An in Vivo CT Imaging Study of GMA-Tulip, I-gel, and LMA Supreme (GLAM-II)

Overview

Laryngeal masks are core devices for supraglottic airway management, and the accuracy of their anatomical position directly impacts ventilation safety and the incidence of complications. Despite their wide clinical application, gaps remain in understanding their in vivo anatomical characteristics. This study aims to evaluate the in vivo anatomical features (e.g., insertion depth, anatomical alignment, tissue compression) of three laryngeal masks (LMA Supreme, I-gel, GMA-Tulip) using CT scanning in anesthetized patients undergoing CT interventional therapy, providing anatomical evidence for optimized laryngeal mask selection and complication prevention.

After approval by the Ethics Committee of Zhejiang Cancer Hospital (Approval Number: IRB-2025-001 (IIT)), this study will be registered on ClinicalTrials.gov prior to participant enrollment. Written informed consent will be obtained from all participants. The study is planned to be conducted from September 2025 to December 2025. Eligible participants are 18-75 years old, ASA physical status I-II, BMI \<30 kg/m², scheduled for CT interventional therapy, and without contraindications (e.g., head/neck airway anomalies, participation in other clinical studies). Pre-procedure Preparation: Patients fast and abstain from fluids as per standard protocols, with no premedication. Upon admission to the operating room, standard monitoring (ECG, HR, BP, SpO₂) is initiated, and an intravenous access is established. Pre-anesthesia baseline HR and BP are recorded. Anesthesia Induction: Pre-oxygenation with 8 L/min oxygen via face mask for 3 minutes. Anesthesia is induced with propofol (3.5 μg/ml) and remifentanil (4 ng/ml). After loss of eyelash reflex, rocuronium (0.9 mg/kg) is administered, and laryngeal mask insertion is performed 2 minutes post-rocuronium injection. Laryngeal Mask Insertion: Participants are randomly assigned (via computer-generated sequence) to one of three groups: LMA Supreme Group (L Group), I-gel Group (I Group), or GMA-Tulip Group (G Group). Each patient receives one laryngeal mask insertion by an anesthesiologist with ≥5 years of experience, following standardized insertion protocols for each device: LMA Supreme: Lubricate the posterior surface; place the head in neutral or sniffing position; advance the mask along the midline of the oral cavity until resistance is felt. I-gel: Lubricate the posterior surface; advance along the hard palate until definite resistance is felt. GMA-Tulip: Lubricate the posterior surface; place the head in sniffing position; avoid tongue entrapment; advance until passing the base of the tongue (no need to seek strong resistance); gently shake to ensure tight fit. Laryngeal mask size is selected based on body weight: L Group: 3# (30-50 kg), 4# (50-70 kg), 5# (70-100 kg); I Group: 3# (30-60 kg), 4# (50-90 kg), 5# (\>90 kg); G Group: 2.5# (\<60 kg), 3# (60-85 kg), 4# (\>80 kg); Anesthesia Maintenance: Propofol (3.5 μg/ml) and remifentanil (2 ng/ml) are infused to maintain BIS 40-60. Additional rocuronium (0.15 mg/kg) or sufentanil (5 μg) is administered as needed. Hemodynamics are maintained within ±20% of baseline using medications (atropine, ephedrine, esmolol, dopamine, norepinephrine, nitroglycerin) if required. At the end of the procedure, propofol and remifentanil are discontinued, and rocuronium is antagonized with sugammadex sodium (200 mg). The laryngeal mask is removed when the patient regains consciousness and can follow commands. Participants recover in the Post-Anesthesia Care Unit (PACU) for ≥1 hour before discharge. Alignment Verification: Mechanical ventilation is initiated with parameters: VT 6-8 ml/kg, I:E 1:2, RR 12-14 breaths/min, maintaining PETCO₂ 35-45 mmHg. Air tightness is confirmed via leak test (25 cmH₂O pressure) and auscultation. Fiberoptic laryngoscopy is used to grade anatomical alignment (Grade I: Only one aryepiglottic fold and partial laryngeal inlet visible, SpO₂ \>98%; Grade II: Bilateral aryepiglottic folds and partial laryngeal inlet visible, SpO₂ \>98%; Grade III: Bilateral aryepiglottic folds, laryngeal inlet, and partial glottis visible; Grade IV: Entire glottis visible). Outcome Assessment: CT scanning is performed to measure insertion depth, anatomical alignment, and tissue compression. Post-procedure follow-up is conducted at 24 hours to assess complications (mucosal injury, hoarseness, sore throat via VAS 0-10, regurgitation).