Exercise testing in patients with cystic fibrosis-importance of ventilatory parameters

Abstract

Background: Ventilatory parameters obtained during exercise predict survival in several chronic diseases; however, long-term changes in exercise ventilatory parameters in patients with cystic fibrosis (CF) have yet to be examined and potential differences between sexes in CF are unknown.

Purpose: We sought to examine the change in exercise ventilatory parameters over time in patients with CF and determine if the change is different between sexes.

Methods: Exercise capacity (VO₂ peak) and exercise ventilatory parameters (V_E/VO₂ peak, V_E/VCO₂ peak, and V_E/VCO₂ slope) were determined from a maximal cardio-pulmonary test on a cycle ergometer on two visits separated by 39 ± 16 months in 20 patients with CF (10 female, 10 male).

Results: No differences between sexes were observed at visit 1 (all p > 0.05). Overall, exercise ventilatory parameters significantly (p < 0.05) deteriorated between visits, with no change (p > 0.05) in VO₂ peak. Moreover, compared to males, female patients exhibited greater deteriorations in V_E/VO₂ peak (p = 0.001), V_E/VCO₂ peak (p = 0.002), and V_E/VCO₂ slope (p = 0.016) between visits.

Conclusions: These data in patients with CF indicate that exercise ventilatory parameters decline over time despite no change in VO₂ peak, and female patients exhibit a more rapid deterioration compared to males.

Keywords: Exercise capacity; Pulmonary function; Ventilatory efficiency.

Figure 1.

Individual and mean (inset) changes in the ratio of minute ventilation (V_E) to oxygen uptake (VO₂) at peak exercise (A), V_E to carbon dioxide output (VCO₂) at peak exercise (B), and the V_E to VCO₂ slope (C) in male and female patients between visits 1 and 2. The time between visits (months) are presented with each column for each patient. *significantly greater in females versus males (p≤0.016).

Figure 2.

Group changes between visits in FeCO₂ at peak exercise (A) and P_ETCO₂ at peak exercise (B). ^†significant group by time interaction; *significant difference between groups at visit 2 (p=0.017).

Figure 3.

Associations between baseline FEV₁ (% predicted) and changes in exercise ventilatory parameters (A, B, and C) and between changes in FeCO₂ at peak and exercise ventilatory parameters (D, E, and F). Lilac and blue dots indicate female and male patients, respectively.