Study objectives: To explore the significance of oxygen
kinetics during early recovery after maximal cardiopulmonary exercise
testing (CPET) in the assessment of functional capacity and severity of
the disease in cystic fibrosis (CF) patients.
Participants: Eighteen patients with CF (9 male/9 female;
mean ± SD age, 23 ± 13 years) and 11 healthy subjects (3 male/8
female; mean age, 29 ± 4 years) underwent maximum CPET on a
treadmill. Breath-by-breath analysis was used for measuring oxygen
consumption (V̇o2), carbon dioxide
production, and ventilation. Maximum V̇o2
(V̇o2peak) and the first-degree slope of
V̇o2 decline during early recovery
(V̇o2/t-slope) were calculated. To assess
the severity of the disease, we used standard indexes like
FEV1 (% predicted), V̇o2peak,
and a widely accepted system of clinical evaluation, the Schwachman
V̇o2/t-slope was significantly lower in CF
patients compared to healthy subjects (0.61 ± 0.31 L/min/min vs
1.1 ± 0.13 L/min/min; p < 0.01) and was closely correlated to
FEV1(r = 0.90, p < 0.001),
V̇o2peak (r = 0.81,
p < 0.001), and the SS (r = 0.81, p < 0.001).
The multivariate analysis showed that the only independent predictor of
the SS is the V̇o2/t-slope.
Conclusion: We conclude that in CF patients, the prolonged
oxygen kinetics during early recovery from maximal exercise is related
to the disease severity.