Effects of oxygen on exercise-induced increase of pulmonary arterial pressure in idiopathic pulmonary fibrosis.

INTRODUCTION: Idiopathic pulmonary fibrosis (IPF) is a severe disease with no known effective therapy. Patients with IPF may develop severe increase of pulmonary arterial pressure (PAP) on exercise, the mechanisms of which is not clearly identified.

OBJECTIVES: To determine whether oxygen may correct the increase of PAP developed during exercise in patients with IPF.

PATIENTS AND METHODS: We performed a prospective study on patients with IPF and no hypoxaemia at rest. The absence of pulmonary hypertension (PH) at rest was confirmed by echocardiography (systolic PAP <35 mmHg). Eight patients underwent echocardiography during exercise in air and with oxygen (to maintain saturation of at least 94%). Right ventricle-right atrium gradient and cardiac output were measured at rest, after each increment and at peak. We then compared the echocardiographic results obtained for air and oxygen.

RESULTS: All patients developed significant increase of SPAP on exercise (73 +/- 14 mmHg in air). Oxygen did not significantly improve SPAP on exercise (SPAP: 76 +/- 15 mmHg). Echocardiographic characteristics were similar between air and oxygen except for exercise tolerance in term of workload (p=0.045) and endurance (p=0.017). Resting pulmonary function tests did not predict the occurrence of increase of PAP on exercise.

CONCLUSION: Our results demonstrate that oxygen does not improve exercise-induced increase of PAP in patients with IPF and support the hypothesis that hypoxic vaso-constriction is not the main mechanism of acute increase of PAP during exercise.