Pulmonary Rehabilitation for COPD: A Model for Chronic Lung Disease
Pulmonary rehabilitation has arguably the greatest impact of any current therapy on reducing disability and improving exertional capacity in patients with COPD62 and has gained acceptance as a key facet of COPD management. As emphasized in the 2013 Statement on Pulmonary Rehabilitation published by the ATS/ERS, it is a “comprehensive intervention” of “patient-tailored therapies, which include, but are not limited to, exercise training, education, and behavior change.”63 Multiple studies have documented the many positive effects of pulmonary rehabilitation in COPD, including improvements in exertional dyspnea, exercise tolerance, and quality of life,64-66 along with reductions in healthcare utilization, including hospitalizations (frequency and/or length) and hospital readmissions for repeat exacerbations.67 Despite its many other benehts, pulmonary rehabilitation has not been shown to consistently improve lung function or impact mortality. Large randomized trials examining its impact on survival are needed.
In COPD, reduced gas exchange and dynamic hyperinflation are common and powerful determinants of diminished exercise capacity. Techniques to reduce dynamic hyperinflation include breathing retraining and inspiratory muscle training. Training in breathing techniques (such as pursed-lip breathing or so-called “yoga” breathing”) was evaluated by a Cochrane meta-analysis and was found to result in improved exercise capacity, without a consistent effect on dyspnea.68 Inspiratory muscle training, specifically designed to combat the flattened diaphragm’s mechanical disadvantage during exercise, has met with mixed results but is advocated by some experts as a helpful component. One meta-analysis examining the effect of inspiratory muscle training on patients with stable COPD found significant increases in inspiratory muscle strength and exercise capacity, with a decrease in reported dyspnea,69 whereas other studies have not been as definitive. It is not currently advocated as a standard component of rehabilitation, but could be considered in selected patients, particularly those with documented hyperinflation.
Other techniques to reduce the ventilatory load in COPD range from the simple to the complex, and include the use of rolling walkers, which improve diaphragmatic function and facilitate use of accessory muscles of respiration; water-based exercise therapies, which may reduce hyperinflated lung volumes due to hydrostatic force on the chest wall; use of continuous positive airway pressure (CPAP) during exercise, which counteracts dynamic hyperinflation and results in improved exercise capacity in selected patients with advanced COPD70; and neuromuscular electrical stimulation (NMES), which was shown to have some benefit in severely limited patients.71 None of these techniques has been universally endorsed, and further investigation is needed.
The universal use of supplemental oxygen during pulmonary rehabilitation is similarly controversial, with some studies suggesting a benefit in increasing exercise capacity (endurance) in patients with moderate to severe COPD, regardless of documented ambulatory hypoxia. In COPD, increasing the FiO2 during exercise has been shown to reduce hyperinflation and dyspnea, thereby increasing exercise capacity in the short term. Overall, however, no longer-term benefit has been established. The ATS/ERS currently recommends individual oximetry testing to identify those who may benefit, particularly those with dynamic hyperinflation or severe exercise-limiting dyspnea.72 Other studies that examined manipulating the fraction of inspired O2 with the use of helium-oxygen mixtures have not found a routine role for this therapy in pulmonary rehabilitation for patients with COPD.
Methods of assessing and improving exercise capacity in the patient with COPD have been developed and validated. Ambulation has been shown to be as effective a tool for increasing aerobic capacity as use of exercise equipment (such as the stationary bicycle or stepper), and the 6-minute walk distance (6MWD) has become a standard tool for assessing physical activity. Resistance training, of both the lower and upper extremities, has been shown to confer additional benefit and improve general functioning, including the ability to complete the activities of daily living (ADL), and has become a standard component of exercise training in pulmonary rehabilitation.73 Unsupported arm exercises have been shown to reduce dyspnea during performance of ADLs,74 and balance training is appropriate in the selected COPD patient with a history of falls. Finally, interval training75 and muscle partitioning76 appear to increase the duration and intensity of exercise in patients with severe respiratory limitation. Interval training (walking for three 10-minute blocks rather than one 30-minute block, for example) also appears to increase exercise adherence in patients with COPD, but longer-term benefit has yet to be defined. Muscle partitioning (cycling with one leg at a time, for example) has been shown to improve endurance while reducing the ventilatory load.
The educational component of pulmonary rehabilitation for patients with COPD should not be overlooked. Breathing exercises, avoidance of tobacco and other precipitants of lung decline, medication and oxygen adherence, early recognition of exacerbations, and encouragement of healthy nutrition and physical activity should be emphasized. Multiple studies support additive improvement in endurance and quality of life measures when educational techniques are combined with structured exercise.77 Many patients also report that the sense of community derived from the group education sessions is helpful.
Although pulmonary rehabilitation improves exercise performance and quality of life measures in patients with COPD, this is not always accompanied by a sustained improvement in physical activity in daily life. Questions remain regarding optimal duration of therapy; intensity, method, and frequency of follow-up; and how best to prolong the many short-term gains attained during rehabilitation. Determining how to encourage our patients with respiratory disease to continue to
FIGURE 21.8 Benefits of pulmonary rehabilitation in COPD. (Adapted from Pulhan, MA et al. 2011. Cochrane Database Syst Rev. (10):CD005305.)
use the tools obtained during structured rehabilitation is an essential area of research if we hope to achieve a lasting benefit as they live with this chronic disease (Figure 21.8).