Is Exercise Important in Chronic Obstructive Pulmonary Disease?

Abstract

Chronic obstructive pulmonary disease impairs the ability of patients to perform maximal physical exercise, particularly in patients with severe lung disease. However, differing perceptions of the meaning and importance of exercise to patients and caregivers is likely to impair patient-physician communication about current medical status and outcomes of therapeutic interventions. Other outcomes of importance to patients including actual performance of functional activity during daily life and health-related quality of life may also be affected by impaired exercise capacity. However, the relationships between exercise, activity, and quality of life are inconsistent. Thus, measurement of physiologic and patient-centered outcomes may provide the best approach to assessing responses to therapeutic interventions. These concepts were explored in a conference sponsored by Boehringer Ingelheim Pharmaceuticals, Inc. and Pfizer Inc and reviewed in the articles generated from the symposium in this issue of COPD.

Keywords::

• COPD
• Exercise
• Quality of life
• Activities of daily living

INTRODUCTION

This article and the 15 which follow in this issue of COPD: The Journal of Chronic Obstructive Pulmonary Disease are based on a meeting held in June 2006. Sponsored by Boehringer Ingelheim Pharmaceuticals, Inc. and Pfizer Inc, the conference, “The Impact of Change in Exercise Toolerance on Activities of Daily living and Quality of Life in COPD,” brought together experts from around the world. This symposium was conceived and developed based on the profound impact that chronic obstructive pulmonary disease (COPD) has on patients with the disorder and the need for physicians and other health care practitioners to achieve patient-centered outcomes in order to reduce the burden of disease ([1], [2]). In 2000, the Confronting COPD International Survey interviewed 3265 patients in the United States, Canada, and Europe ([1]). Over one third (35.5%) were too breathless to leave the house and (60.8%) had to stop for breath every few minutes when walking on level ground. Nevertheless, patients underestimated the global severity of their disease–only one fifth of patients (21%) rated their disease as severe. Marked limitations in activities requiring normal or low levels of exertion were found with about 60% of patients reporting limitations in normal physical exertion, and 40% in household chores. The impact on enjoyable activities was also profound with about 40% of subjects reporting limitations in social activities, about 35% in family activities and over 30% in sex life.

The impact of dyspnea on limiting activity was underscored by the finding that 45.3% of subjects under age 65 reported lost time from work within the past year. Their findings suggested that patients who were younger had a similar burden of disease to those who were older (> 65 years of age). More recently, Barr and colleagues in the United States surveyed 1023 patients and 1051 primary care physicians in 2003–2004 ([2]). Although their subjects reported less severe dyspnea, 86% noted limitations in activities. The impact of symptoms and limitations was reflected in patient perception of their health status with 37% rating their current health as poor or very poor and only 5% rating it as very good or excellent. Based on these reports, it is clear that understanding the meaning and relationship between activities that patients can perform, exercise, and quality of life is important to employing therapies to maximize patient outcomes.

Patients with COPD are encountered on a daily basis by a myriad of different types of physicians and health care providers from pulmonary specialists to general practice physicians and physician extenders with a diverse range of experience and training in lung disease. Nevertheless, all health care practitioners share the goal of assisting patients to lessen the burden of the disease by reducing the impact of the disease and improving disabling symptoms. In order for the patient-health care provider relationship to be effective, both parties need to not only share common goals but also to communicate those goals and management options effectively.

Effective communication requires that COPD patients and health care providers be familiar with universally encountered symptoms such as shortness of breath and commonly used, but less well delineated and more complex constructs such as exercise, activity performance and health-related quality of life. In addition, physicians should recognize and understand that there are a diverse group of potential outcomes of therapies. The categories of potential outcomes that are important and that can currently, or may in the future be achieved in COPD are indeed broad-ranging from short-term symptom reduction to improving survival and reversing disease pathology (Table 1). Based upon patient reports, the most important short-term outcomes for patients with severe COPD are shortness of breath, quality of life, exercise capacity and capacity to perform activities during the course of daily living ([1], [2]).

Table 1 Concepts embodied by the term “exercise” as viewed by different participants in the medical system

Healthy individuals

Recreational activity

Enjoyable activity

Health-promoting regular activity

Patients with COPD

Strenuous

Unsatisfying

Physicians and other health-care providers

Health-promoting strenuous regular physical activity

Pulmonary rehabilitation

Thus, the goal of this conference is to explore the relationship between exercise and other key outcome measures, particularly activities performed during daily life and health-related quality of life in COPD. This symposium was designed to address the following objectives:

1. Delineate the mechanisms of exercise limitation in mild-to-moderate COPD including the roles of hyperinflation and deconditioning.

2. Explore current measures of exercise capacity and review relevant endpoints that can be used to assess the impact of therapeutic interventions.

3. Provide a definition for activities of daily living applicable to COPD patients that can be applied in clinical practice and in clinical trials.

4. Define the activities of daily living most impacted by COPD and how they relate to patient-perceived quality of life.

5. Translate measures of exercise endurance into clinically meaningful activities for COPD patients.

6. Review existing data on interventions that improve exercise capacity in COPD, and describe specific interventions used to improve the activity of the COPD patient.

Table 2 Potential outcomes of therapy in patients with COPD

Patient-Reported Outcomes

Respiratory symptoms

Quality of life

Activities performed during daily life

Functional Capacity

Respiratory function – pulmonary function

Physical function – capacity for physical activity

Neuropsychological function

Disease Course

Exacerbations

Mortality

Disease

Pathophysiology

Pathology

Radiology

Other

Health-care utilization – hospitalization

Medications/therapies

Adverse effects

Healthy behaviors

Satisfaction (with therapy)

Costs (direct, indirect)

Caregiver burden

Physical appearance

Assistive technology use

Differing perceptions about exercise

A central question addressed by this manuscript is whether “exercise” is a meaningful concept that is understood in a similar manner by healthy individuals (including family members of patients with COPD), patients with COPD, general health care providers, and specialists (Table 1). Exercise is of course a broad concept. One definition of exercise is “activity that requires physical or mental exertion, especially when performed to develop or maintain fitness” ([3]). The concept of fitness is embodied in another definition of exercise as “physical activity and movement, especially when intended to keep a person … fit and healthy” ([4]). Similarly, a Google search on “exercise” yielded about 240,000,000 results, the vast majority of which were related to the concept of fitness, reflective of the most common contemporary use of the term.

To individuals without COPD and to patients with mild COPD who are not limited by their disorder, exercise may convey messages of strenuous activity performed for enjoyment or recreation. To younger individuals without medical conditions, “exercise” may be associated with thoughts of enjoyable strenuous activity performed for fun such as roller-blading, cycling, or snow boarding. For somewhat older individuals, “exercise” may mean regular physical activity performed to maintain weight, strength, and endurance as well as to enhance longevity. What does “exercise” mean to patients with COPD especially those with advanced disease who are receiving oxygen therapy or have severe shortness of breath? Exercise is unlikely to be associated with enjoyment or recreation by patients with medical conditions that limit physical ability. Patients with COPD approached with the prospect of “exercise,” might be expected to react with such statements as “Exercise makes me short of breath, and that is really, really uncomfortable¡” or “Exercise is not fun¡” or “I am too old to exercise¡” or even “Fitness is an “f” word¡” Mary Ann Cruse provides a patient perspective on the impact of COPD on her ability to be physically active ([5]).

“Exercise” may conjure to pulmonary physicians other viewpoints that differ from that provided by their patients. From a testing perspective, exercise may suggest formal measurement of the exercise ability or the maximal exercise capacity that is achievable by an individual such as during a laboratory-based test on a treadmill or bicycle using incremental increases in work to assess the intensity of activity. Exercise testing can also be used to assess the endurance or amount of time that an individual can cycle or walk on a treadmill at some submaximal level of exertion ([6]). Alternatively, as explored by Brown and Wise in this manuscript, exercise testing can be performed with field tests that do not involve laboratory settings ([7]). Pulmonary rehabilitation specialists may use the term exercise in the context of a COPD patients to denote a comprehensive program incorporating exercise along with other therapies with the goal of reducing dyspnea and increasing quality of life ([8]). To primary-care physicians, exercise may suggest a regularly performed health-enhancing behavior linked not only to improved general wellness but also to a reduction in cardiovascular mortality.

Another concept of “exercise” based on functional performance and activity is explored in articles by Leidy, Larson, as well as Hill and Goldstein ([9], [10], [11]). Activity refers to what patients actually physically perform during their daily lives to achieve a desired function (functional performance) rather than exercise capacity, or the capacity for activity, determined on a laboratory-based test. Activity is much broader than simply what patients need to do for their basic existence such as eating and toileting for body care, often referred to basic activities of daily living.

Even higher levels of activity required for independent living such as shopping for and preparing meals, instrumental activities of daily living, do not capture the full range of performance of physical activity for recreational and social pursuits, which might be considered as productive or extended activities of daily living. The understanding of these terms among the general public is poor, however. Even physicians frequently use “activities of daily living” or ADL to describe the full range of physical performance during daily life and cannot differentiate the different levels of activities performed by most individuals. As noted by ZuWallack and Belfer, physicians may not even question patients' actual activities as part of their routine medical history ([12], [13]). As noted in other articles in this manuscript, activity can be measured by questionnaires designed for that purpose, through the use of personal activity monitors, and through some of the subscales of quality of life assessments ([10], [14], [15]).

Relation between exercise capacity, activity performance, and quality of life

In COPD, dynamic hyperinflation with exercise, airflow limitation, muscle wasting, poor nutrition, and hypoxemia often combine to limit maximal exercise capacity ([16], [17]). It seems logical to assume that a reduction in the capacity to perform maximal exercise as measured in the laboratory or on field-based testing would eventually impair the ability to be physically active during normal life. Reduced physical activity leading to a reduction in performance of functional activities to achieve desired tasks would be expected to reduce health-related quality of life. Impaired quality of life and reduced functional performance might trigger psychological symptoms, particularly depression, along with anxiety related to the fear-provoking symptom of dyspnea. These effects and interactions are summarized in Figure 1.

Figure 1 Heuristic relationship between physical activity and functional performance on the vertical axis and functional capacity on the horizontal axis. As functional capacity (exercise capacity) measured by exercise testing falls to lower levels, there is a more rapid decline in an individual's functional performance and physical activity. Physical activity can be classified functionally as activities of daily living (ADL) that are basic (required for self-care of one's body such as eating and toileting), instrumental (required to live independently such as food preparation), or extended (social and recreational).

However, as noted by several authors in these conference proceedings, direct relationships between exercise capacity and physical activity and functional performance have been difficult to establish ([9], [18]). The relationship between exercise capacity and quality of life appears to be stronger ([19]). Even when a therapy for COPD does improve exercise capacity, patients may not be instructed to attempt to increase their daily activity and thus not recognize the potential benefits of improved exercise capacity. Complicating the discussion of exercise and physical performance is that the relationship between these constructs is likely not linear as depicted in Figure 2.

Figure 2 Lung dysfunction in COPD results in shortness of breath and reduced exercise capacity. Symptomatic maximal exercise limitation is associated with reduced physical activity and impaired quality of life, along with depression and anxiety.

There are several therapeutic approaches (pulmonary rehabilitation, oxygen therapy, bronchodilators, lung volume reduction surgery) that have been demonstrated to improve exercise capacity as measured on formal testing ([20], [21], [22], [23], [24], [25], [26]). However, exercise capacity is a difficult concept for patients and even for many physicians to integrate into their therapeutic decision-making. The relationship of exercise capacity to other outcomes that may be more easily perceived and understood by patients is not well delineated. For example, what is the relationship between an improvement in incremental cycle ergometry measured in a formal laboratory setting as an outcome of a treatment for COPD and (a) how an individual patient perceives or feels about their health-related quality of life, or (b) whether a patient can participate in routine instrumental or social activities or recreational pastimes, or (c) whether a patient can perform functional activities with less shortness of breath?

SUMMARY

COPD is a lung disorder that leads to a multitude of manifestations that impact patients on a daily basis. The disease and associated limitations imposed upon patients are important not only to patients and their families, but also to health-care providers, insurers and society. There is an increasing interest in assessing a wide variety of outcomes to measure the full impact of new and existing therapies in patients with COPD. Outcomes reported by patients such as dyspnea and quality of life are increasingly viewed as of key importance, but they may not correlate with more traditional laboratory tests of lung function and exercise capacity. Assessment of exercise and activity can be made either directly or through questionnaires. Because of the lack of a consistent relationship between directly measured and patient-reported outcomes, multiple simultaneously determined outcomes currently offer the best approach to assessing new therapies.

ACKNOWLEDGMENT

The authors of the articles from this conference express their appreciation to Boehringer Ingelheim Pharmaceuticals, Inc. and Pfizer Inc for sponsoring this symposium, and to Cheryl Warner for her editorial assistance.