A 71-year-old woman presented with a 1-week history of dyspnoea, right pleuritic chest pain and bilateral ankle oedema. There was no history of cough, fever or haemoptysis. Her body mass index was >30. Her jugular venous pressure was raised with reduced air entry over the right lung base. She was anaemic (haemoglobin 6.8 g/dl, mean corpuscular volume 67) with type II respiratory failure (pH 7.40, oxygen tension 9.30 kPa, carbon dioxide tension 9.32 kPa on 0.5 fraction of inspired oxygen). …