Our team was able, for the first time, to clearly demonstrate that an abnormal mechanics of breathing (dynamic lung hyperinflation and the attendant constraint of VT expansion) played an important role in dyspnoea causation in PAH during cycle exercise. When increased ventilation/perfusion mismatching is superimposed on pre-existing abnormal airway function, greater troublesome exertional symptoms are the result. This finding opens up new horizons for research in the field of dyspnoea mechanisms in PAH: if investigator treats and ameliorates the "lung function" (i.e., the respiratory mechanics abnormalities"), then our team could be able to improve the troublesome exertional symptoms that curtail daily-living activities of PAH patients. The corollary of this is that any therapeutic intervention that effectively reduces and/or delays the rate of onset of DH-induced critical ventilatory constraints, such as administration of inhaled bronchodilators (BDs) as add-ons to vasodilators, should have a positive effect on symptom perception in selected patients with stable PAH. Determining the magnitude of this effect will be the object of the planned experiments. However, it should be borne in mind that the relationship between dyspnoea intensity and the severity of respiratory abnormalities is not linear, but rather exponential. In other words, when a given disease is already responsible for a very intense dyspnoea, a small additional deterioration directly or indirectly related to the disease can make dyspnoea intolerable. Therefore, even small BDs-induced changes in respiratory mechanics could have major effects on dyspnoea intensity on exertion in selected PAH patients, which would undoubtedly have a major impact on their quality of life and their ability to perform daily-living activities.