Comparison of the size 3 and size 4 ProSeal™ laryngeal mask airway in anesthetized, non-paralyzed women: a randomized controlled trial

Based on experimental results, various authors have advocated a size 4 ProSeal (TM) laryngeal mask airway (PLMA) in preference to a size 3 PLMA for women given a neuromuscular blocking agent because the larger size provided a better airway seal. However, spontaneously breathing patients may be ventilated adequately with a lower seal pressure than that needed for mechanical ventilation. Therefore, a smaller size might be preferable as its reduced bulk possibly induces less mucosal damage in non-paralyzed patients. A total of 152 females undergoing general anesthesia for short outpatient gynecological surgeries were randomly allocated in equal numbers to insertion of a size 3 or 4 PLMA. The insertion time, success rate, seal pressure, hemodynamic variables, and complications, such as blood staining and sore throat, were evaluated. The incidence of blood staining was lower with the size 3 PLMA compared to the size 4 PLMA (18 vs. 36 %; P = 0.028). Compared with the size 3 LMA, the size 4 PLMA resulted in higher fluctuations in both blood pressure (P = 0.003) and heart rate (P = 0.01). The insertion time was shorter with the size 3 PLMA (9 vs. 16 s; P < 0.001). The airway seal pressure with the size 3 PLMA, although lower than that of the size 4 PLMA (23 vs. 28 cmH(2)O; P = 0.001), was sufficient for spontaneous ventilation. Due to the reduced incidence of mucosal injury and greater hemodynamic stability, the size 3 PLMA may be preferable to the size 4 PLMA for non-paralyzed females.