Peak Oxygen Uptake and Mortality in Cystic Fibrosis: Systematic Review and Meta-Analysis

Abstract

Background: Aerobic fitness, as measured by peak oxygen uptake (V̇_O2 peak), correlates with survival in children and adults with cystic fibrosis (CF). We sought to evaluate the effects of V̇_O2 peak on mortality rates in subjects with CF.

Methods: An online search in PubMed, Embase, LILACS, and SciELO databases was conducted, and cohort studies that assessed mortality rates after oxygen absorption measurements during a maximal exercise test were included. Data were extracted independently by 2 reviewers. The quality analysis of the selected articles was performed using the Newcastle-Ottawa scale. The main outcome evaluated was the mortality of subjects with CF. Whenever possible, and if appropriate, a random effect meta-analysis was performed.

Results: Six cohort studies were included in this systematic review including 551 subjects. Five studies were classified with high methodological quality. Two analyses were carried out to evaluate the influence of V̇_O2 peak on mortality. Total difference standardized mean between V̇_O2 peak averages in the survival or non-survival groups was -0.606 (95% CI = -0.993 to -0.219, P = .002). In addition, subjects with a lower V̇_O2 peak had a significantly higher mortality risk (relative risk 4.896, 95% CI = 1.086 to 22.072, P = .039) in an 8-y follow-up period.

Conclusion: Low levels of peak oxygen uptake are associated with an increase of 4.9 in the risk of mortality in subjects with CF. This indicates that V̇_O2 could be an important follow-up variable to measure, in addition to FEV₁.

Keywords: cystic fibrosis; exercise capacity; exercise test; mortality; oxygen consumption; survival.