A study of the effect of smoking on vocal cord structure and function evaluated by narrow band imaging and stroboscopy

Background : Inhaling tobacco smoke leads to inflammation of airways. Previous studies have focused on effect of smoking through cadaveric study of vocal cords and study of acoustic parameters. However, literature search did not reveal any study on evaluating effect of smoking on structure and function of vocal cords both. This study was designed with purpose to evaluate effects of smoking on the vocal cord structure and function in adult patients. This study involves 100 participants who came to ENT OPD with complaints related to throat and history of smoking for more than 5 years with at least 5 cigarettes/day. These participants were evaluated for vocal cord function and structure by Stroboscopic evaluation and Narrow band imaging(NBI) with Fibre-optic laryngoscopy . Results : This study included 100 subjects with mean age of 46.65 ±11.58 years and showed male predominance. Fundamental Frequency(Fo) of vocal cords in males was between range of 110-110 Hz in 47 subjects(73.4% of males) and between 111- 120 in 17 cases(26.6% of males). In females, Fundamental Frequency was in range of 200-210 in 31 subjects(86.1% of females) and in 5 subjects(13.9% of females) in range of 220-220 Hz. Among functional findings seen on stroboscopy, 10 subjects had incomplete glottic closure, 14 subjects had asymmetrical and 8 subjects had aperiodic vocal cord vibrations. In terms of mucosal waves, reduced(20.0%), increased(2.0%), and absent(1.0%) mucosal waves were seen in subjects with abnormal mucosal waves with rest of subjects having normal findings. While reduced(21.0%) and increased(2.0%) amplitude was seen in subjects with abnormal amplitudes and rest of subjects having normal findings. Narrow band imaging findings showed a predominance of Type II(63.0%), followed by Type I(22.0%), Type III(13.0%), and Type Vc(2.0%). In this study, various structural pathologies were seen in subjects including bilateral keratosis(5.0%), increased vascularity(3.0%), unilateral keratosis(3.0%), ulcerative growth(3.0%), edematous cord(3%), and few other findings in few subjects. Conclusions : Smoking has effect on function of vocal cords depicted by lower fundamental frequency. Other functional parameters were abnormal only in few subjects. Organic voice disorders were found in only few smokers.