Pulmonary haemodynamics at rest and on exercise in patients with idiopathic pulmonary fibrosis

We studied pulmonary haemodynamics in 34 patients with idiopathic pulmonary fibrosis (IPF). The diagnosis was established clinically and confirmed by a lung biopsy in 13 subjects. At rest pulmonary hypertension was found in 21 patients, the mean pulmonary artery pressure (PPA) for the group being 23.8 +/- 7.7 mmHg (means +/- SD). In 19 patients subjected to steady-state physical exercise, PPA rose from 23.1 +/- 7.7 mmHg to 40.3 +/- 16.6 mmHg and arterial oxygen tension (PaO2) fell from 77.7 +/- 10.1 mmHg to 62.5 +/- 14.3 mmHg. There was a significant correlation between the rise in PPA and fall in PaO2 on exercise. We found no correlation between pulmonary artery pressure referred to barometric pressure at rest and lung function data, except for a weak correlation between PPA and PaO2. However, pulmonary artery transmural pressure correlated more strongly with PaO2, and additional correlation with VC, FEV1, and lung compliance were found. Our results suggest that pulmonary intravascular pressure and pulmonary hypertension in patients with IPF are affected not only by anatomical restriction of the pulmonary vasculature and alveolar hypoxia but also by the negative intrathoracic pressure.