Prediction equations for fractional CO uptake derived from 50 healthy subjects.

Fractional CO uptake was measured in 50 healthy men and women aged 18 to 65 years in the sitting and supine positions and during the steady state of treadmill exercise at four different workloads. The unwanted influence of respiratory frequency and ventilation on fractional uptake and the indirect effect of workload (via changes in total diffusing capacity) were taken into account, according to previous theoretical analysis, in formulating prediction equations. Correlations for the best equations were between 0.816 and 0.971. The extra precision they afford makes the fractional CO uptake a potentially useful clinical measurement, less prone to spurious results than conventional measurements of diffusing capacity.