Selection of Appropriate Size of ProSeal Laryngeal Mask Airway in Obese Patients Using Ideal Body Weight vs Actual Body Weight: A Prospective Randomized Study

Background: Effective airway management in obesity is challenging due to excess upper airway soft tissue and reduced pharyngeal space. The ProSeal laryngeal mask airway (PLMA) is a second-generation supraglottic airway with an improved cuff seal and gastric drain tube, but manufacturers recommend sizing by actual body weight (ABW). In obese patients, ABW-based sizing may oversize the device relative to airway dimensions. We hypothesized that using ideal body weight (IBW) for PLMA size selection would improve insertion conditions and reduce complications compared to ABW-based sizing. Material and Methods: In this prospective, randomized study, 112 obese adults (BMI ≥30 kg/m²) undergoing elective surgery under general anesthesia were allocated to two groups (n=56 each). In Group ABW, PLMA size was chosen by ABW (3 for 30–50 kg, 4 for 50–70 kg, 5 for >70 kg) as per manufacturer’s guideline. In Group IBW, PLMA size was based on Devine’s formula for IBW (males: 50 + 0.9 × [height(cm) – 152], females: 45 + 0.9 × [height(cm) – 152]). An experienced anesthesiologist (blinded to group) attempted PLMA insertion after induction. Primary outcomes were insertion success (first-attempt and overall), number of attempts, and ease of insertion (1 = no resistance to 4 = failed). Secondary outcomes included fiberoptic view grade (Brimacombe & Berry 1–4) and complications (sore throat at 2 h, 24 h). Data were analyzed with chi-square or t-tests; p<0.05 was significant. Results: Demographic and airway characteristics were similar between groups (Table 1). Mean age, height, weight, BMI and Mallampati scores did not differ (p>0.05). Insertion outcomes favored the IBW group: first-attempt success was significantly higher (96% vs 79%, p=0.004), and ease of insertion was markedly better in Group IBW (91% achieved score 1 vs 30% in ABW, p<0.001). [Figure 1] Failed insertions were fewer in Group IBW (1/56, 2%) than ABW (6/56, 11%; p=0.051). Fiberoptic assessment showed significantly more optimal views with IBW sizing: 73% of IBW patients had grade-4 view (only vocal cords seen) versus 38% in ABW. [Figure 2] Mean OLP was slightly higher in IBW group but not statistically different (Group IBW 29.3 ± X cmH₂O vs ABW 27.8 ± Y; p≈0.028). Postoperative sore throat at 2 hours occurred in 16% of IBW patient’s vs 41% of ABW patients (p=0.003), while no patients reported sore throat at 24 h. [Figure 3] Conclusion: In obese patients, sizing PLMA by IBW significantly improved insertion conditions and reduced pharyngolaryngeal complications compared to ABW-based sizing. Using IBW yields smaller masks that still achieve an adequate seal. These findings echo prior studies in overweight patients with various SGAs. We recommend using IBW for PLMA sizing in obesity to enhance ease of use and patient comfort. Future work should confirm these results in larger, multicenter trials.

Keywords: Laryngeal mask airway; Obesity; Airway management; Ideal body weight; ProSeal LMA; Supraglottic airway.