an airway or as a site for a tracheostomy tube to be inserted; this tube allows a person to breathe without the use of his nose or mouth. the opening may be made by a scalpel or a needle (referred to as surgical and percutaneous techniques respectively) and both techniques are widely used in current practice. in order to limit the risk of damage to the recurrent laryngeal nerves (the nerves that control the voice box), the tracheotomy is performed as high in the trachea as possible. if only one of these nerves is damaged, the patient's voice may be impaired (dysphonia); if both of the nerves are damaged, the patient will be unable to speak (aphonia). in the acute setting, indications for tracheotomy are similar to those for cricothyrotomy. in the chronic setting, indications for tracheotomy include the need for long-term mechanical ventilation and removal of tracheal secretions (e.g., comatose patients, or extensive surgery involving the head and neck). children a premature infant weighing 990 grams (35 ounces), intubated and requiring mechanical ventilation in the neonatal intensive-care unit there are significant differences in airway anatomy and respiratory physiology between children and adults, and these are taken into careful consideration before performing tracheal intubation of any pediatric patient. the differences, which are quite significant in infants, gradually disappear as the human body approaches a mature age and body mass index. for infants and young children, orotracheal intubation is easier than the nasotracheal route. nasotracheal intubation carries a risk of dislodgement of adenoids and nasal bleeding. despite the greater difficulty, nasotracheal intubation route is preferable to orotracheal intubation in children undergoing intensive care and requiring prolonged intubation because this route allows a more secure fixation of the tube. as with adults, there are a number of devices specially designed for assistance with difficult tracheal intubation in children. confirmation of proper position of the tracheal tube is accomplished as with adult patients. because the airway of a child is narrow, a small amount of glottic or tracheal swelling can produce critical obstruction. inserting a tube that is too large relative to the diameter of the trachea can cause swelling. conversely, inserting a tube that is too small can result in inability to achieve effective positive pressure ventilation due to retrograde escape of gas through the glottis and out the mouth and nose (often referred to as a "leak" around the tube). an excessive leak can usually be corrected by inserting a larger tube or a cuffed tube. the tip of a correctly positioned tracheal tube will be in the mid-trachea, between the collarbones on an anteroposterior chest radiograph. the correct diameter of the tube is that which results in a small leak at a pressure of about 25 cm (10 in) of water. the appropriate inner diameter for the endotracheal tube is estimated to be roughly the same diameter as the child's little finger. the appropriate length for the endotracheal tube can be estimated by doubling the distance from the corner of the child's mouth to the ear canal. for premature infants 2.5 mm (0.1 in) internal diameter is an appropriate size for the tracheal tube. for infants of normal gestational age, 3 mm (0.12 in) internal diameter is an appropriate size. for normally nourished children 1 year of age and older, two formulae are used to estimate the appropriate diameter and depth for tracheal intubation. the internal diameter of the tube in mm is (patient's age in years + 16) / 4, while the appropriate depth of insertion in cm is 12 + (patient's age in years / 2). newborn infants endotrachael suctioning is often used during intubation in newborn infants to reduce the risk of a blocked tube due to secretions, a collapsed lung, and to reduce pain. suctioning is sometimes used at specifically scheduled intervals, "as needed", and less frequently. further research is necessary to determine the most effective suctioning schedule or frequency of suctioning in intubated infants. in newborns free flow oxygen used to be recommended during intubation however as there is no evidence of benefit the 2011 nrp guidelines no longer do. predicting difficulty 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. 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 due to injury or 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. when taking the patient's medical history, the subject is questioned about any significant signs or symptoms, such as difficulty in speaking or difficulty in breathing. these may suggest obstructing lesions in various locations within the upper airway, larynx, or tracheobronchial tree. a history of previous surgery (e.g., previous cervical fusion), injury, radiation therapy, or tumors involving the head, neck and 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. a detailed physical examination of the airway is important, particularly: the range of motion of the 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 upper jaw and lower jaw, looking especially for problems such as maxillary hypoplasia (an underdeveloped upper jaw), micrognathia (an abnormally small jaw), or retrognathia (misalignment of the upper and lower jaw). the thyromental distance: three of the subject's fingers should be able to fit between the 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 crowns. many classification systems have been developed in an effort to predict difficulty of tracheal intubation, including the cormack-lehane classification system, the intubation difficulty scale (ids), and the mallampati score. the mallampati score is drawn from the observation that the size of the 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, 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. 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. 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. a recent cochrane systematic review examined the sensitivity and specificity of various bedside tests commonly used for predicting difficulty in airway management. in such cases, alternative techniques of securing the airway must be readily available. complications tracheal intubation is generally considered the best method for airway management under a wide variety of circumstances, as it provides the most reliable means of oxygenation and ventilation and the greatest degree of protection against regurgitation and pulmonary aspiration. however, tracheal intubation requires a great deal of clinical experience to master and serious complications may result even when properly performed. four anatomic features must be present for orotracheal intubation to be straightforward: adequate mouth opening (full range of motion of the temporomandibular joint), sufficient pharyngeal space (determined by examining the back of the mouth), sufficient submandibular space (distance between the thyroid cartilage and the chin, the space into which the tongue must be displaced in order for the larygoscopist to view the glottis), and adequate extension of the cervical spine at the atlanto-occipital joint. if any of these variables is in any way compromised, intubation should be expected to be difficult. minor complications are common after laryngoscopy and insertion of an orotracheal tube. these are typically of short duration, such as sore throat, lacerations of the lips or gums or other structures within the upper airway, chipped, fractured or dislodged teeth, and nasal injury. other complications which are common but potentially more serious include accelerated or irregular heartbeat, high blood pressure, elevated intracranial and introcular pressure, and bronchospasm. more serious complications include laryngospasm, perforation of the trachea or esophagus, pulmonary aspiration of gastric contents or other foreign bodies, fracture or dislocation of the cervical spine, temporomandibular joint or arytenoid cartilages, decreased oxygen content, elevated arterial carbon dioxide, and vocal cord weakness. in addition to these complications, tracheal intubation via the nasal route carries a risk of dislodgement of adenoids and potentially severe nasal bleeding. newer technologies such as flexible fiberoptic laryngoscopy have fared better in reducing the incidence of some of these complications, though the most frequent cause of intubation trauma remains a lack of skill on the part of the laryngoscopist. complications may also be severe and long-lasting or permanent, such as vocal cord damage, esophageal perforation and retropharyngeal abscess, bronchial intubation, or nerve injury. they may even be immediately life-threatening, such as laryngospasm and negative pressure pulmonary edema (fluid in the lungs), aspiration, unrecognized esophageal intubation, or accidental disconnection or dislodgement of the tracheal tube. potentially fatal complications more often associated with prolonged intubation or tracheotomy include abnormal communication between the trachea and nearby structures such as the innominate artery (tracheoinnominate fistula) or esophagus (tracheoesophageal fistula). other significant complications include airway obstruction due to loss of tracheal rigidity, ventilator-associated pneumonia and narrowing of the glottis or trachea. the cuff pressure is monitored carefully in order to avoid complications from over-inflation, many of which can be traced to excessive cuff pressure restricting the blood supply to the tracheal mucosa. a 2000 spanish study of bedside percutaneous tracheotomy reported overall complication rates of 10–15% and procedural mortality of 0%, which is comparable to those of other series reported in the literature from the netherlands and the united states. inability to secure the airway, with subsequent failure of oxygenation and ventilation is a life-threatening complication which if not immediately corrected leads to decreased oxygen content, brain damage, cardiovascular collapse, and death. when performed improperly, the associated complications (e.g., unrecognized esophageal intubation) may be rapidly fatal. without adequate training and experience, the incidence of such complications is high. the case of andrew davis hughes, from emerald isle, nc is a widely known case in which the patient was improperly intubated and, due to the lack of oxygen, sustained severe brain damage and died. for example, among paramedics in several united states urban communities, unrecognized esophageal or hypopharyngeal intubation has been reported to be 6% to 25%. although not common, where basic emergency medical technicians are permitted to intubate, reported success rates are as low as 51%. in one study, nearly half of patients with misplaced tracheal tubes died in the emergency room. because of this, recent editions of the american heart association's guidelines for cardiopulmonary resuscitation have de-emphasized the role of tracheal intubation in favor of other