Background: It is often difficult to select an appropriate workload increment for progressive cycle exercise tests in order to achieve optimal test duration (8-12 min). We hypothesize that baseline respiratory function can be systematically used to select appropriate workload increment to optimize test duration in patients referred to the clinical laboratory.
Methodology: One hundred and eighty consecutive exercise tests (with increments of 15 W/min) were retrospectively assessed. Using regression analysis, an equation was generated that predicts the work rate increment that would provide exercise duration of 8-12 min. The validity of this equation was tested prospectively in 231 consecutive tests performed with the calculated workload increment rounded to the nearest 5 watts (W).
Results: The best regression equation was: workload increment (W/min)=1.94 x FEV1 (L) + 0.63 x TLCO (mmol/min per kPa) - 0.07 x age + 1.94 x gender (male=1, female=0) + 4.12 (r=0.85, P < 0.0001). Using this equation allowed selection of the most appropriate workload increment in 79% of tests and reduced the number of tests of non-optimal duration from 72% (for a fixed increment of 15 W/min) to 38%.
Conclusions: Utilization of this regression equation allows standardization in the selection of workload increment, and reduces the number of cycle exercise tests of inadequate duration.