Editorial: Clinical Cardiopulmonary Exercise Testing

Dyspnoea is a debilitating symptom that affects quality of life, exercise tolerance and mortality in various disease conditions/states. In patients with chronic obstructive pulmonary disease (COPD), it has been shown to be a better predictor of mortality than forced expiratory volume in 1 s. In patients with heart disease it is a better predictor of mortality than angina. Dyspnoea is also associated with decreased functional status and worse psychological health in older individuals living at home. It also contributes to the low adherence to exercise training programmes in sedentary adults and in COPD patients. The mechanisms of dyspnoea are still unclear. Recent studies have emphasised the multidimensional nature of dyspnoea in the sensory-perceptual (intensity and quality), affective distress and impact domains. The perception of dyspnoea involves a complex chain of events that depend on varying cortical integration of several afferent/efferent signals and coloured by affective processing. This review, which stems from the European Respiratory Society research symposium held in Paris, France in November 2012, aims to provide state-of-the-art advances on the multidimensional and multidisciplinary aspects of dyspnoea, by addressing three different themes: 1) the neurophysiology of dyspnoea, 2) exercise and dyspnoea, and 3) the clinical impact and management of dyspnoea.

Patients with chronic obstructive pulmonary disease (COPD) primarily describe their exertional dyspnea using descriptors alluding to increased effort or work of breathing and unsatisfied inspiration or inspiratory difficulty. The purpose of this study was to examine the impact of changes in dynamic respiratory mechanics during incremental (INCR) and high-intensity constant work-rate (CWR) cycle exercise on the evolution of dyspnea intensity and its major qualitative dimensions in patients with moderate-to-severe COPD. Sixteen subjects with COPD performed symptom-limited INCR and CWR cycle exercise tests. Measurements included dyspnea intensity and qualitative descriptors, breathing pattern, operating lung volumes, and esophageal pressure (Pes). During both exercise tests, there was an inflection in the relation between tidal volume (Vt) and ventilation. This inflection occurred significantly earlier in time during CWR versus INCR exercise but at a similar ventilation, Vt, and tidal Pes swing. Beyond this inflection, there was no further change in Vt despite a continued increase in ventilation and tidal Pes. During both tests, "work and effort" was the dominant dyspnea descriptor selected up to the inflection point, whereas after this point dyspnea intensity and the selection frequency of "unsatisfied inspiration" rose sharply. Regardless of the exercise test protocol, the inflection (or plateau) in the Vt response marked the point where dyspnea intensity rose abruptly and there was a transition in the dominant qualitative descriptor choice from "work and effort" to "unsatisfied inspiration." Intensity and quality of dyspnea evolve separately and are strongly influenced by mechanical constraints on Vt expansion during exercise in COPD.