Effect of thyroplasty on laryngeal airflow

Thyroplasty has virtually replaced Teflon injection as the procedure of choice for treatment of the unilateral paralyzed vocal cord. Previous studies have shown that Teflon injection, by stiffening the vocal cord, decreases the extrathoracic airway obstruction occasionally measured by pulmonary function testing in patients with unilateral vocal cord paralysis. We became interested in the effect of thyroplasty on extrathoracic airflow. In this prospective study, patients underwent prethyroplasty and postthyroplasty pulmonary function testing. Flow volume loops combined with traditional spirometry were used. Postoperative pulmonary function tests were performed at least 2 months after surgery to allow resolution of surgical edema. Our study results support the previous finding that vocal cord paralysis alone causes some degree of extrathoracic obstruction. However, in contrast to Teflon injection, thyroplasty decreased extrathoracic airflow in all but 1 patient, and by criteria based on the ratio of the midexpiratory flow to the midinspiratory flow, caused new postoperative extrathoracic obstruction in 27% of patients. Symptomatic evidence of this obstruction may be more evident in those active patients with more ventilatory demand.