European Journal of Cardiovascular Medicine

Endotracheal intubation via direct laryngoscopy remains a fundamental skill in anaesthesia and emergency airway management. Optimal visualization of the glottic aperture is essential to secure the airway on first attempt, minimizing trauma, hypoxia, and hemodynamic perturbations associated with prolonged or repeated attempts. Historically, the 'sniffing position' (SP) has been advocated to facilitate alignment of the oral, pharyngeal, and laryngeal axes, thereby improving the line of sight to the glottis. However, the precise parameters that define an optimal SP—particularly the vertical head elevation (pillow height)—remain debated.

ETI establishes definitive airway, prevents aspiration of gastric contents and allows positive pressure ventilation which is usually facilitated by direct laryngoscopy. Despite technological advancement in airway management, placing ETT by direct laryngoscopy is still considered to be a challenging task. ¹

Tracheal intubation remains a challenge in day-to-day practice for the anaesthesiologist even in patients where difficult airway is not anticipated1. If the success rates of ETI are poor, they result in multiple attempts with poor patient outcomes².Proper positioning of the head and neck is essential for laryngeal visualization during direct laryngoscopy. Further, an optimal position for successful laryngoscopy reduces the risk of tracheal injury, duration of the procedure, repeated attempts to laryngoscopy and intubation, ultimately reducing the overall rate of trauma and further complications³.

It has been credited to Chevalier Jackson in 1913, who simply suggested that the patient be placed on a pillow in neutral position with head extended⁴.Inadequate visualization of the laryngeal view may result in prolonged intubation time and repeated attempts to achieve successful intubation which is undesirable⁵." Routine laryngoscopy is usually performed in SP. SP described by Sir Ivan Magil for the first time involves placing a pillow under the occiput and then simply extending the head⁶." SP aligns the oral, pharyngeal and laryngeal axes, permitting the line of vision to fall directly on laryngeal inlet⁷. SP with neck flexion (350 at C4 to C2) and extension of head (150 at atlanto-occipital joint) is traditionally recommended for induction of general anesthesia unless contraindicated, like in trauma with cervical spine injuries⁸.

In study by El-Orbany et al., incidence of difficult laryngoscopy was 8.38% with no head elevation and sniffing position⁹.

Later, in 1944, the TAAT was introduced to explain the anatomical reasoning behind the superiority of sniffing position¹⁰.Several studies have established the benefit of SP for the best laryngeal view for laryngoscopy and intubation¹¹. Traditionally, a 7-10 cm pillow is used to achieve this "sniffing position”¹².

A study by Schmitt and Mang found that elevating the head higher than what is needed for a conventional SP may improve laryngeal exposure in some patients¹³.Hong HJ et al in the comparative study carried out with head elevation using pillows of 4 cm and 8 cm height concluded that a pillow of 8 cm height did not further improve laryngeal view but increased anesthesiologist's discomfort compared to a pillow height of 4 cm during intubation¹⁴.So, even though various studies have shown benefits of head elevation, still there is no conclusive evidence regarding the optimal height required for providing the best glottic view for intubation.

Hence, this study was planned to evaluate optimal pillow height needed for best glottic view beyond the “sniff position” targeting the Indian population.

Several investigators have suggested that individualized or modest head elevation may be superior to the conventional large pillows frequently utilized (7–10 cm). Excessive elevation can paradoxically impede visualization by inducing excessive cervical flexion or misalignment of axes, while inadequate elevation may fail to achieve the favorable angulation of the atlanto-occipital joint. The present study aims to clarify the optimal degree of head elevation by systematically comparing three practical pillow heights (0 cm, 3 cm, and 6 cm) in a consecutive cohort of elective surgical patients, documenting objective laryngeal view metrics and intubation outcomes

Study design and setting: This prospective randomized analytical study was performed at Sri Lakshmi Narayana Institute of Medical Sciences, Puducherry, after Institutional Ethics Committee approval (IEC/C-P/49/2023). The study period spanned May 2023 to November 2024.

Population and sampling: Adult patients (18–65 years), ASA physical status I–II, scheduled for elective surgery under general anaesthesia were recruited. Key exclusion criteria included BMI >30, anticipated difficult airway (Mallampati III–IV, limited mouth opening), significant cardiorespiratory comorbidities, and patient refusal. A sample size of 159 was calculated using Cochran’s formula based on an expected prevalence derived from prior literature, ensuring adequate power to detect clinically meaningful differences.

Randomization and procedure: After informed consent and pre-anaesthetic evaluation, patients were randomized using a computer-generated sequence for order of assessments. Under standardized induction and paralysis, direct laryngoscopy was performed by experienced anaesthesiologists (≥5 years). Each patient was assessed in the three head positions—flat (0 cm), 3 cm pillow, and 6 cm pillow—with intermittent mask ventilation between attempts to maintain oxygenation. The laryngeal view in each position was recorded using the Cormack–Lehane (CL) grading and Percentage of Glottic Opening (POGO) score. The position providing the best glottic view was selected for intubation; IDS and intubation-related outcomes were documented for that intubation.

Outcome measures: Primary outcome was optimal laryngeal view quantified by POGO score. Secondary outcomes included CL grade, IDS, number of attempts, mucosal injury (blood on laryngoscope blade), postoperative throat symptoms (sore throat, cough, dysphagia), and intubation time. Data were entered into MS Excel and analyzed using SPSS v24.0. Categorical variables were compared using Chi-square tests and continuous variables with t-tests or ANOVA where appropriate; a p-value <0.05 was considered statistically significant

Demographics and baseline characteristics: The cohort (n=159) had a mean age of 38.9 ± 13.1 years, mean BMI 23.5 ± 2.1, and balanced gender distribution (56% male). Baseline airway characteristics (interincisor gap, thyromental distance, Mallampati class I–II) were comparable across the sample.

Laryngeal view (CL grade): Across the total 477 laryngoscopic assessments (159 patients × 3 positions), CL grade distributions differed markedly by pillow height. Using CL grade as the metric, the 3 cm position yielded the highest frequency of favorable views (CL 1–2). Detailed counts are depicted in Figure 1.

Table 1. Cormack–Lehane counts per pillow (n=159 observations per pillow):

Figure 1. Cormack–Lehane grade distribution by pillow height.

POGO score distribution: The POGO categorical breakdown (0%, 50%, 100%) showed that a 3 cm pillow markedly increased the likelihood of a high glottic exposure (100% POGO observed in 47.2% of 3 cm assessments compared to 12.6% for 0 cm and 11.9% for 6 cm; p<0.001). This relationship is illustrated in Figure 2.

Table 2. POGO category counts per pillow (n=159 per pillow):

Figure 2. POGO category distribution by pillow height.

Intubation outcomes (IDS): For intubations performed using the position that yielded the best glottic view, the distribution of intubation difficulty favored the 3 cm group. Among the patients intubated in the 3 cm position (n=110), 67.3% were classified as 'easy' (IDS=0) versus 57.1% in the 0 cm (n=21) and 57.1% in the 6 cm (n=28) groups (p<0.001). Figure 3 presents the easy versus difficult proportions per intubation group. Additionally, mucosal injury and postoperative throat complaints were least frequent in the 3 cm cohort.

Table A3. IDS (easy vs difficult) for intubation groups:

Figure 3. Intubation difficulty (easy vs difficult) by pillow height in intubation groups.

Other observations: The rate of first-attempt success was highest when intubation was performed in the 3 cm position (77.3% first attempt) compared to 47.6% (0 cm) and 42.9% (6 cm) (p<0.001). Intubation time did not differ significantly between groups (proportion with time <10 s: 0 cm 85.7%, 3 cm 82.7%, 6 cm 82.1%; p=0.859). These findings suggest improved visualization and reduced manipulation without appreciable prolongation of the procedure.

This study demonstrates that moderate head elevation (3 cm) optimizes laryngeal exposure and eases tracheal intubation in elective, low-risk adult patients. The observed superiority of 3 cm elevation likely reflects an optimal compromise between cervical flexion and atlanto-occipital extension, achieving favorable alignment between airway axes while avoiding the excessive flexion associated with larger pillows.

Comparison with existing literature: Our results align with several prior investigations that reported improved glottic views with modest head elevation (4–5 cm) and with studies that found diminishing returns or increased operator discomfort with excessive elevation (8–12 cm). For example, Fujivara et al.¹⁶ reported better intubation metrics with 4 cm versus 12 cm pillows, and Hong et al.¹⁵ found increased discomfort at 8 cm without improvement in view. Conversely, some studies noted no difference between certain positions, underscoring the influence of patient habitus, neck length, and individualized anatomy.

Clinical implications: From a practical standpoint, a 3 cm elevation is easily reproducible using low-profile gel pads or folded towels and can be implemented in routine clinical practice. Benefits include higher first-attempt success, lower IDS, reduced mucosal injury, and fewer postoperative complaints—outcomes with immediate patient-safety implications. The lack of significant difference in intubation time suggests that improved visualization does not compromise efficiency.

Mechanistic rationale: The sniffing position concept seeks to approximate three-axis alignment; however, exact alignment depends on vertical elevation relative to head and torso geometry. Excessive head raise may increase cervical flexion at lower cervical segments but reduce atlanto-occipital extension, leading to suboptimal visualization. Conversely, minimal elevation may under-correct pharyngeal axis angulation. A modest elevation (~3 cm) appears to restore the balance necessary for an unobstructed line of sight in many patients.

Limitations: This study excluded patients with anticipated difficult airways and BMI >30; thus, results may not be generalizable to obese patients or those with restricted neck movement. Additionally, although assessments were standardized and operators were experienced, some degree of inter-operator variability in subjective metrics (e.g., lifting force) cannot be fully excluded. We used categorical POGO (0/50/100%) instead of continuous percent values as recorded in some studies; this preserves clarity but reduces granularity.

Future directions: Research should evaluate customized head elevation strategies (e.g., aligning external auditory meatus with sternal notch) in diverse populations, including obese and pregnant patients. Quantitative imaging (MRI or video laryngoscopy) studies could elucidate axis alignment changes at various elevations, and randomized trials comparing 3 cm with individualized ramping protocols would further inform practice.

In conclusion, a modest 3 cm head elevation during direct laryngoscopy improves glottic visualization, increases first-attempt success, reduces intubation difficulty and mucosal trauma, and lowers postoperative airway complaints in elective, non-obese adults. Implementing a low-profile 3 cm elevation is a simple, low-cost modification to standard practice that may enhance airway management safety and efficiency. Further studies are warranted to assess applicability in high-risk and obese populations and to compare individualized ramping techniques

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