A case is reported of bronchial stenosis due to a vascular cause in a patient with chronic obstructive lung disease, cor pulmonale and pulmonary arterial hypertension. This led to right lower lobe atelectasis and acute respiratory failure (pHa 7.24; PaCO2 85 mmHg; PaO2 44 mmHg) with important right-to-left shunting. This diagnosis was only suggested on day 7 by fibreoptic bronchoscopy and confirmed a week later by tomography and digital angiography. Nifedipine, used to reduce the pulmonary arterial hypertension, increased the cardiac index (31.min-1.m-2 to 3.3.1.min-1.m-2) and oxygen transport (488 ml.min-1.m-2 to 554 ml.min-1.m-2), despite increasing the shunt effect (Qs/QT: 26% to 31%). This and the antiinflammatory action of methylprednisolone were probably responsible for the favourable outcome.