© 2007 American Thoracic Society
Use of Preoxygenation with the Laryngeal Mask Airway in Critical CareTo the Editor:Positive pressure ventilation (PPV) greatly benefits critically ill patients, but frequently endotracheal intubation is required. The recent article on rapid-sequence intubation (RSI) preceded by noninvasive ventilation (NIV) by Baillard and colleagues may have a tremendous impact on practice (1). RSI was meant to reduce pulmonary aspiration in surgical patients. As little as 30 ml of gastric fluids predisposes the patient to pulmonary aspiration. Thus, supraglottic ventilation is usually avoided (2). In addition, spontaneous vomiting and regurgitation are common during acute illness as predisposing factors for surgery-related aspiration. Even trained anesthesiologists using collapsible flow-filled bags coupled to adjustable pressure relief valves cannot always avoid gastric inflation in healthy patients. Thus, early sealing of the trachea is always warranted. While 1 per 2,000–7,000 adults undergoing general anesthesia aspirates gastric contents, laborious intubations in the critical care setting are associated with much higher rates of regurgitation and aspiration (3). RSI is not a rigid technique but an evolving concept. Recent modifications have included administration of opioids, use of video devices, and omission of cricoid pressure, but avoidance of PPV was considered for over five decades as dogma. Although the benefits of PPV are unquestionable, facial mask PPV is not necessarily safe. The data to support delivering pressures of 15 cm H2O were extrapolated from articles citing work with 9 asphyxiated and 4 fresh stillborn babies as well as 60 anesthetized adults (4, 5). An intermediate approach to preoxygenation in many critical care patients would be the laryngeal mask airway (LMA). Its introduction spares laryngoscopy and demands less pharmacological modulation, resulting in a smooth induction. Initially, the classic LMA was an alternative to the face mask, but it has proved to be an excellent protection to the trachea and an instant bridge to cuffed tubes (6). Like others, we have used these versatile devices in trauma and resuscitation, and in critical care patients. The LMA family also excels in the case of accidental extubations and many difficult airway situations. The LMA ProSeal (LMA North America, Inc., San Diego, CA) seals the airway even more effectively than the classic LMA and has an extra lumen to use in gastric suctioning. Using pressures of up to 20 to 30 cm H2O, this model helps to overcome low compliance lungs. Future studies should define the safety profile of PPV RSI in critical care patients. A recent audit on perioperative pulmonary aspiration disclosed both low morbidity (1/16, 573) and mortality (1/99, 441) when PPV RSI was used (3). Meanwhile, practitioners should keep in mind that the technique proposed is an attractive intervention to ameliorate severe hypoxia in selected patients.
Instituto Nacional de Câncer, Rio de Janeiro, Brazil FOOTNOTES Conflict of Interest Statement: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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