This patient was diagnosed with asbestosis in three years ago following symptoms of unexplained breathlessness. He is an ex-smoker with a smoking history of approximately 50 pack years. His current exercise tolerance is 150 yards and he complains of leg weakness which limits his exercise abilities.
He complains of thick yellow sputum that he has difficulty shifting but the salbutamol inhaler seems to ease this a little.
His X-ray shows persistent fibrotic changes and increasing opacity in the left base. His resting SpO2 was well preserved at 97%, HR 86bpm on room air.
You perform spirometry.