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Endotracheal tubes (ETT) are an essential and familiar element of anesthesiology practice. The presence of an ETT maintains airway patency, permits oxygenation and ventilation, allows for suctioning of secretions, lowers the risk of aspiration of gastric contents or oropharyngeal secretions, and facilitates the use of inhalation anesthetics.
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The most commonly used ETT material in the United States is polyvinyl chloride (PVC), a transparent plastic that allows the visualization of exhalational condensation (“breath fogging”), secretions, and other foreign materials within the tube. PVC is a semi-rigid material at room temperature, but relatively more pliable as it warms following placement in the trachea, which permits easy manipulation of the tube tip during intubation while reducing the risk of mucosal ischemia following placement. Although not used as commonly, ETTs made of other materials, including nylon, silicone, and Teflon, are also available in the United States.
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The size of an ETT signifies the inner diameter of its lumen in millimeters. Available sizes range from 2.0 to 12.0 mm in 0.5 mm increments. For oral intubations, a 7.0–7.5 ETT is generally appropriate for an average woman and a 7.5–8.5 ETT for an average man. However, the appropriate tube size is a multifactorial clinical decision based on patient height and weight, type of procedure or surgery, and the presence of pulmonary or airway disease. For nasal intubations, a reduction in size of 0.5–1.0 mm is appropriate. Length is directly proportional to the ETT size. Nasotracheal tubes are approximately 2 cm shorter than orotracheal tubes. Because anatomic variations of tracheas can be difficult to predict, several sizes of ETT should be readily available prior to intubation.
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The appropriate pediatric tube size can be calculated using the formula ID = age in years/4 + 4. For example, a size of 6.0 ETT would generally be appropriate for an 8-year-old patient.
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The patient end, also known as the distal or tracheal end, is placed into the trachea and commonly has an inflatable cuff, which provides a seal that prevents the aspiration of gastric contents and reduces air leakage during positive pressure ventilation. A cuff is inflated through its pilot balloon, which is located at the machine end (or proximal end) of the ETT. The pilot balloon is connected to the cuff by a pilot tube that runs the length of the ETT and contains a one-way valve that maintains the inflation of the cuff once the inflating syringe is removed. Generally, cuffed tubes are used in patients older than 6 years of age.
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ETTs can be beveled or nonbeveled. A bevel allows better visualization of the glottis ahead of the ETT tip while permitting it to more easily pass through the vocal folds. In orotracheal tubes, the bevel faces left and is at a 45-degree angle. In ...