Comparison of intubating conditions in supine (sniffing) and 25° back-up position using channelled and non-channelled video laryngoscopes - A randomised controlled study.

Abstract

The 25°back-up position is proposed to increase the efficacy of preoxygenation and provide better tracheal intubating conditions when using a direct laryngoscope. This study aimed to compare the ease of tracheal intubation between supine and 25° back-up positions when using two video laryngoscopes (VLS). One hundred adults with normal airways and belonging to the American Society of Anesthesiologists physical status classes I and II, requiring general anaesthesia, were randomised in groups K and M. The trachea was intubated using King Vision and McGrath VLS in either supine (groups K1 and M1) or 25° back-up (groups K2 and M2) positions. The 25° backup position was given by raising the operating table from the horizontal position by flexing the torso at the hips so that an imaginary line connected the patient's external auditory meatus to the sternal notch. Modified Intubation Difficulty Scale (mIDS) was the primary outcome, and intubation time, the number of intubation attempts, vital parameters, and complications were compared secondarily. Statistical analysis was done using MedCalc software by applying an independent t-test for parametric data and a Chi-square test for categorical data and finding the risk ratio. Mean (Standard deviation) mIDS was significantly reduced using both VLS in the 25° back-up position [0.92 (0.75) versus 0.48 (0.58), P = 0.025, degree of freedom (DF): 48, mean difference (95% confidence interval [CI]):-0.44 (-0.821 to - 0.059) in group K1 versus group K2 and 0.76 (0.59) versus 0.36 (0.48), P = 0.012, DF: 48, mean difference (95% CI): -0.40(-0.706 to - 0.094) in group M1 versus group M2, respectively]. The risk ratio comparing both the positions for the total number of patients requiring manoeuvres during intubation using both the VLS was 0.48 with P = 0.0004 and 95% CI = 0.305 - 0.765. Intubation time was shorter in the 25° backup position by using King Vision (P = 0.005) and McGrath (P = 0.042) VLS. The 25° backup position helps provide ease of intubation using both the channelled (King Vision) and non-channelled (McGrath) VLS.