Successful endotracheal intubation is fundamental for safe general anesthesia. Traditionally, the supine or "sniffing" position has been employed to align the oral, pharyngeal, and laryngeal axes, promoting better visualization during laryngoscopy. However, emerging evidence suggests that modifications such as the 25° back-up position may enhance the intubation process.

The rationale for exploring alternative positions stems from the potential for improved ergonomics, increased POGO scores, and reduced need for additional optimization maneuvers. This study compares these two positions to determine the optimal patient alignment for effective and safe tracheal intubation.

Study Design and Population: After approval by the institutional ethical committee and written informed consent, the study was conducted at the Department of Anaesthesiology, People's Hospital, Bhopal. This was a prospective observational study.

60 adult patients of ASA grade I and grade II aged 18 to 60 years, of either sex, scheduled for elective surgeries under general anaesthesia were included. Patients with ASA grade 3 or more, with anticipated difficult airway, with body mass index more than 35 kg/m2 and those who failed to provide written informed consent were excluded from the study.

Methodology:

A day before surgery, all patients underwent standard pre-anaesthetic evaluation by the anaesthesiologist. Patients were kept nil per oral from midnight. On the day of surgery, in the pre-operative room, intravenous access was checked and baseline vitals were noted. Upon arrival in the operation theatre, intravenous fluid was started, and ASA standard monitors were attached. Patients were preoxygenated for 3 mins with 100 % oxygen. Premedication with IV inj. Glycopyrrolate 0.004 mg/kg, inj. Midazolam 0.05 mg/kg, inj. Ondansetron 0.1 mg/kg and inj. Pentazocine 0.3 mg/kg, were given to the patients and were induced with Inj. Propofol 2 mg/kg and inj. Succinylcholine 1-2 mg/kg. Group S: Patients were positioned supine with a 7 cm pillow to achieve sniffing position. Group B: Operating table inclined at 25° to align the external auditory meatus with the sternal notch. Intubation was performed according to the group allocation. Experienced anesthesiologists (anaesthesiologist with more than 5 years of experience and expertise to use video laryngoscope) performed intubation using a video laryngoscope (BPL VL-02). The POGO score, number of optimization maneuvers, intubation attempts, and operator comfort were recorded.

Statistical Analysis:

Statistical analysis was conducted using Microsoft Excel and SPSS software Version 27.0. Data were expressed as mean and standard deviation. Continuous variables were expressed as mean ± standard deviation and compared using the unpaired Student's t-test. Comparisons between groups were performed using t-tests, with p < 0.05 considered statistically significant.

Glottic Visualization:

The mean POGO score was significantly higher in the 25° back-up group (p<0.05), indicating improved glottic view.

Optimization Maneuvers:

Fewer maneuvers were required in the 25° back-up group compared to the supine group (p<0.05).

Intubation Ease and Safety:

Intubation was subjectively rated easier in the back-up group. No significant complications such as hypoxemia or airway trauma occurred in either group.

Assessment of airway visualization during laryngoscopy¹³

POGO (Percentage of Glottic Opening) Score:

• 100% denotes visualization of the entire glottis from another commissure of the vocal cords to the areytenoid notch.
• 0% denotes none of the glottic opening visualized.
• 1-99% denotes partial view of glottic opening.

Table 1: Comparing POGO score with position

Inference:

Improved glottic view in 25° back-up position.

Graph 1: Comparing POGO score with position

Table 2: Comparing Optimization Maneuvers with position

Inference: Fewer maneuvers required in the 25° back-up group

Graph 2: Comparing Optimization Maneuvers with position

In this study, our findings were suggestive of that the 25° back-up position significantly improves glottic visualization, as reflected by higher POGO scores compared to the traditional supine (sniffing) position.

In the 25° back-up position, laryngeal structures move a little more caudally by the gravity than in the supine position and the angle between laryngeal axis (LA) and line of vision (LV) can be further decreased. In the paralysed patients, the muscle tone to support the laryngeal structures will be lessened and the effect of gravity will be even more than that seen in awake and unparalysed patients. Thus, the change of effect of gravitational force in the caudal direction cannot be neglected.1

Similar to our findings, Lee et al1, in their study demonstrated significantly improved POGO scores by performing laryngoscopy in the 25° back-up position instead of the supine position as the mean POGO scores during increased from 42.2% in the supine position to 66.8% in the 25° back-up position.

A 45° direction to lift the handle of the laryngoscope in the supine-horizontal position decreases to about 20° in the 25° back-up position. A change of direction to lift the handle leads to a change of force and torque. Vertical force against gravity will be decreased and horizontal force increased in the back-up position. In the back-up position, a laryngoscopist can push the blade of the laryngoscope forward rather than upward with the same force and get an improved view of the larynx.1

Levitan et al11, assessed glottic opening during laryngoscopy on fresh cadavers and concluded that by increasing head elevation and laryngoscopy angle (neck flexion) significantly improves POGO scores during laryngoscopy on fresh human cadavers. Pachisia et al6, compared laryngeal view and intubating conditions in the sniffing position and position acquired by aligning the external auditory meatus and sternal notch horizontally by using an inflatable pillow (AM-S) and found a significant reduction in the intubation difficulty scale with improved Cormack Lehane grading of laryngeal view in the AM-S position using Macintosh laryngoscope. Wai and Graham5, found an improvement of 8% in the POGO score by using Glidescope VL in the ramped position compared to the supine position on the human patient simulator when used by novice laryngoscopists.

Jun et al.3 evaluated laryngeal visualization and ease of tracheal intubation in the back-up position using an individualized table-ramp angle (17.5 +/- 4.1 degrees) to align the sternal notch and EAM. They concluded that when compared with neutral position, use of the back-up position to align the EAM and sternum in the same horizontal plane not only improved glottic visualization but also facilitated successful tracheal intubation, as indicated by the reduced proportion of patients for whom optimization maneuvers were performed during Mac-VL-guided tracheal intubation.3

As per Tsan et al7, Macintosh laryngoscopy in the bed up head elevated position provides a non-inferior laryngeal view to Glidescope laryngoscopy but is superior to the view acquired in the sniffing position among the general population.

In our study we also found that there is significant reduction in optimization maneuvers (e.g. requirement of BURP) during intubation in the 25° back-up position when compared with the routine supine position. The 25° back-up position also contributed to better ergonomics for the anaesthesiologist for laryngoscopy, potentially improving intubation success rates and reducing time and effort.

Desai et al2, in their study drew the inference that the 25° back-up position is useful in providing the channelled (King Vision) nd non-channelled (McGrath) VLS with less requirement of ancillary manoeuvres an shorter intubation time without complications, which were similar to our findings.

Tsan et al8, Reddy et al9 and Gudivada et al10 also reported less frequently required ancillary laryngeal manoeuvres in either ramp or 25° back-up position compared to supine position with direct laryngoscopy.2

Nandhakumar et al 4, conducted a study of comparing the glottic view in a HELP position between supine and 25° back-up position. They considered both the POGO score and CL grading for assessing the glottic view. They found that the 25° back-up HELP position improved the glottic view significantly in comparison to the supine HELP position and had lower incidence of anaesthesiologist’s stooping and lesser use of external laryngeal manoeuvre and/or Bougie with comparable laryngoscopy time and intubation attempts.4

Easier endotracheal intuabtion (assessed on Likert Scale), lower incidence of anaesthesiologist’s stooping and lesser use of external laryngeal manoeuvre and/or Bougie during intubation in group B could be due to better alignment of laryngoscopy line with performer’s line of vision and change in the direction of the force with the laryngoscope handle in the 25° backup position.12

Our study also had a few limitations. First, we cannot infer the result of our study in patients with anticipated difficult airway, with BMI > 35 kg/m3 and with ASA grade III and more, as such patients were excluded. Second, the use of single blade design for laryngoscopy (Macintosh) also limits us for further enhancement in the study. Third, we included patients which were enrolled for elective surgeries. The role of 25° backup position for intubation during emergency set up, needs further research.

The 25° back-up position provides a clinically significant improvement in intubation conditions compared to the traditional supine position, by improving POGO score and requiring fewer optimization maneuvers. The 25° back-up position can be considered a superior alternative for routine laryngoscopy and intubation in elective surgical settings.

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