Reduced exercise ventilatory efficiency in Cystic Fibrosis adults with normal to moderately impaired lung function.

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Di Paolo M; Teopompi E; Savi D; Crisafulli E; Longo C; Tzani P; Longo F; Ielpo A; Pisi G; Cimino G; Simmonds NJ; Neder JA; Chetta A; Palange P;

Journal Of Applied Physiology (Bethesda, Md.: 1985) [J Appl Physiol (1985)] 2019 Jun 20. Date of Electronic Publication: 2019 Jun 20.

Rationale: Despite being a hallmark and an independent prognostic factor in several cardiopulmonary diseases, ventilatory efficiency – i.e. minute ventilation/carbon dioxide output relationship (V’E/V’CO2) has never been systematically explored in cystic fibrosis (CF).
Objective: To provide a comprehensive frame of reference regarding measures of ventilatory efficiency in CF adults with normal to moderately impaired lung function and to confirm the hypothesis that V’E/V’CO2 is a sensitive marker of early lung disease.
Methods: CF patients were divided into 3 groups according to their spirometry: normal (G1), mild impairment (G2) and moderate impairment (G3) in lung function. All participants underwent incremental cardiopulmonary exercise testing on a cycle-ergometer. Lowest V’E/V’CO2 ratio (nadir) and the slope and the intercept of the linear region of the V’E/V’CO2 relationship were contrasted in a two-center retrospective analysis involving 72 CF patients and 36 healthy controls (HC).
Results: Compared to HC, CF patients had significantly higher V’E/V’CO2 nadir, slope and intercept (p<0.001, p<0.001 and p=0.049, respectively). Subgroup analysis revealed significant differences in nadir (p=0.001) and slope (p=0.012) values even between HC and G1. Dynamic hyperinflation related negatively with slope (p=0.045) and positively with intercept (p=0.001), whilst no impact on nadir was observed.
Conclusions: Ventilatory inefficiency is a clear feature of adults with CF, even among patients with normal spirometry. V’E/V’CO2 nadir seems to be the most reliable metric to describe ventilatory efficiency in CF adults. Further prospective studies are needed to clarify whether V’E/V’CO2 could represent an useful marker in the evaluation of early lung disease in CF.