CHARACTERIZATION OF FATIGUE AND EFFECT OF EXERCISE TRAINING IN SEVERE COPD

Fatigue can be described as perceptive fatigue (PF), the subjective feeling of tiredness, exhaustion, or lack of energy, which occurs in daily life, and neuromuscular fatigue (NMF), the reduction of muscle strength and neuromuscular activation during a given task. Both aspects have been described as having a strong impact on the activity of daily life and the quality of life of COPD patients. Very few studies have so far described the presence of both types of fatigue and the impact of exercise training on it in the severest COPD patients, who have already developed chronic respiratory failure (CRF) and are undergoing long-term oxygen therapy. This PhD work aimed to describe the relationship between PF and NMF, comparing patients with and without CRF,to evaluate the scientific literature regarding the effect of exercise training on both PF and NMF in COPD patients, and to study the effect of a pulmonary rehabilitation intervention, including exercise training, in CRF patients. These objectives were evaluated through three dedicated projects described in this thesis. The results can be summarized in the following key points: a) Patients with severe COPD with CRF in LTOT develop higher levels of perceived fatigue and dyspnoea than COPD patients without CRF, while the extent of neuromuscular fatigue is similar in both groups; b) The literature describes the overall beneficial effect of physical training on PF in the COPD population, but no randomized controlled trials have been evaluated the impact on NMF; c) Pulmonary rehabilitation, including exercise training, can reduce PF and improve exercise tolerance and quality of life in COPD with CRF; d) Patients with severe baseline PF and peripheral NMF improve after rehabilitation more than patients without fatigue. Patients with peripheral NMF at baseline had a twofold improvement in exercise tolerance; e) There is a clear mismatch between the perception of fatigue and objective neuromuscular fatigue at baseline and in the change achieved after rehabilitation. A better understanding of the determinants of fatigue may allow the design of new individualized strategies to increase the acute muscle load during the training session and counteract the negative influences of fatigue on daily life. For this [Digitare qui] 4 reason, a specific assessment for both aspects of fatigue should be mandatory in the clinical and rehabilitation settings. Further evaluations are needed about tailored interventions.