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The Proceedings of the American Thoracic Society 4:549-553 (2007)
© 2007 The American Thoracic Society
doi: 10.1513/pats.200701-015FM
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The Nonpharmacologic Treatment of Chronic Obstructive Pulmonary Disease

Advances in Our Understanding of Pulmonary Rehabilitation

Richard ZuWallack1,2

1 Section of Pulmonary and Critical Care, St. Francis Hospital and Medical Center, Hartford, Connecticut; and 2 University of Connecticut School of Medicine, Farmington, Connecticut

Correspondence and requests for reprints should be addressed to Richard ZuWallack, M.D., Pulmonary and Critical Care, St. Francis Hospital and Medical Center, 114 Woodland Street, Hartford, CT 06105. E-mail: rzuwalla{at}stfranciscare.org

ABSTRACT

The optimal care of patients with chronic obstructive pulmonary disease generally requires combining pharmacologic and nonpharmacologic therapies. The latter include smoking cessation, the encouragement of physical activity and exercise, influenza and pneumonia vaccinations, education on adherence to medical therapy, collaborative self-management strategies, such as a plan to manage exacerbations, and advance directives. Although each of these is a component of good medical practice, they can be given together in the form of a comprehensive outpatient pulmonary rehabilitation program. Pulmonary rehabilitation, which includes exercise training, education, psychosocial support, and nutritional intervention, has demonstrated effectiveness over multiple outcome areas, despite the fact that it has virtually no direct effect on the underlying pathophysiology of the lung. This intervention works primarily through its beneficial effects on associated morbidity, such as physical deconditioning. Pulmonary rehabilitation is indicated when respiratory symptoms or functional limitations persist despite otherwise standard medical therapy. Combining optimal bronchodilator therapy and/or supplemental oxygen therapy with exercise training will enhance the effectiveness of the latter.

Key Words: activity • chronic obstructive pulmonary disease • exercise • pulmonary rehabilitation

The optimal medical care for individuals with chronic obstructive pulmonary disease (COPD) generally requires combining pharmacologic and nonpharmacologic therapies. The latter include the promotion of a healthy lifestyle, including smoking cessation and the encouragement of exercise and physical activity, providing vaccinations, education on adherence with medical therapy, development of collaborative self-management strategies, such as an action plan for the early and effective treatment of exacerbations, and advance directives as part of end-of-life planning. The incorporation of the above interventions, when necessary, is simply good medical practice. This concept has been emphasized in the recent Statement on Pulmonary Rehabilitation developed by the American Thoracic Society (ATS) and the European Respiratory Society (ERS):

In a broader sense, pulmonary rehabilitation includes a spectrum of intervention strategies integrated into the lifelong management of patients with chronic respiratory disease and involves a dynamic, active collaboration among the patient, the family, and health care providers. (1)

An efficient and effective method of bundling the above therapies for patients with COPD of moderate severity or greater is often in the form of a comprehensive pulmonary rehabilitation program. However, not all individuals are candidates for pulmonary rehabilitation or even have access to this therapy, so efforts should be made to foster the application of this good medical care across the spectrum of COPD. This is usually done in piecemeal fashion by healthcare providers. Some other general approaches to the integrated care of COPD include self-management programs (2, 3), nurse-led chronic disease management for patients with COPD (4), "Hospital at Home" programs for patients with COPD with acute exacerbations (5), and integrated care programs for patients after discharge for COPD exacerbations (6). These innovative approaches have been recently discussed in an editorial (7); the pulmonary rehabilitation approach will be presented subsequently here.

WHAT PULMONARY REHABILITATION IS, WHAT IT DOES, AND HOW IT WORKS

Definition of Pulmonary Rehabilitation
The ATS/ERS statement has defined pulmonary rehabilitation as

... an evidence-based, multidisciplinary, and comprehensive intervention for patients with chronic respiratory diseases who are symptomatic and often have decreased daily life activities. Integrated into the individualized treatment of the patient, pulmonary rehabilitation is designed to reduce symptoms, optimize functional status, increase participation, and reduce health care costs through stabilizing or reversing systemic manifestations of the disease. (1)

The ATS/ERS statement goes on to describe further the process of pulmonary rehabilitation:

Pulmonary rehabilitation programs involve patient assessment, exercise training, education, nutritional intervention, and psychosocial support. (1)

When indicated, nutritional intervention and psychosocial support may also be given. As the above definition and description indicate, pulmonary rehabilitation is usually provided by an interdisciplinary team in collaboration with the patient and family. Components of pulmonary rehabilitation are listed in Table 1. Pulmonary rehabilitation is tailored to the specific needs of the individual patient; therefore, the emphasis and application of each of these components of care varies considerably among patients.


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  		TABLE 1. COMPONENTS OF COMPREHENSIVE PULMONARY REHABILITATION PROGRAMS

 
How Pulmonary Rehabilitation Works
Pulmonary rehabilitation has no substantial effect on the lung impairment, such as the FEV1, of patients with COPD or other chronic respiratory diseases. Despite this, pulmonary rehabilitation usually results in beneficial outcomes in several important aspects of health and well-being, including dyspnea, exercise performance, disability, and quality of life. This apparent paradox is explained by the fact that patients with COPD usually have substantial, associated morbidity that is responsive to the pulmonary rehabilitation interventions. Some examples of this potentially reversible associated morbidity include physical deconditioning from adopting a sedentary lifestyle, peripheral muscle dysfunction, nutritional and body composition abnormalities, fear of dyspnea-producing activities, and improper pacing.

Positive Outcomes from Pulmonary Rehabilitation
Despite the fact that pulmonary rehabilitation has no direct effect on the specific respiratory impairment in COPD, a large body of scientific evidence demonstrates its beneficial effects over multiple outcome areas (8) (Table 2).


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  		TABLE 2. POSITIVE OUTCOMES ASSOCIATED WITH PULMONARY REHABILITATION

 
In most cases, the positive signal from pulmonary rehabilitation in areas such as dyspnea relief and exercise performance enhancement is appreciably greater than that from other conventional treatments, including long-acting bronchodilators. Pulmonary rehabilitation and pharmacologic therapy should be considered complementary to each other: (1) if a patient with COPD remains symptomatic despite bronchodilators, pulmonary rehabilitation would likely provide additional benefit, and (2) optimal bronchodilation allows for higher intensity exercise training during pulmonary rehabilitation, thereby enhancing its effects.

DEVELOPING AREAS IN THE SCIENCE AND APPLICATION OF PULMONARY REHABILITATION

Activity and Exercise in COPD
The progression of COPD is often characterized by deteriorating respiratory physiology (such as a declining FEV1) and progressive limitation in exercise capacity and physical activity levels. There are multiple reasons for this reduction in exercise capacity in COPD. Dyspnea from ventilatory limitation, gas exchange abnormalities, and hyperinflation limits exercise performance (9, 10). Peripheral muscle abnormalities, including reductions in oxidative enzymes and reductions in muscle mass of the lower extremities, contribute substantially to exercise limitation (11). In response to the dyspnea and fatigue associated with physical exertion, the patient with COPD often subconsciously adopts a more sedentary lifestyle, limiting or giving up some more strenuous physical activities (12). Although this reduces distressing symptoms (one cannot have exertional dyspnea without exertion), the activity limitation is itself detrimental, being associated with higher risk of mortality and hospital resource use (13).

Although clinicians have long recognized that patients with COPD are quite sedentary, only recently was this proven with direct activity assessments (14) (Figure 1). This study, which used accelerometer activity monitors on the waist and leg of patients with COPD, demonstrated that they spent considerably less time walking and standing than control subjects without COPD. Overall activity correlated highly (r = 0.76) with the six-minute-walk distance. Physical activities appear to be particularly reduced in the period after the exacerbation of COPD (15) and with the use of long-term oxygen (O2) therapy (16). Pulmonary rehabilitation would appear to be particularly indicated in these two settings.


Figure 1
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  		Figure 1. Activity limitation in patients with chronic obstructive pulmonary disease (COPD). Horizontal bars represent the percentages of time spent in each of the activities or body positions in age-matched healthy subjects and patients with COPD. Patients with COPD spent less time walking and standing, and more time sitting and lying, than did control subjects. Reprinted by permission from Reference 14.

 
It is reasonable to assume that improved exercise tolerance from pulmonary rehabilitation will lead to increased physical activities in patients with COPD, but this has yet to be proven. Pulmonary rehabilitation is more than just exercise training, and these interventions also will increase physical activities of daily living, independent of an enhancement of exercise performance. For example, improved pacing and increased self-efficacy for walking may increase activity despite no demonstrable improvement in exercise testing. Further investigation is needed in the effect of pulmonary rehabilitation on activity.

Decreases in both functional exercise capacity and physical activity appear to be related to increased health care use and mortality in COPD (17–21). It also remains to be determined whether improvements in these areas, resulting from pulmonary rehabilitation, will lead to improved outcomes in these important areas—although this is certainly plausible.

Collaborative Self-Management Strategy
Self-management education, as an important component of comprehensive pulmonary rehabilitation (22), modifies health behavior by promoting skills to help control the effects of the respiratory disease and its comorbidity (23). Probably the most important component of a self-management strategy approach is instruction in the prevention and early treatment (by way of an action plan) of the COPD exacerbation. Early treatment of the COPD exacerbation hastens recovery (24) and reduces health care use (23). The action plan, which requires collaboration between the health care provider and the patient, usually consists of initiating a predetermined medication regimen (such as oral steroids and antibiotics) early in the exacerbation, followed by communication with the health care provider.

Initiating Pulmonary Rehabilitation Immediately after the COPD Exacerbation
Patients with COPD are usually sent to pulmonary rehabilitation when, despite otherwise optimal medical therapy, they still have bothersome symptoms, such as dyspnea or fatigue, or persistent disability, especially physical activity limitation. Although a referral might be made at discharge after a hospitalization for an exacerbation of COPD, patients are commonly sent to rehabilitation in a relatively stable state (25). However, as recent studies indicate, referring patients to pulmonary rehabilitation shortly after hospitalization for a COPD exacerbation may substantially reduce subsequent health care use and—possibly—mortality risk (26). New self-management strategies, such as early treatment of subsequent exacerbations, plus enhanced exercise capacity and physical activity probably underlie these beneficial health benefits.

Exercise Training and Hyperinflation in COPD
Exercise capacity in patients with COPD is limited in part by dyspnea resulting from static and dynamic hyperinflation (27). By breathing at increased lung volumes, the elastic work of breathing is increased, and the respiratory muscles are placed at more of a mechanical disadvantage (28). Furthermore, the increased metabolic demand from exercising deconditioned muscles of ambulation requires increased minute ventilation. During exercise, the increased minute ventilation is usually via primarily an increased tidal volume, then an increased respiratory rate. The combination of increased dyspnea, prolonged expiratory time, and increased respiratory rate causes the patient to breathe in before the preceding breath is fully exhaled. This dynamic hyperinflation contributes to the exertional dyspnea of COPD.

Exercise training in COPD indirectly reduces dynamic hyperinflation if the latter is measured at isowork or isotime during exercise testing. After the beneficial training effects on the muscles of ambulation are achieved through exercise training, the respiratory rate at isotime or isowork levels is decreased (29). The lower respiratory rate during exercise will allow for more complete lung emptying with each breath—thereby reducing dynamic hyperinflation. Figure 2 depicts this indirect beneficial effect on lung volumes. The reduction in hyperinflation undoubtedly contributes to the positive effects pulmonary rehabilitation exercise training has on exercise performance.


Figure 2
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  		Figure 2. Higher inspiratory capacity (IC) values reflect lower end-expiratory lung volumes. IC dropped rapidly at baseline (line with circles) during exercise in untrained subjects with COPD, indicating the rapid development of dynamic hyperinflation. After exercise training, not only was exercise endurance time (x axis) prolonged, but there was considerably less dynamic hyperinflation (line with triangles). Reprinted by permission from Reference 29.

 
Enhancing Exercise Training Effects in Pulmonary Rehabilitation
Substantial improvement in exercise performance is often attained after a supervised exercise training program for patients with COPD. However, similar to that with healthy individuals, beneficial effects are dose dependent—higher levels of training lead to greater physiologic gains (30–32). Decreasing the limitations to higher-intensity exercise in patients with COPD would allow them to train at higher intensities. Two strategies that might achieve these results will be discussed subsequently here: bronchodilators and supplemental O2 therapy.

Bronchodilators
Bronchodilator therapy in COPD reduces dyspnea and improves exercise tolerance in COPD (33–35). Although reducing the resistive work of breathing through increasing airway caliber decreases dyspnea, reducing the elastic work of breathing through decreasing static and dynamic hyperinflation is probably of equal importance (36, 37). Peripheral muscle dysfunction is also an important factor limiting exercise in COPD, and there is some evidence to suggest that those with more fatigue of their ambulatory muscles may have less improvement in exercise capacity after bronchodilator therapy (38). Bronchodilator therapy may allow patients with COPD to exercise train at higher intensities, thereby increasing the likelihood of a substantial gain in exercise performance (39). Bronchodilator therapy may even change the primary cause of exercise limitation from exertional dyspnea to leg fatigue; the latter being particularly amenable to exercise training.

Supplemental O2
Long-term oxygen therapy prolongs survival in patients with COPD with severe hypoxemia (40, 41), and—for obvious reasons—it makes sense to use O2 therapy during exercise training in these patients with hypoxemia. It is also reasonable (both from a safety perspective and to enhance outcome) to administer supplemental O2 during exercise and activity in those patients not requiring continuous O2 therapy, but who demonstrate significant exercise-induced hypoxemia (42). Although the prescription of ambulatory O2 therapy with portable devices for these individuals makes clinical sense, it does not have a substantial evidence base (43).

From a pulmonary rehabilitation perspective, it has become evident that patients with COPD for whom ambulatory O2 therapy is prescribed are generally very sedentary (44). Furthermore, it appears that the ambulatory O2 prescription does not significantly increase activity. Part of this stems from the fact that it is used very little by these patients (44). Referring patients with COPD to pulmonary rehabilitation when O2 therapy is started might help with both adherence to O2 therapy and promotion of activity.

Supplemental O2 therapy can also be considered an adjunct to exercise training in pulmonary rehabilitation. Supplemental O2, through reducing dyspnea, may permit greater intensities of exercise training in symptom-limited patients with COPD (45). This reduction in dyspnea, which may be present even for those without exercise-induced hypoxemia, may be mediated in part by reductions in dynamic hyperinflation (46). The presumed rationale behind this intriguing finding is that reduced dyspnea sensation from O2 therapy will promote lower respiratory rates during exercise and allow for prolonged expiratory time and more complete emptying of the lungs during exhalation.

Although the acute effects of O2 administration on increasing exercise capacity have been demonstrated in the laboratory (42), studies showing the superiority of supplemental O2 to room air use during exercise training in pulmonary rehabilitation have had mixed results (47–49). This probably reflects differences in study design, especially with regard to training intensity. More recently, supplemental O2 has been tested as an adjunct to exercise training in patients with COPD who did not demonstrate severe exercise hypoxemia (50). Patients exercised for 21 sessions over 7 weeks while breathing O2 or room air in this randomized, double-blind trial. Those receiving O2 were able to train at higher intensities, and—after completing exercise training—had greater increases in exercise performance. Thus, supplemental O2 was effective, even in patients not demonstrating severe exercise-associated hypoxemia, but the maintenance of this effect in the long term after discontinuing supplemental O2 was not tested. Whether supplemental O2 will become standard-of-care as an exercise enhancer for nonhypoxemic patients with COPD in the pulmonary rehabilitation setting remains to be determined.

PROMOTING LONG-TERM ADHERENCE

Randomized trials of pulmonary rehabilitation usually demonstrate that its beneficial effects on exercise performance, while substantial in the postrehabilitation period, decrease gradually over time, and reach control levels by about 18 months (51). Beneficial effects on health status may last somewhat longer. Although this gradual drop-off in effectiveness probably has multiple reasons; failure to maintain long-term adherence with the postrehabilitation plan is usually considered most important. Patients with COPD seem to gradually reduce the amount of their structured exercise over time. This is particularly relevant to the period after the COPD exacerbation, when patients frequently resume a much more sedentary lifestyle (52). Thus far, interventions designed to improve long-term adherence have had modest success (52, 53). There are some data that suggest that longer-lasting pulmonary rehabilitation programs may enhance longer-term adherence (54), but this is probably not practical in our current health care system. Further research is necessary in this area, especially in incorporating principles of pulmonary rehabilitation into the home setting.

CONCLUSIONS

Optimal therapy of the patient with COPD usually requires both pharmacologic and nonpharmacologic therapy. The latter is simply good medical care applied at the right time. Depending on the needs of the patient, it can include smoking cessation intervention, promotion of a healthy lifestyle (including activity), regular exercise, collaborative self-management strategies to treat the COPD exacerbation early and appropriately, and advance directives. Comprehensive pulmonary rehabilitation provides a convenient and very effective way of providing these important components of health care. The beneficial effects of the exercise training component of pulmonary rehabilitation may be enhanced with optimal bronchodilation and supplemental O2 therapy.

FOOTNOTES

Conflict of Interest Statement: R.Z. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript.

(Received in original form January 15, 2007; accepted in final form April 2, 2007)

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