Abstract
We examined the impact of changes in ventilatory profile and dynamic operating lung volumes during symptom-limited incremental cardiopulmonary cycle exercise testing (CPET) on the intensity of dyspnoea in patients with pulmonary hypertension (PH). Twenty non-smokers PH patients (n=13 idiopathic, n=7 chronic thromboembolic disease) with no evidence of spirometric obstruction (FEV1/FVC = 85±7% pred) and 10 age-matched healthy subjects performed a CPET to the limit of tolerance. Ventilatory profile, operating lung volumes [derived from inspiratory capacity (IC) measurements], and dyspnoea intensity (by Borg scale) were assessed throughout CPET. In 70% of PH patients (n=14), IC decreased progressively throughout CPET by 0.35L on average (dynamic hyperinflation), whereas in all healthy subjects IC increased by 0.2L. Dyspnoea intensity and minute ventilation (V'E) were greater in PH patients at any stage of CPET compared with healthy controls: at standardized work rate of 60watts, dyspnoea rating and V'E were 5 Borg units and 45L/min respectively in PH patients compared with 1 Borg unit and 33L/min respectively in healthy subjects. At standardized V'E of 60L/min, PH patients presented with greater dyspnoea (by 4 Borg units) and dynamic hyperinflation (by 0.3L) compared with healthy controls. Dynamic hyperinflation and the excessive ventilatory response to CPET seem to be potential contributors to increased exertional dyspnoea intensity in patients with PH.
Supports: 1) Seventh Framework Programme of the European Union, International Re-integration Grants, FP7-PEOPLE-2010-RG, Grant PIRG07-GA-2010-268396-EDPAH; 2) PFIZER Investigator-Initiated Research, Grant WS 942458.
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