Inspiratory muscle function, dynamic hyperinflation and exertional dyspnoea in pulmonary arterial hypertension.

Despite a preserved forced expiratory volume in 1 s (FEV1)/vital capacity (VC), patients with idiopathic or heritable pulmonary arterial hypertension (PAH) may dynamically decrease their inspiratory capacity (IC) during cycle exercise (i.e. dynamic hyperinflation) [1–3] and this could increase exertional dyspnoea [1, 3, 4]. Little information is currently available about whether the reduced IC during cycle exercise is related to respiratory mechanics abnormalities or to impaired inspiratory muscle function (fatigue or weakness). The aim of this study was to evaluate the relationship between inspiratory muscle activity, dynamic changes in IC and the intensity of dyspnoea in PAH patients undergoing incremental symptom-limited cardiopulmonary cycle exercise test (CPET).