Comparison of the 'sniffing the morning air' position and simple head extension for glottic visualization during direct laryngoscopy

Abstract

Background: This was a prospective randomized single-blinded clinical trial comparing the glottic views obtained during direct laryngoscopy between the 'sniffing the morning air' position and simple head extension.

Methods: A sample of 378 patients, aged 18 to 75 years old with ASA physical status I or II, scheduled for elective surgery under general anesthesia with endotracheal intubation, were randomized into 2 groups. Group A used the sniffing position during the first laryngoscopy while Group B was put in simple head extension position. Positions were then interchanged for the second laryngoscopy. Sniffing position was obtained by placing a 7 cm height non-compressible cushion under the patient's head. In simple head extension, patient's head was placed flat. Glottic visualization was assessed based on the Cormack & Lehane scale. Intubation was performed after second laryngoscopy and success rate of first attempt intubation was compared.

Results: The distribution of patients with different Cormack & Lehane scores between the two intubation positions were significantly different (p < 0.001). Changing over to the 'Sniffing position' resulted in improvement of the Cormack & Lehane scores in 109 (57.7%) patients, no change in 75 (39.7%) or worsening in 5 (4.8%) patients. Successful intubation at first attempt was better (p < 0.05) with Group A: 156 (83.5%) while Group B: 121 (64.0%).

Conclusion: Sniffing position provided better glottic visualization score and increased the successful rate of intubation as compared to simple head extension.