Exercise capacity in idiopathic pulmonary fibrosis: The effect of pulmonary hypertension

Background and objective: Increased pulmonary arterial pressure (PAP) usually coexists with impaired lung function in IPF. Data on the effect of pulmonary hypertension (PH) on cardiopulmonary responses during exercise in IPF patients is very limited. We sought to investigate the impact of PH on exercise capacity and the correlation between systolic PAP (sPAP) and pulmonary function testing, as well as cardiopulmonary exercise parameters, in patients with IPF and PH. Methods: Eighty-one consecutive patients with IPF, who were evaluated over a 6-year period, were retrospectively studied. Patients underwent pulmonary function testing, Doppler echocardiography and maximal cardiopulmonary exercise testing. PH was defined as sPAP > 35 mm Hg. Results: PH was diagnosed in 57% of the patients. Categorization of patients according to severity of PH indicated a significant reduction in maximum work rate, peak O-2 uptake, anaerobic threshold and peak O-2 pulse in those with sPAP > 50 mm Hg. In IPF patients with PH, estimated sPAP correlated with peak O-2 uptake, anaerobic threshold, peak O-2 pulse and end-tidal CO2 at anaerobic threshold, while the strongest correlation was between sPAP and ventilatory equivalent for CO2 at anaerobic threshold (r = 0.611, P < 0.001). There were no differences in pulmonary function or exercise parameters indicative of lung volume reduction, across the patient categories, and none of these parameters correlated with sPAP. Conclusions: PH has a negative impact on exercise capacity in IPF patients. In IPF patients with PH, resting sPAP correlated with exercise parameters indicative of gas exchange and circulatory impairment, but not with defective lung mechanics.