PT  - JOURNAL ARTICLE
AU  - Kaminsky, David A.
AU  - Knyazhitskiy, Alexey
AU  - Sadeghi, Ali
AU  - Irvin, Charles G.
TI  - Assessing Maximal Exercise Capacity: Peak Work or Peak Oxygen Consumption?
AID  - 10.4187/respcare.02253
DP  - 2013 Jun 18
TA  - Respiratory Care
PG  - respcare.02253
4099  - http://rc.rcjournal.com/content/early/2013/06/18/respcare.02253.short
4100  - http://rc.rcjournal.com/content/early/2013/06/18/respcare.02253.full
AB  - Background: Exercise capacity assessed by cardiopulmonary exercise testing is usually measured by peak oxygen consumption (peak V̇O2). However, not uncommonly, patients achieve a relatively higher Work load (peak Work) compared to their peak V̇O2. In these situations, it is difficult to know which parameter to use in assessing exercise capacity. The purpose of this study was to determine whether there are distinguishing physiological characteristics of patients with discordance between percent predicted peak Work vs. peak V̇O2 in order to understand how to use these measures in interpreting exercise capacity. Methods: We conducted a retrospective study of 172 cardiopulmonary exercise tests performed at our institution between 2003 and 2010. Subject characteristics were compared by ANOVA and multivariate logistic regression analysis. Results: The patients in the higher peak Work group demonstrated higher ventilatory efficiency (lower VE / V̇CO2 slope) and lung function (FEV1 and FVC), a greater breathing reserve (higher BR, lower VE /MVV), and achieved a higher maximal heart rate. Patients in the higher max V̇O2 group were heavier, had lower ventilatory efficiency, and had a reduced breathing reserve. Multivariate logistic regression analysis showed that the predominant independent factors associated with group assignment were BMI, breathing reserve, and peak heart rate, with patients achieving higher percent predicted peak Work than peak V̇O2 having a lower BMI, a greater breathing reserve and a higher peak heart rate. Conclusion: The observation that there are distinguishing physiological features between those who have a higher peak Work than peak V̇O2 provides insight into the underlying processes determining maximal exercise capacity.