Disturbances in airflow dynamics and tracheal sounds during forced and quiet breathing in subjects with unilateral vocal fold paralysis

Variable extra thoracic obstruction has been found in spirometric studies in subjects with unilateral vocal fold paralysis. The aim of the study was to further evaluate airflow dynamics in these subjects with body plethysmography and tracheal sound analysis. Ten patients with unilateral vocal fold paralysis without a history of chronic pulmonary diseases and 10 healthy control subjects were studied. Flow‐volume spirometry, body plethysmography and tracheal sound analysis were performed within 1 day. The study shows that peak inspiratory flow (PIF) and specific airway conductance (SG_aw) expressed as percentage of Finnish reference values were significantly lower and airway resistance (R_aw) was higher among the patients than among the controls (P=0·004, P=0·026 and P=0·004, respectively). The patients had higher sound amplitude of both inspiratory and expiratory tracheal sounds than the controls [root mean square (RMS) values of the power spectra were 31·5 and 25 dB, P=0·006 in inspiration and 31·5 and 26 dB, P=0·013 in expiration, respectively]. Quartile frequencies (F25 and F50) and RMS of expiratory tracheal sounds had significant negative correlation with PIF (P=0·02, P<0·001, P=0·02, respectively) and forced inspiratory volume in 1 s (FIV₁) (P=0·01, P<0·001, P=0·01, respectively). There was also an association between F50 and peak expiratory flow (PEF) (P=0·02). According to the present study, both quiet breathing and forced inspiration are disturbed in subjects with unilateral vocal fold paralysis. A close relationship between tracheal sounds and respiratory function tests exists.