Interpretive Algorithms for the Symptom-Limited Exercise Test

Interpretation of symptom-limited exercise testing requires analysis of a large body of simultaneously recorded cardiopulmonary data. Karlman Wasserman has recommended an algorithmic approach to interpretation (WA) that leads to a dichotomous choice between pulmonary and cardiovascular impairment. An alternative algorithm published by William Eschenbacher (EA) provides for concurrent assessment of cardiovascular and pulmonary exercise impairment. We analyzed a group of 29 individuals referred to the Pulmonary Physiology Laboratory at the Washington Veterans Affairs Medical Center for evaluation of dyspnea following service in the Persian Gulf War to assess the concordance of the two algorithms in determining the cause of dyspnea and exercise impairment in these individuals. They each performed a progressive, ramped, symptom-limited exercise test on a bike for a minimum of 6 min. Exercise measurements were analyzed by both interpretive algorithms. Concordance was found in 28% of tests. The greatest discordance occurred in identifying pulmonary limitation. Eleven had pulmonary limitation by EA; of these, WA found l to have pulmonary limitation, 5 to be normal, 4 indeterminate, and l musculoskeletal limitation. Of the 11 with pulmonary limitation by EA, but not by WA, 5 had abnormal resting pulmonary function measurements. Analysis of the differences between these two interpretive approaches is given. The EA algorithm may be more sensitive for detecting exercise impairment of pulmonary origin, but its specificity remains to be determined.