Background: The authors compared the manufacturer's weight-based formula (size 3 for weight < 50 kg, size 4 for weight 50-70 kg, and size 5 for weight > 70 kg) with a sex-based formula (size 4 for women and size 5 for men) for selecting the appropriate size of ProSeal laryngeal mask airway.
Methods: Two hundred thirty-seven healthy, anesthetized, paralyzed adult patients (American Society of Anesthesiologists physical status I or II; age, 18-80 yr) were randomly allocated for weight- or sex-based size selection. An experienced user inserted the ProSeal laryngeal mask airway with the digital technique. The following were compared: ease of insertion, oropharyngeal leak pressure, ease of ventilation, gas exchange, location of gas leak, anatomic position, mucosal injury, and postoperative pharyngolaryngeal problems. Intraoperative and postoperative data collection were unblinded and blinded, respectively.
Results: Ease of insertion, anatomic position, gas exchange, mucosal injury, and postoperative pharyngolaryngeal problems were similar between groups. For the sex-based group, larger ProSeal laryngeal mask airways were selected more frequently (P < 0.0001), oropharyngeal leak pressure (P = 0.02) was higher, leak volume (P = 0.004) and leak fraction (P = 0.007) were lower, and oropharyngeal leaks (P = 0.03) were detected less frequently.
Conclusion: Size selection for the ProSeal laryngeal mask airway is equally effective using the manufacturer's weight-based formula or the sex-based formula in healthy, anesthetized, paralyzed adult patients, but leakage of small volumes of air from the mouth occurs less frequently with the sex-based formula.