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Respir Physiol Neurobiol. 2013 Jan 15;185(2):374-9. doi: 10.1016/j.resp.2012.08.026. Epub 2012 Sep 28.

Tidal volume inflection and its sensory consequences during exercise in patients with stable asthma.

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Université Pierre et Marie Curie (Paris VI), Equipe de Recherche ER 10 UPMC, Laboratoire de Physio-Pathologie Respiratoire, Faculté de Médecine Pierre et Marie Curie (site Pitié-Salpêtrière), Paris 75013, France.


Sixteen patients with stable asthma performed a symptom-limited constant work-rate CWR cycle exercise during which breathing pattern, operating lung volumes, dyspnea intensity and its qualitative descriptors were measured. An inflection in the relation between tidal volume (V(T)) and ventilation (V˙(E)) was observed in each subject. The sense of "work/effort" was the dominant dyspnea descriptor selected up to the V(T)/V˙(E) inflection, whereas after it dyspnea intensity and the selection frequency of "unsatisfied inspiration" rose steeply in 37.5% of subjects in whom inspiratory reserve volume (IRV) had decreased to a critical level of 0.6L at the V(T) inflection point. In contrast, dyspnea increased linearly with exercise time and V˙(E), and "work/effort" was the dominant descriptor selected throughout exercise in 62.5% of subjects in whom the V(T)/V˙(E) inflection occurred at a preserved IRV. The V(T) inflection during exercise in patients with stable asthma marked a mechanical event with important sensory consequences only when it occurred at a critical reduced IRV.

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