Pulmonary airway resistance with the endotracheal tube versus laryngeal mask airway in paralyzed anesthetized adult patients

Background: The hypothesis that airway resistance is less with the laryngea l mask airway than with the endotracheal tube was tested. Methods: Thirty-six paralyzed, anesthetized adult patients with no respirat ory disease (American Society of Anesthesiologists physical status 1-3; age , 18-80 yr) were randomly allocated (9 men, 9 women in each group) to recei ve either a size-4 laryngeal mask airway or an endotracheal tube (men, 9-mm ID; women, 8-mm ID). A pulmonary monitor with flow transducer and esophage al balloon was used to measure peak airway pressure and mean airway resista nce (device resistance plus pulmonary airway resistance) at three different tidal volumes (5, 10, and 15 ml/kg). Device resistance was measured in vit ro with the distal end of the endotracheal tube or laryngeal mask airway op en to the atmosphere and using the same ventilator settings. Pulmonary airw ay resistance was derived by subtracting the mean device resistance from th e mean airway resistance. Results: Peak airway pressure, mean airway resistance, device resistance, a nd pulmonary airway resistance were greater for the endotracheal tube (all P < 0.0001). Conclusions: The laryngeal mask airway triggers less bronchoconstriction th an does the endotracheal tube in paralyzed anesthetized adult patients. Thi s may have implications for maintaining intraoperative pulmonary function a nd reducing the risk for atelectasis and pulmonary infection.