الفهرس 
Introduction
Definition of difficult intubationOnly 14 pages are availabe for public view
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Abstract
Difficult intubation is defined as the need for more than three attempts for intubation or more than 10 min to accomplish it, a situation that occurs in 1.5-8% of general anesthetic procedures (Wasem et al., 2009).
Difficult intubation is a frequent cause of morbidity and mortality resulting from anesthesia (Eberhart et al., 2005). It is important for the anesthesiologist to recognize thi-s problem during the preoperative examination (Wilson et al., 1988). The American Society of Anesthesiologists (ASA) defined a difficult airway as the existence of clinical factors that complicate both ventilation administered through a face mask or intubation performed by an experienced person (Salimi et al., 2008).
Difficult ventilation is defined as the inability of a trained anesthesiologist to maintain oxygen saturation >90% using a face mask, with a goal of oxygen fraction of 100% (Naguib et al., 1999). Difficult intubation is defined as the need for more than three attempts for intubation of the trachea or more than 10 min to achieve it (Cattano et al., 2004). The greater the degree of difficulty in intubation, the greater the incidence and severity of the complications (Oriol-López et al., 2009). Up to 30% of anesthetic deaths can be attributed to a compromised airway (Rios-García & Reyes-Cedeño 2005). This has generated the need for highly predictive tests for the identification of an airway with assumed intubation difficulty to be applicable in all anesthetic and surgical procedures (Lee et al., 2006). In 1985, Mallampati et al. introduced a screening test that classifies the visibility of the oropharynx. Patil-Andreti measured the distance from the thyroid notch to the chin, also measuring the existing trajectory between the top edge of the manubrium of sternum and the chin (sternomental distance) (Mallampati et al., 1985). A simple sum of risk factors (Wilson’s score) was recognized as a tools for the prediction of tracheal intubation (TI) (Paix et al., 2005). On the other hand, the scale proposed in 1984 by Cormack and Lehane describes four grades of the glottic exposure during direct laryngoscopy (Shiga et al., 2005).
Orozco-Díaz et al. evaluated some of the predicted factors of a difficult airway such as oral opening; pharyngeal structures (Mallampati), thyromental distance (Patil-Aldreti), neck extension, dental, mandibular and laryngeal structures (Cormack and Lehane) and obesity in a university tertiary care center (Janssens & Hartstein 2001). Their study was in accordance with the recommendations proposed in the algorithm designed by the ASA(American Society of Anesthesiologists 2003) for the management of difficult airway according to what is shown in Table 1 (Randell 1996). They found that grades III and IV Mallampati (84%) and limited extension and flexion of the head and neck (99%) showed a high specificity for predicting difficult intubation (Behringer 2002). Other factors associated with difficult intubation were related to micrognathia, limited mouth opening and teeth with anatomic abnormalities (Orozco-Díaz, et al., 2010).