Background: Dyspnea is a common, distressing symptom of cardiopulmonary and neuromuscular diseases. Since the ATS published a consensus statement on dyspnea in 1999, there has been enormous growth in knowledge about the neurophysiology of dyspnea and increasing interest in dyspnea as a patient-reported outcome. Purpose: The purpose of this document is to update the 1999 ATS Consensus Statement on dyspnea. Methods: An interdisciplinary committee of experts representing ATS assemblies on Nursing, Clinical Problems, Sleep and Respiratory Neurobiology, Pulmonary Rehabilitation, and Behavioral Science determined the overall scope of this update through group consensus. Focused literature reviews in key topic areas were conducted by committee members with relevant expertise. The final content of this statement was agreed upon by all members. Results: Progress has been made in clarifying mechanisms underlying several qualitatively and mechanistically distinct breathing sensations. Brain imaging studies have consistently shown dyspnea stimuli to be correlated with activation of cortico-limbic areas involved with interoception and nociception. Endogenous and exogenous opioids may modulate perception of dyspnea. Instruments for measuring dyspnea are often poorly characterized; a framework is proposed for more consistent identification of measurement domains. Conclusions: Progress in treatment of dyspnea has not matched progress in elucidating underlying mechanisms. There is a critical need for interdisciplinary translational research to connect dyspnea mechanisms with clinical treatment and to validate dyspnea measures as patient-reported outcomes for clinical trials.

To investigate the hypothesis that clinical methods and psychophysical testing provide different information about breathlessness, we compared dyspnea ratings from a modified Medical Research Council (MRC) scale, the Oxygen-Cost Diagram (OCD), and the Baseline Dyspnea Index (BDI) with the perceived magnitude of added loads in 24 patients with obstructive airway disease (OAD) who experienced dyspnea on exertion. Age of the patients was 55.8 ± 13.7 yr (mean ± SD), FEV1 was 1.77 ± 0.81 L, and FEV1/FVC ratio was 52.6 ± 10.5%. Dyspnea ratings were obtained for each clinical method by 2 independent observers; estimates of the magnitude of 5 resistive loads (10 to 85 cm H2O/L/s) were obtained using the Borg category scale (0 to 10). For comparative purposes, 12 age-matched (48.9 ± 13.5 yr) healthy subjects were also studied. Clinical ratings of dyspnea obtained in patients for MRC (range, 0 to 4), OCD (range, 23 to 98), and BDI (range, 0.5 to 12.0) were all highly interrelated (rs = 0.79, −0.83, and −0.71; p < 0.001 for all comparisons). Exponents of the psychophysical power function for resistive breathing loads were similar for patients with OAD (0.57 ± 0.27) and control subjects (0.63 ± 0.18) (p = NS). Clinical dyspnea scores were significantly correlated with both FEV1 and FVC; however, neither dyspnea ratings nor lung function were significantly related to the exponent for added breathing loads in the patient group. These comparisons indicate that in patients with symptomatic OAD, clinical methods for rating dyspnea are interrelated and are correlated with lung function, but are independent of perception of resistive breathing loads. These findings demonstrate that clinical methods are more appropriate for evaluating the impact of dyspnea on a patient's daily activities.

The purposes of this study were: to examine the decriptors of breathlessness chosen by a large sample of patients with cardiorespiratory disease; to determine test-retest reliability of a patient's selection of the descriptors; and to assess whether a patient's recall of the experience of breathlessness is the same as that provoked by physical activity. Questionnaire data were collected at an initial visit for patients who complained of breathlessness and at a second visit in a subgroup of patients. A total of 218 patients who sought medical care for difficulty breathing due to one of seven different conditions were recruited from an outpatient pulmonary disease clinic at a university medical center. Patients selected statements that described qualities of breathlessness from a 15-item questionnaire and completed pulmonary function tests. At a subsequent visit (4 to 15 d later) a subgroup of 16 patients with chronic obstructive pulmonary disease (COPD) repeated the questionnaire at rest (to assess reliability) and after walking in a hallway to provoke a moderate intensity of breathlessness (to compare recall with direct experiences). The relationship among descriptors was evaluated by cluster analysis. The "work/effort" cluster was common for all diagnoses. Each condition was characterized by more than one cluster except COPD. Each diagnosis was associated with a unique set of dusters (e.g., asthma with "work/effort" and "tight," interstitial lung disease with "work/effort" and "rapid" breathing). Percent agreement for all descriptors selected at Visits 1 and 2 (recall) was 79% (r = 0.82; p = 0.001). Percent agreement at Visit 2 between descriptors for recall and for breathlessness provoked by walking was 68% (r = 0.69; p = 0.004). We conclude that patients with different cardiorespiratory conditions experience distinct qualities of breathlessness. Patients' recall of their sensations of breathlessness is reliable and comparable to dyspnea with walking. Employing a questionnaire containing descriptors of breathlessness may help to establish a specific diagnosis and to identify mechanisms whereby a specific intervention relieves dyspnea.

The purpose of this study was to demonstrate that clinical ratings of dyspnea and physiologic function are separate dimensions underlying the pathophysiology of chronic obstructive pulmonary disease (COPD). We used principal-components factor analysis to confirm these dimensions using data collected prospectively in 86 symptomatic patients with COPD. Three different instruments were used to rate dyspnea: a modified Medical Research Council (MRC) scale, the oxygen cost diagram (OCD), and the baseline dyspnea index (BDI). Measures of physiologic function included standard spirometric measures (forced vital capacity [FVC] and forced expiratory volume in one second [FEV1]) and maximal inspiratory (Pi max) and expiratory (Pe max) mouth pressures. Age of the 65 male and 21 female subjects was 62.9 ± 1.2 yr (mean ± SEM). All three clinical scales were significantly correlated with physiologic function (range of r values, 0.32 to 0.45; p < 0.05), except for the relationship between the MRC scale and Pe max (r = −0.14;p = NS). The factor analysis yielded three factors that accounted for 71.9% of the total variance of the data: clinical ratings of dyspnea (MRC scale, OCD, and BDI) loaded on the first factor; maximal respiratory pressures and gender loaded on the second factor; and lung function and age loaded on the third factor. Additional post hoc factor analysis provided similar results when the sample was divided into two subgroups by randomization, by severity of dyspnea ratings, or by severity of airflow obstruction. We conclude that dyspnea ratings, maximal respiratory pressures, and lung function are separate factors or quantities that independently characterize the condition of patients with COPD. These results suggest that the clinical evaluation of patients with COPD should include the routine measurement of dyspnea in addition to spirometry and respiratory muscle strength.

To investigate whether the language of dyspnea provides relevant clinical information in addition to that provided by ratings of overall dyspnea intensity when assessing subjective response to therapy, we conducted a prospective study in a cohort of 25 patients with acute asthma presenting to the emergency department of a tertiary care hospital. Patients received nebulized albuterol treatments every 20 min with a maximum of three doses. At presentation and after each treatment, patients completed spirometry, rated overall dyspnea intensity on a modified Borg scale, and selected phrases that described qualities of breathlessness from a 15-item questionnaire. Paired Student's t tests revealed significant improvements in FEV1 (from 1.39 ± 0.66 L to 1.80 ± 0.76 L, p < 0.001) and reductions in dyspnea intensity (from 5.12 ± 2.08 to 2.82 ± 1.59, p < 0.001) after the first albuterol treatment. Dyspnea intensity continued to decrease significantly in response to the second treatment, modified Borg rating 2.26 ± 1.52, although there was no positive bronchodilator response. The results from Cochran Q tests revealed that the frequency of the experience of “chest tightness” decreased significantly across the phases of treatment. However, the sensations of “work” or “breathing effort” persisted at the same time that the FEV1 revealed ongoing airways obstruction. We conclude that attention to the language of dyspnea would alert health care providers to residual air flow obstruction despite decreases in overall dyspnea intensity.