Symptoms, lactate and exercise limitation at peak cycle ergometry in adults with cystic fibrosis

Abstract

The purpose of this study was to investigate symptoms, lactate accumulation and limiting factors at peak exercise in cystic fibrosis (CF) patients.In total, 104 CF adults attending an adult CF centre and 27 controls performed progressive cycle ergometry to a symptom-limited maximum. Measurements taken at peak exercise included: heart rate, ventilation, oxygen uptake, carbon dioxide output, oxygen saturation and blood lactate. Symptom scores of perceived breathlessness and muscle effort were recorded using Borg scales.The CF subjects had a lower mean body mass index, forced expiratory volume in one second (FEV1) and peak oxygen uptake than controls. Peak lactate concentrations were very similar to controls (mean¡SD 6.8¡2.0 mmol?L -1 versus 7.4¡1.0 mmol?L -1 ). Symptom scores were no different to controls for either breathlessness (4.5¡2.0 versus 4.3¡1.0) or perceived muscle effort (6.1¡2.0 versus 6.5¡1.0), with higher scores for muscle effort than breathlessness in both groups. In addition, peak ventilation was lower than the predicted maximum, and high peak heart rates were recorded supporting nonpulmonary factors as important in limiting peak exercise. Peak oxygen uptake was correlated with FEV1.Comparison of CF subjects with mild or moderate pulmonary disease and controls revealed similar exercise responses. In contrast, those CF patients with severe lung disease (FEV1 ,40% predicted) had significantly higher breathlessness, lower muscle effort scores, lower peak lactate, lower peak heart rate and a mean ventilation exceeding predicted, thus confirming that ventilation was the major factor limiting exercise.In conclusion, cystic fibrosis subjects have a reduced peak exercise capacity, but their exercise response is similar to controls in generating high blood-lactate concentrations and symptoms of muscle effort in excess of dyspnoea. Nonpulmonary factors influence peak performance more in those without severe disease.

Skeletal Muscle Metabolism in Cystic Fibrosis and Primary Ciliary Dyskinesia

“…Although this might seem to be contradictory, we suggest that although intramyocellular dysfunction exists in the patients in this study, there may have been adaptations that compensate for this dysfunction in the oxygen transport pathway. Direct in vivo measurement of muscle oxidative function in humans with CF and PCD has not been previously reported, although investigators have reached similar conclusions based on results from pulmonary gas exchange in CF patients with more advanced disease than those in this cohort (3,36,37). The CF and PCD patients in this study were relatively healthy (FEV 1 Ͼ75%), and it is unlikely that gas exchange was limited as this degree of mild airflow limitation has not been associated with maximal exercise limitation.…”

Static Hyperinflation Is Associated With Decreased Peak Exercise Performance in Children With Cystic Fibrosis

“…Lactate concentration positively correlates with peak V O 2 in adult patients with CF. 32 Moderate elevation in lactate concentration at W peak and high Borg muscle fatigue scores in all patients suggest relatively good skeletal muscle conditioning. In the presence of good muscle conditioning, low peak V O 2 in static hyperinflation subjects may be primarily due to ventilatory reasons.…”

Exhaled nitric oxide in cystic fibrosis: relationships with airway and lung vascular impairments

“…At rest, CA,NO correlated positively with Vc/ VA, which may argue for both NO-related vasodilation or vascular release of NO [12]. Vascular impact of CF disease suggested by exercise test results CF subjects have a reduced peak exercise capacity that seems partly related to nonpulmonary factors in patients with mild to moderate disease [28]. In more severe patients (FEV1 ,40%), ventilatory limitation seems to become a main limiting factor to exercise [28].…”