Mrs Jackson is 55 years old and has ‘struggled with her chest on and off’ for the last 5 years. On further questioning she says she has frequent bouts of ‘bronchitis’ and gets short of breath on exertion. She has quit her long term habit of smoking 2 months ago but has found her breathing has deteriorated since. She is now short of breath on minimal exertion and feels tired in general. There is no chest pain or weight loss. Before examining her chest, you find bilateral pitting ankle oedema and mild hepatomegaly.
What is the most likely diagnosis?