Transverse forces exerted on the maxillary incisors during laryngoscopy

Purpose: In this study the effect of level of experience of the intubator on the forces applied by the Macintosh laryngoscope on the maxillary incisors in both the axial and transverse direction were investigated. Methods: Five groups of different levels of experience (15 per group), staff anaesthetists, residents, nurse anaesthetists, surgeons and students, performed one laryngoscopy and subsequent intubation on an intubation manikin equipped with sensors to measure these forces. Results: Maximal transverse forces oriented toward the base of the skull (Fmtpmax) were between 0 and 10 N in 46 cases (61%), between IO and 20 N in 21 (28%) and greater than or equal to 20 N (maximum 46.5 N) in eight cases (11%). The maximal values of the transverse forces oriented toward the intubator (Fmtnmax) were between 0 and 10 N in 69 cases (92%), between 10 and 20 N in 3 (4%) and greater than or equal to 20 N(maximum 36.4 N) in 3 (4%). Level of experience was related to Fmtpmax (Spearman: P = 0.04, r = 0.24). In addition, Fmtnmax was less in experienced intubators (anaesthetist and residents) than in inexperienced intubators (all other groups) (Student's t test: P = 0.04). Conclusion: In contrast to the effect on forces exerted in the axial direction, experience proved to have a beneficial effect on the forces in the transverse direction.