Exercise Training in Chronic Obstructive Pulmonary Disease - 05/09/11
Resumen |
Exercise intolerance is a characteristic and greatly troubling manifestation of chronic obstructive pulmonary disease (COPD). Patients with moderate to severe COPD are limited commonly in their abilities to perform usual tasks, such as work activities, recreational exercise, and hobbies. When tested in the laboratory setting, patients with COPD typically have higher metabolic cost of exercise with early-onset lactic acidosis and reduced maximal work rate and oxygen consumption compared with healthy persons of comparable age. In the presence of advanced disease, patients experience increasing difficulty in performing activities of daily living such as self care and household maintenance. The resultant inactivity leads to progressive deconditioning that further increases the sense of respiratory effort related to any task. As exercise intolerance worsens over time, patients often become progressively homebound and isolated from colleagues, friends, and family members. This sequence of events frequently impairs the patient's quality of life (QOL). Concomitantly, some individuals develop worsening depression and anxiety and may withdraw progressively from their usual routines.
The basis of exercise intolerance in COPD is complex and multifactorial.50 The physiologic mechanisms of exercise intolerance are discussed in detail in the article by Nici elsewhere in this issue. In brief, increased airways resistance, ineffective ventilation, hyperinflation and increased elastic load to breathing, gas exchange abnormalities, and mechanical disadvantage (and in some cases weakness) of the respiratory muscles all contribute to ventilatory limitation during exertion and exercise.50, 119 Skeletal muscle dysfunction is another important factor that can contribute to exercise intolerance.7 This skeletal muscle dysfunction (discussed in detail in the article by Maltais and colleagues in this issue) is characterized by reduction in muscle mass and strength,11, 18 atrophy of type I65, 69 and type IIa muscle fibers,68 reduction in fiber capillarization133 and oxidative enzyme capacity,70, 92 and reduced muscle endurance.7, 84, 131 Both resting and exercise muscle metabolisms are impaired.7, 89, 92 The impaired muscle strength is associated with reduced exercise capacity55, 62 and increased use of health care resources by patients with COPD.43 Oxygen delivery and consumption by the legs is unaffected at submaximal exercise89 but may be severely impaired at peak exercise because of complex interactions involving central and peripheral factors.89 Cardiocirculatory, nutritional, and psychologic factors can also affect exercise performance. In addition to the pathophysiologic processes underlying exercise intolerance in COPD, the symptom of dyspnea is a nearly universal complaint and is the usual cause of exercise limitation cited by the patient.75 Leg fatigue and discomfort are also common reasons for cessation of exercise.75
Importantly, although COPD (in particular, emphysema) is characterized by irreversible structural alterations in lung architecture, the exercise tolerance of patients with COPD can be improved. Medical therapy and breathing strategies such as pursed-lip breathing can improve the ventilatory limitations to exercise. Oxygen143 and nutritional intervention162 can improve exercise performance. Psychologic support and slow, deep breathing can reduce anxiety and minimize lung hyperinflation during exercise. Finally, exercise training has now been proved to be highly beneficial for patients with COPD.
Exercise training has been used in the treatment of patients with COPD since the early 1960s.26, 100 The use of widely variable exercise protocols in differing types of settings, for patients of varied disease severity and the initial predominance of uncontrolled clinical trials, however, raised some skepticism regarding the clinical benefits of exercise training for these persons. In recent years, exercise training has been shown conclusively to improve the exercise tolerance of patients with COPD.** It also improves breathlessness, leg fatigue, and health-related QOL.5, 6, 54, 79, 83, 129, 159
In this article, the authors review the data supporting the use of exercise training for patients with COPD. They also discuss the effects of training at different intensities and the mechanisms by which exercise performance improves. It must be noted, however, that although some clinical trials demonstrating benefits of exercise training have been undertaken in an exercise laboratory, many others have been conducted in the context of a comprehensive pulmonary rehabilitation (PR) program. As a result, although exercise training is a crucial core process of PR, the benefits of the training noted in these trials cannot be viewed as separate from the contributing benefits of the many other important treatment strategies included in PR, such as patient and family education, training with pacing, energy conservation and breathing techniques (e.g., pursed-lip breathing), anxiety and dyspnea management, optimization of oxygen therapy, medical management, and nutrition. Indeed, although not the focus of this review, these additional processes likely enhance and maximize the benefits of exercise training.5, 6 As such, when possible, exercise training for patients with COPD optimally should be pursued initially in the setting of a formal PR program. It is hoped that the techniques and strategies learned in PR will then be transferred into and continued within the home environment for maintenance of the benefits achieved over the long term.
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| Address reprint requests to Carolyn L. Rochester, MD, Section of Pulmonary and Critical Care, Yale University School of Medicine, Building LCI-105, 333 Cedar Street, New Haven, CT 06520, e-mail: carolyn.rochester@yale.edu |
Vol 21 - N° 4
P. 763-781 - décembre 2000 Regresar al número
Artículo precedente
- Nutritional Abnormalities and Supplementation in Chronic Obstructive Pulmonary Disease
- A.M.W.J. Schols, E.F.M. Wouters
- Noninvasive Ventilation in Chronic Obstructive Pulmonary Disease
- Nicholas S. Hill
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