Abstract
Platypnoea-orthodeoxia syndrome is characterised by dyspnoea and oxygen desaturation in the upright position usually caused by an extracardiac shunt and less often due to dynamic factors that accentuate an intracardiac right-to-left shunt. In our patient, the collapse of lower lobe of left lung secondary to bronchial stenosis due to endobronchial tuberculosis and resultant mediastinal shift was the factor that led to an otherwise unrecognised intracardiac right-to-left shunt leading to platypnoea-orthodeoxia. We postulate that there would have been an increased stretching and widening of a patent foramen ovale in the upright position due to gravity resulting in an increased shunt despite normal intracardiac pressures. Once the patency of the left main bronchus was restored by deploying a stent, the left lower lobe expanded, the mediastinum returned to its normal position and there was resultant resolution of the platypnoea-orthodeoxia. This interesting observation may be useful in managing similar scenarios in the future.