Resting respiratory variables and exercise capacity in adult patients with cystic fibrosis.

INTRODUCTION: Cystic fibrosis (CF) is the most common life-limiting, recessively inherited disease in the white population, associated with significantly high morbidity and mortality rates; CF pulmonary disease, assessed by pulmonary function tests, arterial blood gases and the Schwachman score, remains the most prevalent in terms of morbidity in the adult CF population. OBJECTIVES: The aim of the present study was to evaluate the relationship between resting respiratory variables and exercise capacity in adult patients with CF. RESULTS: Study investigations undertaken in 18 CF patients and 11 healthy volunteers showed that among the resting lung function parameters, inspiratory capacity (IC) at rest was the only significant predictor of VO(2) peak (r=0.67, p<0.007) and VO(2)/t-slope (r=0.86, p<0.0001). The percentage of predicted FEV(1) in adult CF patients was 77+/-33% pred. vs 104+/-16% pred. in healthy subjects (p<0.006); the corresponding percentage of IC at rest was 82+/-36% pred. in patients vs 116+/-20% pred. in healthy (p<0.003). CF patients presented with a significantly prolonged rapid breathing after exercise (32br per minute at recovery for CF vs 22 for healthy; p<0.001), as well as a shortened inspiratory time. CONCLUSION: Adult patients with CF show a limited exercise capacity with lower peak oxygen consumption and prolonged oxygen kinetics. Interestingly, decreased IC qualified as the only significant predictor of exercise capacity in our study.

Prolonged oxygen kinetics during early recovery from maximal exercise in adult patients with cystic fibrosis.

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 (VO(2)), carbon dioxide production, and ventilation. Maximum VO(2) (VO(2)peak) and the first-degree slope of VO(2) decline during early recovery (VO(2)/t-slope) were calculated. To assess the severity of the disease, we used standard indexes like FEV(1) (% predicted), VO(2)peak, and a widely accepted system of clinical evaluation, the Schwachman score (SS). RESULTS: VO(2)/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 FEV(1)(r = 0.90, p < 0.001), VO(2)peak (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 VO(2)/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.