Effects of Continuous Monitoring and Progressive Regulation of Inflatable Laryngeal Mask Airway Cuff Pressure on Postoperative Pharyngolaryngeal Complications in Elderly Patients

The laryngeal mask airway (LMA) is a supraglottic ventilation device designed based on human anatomy, developed by Dr. Archie Brain from the United Kingdom in 1981, aiming to overcome the limitations of tracheal intubation and mask ventilation. Due to its advantages of easy operation, minimal airway stimulation, and stable hemodynamics, LMA has been widely used in clinical practice. In the past, tracheal intubation was the standard method for airway control during general anesthesia. Nowadays, in China, Europe, and the United States, the proportion of general anesthesia using LMA for ventilation has increased significantly over the past decade. By 2022, as an emergency airway device, the utilization rate of LMA in China had risen to 95.96% . With continuous improvement and development, LMA can also establish safe airway management in special positions such as lateral and prone positions, as well as in long-duration and special-site surgeries.

However, the widespread application has also exposed critical issues. Malposition, airway obstruction, laryngospasm, regurgitation, and aspiration may occur during LMA use, leading to a series of pulmonary and extrapulmonary complications. Studies have shown that many adverse events during LMA insertion may be related to cuff pressure monitoring. The lack of pressure monitoring results in pressure imbalance; inappropriate pressure management may lead to poor fitting between the LMA and the pharyngeal mucosa. Combined with intraoperative position changes and postoperative transportation, the risks of postoperative sore throat and LMA displacement are increased. Therefore, there is an urgent need for dynamic pressure monitoring during LMA use.

In terms of LMA pressure management, first, precise control of cuff pressure is the core. Cuff pressure refers to the pressure inside the LMA cuff after inflation, which is related to the inflation volume, LMA size, temperature, and other factors. For inflatable LMAs, clinicians usually inflate the pilot balloon and valve via a syringe empirically, judging cuff distension by the appearance of the pilot balloon, with the goal of achieving an airtight seal, adequate tidal volume, and normal peak airway pressure.

Insufficient cuff pressure may lead to inadequate ventilation, while excessive pressure compresses the pharyngeal mucosa and causes postoperative pharyngolaryngeal complications. In addition, nitrous oxide (N₂O) inhalation during clinical anesthesia can increase cuff pressure; thus, regular monitoring of cuff pressure is of great significance. Previous clinical studies used homemade cuff pressure gauges to monitor LMA cuff pressure and set cuff pressure according to peak airway pressure, showing that appropriate inflation volume under cuff pressure monitoring and setting LMA cuff pressure at Ppeak + 0-5 cmH₂O during general anesthesia with LMA ventilation can achieve a satisfactory seal and reduce the incidence of postoperative pharyngolaryngeal complications. Studies exploring appropriate inflation volumes for LMA cuffs have suggested that low cuff pressure is conducive to enhanced postoperative recovery.

Second, the sealing pressure of the LMA refers to the pressure required to form an effective seal between the LMA and the surrounding laryngeal tissues, formed by matching and compression between the cuff and the periglottic structures. It reflects LMA positioning and pharyngeal fitting, and is related to LMA type and patient laryngeal anatomy. Leak pressure is defined as the pressure at which gas escapes from the edge of the LMA as airway pressure gradually increases. Oropharyngeal leak pressure (OPLP) is commonly used clinically to evaluate the reliability of LMA sealing during ventilation. Some studies have suggested that it is the most accurate description of peripharyngeal gas leak pressure, which is affected by upper airway anatomy, anesthetic agents, LMA size, surgical position, and other factors.

Thus, maintaining appropriate LMA pressure to ensure correct positioning, effective ventilation, and reduced adverse events is extremely important. However, current clinical practice does not mandate monitoring of cuff pressure or other pressure indicators; there is no standardized pressure measurement method, nor are there sufficient studies investigating LMA pressure values in different positions or defining optimal pressure ranges.

A previous study explored appropriate cuff inflation volumes for LMA, defining the optimal inflation volume as that achieving positive pressure ventilation > 17 cmH₂O, LMA cuff pressure of 40-80 cmH₂O, and oropharyngeal leak pressure > 20 cmH₂O, but this study was limited to size 4 LMA. Regarding cuff pressure monitoring using a manometer, one study compared the accuracy of the digital palpation method, passive deflation method, and minimal occlusive volume method in endotracheal tube cuff pressure monitoring, indicating that the passive deflation method provided the highest accuracy.

In this field, Wang et al. developed a mobile application for real-time monitoring and adjustment of endotracheal tube cuff pressure, which maintained cuff pressure within a reasonable range and significantly reduced postoperative adverse events. Whether such methods are applicable to LMA pressure monitoring requires further investigation. Expert consensus on the clinical application and management of laryngeal mask airways also emphasizes the importance of measuring LMA-related pressures such as cuff pressure.

Especially in the elderly population, due to atrophy of pharyngeal mucosa and muscles, weakened cough reflex, and decreased chest wall compliance, adverse pharyngeal reactions tend to occur after mechanical ventilation. Furthermore, elderly patients have lower oropharyngeal leak pressure than ordinary patients, making LMA displacement more likely and increasing the incidence of pulmonary and extrapulmonary complications. In patients with atherosclerosis, LMA displacement and high cuff pressure may compress the cervical arteries, veins, and surrounding tissues, increasing the risk of stroke in the elderly.

Effective and safe anesthetic airway and respiratory management during general anesthesia directly affects the occurrence of postoperative pulmonary complications (PPCs) in elderly patients. Globally, the incidence of PPCs ranges from 11% to 59%. PPCs not only prolong hospital stay and increase medical costs but also impair prognosis, raise perioperative mortality, and impose a heavy socioeconomic and medical resource burden. Continuous monitoring and regulation of LMA cuff pressure may alleviate these problems.

Currently, there is a lack of large-scale, reliable evidence-based medical data evaluating the effects of continuous monitoring and progressive regulation of LMA cuff pressure on postoperative pharyngolaryngeal complications, especially regarding the safety and short- and long-term outcomes of extensive LMA use in elderly patients, a high-risk population for PPCs. Therefore, it is particularly urgent to conduct research on the effects of LMA cuff pressure monitoring and regulation on postoperative pharyngolaryngeal complications in elderly patients and to further explore the optimal range of LMA cuff pressure.

Based on the concept of enhanced recovery after surgery (ERAS), this study will not only fill the current research gap but also provide solid support for safe and efficient perioperative airway management in elderly patients, effectively promoting further optimization of clinical practice, with important clinical significance and practical value.

This study is a prospective, single-center, randomized controlled clinical trial.

It aims to investigate the effects of continuous monitoring and progressive regulation of inflatable laryngeal mask airway (LMA) cuff pressure on postoperative pharyngolaryngeal complications such as sore throat and hoarseness in elderly patients, compared with conventional empirical LMA inflation. The composite outcome measure of this study includes the incidence of postoperative sore throat, hoarseness, supraglottic mucosal injury, blood on the LMA surface or in sputum, and dysphagia in subjects. Based on the results of preliminary pilot studies, the incidence of the composite outcome was 23.5% in the experimental group and 50% in the control group. With a two-sided α = 0.05 and a power of 90%, PASS 15.0 software was used to calculate the sample size: 65 cases in the experimental group (N1 = 65) and 65 cases in the control group (N2 = 65). Considering a 10% rate of loss to follow-up and refusal to participate, a minimum of 73 subjects were required in each group, with a total of at least 146 subjects to be enrolled. Subjects were randomly assigned to the experimental group or the control group using a random number table method.

Experimental group (Pressure monitor + progressive cuff pressure regulation group): After the anesthesiologist performed empirical inflation of the LMA cuff, a pressure monitor was used for continuous monitoring and progressive regulation of the LMA cuff pressure throughout the procedure.

Control group (Pressure monitor + no cuff pressure intervention group): After the same anesthesiologist performed empirical inflation of the LMA cuff, a pressure monitor was used for continuous monitoring of the LMA cuff pressure throughout the procedure, but no intervention was made on the cuff pressure. The anesthesiologist was blinded to the cuff pressure values.

Primary outcome measure: The composite outcome measure includes the incidence of postoperative sore throat, hoarseness, supraglottic mucosal injury, blood on the LMA surface or in sputum, and dysphagia in subjects.

Secondary outcome measures: Grading of LMA insertion difficulty; number and duration of LMA insertion attempts (from the start of insertion to successful placement and verification); epiglottis morphology and LMA positioning score under bronchoscopy; other perioperative airway complications (e.g., laryngospasm, LMA displacement, hypoxemia); incidence of pulmonary complications within 7 days and 30 days after surgery; length of hospital stay and medical costs; patient satisfaction, etc.