# Cadaveric Study on Comparison of Neck Extension Angles for Endotracheal Intubation in Rabbits Using a Rigid and Flexible Endoscope

## TL;DR

This study finds that extending a rabbit's neck to 110 or 120 degrees improves success rates for endotracheal intubation using endoscopes.

## Contribution

The study identifies optimal head extension angles for rabbit intubation using endoscopes, aiding inexperienced veterinarians.

## Key findings

- Head extension angles of 110 and 120 degrees achieved the highest success rates for endotracheal intubation in rabbits.
- Both rigid and flexible endoscopes showed high success rates (97.2% and 95.9%) at optimal angles.
- Intubation success was significantly affected by head placement angle but not by endoscope type.

## Abstract

Rabbit endotracheal intubation is often challenging for anesthetists. Employing an endoscope guided by adjusting the angle of head extension can significantly aid anesthetists in accurately locating and executing rabbit endotracheal intubation, reducing the risk of breathing difficulties during the process. This study explores how specific head extension angles impact endotracheal intubation success rates and time taken. The findings recommend utilizing angles of 110 and 120 degrees for optimal rabbit head extension during endotracheal intubation to enhance success rates and efficiency.

Endotracheal intubation in rabbits is always challenging due to the unique anatomical conformation. To improve endotracheal intubation success, this study determined the relationship between head placement angles guided by endoscope-assisted visualization techniques and the endotracheal intubation success rate. Thirty-two rabbit cadavers were used in the study. Six veterinary practitioners who had no experience with rabbit endotracheal intubation were randomly assigned to intubate rabbit cadavers using the guidance of either a rigid endoscope (RE) or flexible endoscope (FE), with the head placement angles with an ascending neck at 90, 100, 110, 120 and 130 degrees. The endotracheal intubation completed in 90 s was determined to be a success. The success rates using RE and FE were 97.2% and 95.9%, respectively. The means and standard error of means (SEM) of endotracheal intubation times guided by RE and FE were 53.7 ± 4.68 and 55.2 ± 4.24 s, respectively. Results from survival time analysis show that the five veterinarians successfully intubated the rabbit within 90 s, regardless of the different types of endoscopes. Angle was the only significant factor that affected the endotracheal intubation success. The head placement angle at 110 and 120 degrees had the highest success rate of endotracheal intubation compared to 90 degrees (p ≤ 0.05). In conclusion, for inexperienced veterinarians, the success of endotracheal intubation in rabbits, guided by endoscope-assisted visualized techniques regardless of rigid endoscope or flexible endoscope guidance, is improved when the head extension is 110 and 120 degrees.