Evolution of dyspnea during exercise in COPD: impact of critical volume constraints
2011 (English)In: American Journal of Respiratory and Critical Care Medicine, ISSN 1073-449X, E-ISSN 1535-4970, Vol. 184, no 12, 1367-1373 p.Article in journal (Refereed) Published
Rationale: Patients with COPD primarily describe their exertional dyspnea using descriptors alluding to increased effort or work of breathing and unsatisfied inspiration or inspiratory difficulty. Objective: 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. Methods: Sixteen COPD subjects 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). Measurements and Main Results: 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/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. CONCLUSIONS: 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/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.
Place, publisher, year, edition, pages
2011. Vol. 184, no 12, 1367-1373 p.
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:umu:diva-50438DOI: 10.1164/rccm.201106-1128OCPubMedID: 21885624OAI: oai:DiVA.org:umu-50438DiVA: diva2:472535