The effect of brief pre-anesthetic exercise therapy of jaw and neck joints on mouth opening, neck extension, and intubation conditions during induction of general anesthesia: a randomized controlled trial

Background The effort to improve tracheal intubation process is clinically valuable. We hypothesized that a preoperative brief exercise therapy would increase mouth opening and neck extension, enhancing intubation conditions during general anesthesia. Methods Patients undergoing general anesthesia were randomized into two groups. The exercise group performed the exercise regimen including masseter muscle massage and stretching of jaw and neck joints before anesthetic induction, while the control did not. Before (baseline) and after the intervention, we evaluated Mallampati score, mouth aperture size, and sternomental distance. After tracheal intubation, intubation difficulty scale with direct laryngoscope and oropharyngeal soft tissue injury were also evaluated. Results A total of 138 patients completed the analysis (control = 68, exercise = 70). Baseline characteristics did not differ between groups. At anesthetic induction, there was a significant difference in Mallampati score between the two groups (P = 0.039) and the incidence of Mallampati scores of 1 was higher in the exercise group (odds ratio [95% CI]: 2.1 [1.0–4.3], P = 0.043). Mouth opening after the intervention was greater in the exercise group than in the control group (estimated difference [95% CI]: − 2.4 [− 4.8 – -0.1], P = 0.042) and sternomental distance was similar between the two groups (estimated difference [95% CI]: − 3.7 [− 9.0–1.7, P = 0.175). The exercise group showed less soft tissue injuries (odds ratio [95% CI]: 0.2 [0.1–0.8], P = 0.009), however, intubation difficulty scale did not differ between the study groups (P = 0.112). Conclusions The brief pre-anesthetic exercise improved intubation conditions and enabled faster tracheal intubation with less injury to oropharyngeal soft tissue. Trial registration Clinical Research Information Service (registration number: KCT0002618), registered at December 28, 2017.