*Department of Anesthesiology, University Hospital of Lübeck, Lübeck, Germany; and †Department of Anesthesiology and Critical Care Medicine, The Leopold-Franzens-University of Innsbruck, Innsbruck, Austria
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The face mask, laryngeal mask, and the Combitube® (Tyco Healthcare/Sheridan, Argyle, NY) are devices commonly used to ventilate the lungs of nonintubated patients (1,2), but some disadvantages may result in inadvertent ventilation-associated complications. For example, the face mask is associated with large dead space ventilation, leakage, and gastric inflation (3). In contrast, the laryngeal mask is an alternative airway adjunct that is simple to use, resulting in both minimal dead space ventilation and gastric inflation (4,5). Nevertheless, a possible limiting feature of the laryngeal mask may be the risk of aspirating gastric contents (6) because fiberoptic studies have found 6%–9% visualization of the esophagus (7,8). Although the Combitube® was developed as an alternative to endotracheal intubation to secure the airway in an emergency setting, its complex structure requires extensive instruction and training to ensure correct placement within an acceptable time (9). The purpose of this study was to assess whether the newly developed Laryngeal Tube (VBM Medizintechnik GmbH, Sulz, Germany), somewhat a single-lumen, shortened Combitube®, can provide sufficient ventilation and adequate oxygenation in patients undergoing routine induction of anesthesia.MethodsThe Laryngeal Tube is a multiple-use, single-lumen, silicon tube with an oropharyngeal and esophageal low pressure cuff and a ventilation outlet between these cuffs (Figure 1). With the patient’s head in the neutral position, the tube is placed into the oropharynx until a distinct resistance is felt; both cuffs are subsequently inflated with a cuff pressure manometer. Inflation of the oropharyngeal cuff closes the oropharynx; the esophageal inlet is closed by inflating the lower cuff. Accordingly, the ventilation outlet of the Laryngeal Tube is placed in front of the vocal cords (Figure 2).After approval of the institutional review board and written, informed consent, 30 adult ASA physical status I and II patients (age, 26–82 yr; Mallampati 1/2) participated in our study and underwent general anesthesia with usual monitoring for routine surgery. After breathing oxygen for 3 min, the induction of anesthesia was initiated with IV alfentanil (15 μg/kg) and IV propofol (2.5 mg/kg; maintenance, 10–15 mg · kg−1 · h−1 IV). The Laryngeal Tube was always inserted by the same anesthetist. Ventilation (fraction of inspired oxygen: 0.4; fraction of inspired nitrous oxide: 0.6) was controlled with a tidal volume of 7 mL/kg, respiratory rate of 10 breaths/min, and monitored with a cardiorespiratory monitor.After insertion of the Laryngeal Tube, and after 2, 5, and 10 min of ventilation, end-tidal carbon dioxide, expiratory tidal volume, and peak airway pressure were recorded. Additionally, two capillary blood gas samples were taken during room air breathing before the induction of anesthesia, and after 10 min of ventilation. Time of insertion was measured from loss of the eyelash reflex to delivering the first tidal lung volume. Oropharyngeal leak pressure was measured with the head in neutral position at cuff inflation pressures from 60–90 mm Hg (increments, 10 mm Hg). The expiratory valve of the circle system was closed at a fixed gas flow of 3 L/min, and the airway pressure at which the aneroid manometer reached equilibrium was noted (10). To prevent lung barotrauma, the expiratory valve was opened as soon as peak airway pressure reached 40 mm Hg; occurrence of gastric inflation was assessed with a stethoscope placed on the epigastrium. Placement of the Laryngeal Tube was controlled with fiberoptic endoscopy.