ATS Issues Joint Statement on the Mechanisms, Assessment and Management of Dyspnea
The ATS has issued a new statement on the mechanisms, assessment and management of dyspnea, updating its 1999 Consensus Statement on Dyspnea to highlight recent advances in the field. The statement was published in the February 15 American Journal of Respiratory and Critical Care Medicine.
The updated statement was the work of an expert panel composed of members of the ATS Assemblies on Nursing, Pulmonary Rehabilitation, Clinical Problems, Behavioral Science, and Sleep and Respiratory Neurobiology. The committee was co-chaired by Mark B. Parshall, PhD, RN, associate professor at the University of New Mexico College of Nursing in Albuquerque, and Richard M. Schwartzstein, MD, associate chief of the Division of Pulmonary and Critical Care Medicine at Beth Israel Deaconess Medical Center and Ellen and Melvin Gordon Professor of Medicine and Medical Education at Harvard Medical School in Boston.
“Dyspnea is a very common and often disabling symptom. It affects up to 50 percent of inpatients and 25 percent of outpatients in the U.S. and accounts for three to four million emergency department visits annually,” noted Dr. Parshall. He went on to observe that “there have been substantial advances in the understanding of neurophysiological mechanisms underlying dyspnea since the publication of the 1999 statement, but there has not been equivalent progress in developing new treatments targeting dyspnea.”
The statement defines dyspnea as “a subjective experience of breathing discomfort that consists of qualitatively distinct sensations that vary in intensity.” According to the statement, there is accumulating evidence that “distinct mechanisms and afferent pathways are associated with different sensory qualities” of dyspnea. Those sensations “most often do not occur in isolation” and “vary…in their emotional and behavioral significance.” Adequate assessment of dyspnea, according to the statement, depends on patient self-report.
The best characterized physiological mechanisms and pathways underlying the perception of dyspnea are those involved in the perceptions of work or effort, tightness, and air hunger/unsatisfied inspiration. The sensory-perceptual mechanisms underlying sensations of work or effort in breathing are similar to those underlying similar sensations in skeletal muscle during exercise. The mechanisms underlying the sensation of “tightness” likely involve stimulation of rapidly adapting airway receptors in conjunction with bronchoconstriction. The physiological processes involved in air hunger/unsatisfied inspiration include imbalances among inspiratory drive, efferent activation (outgoing motor command from the brain), and afferent feedback from receptors in the diaphragm, thorax, lungs, and airways.
Recent three-dimensional neuroimaging studies have deepened our understanding of the cerebral processing of dyspnea, showing that dyspnea activates cortico-limbic structures that are also implicated in interoceptive awareness, nociceptive sensations such as pain, and in processing of aversive emotional responses. According to the authors, neuroimaging studies have the potential to help delineate sensory from affective components of dyspnea and improve our understanding of the impact of emotional, cognitive, and experiential processes associated with dyspnea. Data from these studies may ultimately contribute to the development of more effective treatments.
A section of the statement is devoted to issues pertaining to reliable and valid dyspnea measurement. The authors of the statement note that there are many more instruments for measuring dyspnea than there are treatments. Lack of clarity about which aspects of dyspnea are being measured has made it difficult to compare results across studies and draw evidence-based conclusions. The statement proposes a classification scheme for dyspnea measures consisting of several domains: sensory perceptual experience, affective distress, and symptom/disease impact or burden.
Because of the large number of clinical conditions that can give rise to dyspnea, an adequate history and physical examination remain the mainstays of clinical evaluation for new onset or exacerbated chronic dyspnea. While there have been advances in pharmacological treatments for a number of diseases associated with dyspnea, relatively few treatments have demonstrated efficacy in relief of dyspnea in patients with refractory dyspnea. These include pulmonary rehabilitation, oxygen in patients who are hypoxemic at rest and opioids for palliative care of end-stage cardiopulmonary disease.
The statement concludes that advances in our understanding of the mechanisms underlying dyspnea have not yet led to improved treatments for the relief of dyspnea. Many studies involve small numbers of patients. Some are uncontrolled or poorly controlled. There are no drugs specifically approved for the relief of dyspnea, as opposed to being approved for the treatment of diseases in which dyspnea is a prominent symptom. Many patients continue to experience dyspnea, despite otherwise optimal pharmacological treatment for their diagnosis. The focus of future research should be on the development and testing of treatments “specifically aimed at the underlying mechanisms of dyspnea.”
The full statement, with all authors listed, is available at http://ajrccm.atsjournals.org/content/185/4/435.abstract. “ATS members interested in learning more should also consider attending the scientific symposium "Dyspnea and the Road Ahead" at ATS 2012, which will summarize the statement’s major sections and highlight several controversies as well as future directions for dyspnea research and clinical practice.”