thanks for your question after lung surgery there can be excessive sputum or phlegm production because of the inflammatory process or due to a secondary infection regarding excessive salivation it s more common in children and causes can be Mental retardation Cerebral palsy Parkinson s disease Pseudobulbar Bulbar palsy Stroke Medication side effects (tranquilizers, anticonvulsants) Gastroesophageal reflux Toxin exposure (mercury vapor) you should visit a neurophysician who can investigate and examine and lead to a diagnosis I d its increased phlegm and infection antibiotics need to be started and that will cure the disease thanks