Hi doctors, can you tell me what is primary lung infection with slight regression hyperaerated lung fields?

Probably....: A primary lung infection usually refers to pneumonia. Hyper aerated lung fields usually means there is airway obstruction present which results in the inability to expire air completely out of the lungs. And, "slight regression" needs more info to explain, as in a slight regression of what? If the infection is regressing, it means it is improving.