Letters to the Editor: Letters & Announcements
Dr. Greenland asserts1 that his new theory2 explains the superiority of the sniffing position over other head positions when performing direct laryngoscopy. Other theories previously proposed to explain this superiority include the 3-axis alignment theory,3 Chou and Wu 2 axes theory,4 and the “obstacle theory” by Isono.5 All of these theories, including Greenland's, can be a subject of debate,6 but none should decrease the use of the sniffing position.
To validate the 2-curve theory, Greenland should define the start and end points of each curve and demonstrate the existence of the second curve (from the accompanying figure, it seems that a line can connect the start and end points of the proposed second curve). The ramped position is recommended for the obese patient before direct laryngoscopy7 and therefore Greenland's theory should be tested using magnetic resonance imaging in obese patients in the ramped position as well as other head positions. This will verify the existence of these curves and the changes occurring to them with positional changes in this patient population.
Mohammad El-Orbany, MD
Department of Anesthesiology
Medical College of Wisconsin
1. Greenland K. The ramped position and its relationship to the 2-curve theory. Anesth Analg 2011;113:1524
2. Greenland KB, Edwards MJ, Hutton NJ, Challis VJ, Irwin MG, Sleigh JW. Changes in airway configuration with different head and neck positions using magnetic resonance imaging of normal airways: a new concept with possible clinical applications. Br J Anaesth 2010;105:683–90
3. Bannister FB, Macbeth RG. Direct laryngoscopy and tracheal intubation. Lancet 1944;2:651–4
4. Chou HC, Wu TL. Rethinking the three axes alignment theory for direct laryngoscopy. Acta Anaesthesiol Scand 2001;45:261–2
5. Isono S. Common practice and concepts in anesthesia: time for reassessment—is the sniffing position a “gold standard” for laryngoscopy? Anesthesiology 2001;95:825–7
6. Lee LC. Two curves theory does not clearly explain laryngoscopy and intubation. Br J Anaesth 2011;106:909–110
7. Collins JS, Lemmens HJ, Brodsky JB, Brock-Utne JG, Levitan RM. Laryngoscopy and morbid obesity: A comparison of the “sniff” and “ramped” positions. Obes Surg 2004;14:1171–5