WORK OF BREATHING IN ANESTHETIZED PATIENTS - LARYNGEAL MASK AIRWAY VERSUS TRACHEAL TUBE

Study Objective: To compare the work of breathing associated with the laryngeal mask airway (LMA) and tracheal tube (TT) in spontaneously br eathing anesthetized patients. Design: Randomized, prospective, contro led trial. Setting: University teaching hospital, Subjects: 20 ASA phy sical status I and II patients scheduled for elective peripheral surge ry with general anesthesia. Interventions and Measurements: Al standar dized anesthetic protocol was utilized and patients were allowed to br eathe spontaneously through a circle absorption system. Patients were randomly assigned to receive either LMA (n = 10) or TT (n = 10) for ai rway management. Work of breathing was determined after the patients' ventilatory status had been allowed to stabilize for 15 minutes and be fore the onset of the surgical stimulus. Airflow and esophageal pressu res were measured using a pneumotachograph and an esophageal balloon, respectively, and the values were subsequently integrated to determine work of breathing. Main Results: The two groups were similar with res pect to demographic characteristics and the end-tidal concentrations o f carbon dioxide and isoflurane. Work of breathing per minute through the LMA (1.4 +/-0.3 J/min) was significantly lower than that through t he TT (1.9 +/- 0.4 J/min). Conclusion: In healthly, anesthetized spont aneously breathing patients, work of breathing is significantly lower through the LMA than the TT. (C) 1998 by Elsevier Science Inc.