Ventilatory Threshold and Risk of Pulmonary Exacerbations in Cystic Fibrosis

BACKGROUND: Whereas pulmonary exacerbations and aerobic fitness play a key role in the prognosis of cystic fibrosis (CF), the use of ventilatory threshold data as markers of exacerbation risk has been scarcely addressed. This study sought to examine the association between aerobic fit-ness, assessed through ventilatory threshold variables recorded during cardiopulmonary exercise testing (CPET), and the risk of exacerbations in individuals with CF. METHODS: Participants of this retrospective cohort study were subjects from 6 y of age. Over a 4-y period, the following data were recorded: lung function indicators, CPET variables, time to first exacerbation and an-tibiotic use, along with demographic, clinical, and anthropometric data. RESULTS: The mean age of 20 subjects included was 16 +/- 5.4 y. Univariate regression analysis revealed that lung function (FEV1: Cox hazard ratio [HR] 0.97, P = .03; and forced expiratory flow between 25- 75% of vital capacity [FEF25-75]: Cox HR 0.98, P = .036) and aerobic fitness (oxygen consump-tion [VO2] at ventilatory threshold: Cox HR 0.94, P = .01; and ventilatory equivalent for carbon dioxide [VE/VCO2] at ventilatory threshold: Cox HR 1.13, P = .049) were associated with exacerba-tion risk, whereas in the multivariate model, only VO2 at the ventilatory threshold (%max) (Cox HR 0.92, P = .01) had a significant impact on this risk. Consistently, individuals experiencing exacerba-tion had significantly lower VO2 values (%max) at the ventilatory threshold (P = .050) and higher ventilatory equivalent for oxygen consumption (VE/VO2) (P = .040) and VE/VO2 (P = .037) values at the ventilatory threshold. Time to exacerbation was significantly correlated with VO2 at the ventila-tory threshold (r = 0.50, P = .02), VE/VO2 (r = -0.48, P = .02), and VE/VCO2 (r = -0.50, P = .02). CONCLUSIONS: Our results suggest an association between CPET variables at the ventila-tory threshold and exacerbations. Percentage VO2 at the ventilatory threshold could serve as a complementary variable to monitor exacerbations in people with CF.