Values of laryngeal stroboscopy in patients with chronic laryngitis exposed to occupational factors
Authors: Shidlovskaya Tetiana A. , Kovalchuk Petro M. 
Published: December 2021

Topicality: Chronic laryngitis occupies one of the leading positions in the structure of laryngeal pathology.
Among other things in the etiology of chronic laryngitis, occupational factors, including a chemical exposure, play an important role. Laryngeal storoboscopy is one of the most informative methods of examination of the vocal apparatus in phoniatrics that allows observing rapid oscillating motion of the vocal folds during phonation, which cannot be seen without instrumental methods.
Aim: to investigate the functional condition of the vocal apparatus based on the values of laryngeal storoboscopy in patients with chronic laryngitis who were exposed to chemical factors.
Materials and methods: Seventy-five patients with chronic laryngitis and 15 healthy individuals of the control group were examined. The patients were divided into groups based on the type of chronic laryngitis (group 1 one was made up of those who had a catarrhal type, group 2 had subatrophic type patients) and the intensity of chemical factors in the production of nitrogen compounds (subgroup A included patients who worked in manufacturing workshops where the level of chemicals in the air did not exceed maximum allowable levels, whereas subgroup B experienced an exposure to elevated chemical levels). Groups 1A and 2A included 23 and 20 patients, respectively; groups 1 B and 2B were composed of 17 and 15 patients, respectively. The patients underwent a specialized phoniatric examination and they were determined the maximum phonation time (MPT). We performed a video laryngeal stroboscopic examination on the equipment complex of «Karl Storz» (Germany). The results were evaluated by calculating the integrated score of phonator oscillations recorded during a stroboscopic study.
Results and discussion: Patients with chronic laryngitis – employees of the public joint-stock company «AZOT» were examined. This is a large chemical production with several manufacturing workshops involved into various technological processes. According to the intensity of the influence of chemical factors, the manufacturing workshops differ significantly; therefore the intensity of the influence of the factors of the production environment on the upper respiratory tract varies in those working in the production of nitrogen-containing compounds. We compared the results of the survey of patients included in subgroups A and B. The MPT in patients of group 1A was 18.6±1.6 sec versus 13.6±1.2 sec in group 1B; in group 2A, it was 13.4±1.1 sec versus 10.8±0.8 sec in group 2B and 21.2±1.6 sec in the control group. Values in all study groups significantly (p<0.05) differed from the control. Also in groups 1B, 2A and 2B, the MPT was significantly lower than in group 1A. Thus, in patients with chronic laryngitis, who worked in conditions of increased exposure to chemicals present in the air of the production environment, the recorded MPT was significantly lower than in the controls, which is indicative of the impaired function of the vocal apparatus.
Based on laryngeal stroboscopy findings, voice dysfunction revealed in patients with chronic laryngitis was more often manifested by changes in the vibratory cycle, desynchronized vocal apparatus and weakened amplitude of oscillations. According to the average score of video laryngeal stroboscopy in all groups of examined patients with chronic laryngitis, a significant (p &lt;0.05) difference was revealed in comparison with controls, as well as between some groups. In particular, in group 1A the integrated score of laryngeal stroboscopy data was 7.9±0.2, in 1B – 8.8±0.6, in 2A – 10.5±0.8 and in 2B – 12.1±1.0. The normal value is 5.010±0.001. Patients with higher scores had more severe laryngeal impairments and disease course. In group 2 (both A and B subgroups), changes according to video laryngeal stroboscopy were significantly more pronounced than in group 1A. In group 2B, the impairments were more severe as compared with both subgroups of group 1 and group 2A. Thus, in all studied groups of patients with chron ic laryngitis there are seen significant impairments of the vocal apparatus. At the same time, based on the findings of clinical methods and objective instrumental examination, there is a tendency to the deterioration in the functional condition of the vocal apparatus with increased chemical exposure in production. In particular, in groups B, compared with groups A, there is a marked increase in the desynchronization of vibrational oscillations, the number of cases with lack of stroboscopic comfort increases, the number of cases of hypertonia of the vestibular larynx increases. Similar trends apply to other parameters of video laryngeal stroboscopy in groups.
On the whole, a quantitative assessment with the help of scores of integrated laryngeal stroboscopy allows accurate determining the severity of changes in the phonatory activity of the vocal apparatus and objectifying the diagnosis of chronic laryngitis against the background of chemical factors.
The obtained data will be useful for improving the quality of diagnosis of voice disorders in chronic laryngitis, they can also be beneficial for vocational selection and addressing issues of occupational examination.
Conclusions:
1. An impaired voice function according to laryngeal stroboscopy in patients with chronic laryngitis was manifested by changes in the vibratory cycle, mainly by desynchronized vocal apparatus and weakened amplitude of oscillations.
2. With the help of video laryngeal stroboscopy it is possible to objectify, quantify and determine the severity of phonatorial disorders in chronic laryngitis against the background of the exposure to chemical factors.
3. The degree of voice dysfunction according to laryngeal stroboscopy in patients with chronic laryngitis depends on the level of chemical exposure.