How is the rate of workload incrementation determined in cardiopulmonary stress testing?

Updated: May 14, 2020
  • Author: Kevin McCarthy, RPFT; Chief Editor: Nader Kamangar, MD, FACP, FCCP, FCCM  more...
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Answer

Determining the proper rate of workload incrementation: The workload incrementation rate should be chosen to produce a test of 8-12 minutes in length. If the workload incrementation is too high, the test will be too brief. In this circumstance, the patient should be allowed to recover and should be retested. If the workload incrementation is too small, fatigue may prevent a valid second test. Below is Wasserman's method for estimating the workload increment size for cycle ergometry:

  • Estimate the unloaded oxygen consumption per minute (VO2): Unloaded VO2 (mL/min) = 150 + (6 × weight [kg])

  • Estimate the peak VO2: Peak VO2 (mL/min) = (height [cm] – age [y]) × 20 for sedentary men or peak VO2 (mL/min) = (height [cm] – age [y]) × 14 for sedentary women

  • Estimate the work rate increment: Work rate increment (watts/min) = (peak VO2 (mL/min) – unloaded VO2 (mL/min)/100

Patients with significant reductions in the predicted VEmax (FEV1 below 50% of predicted) should use an increment of 10 watts/min or less. Patients with severe obstruction resulting in a preexercise maximum voluntary ventilation (MVV) of less than 40 L/min should use an incrementation rate of 5 watts/min.


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