Trachea

Lungs removed from the chest cavity were fixed by injection of 4% buffered paraformaldehyde into the tracheal cannula at a pressure of 20 cm H₂O and immersed in paraformaldehyde for 24 h. Lobes were sectioned sagitally, embedded in paraffin, cut into 5 μm sections, and stained with H&E for histological analysis. Additional sections were stained with alcian blue/PAS to identify mucus-containing cells. The severity of peribronchial inflammation was graded semiquantitatively for the following features: 0, normal; 1, few cells; 2, a ring of inflammatory cells 1 cell layer deep; 3, a ring of inflammatory cells 2–4 cells deep; 4, a ring of inflammatory cells of >4 cells deep. The numerical scores for the abundance of PAS-positive mucus-containing cell in each airway were determined as follows: 0, <0.5% PAS-positive cells; 1, 5–25%; 2, 25–50%; 3, 50–75%; 4, >75% (28 (link)).

The Difficult Airway Society commissioned a working group to update the guidelines in April 2012. An initial literature search was conducted for the period January 2002 to June 2012 using databases (Medline, PubMed, Embase, and Ovid) and a search engine (Google Scholar). The websites of the American Society of Anesthesiologists (http://www.asahq.org), Australian and New Zealand College of Anaesthetists (http://www.anzca.edu.au), European Society of Anesthesiologists' (http://www.esahq.org/euroanaesthesia), Canadian Anesthesiologists' Society (http://www.cas.ca), and the Scandinavian Society of Anesthesiology and Intensive Care Medicine (http://ssai.info/guidelines/) were also searched for airway guidelines. English language articles and abstract publications were identified using keywords and filters. The search terms were as follows: ‘Aintree intubating catheter’, ‘Airtraq’, ‘airway device’, ‘airway emergency’, ‘airway management’, ‘Ambu aScope’, ‘backward upward rightward pressure’, ‘Bonfils’, ‘Bullard’, ‘bronchoscopy’, ‘BURP manoeuvre’, ‘can't intubate can't ventilate’, ‘can't intubate can't oxygenate’, ‘C-Mac’, ‘Combitube’, ‘cricoid pressure’, ‘cricothyroidotomy’, ‘cricothyrotomy’, ‘C trach’, ‘difficult airway’, ‘difficult intubation’, ‘difficult laryngoscopy’, ‘difficult mask ventilation’, ‘difficult ventilation’, ‘endotracheal intubation’, ‘esophageal intubation’, ‘Eschmann stylet’, ‘failed intubation’, ‘Fastrach’, ‘fiber-optic scope’, ‘fibreoptic intubation’, ‘fiberoptic scope’, ‘fibreoptic stylet’, ‘fibrescope’ ‘Frova catheter', ‘Glidescope’, ‘gum elastic bougie’, ‘hypoxia’, ‘i-gel’, ‘illuminating stylet’, ‘jet ventilation catheter’, ‘laryngeal mask’, ‘laryngeal mask airway Supreme’, ‘laryngoscopy’, ‘lighted stylet’, ‘light wand’, ‘LMA Supreme’, ‘Manujet’, ‘McCoy’, ‘McGrath’, ‘nasotracheal intubation’, ‘obesity’, ‘oesophageal detector device’, ‘oesophageal intubation’, ‘Pentax airway scope’, ‘Pentax AWS’, ‘ProSeal LMA′, ‘Quicktrach’, ‘ramping’, ‘rapid sequence induction’, ‘Ravussin cannula’, ‘Sanders injector’, ‘Shikani stylet’, ‘sugammadex’, ‘supraglottic airway’, ‘suxamethonium’, ‘tracheal introducer’, ‘tracheal intubation’, ‘Trachview’, ‘Tru view’, ‘tube introducer’, ‘Venner APA’, ‘videolaryngoscope’, and ‘videolaryngoscopy’.
The initial search retrieved 16 590 abstracts. The searches (using the same terms) were repeated every 6 months. In total, 23 039 abstracts were retrieved and assessed for relevance by the working group; 971 full-text articles were reviewed. Additional articles were retrieved by cross-referencing the data and hand-searching. Each of the relevant articles was reviewed by at least two members of the working group. In areas where the evidence was insufficient to recommend particular techniques, expert opinion was sought and reviewed.^{8 (link)} This was most notably the situation when reviewing rescue techniques for the ‘can't intubate can't oxygenate’ (CICO) situation.
Opinions of the DAS membership were sought throughout the process. Presentations were given at the 2013 and 2014 DAS Annual Scientific meetings, updates were posted on the DAS website, and members were invited to complete an online survey about which areas of the existing guidelines needed updating. Following the methodology used for the extubation guidelines,^{5 (link)} a draft version of the guidelines was circulated to selected members of DAS and acknowledged international experts for comment. All correspondence was reviewed by the working group.