Abnormal sputum Increased sputum production Increased phlegm An increase in the amount of airway mucus. This feature may be characterized by frequent or excessive throat clearing (exhalation through tightly constricted laryngopharyngeal tissues accompanied by vibration of the palatoglossal arch and the vocal folds serving to clear mucus from the airway). If excessive sputum production is manifested by frequent and often involuntary coughing, the HPO term Productive cough should be used.