What are normal findings on a cardiopulmonary stress test?

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

Answer

A normal CPX test demonstrates a normal peak VO2, the peak HR at or below the predicted maximum HR, and demonstration of ventilatory reserve (peak ventilation/predicted maximum ventilation <65-70%). When the VO2 peak is low, the peak HR is compared to the predicted maximum HR to determine cardiovascular reserve. A ratio of HRpeak to HRpredicted maximum that approaches or exceeds one indicates a clear cardiovascular limitation to exercise.

Likewise, the peak expired volume (minute ventilation, VE) is compared to the larger of a pretest MVV or FEV1 multiplied by 40 to determine the pulmonary reserve. A ratio of VE peak to VE predicted maximum that approaches or exceeds one is a clear indication of pulmonary limitation. A VO2 peak below 15 mL/min/kg often is used as an indication of disability. Pulmonary limitation also may cause significant oxygen desaturation due to the reduction of the transit time of the pulmonary capillary blood to a point where diffusion limitation can occur. In the absence of cardiovascular or pulmonary limitation, peripheral circulatory or skeletal muscle limitation may exist. This must be distinguished from poor effort or malingering.


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