CRC DYSPNEA PDF

Preface

Dyspnea, or breathing difficulty, is the primary complaint of patients with respiratory disease because it limits their ability to live. Frequently, such individuals consider that they are ‘‘getting older'' as a likely explanation for their breathlessness; and, in an unconscious manner, they typically reduce occupational and/or recreational activities to avoid or minimize the discomfort of breathing. Over time, the problem of breathlessness may impact their ability to function at a desired or expected capacity. Yet, the person must perform certain daily activities that eventually become compromised by ‘‘shortness of breath.''

The prevalence of dyspnea and the overall burden of chronic respiratory diseases, particularly asthma, chronic obstructive pulmonary disease (COPD), and interstitial lung disease, have prompted the medical community to learn more about the complex nature of dyspnea. Why has this happened? The renewed interest in dyspnea has been a direct result of the scientific inquiry into the efficacy and effectiveness of different treatment options for our patients. What are the results? Two large randomized, controlled trials (RCTs) performed in the 1990s (Lung Health Study I and II) yielded negative findings as related to their hypotheses (neither regular use of an inhaled short-acting bronchodilator (ipratropium bromide) nor an inhaled corticosteroid (triamcinolone) altered the progressive decline in lung function). Nevertheless, these results, combined with those from other studies, have led investigators, physicians, industry representatives, and regulatory agencies to re-examine the goals of treatment. For example, there is now wide recognition and acceptance (as reflected in the GOLD guidelines) that treatment of COPD should consider outcomes that are important to our patients (i.e., dyspnea, quality of life, exercise capacity, and exacerbations) rather than to focus predominantly on lung function, arterial blood gases, and radiographic imaging. Clearly, these clinical outcomes reflect the daily impact of the various chronic respiratory conditions that are important to individual patients.

As part of this ‘‘new understanding'' investigators have pursued three separate, but related, directions in the study of dyspnea.

One approach examines the mechanism(s) contributing to breathlessness in patients with respiratory disease rather than the study of sensory physiology of breathing in healthy subjects under conditions of mechanical and chemical loading (as has been the focus of investigation in the past).

A second approach considers the development and testing (validity, reliability, and responsiveness) of different instruments that could be used to measure dyspnea in clinical trials. For example, how can we know if a treatment is beneficial for the patient unless the individual's experience can somehow be quantified? Using the principles of psychophysics (the study of the stimulus–response relationship), instruments have been developed, refined, and/or applied to measure the patient's perception of dyspnea.

The third approach investigates the efficacy and effectiveness of both old and new treatments for the relief of dyspnea as part of multicenter RCTs. These distinct but complementary approaches provide the framework for our book entitled Dyspnea: Mechanisms, Measurement, and Management.

Although dyspnea affects almost all respiratory conditions as well as cardiac diseases and musculoskeletal disorders, most of the material presented in this book involves COPD. Why? it is because of the high prevalence of COPD worldwide, and because patients with COPD seek medical attention for relief of dyspnea in far greater numbers than do patients with other conditions. As a result, patients with COPD have participated as subjects in clinical investigations with the hope of achieving some improvement in their breathing. Certainly, patients who experience dyspnea due to other cardiorespiratory conditions also deserve the same attention and consideration.

We are pleased that experts from various backgrounds and leaders in the study of dyspnea have contributed enthusiastically to this book. Our aim was to provide up-to-date practical information on how best to assess and alleviate respiratory discomfort across the spectrum of pulmonary diseases and at the end of life. Our collective hope and aspirations are that this book will provide both a ‘‘state of the art'' review of the topics related to dyspnea, but will also serve to identify ‘‘new directions'' in our understanding and treatment of this most important outcome for our patients. One of these emerging ‘‘new directions'' is our realization that the past nihilism related to treating many chronic respiratory diseases, especially COPD, can be replaced with optimism by considering dyspnea, not lung function, as a major outcome in the treatment paradigm.