessed by repeated measurements in a number of normal subjects. The 90 % C.I. is +/- 11% at these workloads.

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Citations should be made in the following way:
R. G. Grevink, J. Bouwman, M. D. Swierenga, M. P. Farenhorst, T. W. van der Mark (Groningen, The Netherlands). Precision of exercise measurements: a statistical approach. Eur Respir J 2002; 20: Suppl. 38, 988

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