Circulatory Effects of Force Applied to the Soft Tissue during a Laryngoscopy

Suh, Yung Ho; Jee, Dae Lim

Abstract

BACKGROUND
During laryngoscopy, force applied to the soft tissue are assumed to cause circulatory response. The aim of the study was to evaluate this circulatory response and to analyze the relationship between the intensity of the force and the magnitude of the associated circulatory responses.
METHODS
Sixty-three healthy patients, aged 17 to 29 years, were randomly allocated to one of three groups according to the three different subjective forces applied intentionally. Subjects in group 1 received minimal force enough to stimulate circulatory response, but not enough to expose the glottis. Group 2 received the optimal force necessary to expose the glottic opening. Group 3 received excessive force to expose the glottic opening. The axial forces of the laryngoscope handle with a Macintosh blade were measured during a ten-second laryngoscopy, and peak force, mean force, and area under the curve were calculated. Then, arterial pressure and heart rate were recorded after the laryngoscopy at 30 seconds intervals for 3 minutes. The data was compared among groups and with the baseline post-induction values.
RESULTS
No significant difference was found in heart rate and blood pressure at each interval among the three groups, with increasing arterial pressure and heart rate after the laryngoscopy. Blood pressure and heart rate were maintained high, being progressively higher in the groups receiving a higher force.
CONCLUSIONS
We conclude that little association was found between the force and the magnitude of circulatory response although higher forces cause longer circulatory responses.