Introduction
Exercise ventilation efficiency index in cardiopulmonary exercise testing (CPET) is elevated in patients with heart failure providing useful information on disease progression and prognosis. Few data, however, exist for ventilation efficiency index among cystic fibrosis (CF) patients.
Aims
To assess ventilation efficiency index (ΔVE/ΔVCO2 or V′E/V′CO2 slope) and intercept of ventilation (VE‐intercept) in CF patients with mild, moderate, and severe cystic fibrosis (CF) lung disease. To assess possible correlations with ventilation inhomogeneity and structural damages as seen on high resolution computed tomography (HRCT).
Methods
CF patients with mild (FEV1 > 80%, n = 47), moderate (60% < FEV1 < 80%, n = 21), and severe (FEV1 < 60%, n = 9) lung disease, mean age 14.9 years participated. Peak oxygen uptake (VO2peak), pulmonary ventilation at peak exercise (VE), respiratory equivalent ratios for oxygen and carbon dioxide at peak exercise (VE/VO2, VE/VCO2), end‐tidal CO2 (PetCO2), and ΔVE/ΔVCO2, ΔVE/ΔVO2 in a maximal CPET along with spirometry and multiple breath washout indices were examined. HRCT scans were performed and scored using Bhalla score.
Results
Mean ΔVE/ΔVCO2 showed no significant differences among the three groups (P = .503). Mean VEint discriminated significantly among the different groups (p
2< 0.001). Ventilation efficiency index did not correlate either with LCI or Bhalla score. However, VE together with ΔVE/ΔVCO2 slope could predict Bhalla score (r
2 = 0.869, P = .006).
Conclusion
No significant differences were found regarding ΔVE/ΔVCO2 slope levels between the three groups. Ventilation intercept (VEint) was elevated significantly as disease progresses reflecting increased dead space ventilation. CF patients retain their ventilation efficiency to exercise even as lung function deteriorates by adopting a higher respiratory rate along with increased dead space ventilation.
As Cystic Fibrosis (CF) treatment advances, research evidence has highlighted the value and applicability of Lung Clearance Index and Cardiopulmonary Exercise Testing as endpoints for clinical trials. In the context of these new endpoints for CF trials, we have explored the use of these two test outcomes for routine CF care. In this review we have presented the use of these methods in assessing disease severity, disease progression, and the efficacy of new interventions with considerations for future research.
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