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When face mask ventilation is inadequate to provide necessary airway support, or when long term positive pressure ventilation is required, an endotracheal tube (ETT) should be placed. In most circumstances, direct laryngoscopy is the simplest and most readily applied means of placing the ETT. Indications for direct laryngoscopy and endotracheal intubation are summarized below.
During direct laryngoscopy the provider must bring his/her line of sight into alignment with the glottic opening in order to facilitate visualization of ETT placement. Most sources recommend that the oral, pharyngeal, and laryngeal axes be aligned by the process of patient positioning and direct laryngoscopy, to guarantee the best view of the glottic opening. However, even if one cannot peer down the laryngeal axis into the trachea, placement of the endotracheal tube is usually readily accomplished if the laryngeal inlet is visible. Evaluation of the alignment of the oral, pharyngeal, and laryngeal axes utilizing magnetic resonance imaging when the head and neck are in neutral position, in simple extension, or in “sniffing position,” reveals that these three lines seldom, if ever, become well-aligned (Fig. 3.1)
The forces brought to bear on the soft tissues of the oral cavity and pharynx in direct laryngoscopy must be appropriately directed. Whether a curved or straight laryngoscope blade is utilized, the operator should lift upward and away from himself/herself, a stressful maneuver that requires practice, and when prolonged, causes fatigue. When the laryngoscopist pulls towards himself/herself to create mechanical advantage, he/she is creating leverage, but the upper teeth are often contacted and in danger of injury. This maneuver is common among trainees learning laryngoscopy and must be actively discouraged. |