Although systemic oxygen consumption (V̇O2) is independent of O2 delivery (Q̇O2) in normal subjects, studies have suggested that supply dependence of V̇O2 may occur in patients with chronic diseases associated with reduced Q̇O2. In this regard, we previously found that Q̇O2 and V̇O2 increased when cardiac output was improved after balloon valvuloplasty in patients with aortic stenosis. However, their increases in Q̇O2 were relatively small, and it was not known whether the increase in V̇O2 was caused by the increase in delivery or was merely a response to the transient hypotension induced by valvuloplasty. Because patients with mitral stenosis frequently exhibit greater improvements in cardiac output after valvuloplasty than do patients with aortic stenosis, the present study sought to determine (1) whether V̇O2 is increased after valvuloplasty in patients with mitral stenosis, and (2) whether the magnitude of the increase in V̇O2 correlates with the magnitude of the improvement in cardiac output and Q̇O2. Oxygen delivery, V̇O2, and hemodynamics were measured in 57 patients with mitral stenosis before and 20 to 30 min after undergoing balloon valvuloplasty. After valvuloplasty, Fick-derived oxygen delivery increased by 13.0% (95% confidence interval: 10.8 to 15.2%), whereas V̇O2 (expired gas) increased by 8.3% (95% confidence interval: 9.5 to 12.3%). A correlation between Fick- derived Q̇O2 and V̇O2 was found (p < 0.005) with a slope of 0.66 (95% confidence interval: 0.07 to 1.24), but the O2 extraction ratio did not change (-1.0%; 95% confidence interval: -2.7 to 0.5%). A significant correlation between the change in Q̇O2 and the change in V̇O2 was also seen (p < 0.02). These findings suggest that the increase in V̇O2 may have been a consequence of the increase in Q̇O2 rather than a response to the procedure itself.
|Original language||English (US)|
|Number of pages||7|
|Journal||American journal of respiratory and critical care medicine|
|State||Published - 1996|
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Critical Care and Intensive Care Medicine