Breathing Reserve (%) Calculator

Breathing Reserve (BR%) Calculator: Explanation and Clinical Context Breathing Reserve is the difference between the predicted maximal voluntary ventilation (VEmax) and the peak exercise ventilation (VEpeak), expressed as a percentage of VEmax. It reflects the ventilatory capacity left unused at peak exercise. A normal BR% is typically 20-40%, indicating adequate ventilatory reserve.

A lower BR% (<20%) suggests a ventilatory limitation to exercise, commonly seen in obstructive or restrictive lung disease, pulmonary vascular disease, or heart failure. This measure is essential for cardiopulmonary exercise testing (CPET) interpretation, helping clinicians identify whether exercise intolerance is due to pulmonary, cardiac, or deconditioning causes.