Background: Although previous studies have shown that peripheral airway obstruction can occur in idiopathic PAH (IPAH), pulmonary function tests have not been well-studied in patients with PAH associated with congenital heart disease (CHD-PAH) and connective tissue disease (CTD-PAH).
Methods: A multicenter prospective study was performed in PAH patients in China. Pulmonary function tests were evaluated in 190 PAH patients.
Results: Total lung capacity (TLC), residual volume (RV) and total airway resistance (Rtot) were similar in PAH patients and controls. However, measures of airflow, including vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in 1s (FEV(1)), FEV(1)/FVC and MEF(50) were decreased in PAH group. Single-breath diffusion capacity for carbon monoxide (DL(CO)) was also decreased in PAH patients. Expiratory flow-volume curves showed reduction and a curvilinear appearance in patients with PAH. Similar changes were observed among the various subgroups of IPAH, CHD-PAH, and CTD-PAH patients. More CTD-PAH patients had abnormal DL(CO).
Conclusions: Airway obstruction is common in IPAH, CHD-PAH and CTD-PAH patients. CTD-PAH patients have lower DL(CO). Hemodynamics, serum markers and exercise capacity parameters did not correlate well with pulmonary function indices.