Use of 445 nm laser in laryngeal surgery: experimental study

Abstract

Introduction. The problem of phonosurgery remains relevant today since the prevalence of benign and tumor-like laryngeal lesions is up to 55%–70% among diseases of the upper respiratory tract. Photoangiolytic lasers are actively used among laser systems in phonosurgery today. A new 445 nm surgical laser (TruBlue, A.R.C. Laser Company), having a high hemostatic and resection effects, was certified for the medical market in 2018. TruBlue laser operation is possible in an atmosphere of inert gas (helium) by connecting the optional Flow Control unit. To date, there are very few works in foreign and Russian literature devoted to the use of that laser device in ENT practice, particularly, in laryngology. Objective. To select the optimal 445 nm laser mode for use in phonosurgery based on an experimental study of biological material. Material and methods. An experimental study was conducted on a model of the larynx (chicken muscle tissue) using a 445 nm laser in contact constant and pulsed modes, including an atmosphere of an inert gas (helium). The zones of destruction, coagulation necrosis, and ischemia were measured by histological examination using a morphometry system. The total number of experiments was 142, the total number of micro-preparations studied was 284. Results. While working in continuous wave mode, we received an extensive zone of thermal exposure, which in clinical practice correlates with deep damage of the vocal fold and violation of its vibratory function. This confirms the axiom that the optimal mode for laryngeal surgery is a pulsed one. According to the evaluation results of the pulse mode at standard laser settings (without helium supply), the parameters with the smallest pause between pulses—that is, 8 W pulse 10–20 ms, 9–10 W pulse 10 ms with a pause of 150 ms—were the most optimal for practical activity in terms of combined resection and coagulation effect. These parameters are acceptable for use in phonosurgery since the maximum destruction zone does not exceed 600 nm. While working in an inert gas atmosphere, we recommend using a laser at a power of 6–8 W with a pulse duration of 10 ms and a pause of 100–130 ms; with an increase in the pulse, lengthen the pause 6–7 W 20 ms 120–130 ms, 8 W 20 ms with a pause of 130 ms. Conclusion. During the experiment, blue laser showed high resection and coagulation effects. According to the results of the study, the parameters of laser exposure were obtained, which are optimal for the surgical treatment of benign and tumor-like laryngeal lesions.