Impact of two different head and neck alignment planes on glottic visualization at laryngoscopy in adults

Background: Optimal head and neck positioning is key to rapid, successful tracheal intubation enabling circumvention of peri-intubation sequelae; thus, scientific search for definite anatomical landmarks to serve as reference points for favorable head and neck alignment during laryngoscopy is warranted. Methods: Ethical approval obtained, 78 adults aged 18-60 years, of American society of anesthesiologists (ASA) class I and II, were randomized into groups A and B, of 39 each. All patients had general anaesthesia with oro-tracheal intubation. Group A had the suprasternal notch and external auditory meatus (SN-EAM) plane aligned horizontally, while group B had the sternal angle of Louis and external auditory meatus (SAL-EAM) plane horizontally aligned, for direct laryngoscopy. Glottic view achieved and external laryngeal manoeuvre with backward, upward, rightward pressure (BURP) application was assessed using Cormack-Lehane grading and four-point Likert scale respectively; intubation attempts, immediate post-intubation arterial oxygen saturation (SpO2), and time to orotracheal intubation (TTOTI) defined as the period from removal of preoxygenating face mask to first capnographic evidence of correct tracheal intubation, were recorded. Results: All 78 subjects completed the study. Groups A and B were similar in degree of glottic visualization (p=0.642) and TTOTI (33.38±5.09 versus 33.18±5.77, p=0.868); tracheal intubation attempts, BURP application and immediate post-intubation SpO2 (98.25±0.72 versus 98.23±0.81, p=0.833) were also comparable. Conclusion: Aligning the SN-EAM plane horizontally achieved degree of glottic visualization comparable to keeping horizontally the SAL-EAM plane, during direct laryngoscopy in adults.