This airway study is a neat little randomised-but-not-blinded study of the effect of head rotation on the oropharyngeal leak pressure of both the i-gel and LMA Supreme 2nd generation supraglottic airways.

The researchers investigated the leak pressure (OPLP) of the i-gel and LMA Supreme in paralysed patients with the head: 1. neutral, 2. rotated 30°, and 3. rotated 60°. They found that rotation of the head through 30° and 60° progressively increased OPLP by a clinically-significantly amount (0° vs 60° 5.5 cmH₂O (3.3-7.8) & 6.5 cmH₂O (5.1-8.0) respectively).

Before you get too excited...

The result however may not be reliably applicable to all populations, notably the study subjects were overwhelmingly small (x̄ ~160cm & 60kg) Japanese women (71%), receiving a TIVA muscle-relaxant anaesthetic (propofol, remifentanil, rocuronium). How well this improvement-with-rotation holds up among, for example, spontaneously ventilating large Caucasian males, is unclear.

Bottom-line

When using an i-gel or LMA Supreme 2nd generation supraglottic airway, careful head rotation to 60° may increased oropharyngeal leak pressure and so assist with ventilation troubleshooting. However head and neck rotation of anaesthetised, paralysed patients should be performed gently and cautiously – you are after all, not a chiropractor!

summary

• Tomohiro Chaki, Shunsuke Tachibana, Sho Kumita, Honami Sato, Kosuke Hamada, Yasuyuki Tokinaga, and Michiaki Yamakage.
• From the Department of Anesthesiology, Sapporo Medical University School of Medicine, Sapporo, Japan.
• Anesth. Analg. 2021 Mar 1; 132 (3): 818826818-826.

BackgroundSecond-generation supraglottic airway (SGA) devices are useful for airway management during positive pressure ventilation in general anesthesia and emergency medicine. In some clinical settings, such as the anesthetic management of awake craniotomy, SGAs are used in the head-rotated position, which is required for exposure of the surgical field, although this position sometimes worsens the efficiency of mechanical ventilation with SGAs. In this study, we investigated and compared the influence of head rotation on oropharyngeal leak pressures (OPLP) of the i-gel and LMA® Supreme™, which are second-generation SGA devices.MethodsPatients who underwent elective surgery under general anesthesia were enrolled in this study and randomly divided into i-gel or LMA Supreme groups. After induction of anesthesia with muscle relaxation, the i-gel or LMA Supreme was inserted according to computerized randomization. The primary outcome was the OPLP at 0°, 30°, and 60° head rotation. The secondary outcomes were the maximum airway pressure and expiratory tidal volume when patients were mechanically ventilated using a volume-controlled ventilation mode with a tidal volume of 10 mL/kg (ideal body weight), ventilation score, and fiber-optic views of vocal cords.ResultsThirty-four and 36 participants were included in the i-gel and LMA Supreme groups, respectively. The OPLPs of the i-gel and LMA Supreme significantly decreased as the head rotation angle increased (mean difference [95% confidence interval], P value: i-gel; 0° vs 30°: 3.5 [2.2-4.8], P < .001; 30° vs 60°: 2.0 [0.6-3.5], P = .002; 0° vs 60°: 5.5 [3.3-7.8], P < .001, LMA Supreme; 0° vs 30°: 4.1 [2.6-5.5], P < .001; 30° vs 60°: 2.4 [1.1-3.7], P < .001; 0° vs 60°: 6.5 [5.1-8.0], P < .001). There were statistically significant differences in expiratory tidal volume and ventilation score between 0° and 60° in the i-gel group and in ventilation score between 30° and 60° in the LMA Supreme group. There was no statistically significant difference between the 2 devices in all outcome measures. The incidences of adverse events, such as hoarseness or sore throat, were not significantly different between i-gel and LMA Supreme.ConclusionsHead rotation to 30° and 60° reduces OPLP with both i-gel and LMA Supreme. There is no difference in OPLP between i-gel and LMA Supreme in the 3 head rotation positions.Copyright © 2020 International Anesthesia Research Society.

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