Jet Ventilation

Some physicians contend that optimal surgical conditions and patient safety can be obtained with jet ventilation. This technique takes advantage of Bernoulli's principle to augment the ventilation produced by a narrow, high-speed gas stream in a Venturi tube. In practice, jet ventilation uses an intermittent high-pressure oxygen supply, directed at the glottis through a small metal tube, such as a ventilating bronchoscope or even a 12-gauge blunt needle.^{[86] [87] [88] [89] [90] [91]} A retrospective review of 942 cases of microdirect laryngoscopy using endolaryngeal jet ventilation found only four complications.^[92] Jet ventilation with air also has been used through a bronchoscope when resecting distal tracheal and bronchial tumors.^{[93] [94] [95] [96]} It has been suggested that patients undergoing laser resections of airway tumors during jet ventilation may absorb carbon monoxide from entrained laser smoke in the pharynx. The carbon monoxide can result in an overestimate of arterial oxygen saturation by pulse oximetry. Goldhill and colleagues^[95] found neither a significant increase in caboxyhemoglobin during Nd:YAG bronchoscopy nor a difference in pulse oximetry reading versus in vitro CO-oximeter measurement of arterial oxygen saturation.

Although jet ventilation generally provides adequate ventilation without introducing flammable material or a large obstacle to the surgical field, potential disadvantages include the risk of barotrauma, pneumothorax, or crepitus; the restriction to intravenous anesthetic agents; gastric distention; and the relative requirement for compliant lungs. In the presence of papillomas, a common indication for laryngeal laser surgery, jet ventilation could cause distal bronchial seeding with active virus. However, Shikowitz and colleagues^[92] found no evidence of this phenomenon in 96 patients who had multiple laser procedures and were followed over time. Cozine and colleagues,^[97] in a survey of 58 institutions (15,701 cases) performing CO₂ laser airway surgery, found a higher rate of ventilatory complications with jet ventilation than with a standard endotracheal tube ( Fig. 67-9 ), but the only fatality was caused by an endotracheal tube fire.^[97] The investigators concluded that no single mode of ventilation proved superior during laser surgery.

To reduce obstruction of the surgical field by ventilatory instrumentation even further, several researchers have advocated complete removal of such instrumentation combined with the technique of spontaneous ventilation or intermittent apnea, with general anesthesia provided by nasal insufflation or bronchoscopic delivery of a potent inhaled anesthetic^{[7] [72] [98] [99]} or use of an intravenous anesthetic.^[100] Cohen and associates ^[101] and Hawkins and Joseph^[102] advocated modest hyperventilation followed by intermittent tracheal extubation by the surgeon for periods of 90 to 120 seconds, during which the laser is used. Pulse oximetry adds a measure of safety by confirming

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Figure 67-9 Complications of laser airway surgery. Pneumothorax was relatively common with jet ventilation, but potentially lethal airway fires occurred with endotracheal intubation. ETT, endotracheal tube. (Data from Cozine K, Stone JG, Shulman, et al: Ventilatory complications of carbon dioxide laser laryngeal surgery. J Clin Anesth 3:20, 1991.)