Editing Tracheal intubation (section)

==Predicting difficulty==
[[File:Ameloblastoma2.jpg|thumb|alt=A child with a massive ameloblastoma of the mandible|Tracheal intubation is anticipated to be difficult in this child with a massive [[ameloblastoma]]]]

Tracheal intubation is not a simple procedure and the consequences of failure are grave. Therefore, the patient is carefully evaluated for potential difficulty or complications beforehand. This involves taking the [[medical history]] of the patient and performing a [[physical examination]], the results of which can be scored against one of several classification systems. The proposed surgical procedure (e.g., surgery involving the head and neck, or [[bariatric surgery]]) may lead one to anticipate difficulties with intubation.<ref name=Stone2000/> Many individuals have unusual airway anatomy, such as those who have limited movement of their neck or jaw, or those who have tumors, deep swelling [[hematoma|due to injury]] or [[angioedema|to allergy]], developmental abnormalities of the jaw, or excess fatty tissue of the face and neck. Using conventional laryngoscopic techniques, intubation of the trachea can be difficult or even impossible in such patients. This is why all persons performing tracheal intubation must be familiar with alternative techniques of securing the airway. Use of the flexible fiberoptic bronchoscope and similar devices has become among the preferred techniques in the management of such cases. However, these devices require a different skill set than that employed for conventional laryngoscopy and are expensive to purchase, maintain and repair.<ref name=Rozman2009/>

When taking the patient's medical history, the subject is questioned about any significant [[Medical sign|signs]] or [[symptom]]s, such as [[dysphonia|difficulty in speaking]] or [[dyspnea|difficulty in breathing]]. These may suggest obstructing [[lesion]]s in various locations within the upper airway, [[larynx]], or tracheobronchial tree. A history of previous surgery (e.g., previous [[Anterior cervical discectomy and fusion|cervical fusion]]), injury, [[radiation therapy]], or [[tumor]]s involving the head, neck and [[mediastinum|upper chest]] can also provide clues to a potentially difficult intubation. Previous experiences with tracheal intubation, especially difficult intubation, intubation for prolonged duration (e.g., intensive care unit) or prior tracheotomy are also noted.<ref name=Stone2000/>

A detailed [[physical examination]] of the airway is important, particularly:<ref name=Reed2007/>
*the range of motion of the [[Cervical vertebrae|cervical spine]]: the subject should be able to tilt the head back and then forward so that the chin touches the chest.
*the range of motion of the jaw (the [[temporomandibular joint]]): three of the subject's fingers should be able to fit between the upper and lower incisors.
*the size and shape of the [[maxilla|upper jaw]] and [[Human mandible|lower jaw]], looking especially for problems such as [[maxillary hypoplasia]] (an underdeveloped upper jaw), [[Micrognathism|micrognathia]] (an abnormally small jaw), or [[Retrognathism|retrognathia]] (misalignment of the upper and lower jaw).
*the [[thyromental distance]]: three of the subject's fingers should be able to fit between the [[thyroid cartilage|Adam's apple]] and the chin.
*the size and shape of the tongue and [[palate]] relative to the size of the mouth.
*the teeth, especially noting the presence of prominent maxillary incisors, any loose or damaged teeth, or [[Crown (dentistry)|crowns]].

Many classification systems have been developed in an effort to predict difficulty of tracheal intubation, including the [[Cormack-Lehane classification system]],<ref name=Zadrobilek2009/> the Intubation Difficulty Scale (IDS),<ref name=Adnet1997/> and the [[Mallampati score]].<ref name=Mallampati1985/> The Mallampati score is drawn from the observation that the size of the [[Posterior tongue|base of the tongue]] influences the difficulty of intubation. It is determined by looking at the anatomy of the mouth, and in particular the visibility of the base of [[palatine uvula]], [[Fauces (anatomy)|faucial pillars]] and the [[soft palate]]. Although such medical scoring systems may aid in the evaluation of patients, no single score or combination of scores can be trusted to specifically detect all and only those patients who are difficult to intubate.<ref name=Shiga2005/><ref name=Gonzalez2008/> Furthermore, one study of experienced anesthesiologists, on the widely used Cormack–Lehane classification system, found they did not score the same patients consistently over time, and that only 25% could correctly define all four grades of the widely used Cormack–Lehane classification system.<ref name=Krage2010/> Under certain emergency circumstances (e.g., severe head trauma or suspected cervical spine injury), it may be impossible to fully utilize these the physical examination and the various classification systems to predict the difficulty of tracheal intubation.<ref name=Levitan2004-article/> A Cochrane systematic review examined the sensitivity and specificity of various bedside tests commonly used for predicting difficulty in airway management.<ref name="Roth2018">{{cite journal | vauthors = Roth D, Pace NL, Lee A, Hovhannisyan K, Warenits AM, Arrich J, Herkner H | title = Airway physical examination tests for detection of difficult airway management in apparently normal adult patients | journal = Cochrane Database Syst Rev | volume = 5 | pages = CD008874 | date = May 2018 | issue = 5 | pmid = 29761867 | pmc = 6404686 | doi = 10.1002/14651858.CD008874.pub2 }}</ref> In such cases, alternative techniques of securing the airway must be readily available.<ref name=Levitan2004-book/>