What is the most likely diagnosis?
Emphysema. Most likely centrilobular due to smoking.
What are the different types of emphysema?
Centrilobular (most common), panlobular, paraseptal and paracicatricial emphysema.
Chest xrays demonstrates very marked hyperinflation of both lungs. Over 11 posterior ribs are seen, the diaphragms are flattened and there is enlargement of the retrosternal airspace. Pulmonary vasculature not terribly distorted, although there is some prominence of the pulmonary arteries.