Noninvasive assessment of normality of VD/VT in clinical cardiopulmonary exercise testing utilizing incremental cycle ergometry.

Dead space to tidal volume ratio (V(D)/V(T)), a measure of pulmonary gas exchange efficiency, cannot be accurately calculated without arterial blood sampling. We sought to determine, in patients presenting for diagnostic cardiopulmonary exercise tests, whether there are ranges of the ratio of exhaled ventilation to carbon dioxide output (V(E)/VCO(2)) measured at the lactate threshold that are highly predictive of normality or abnormality of exercise V(D)/V(T) (below or above 0.3) and whether other demographic or physiologic variables aid in this prediction.