A Left-Side Channel Design Improving Insertion of Gastric Tube via the Supraglottic Airway Device
Supraglottic airway devices (SADs) are widely used in clinical anesthesia for airway management. Among these devices, second-generation SADs are particularly notable for their additional gastric drainage channel, which allows for gastric decompression during surgery. This feature is especially beneficial in procedures such as laparoscopic cholecystectomy and cesarean delivery, where gastric decompression can improve surgical conditions and reduce the risk of complications. However, a common design feature of second-generation SADs is the placement of the gastric tube channel opening at the center of the distal tip. This central placement can sometimes lead to difficulties in inserting the gastric tube, particularly if the device tip is not optimally positioned in the upper esophageal aperture.
In normal anatomy, the upper esophageal aperture is inclined to the left side of the trachea. This anatomical observation led to the hypothesis that placing the gastric drainage channel on the left side of the SAD tip might facilitate easier insertion of the gastric tube into the esophagus. To test this hypothesis, a pilot randomized controlled study was conducted to compare the performance of a modified Oro-Pharyngo-Laryngeal Airway Cap (OPLAC) device with the laryngeal mask airway (LMA) Supreme in anesthetized adult patients.
The study protocol was approved by the Ethical Committee of Beijing Friendship Hospital and registered in the Chinese Clinical Trial Registry. Patients undergoing elective laparoscopic cholecystectomy under general anesthesia were recruited for the study. Exclusion criteria included patients who refused to sign informed consent or those with head and neck tumors or abnormalities. After obtaining written informed consent, patients were randomly allocated to receive either the LMA Supreme or the modified OPLAC device.
The modified OPLAC device was created by attaching a silicone tube with a 5 mm internal diameter and 20 cm length to the left side of the tip of the expandable silicone membranous cap of the original OPLAC device. This attached silicone tube served as a conduit for the insertion of the gastric tube. Anesthesia was induced with fentanyl, propofol, and atracurium, and the patient’s head was placed in a neutral position. The LMA Supreme or modified OPLAC device was then inserted by an experienced operator following the manufacturer’s recommendations. The device was connected to an anesthesia ventilator for volume-controlled ventilation, with adjustments made to maintain end-tidal carbon dioxide levels within the range of 35 to 40 mmHg.
The time required for device insertion was recorded as the time between the operator picking up the device and the establishment of adequate ventilation. Correct positioning of the device was confirmed by bilateral chest movements and capnography. Three attempts were allowed for successful placement of the device. During mechanical ventilation, peak airway pressures and expired tidal volumes were measured. A size F14 gastric tube was inserted through the drainage channel of the LMA Supreme or the conduit added to the modified OPLAC device. The ease of gastric tube insertion was assessed and scored as 1 (easy), 2 (difficulty, needing force to overcome resistance), or 3 (very difficult, needing adjustment of the device position to overcome resistance). Correct placement of the gastric tube was confirmed by aspiration of gastric fluid or detection of injected air by auscultation over the epigastrium.
Airway sealing pressure and peak airway pressure were recorded before and during pneumoperitoneum, at the head-up position, and at the end of surgery in both groups. Airway sealing pressure was detected by closing the adjustable pressure limiting valve against a 5 L/min fresh gas flow and recording the airway pressure at equilibrium or when an air leak was heard in the oropharynx, up to a maximum airway pressure of 40 cmH2O.
The primary endpoint of the study was the ease of gastric tube insertion. The sample size was calculated to detect a 10% difference in the rate of easy gastric tube insertion between devices with a type-1 error of 0.05 and a power of 90%, requiring 25 patients per group. Thirty patients were recruited for each group to accommodate potential dropouts. Data distribution was analyzed using the Kolmogorov-Smirnov test. Normally distributed data were analyzed using the paired t-test, while other data were analyzed by the Chi-squared test or Mann-Whitney U test. Data were analyzed using SPSS version 20, with a P < 0.05 considered statistically significant.
The demographic data, including age, weight, height, gender ratio, and operating time, were not significantly different between the two groups. The rates of smooth device insertion were similar between the two groups, but the modified OPLAC device took a significantly shorter insertion time than the LMA Supreme. The ease of gastric tube insertion was significantly improved with the modified OPLAC device, with no significant difficulty encountered during gastric tube insertion via the modified OPLAC device. In contrast, there was one case of difficult insertion and seven cases of very difficult insertion in the LMA Supreme group. Both the airway sealing pressure and peak airway pressure were not significantly different between the two devices, and all other ventilation profiles during the operation were similar for both devices.
The study demonstrated that both the LMA Supreme and modified OPLAC device could be successfully inserted on the first attempt by an experienced operator. The addition of a gastric tube insertion accessory on the left side of the expandable silicone membranous cap did not interfere with the insertion of the OPLAC device. As hypothesized, the ease of gastric tube insertion via the modified OPLAC device was significantly better than that of the LMA Supreme, with a 100% success rate and no difficulties encountered. This suggests that placing the gastric tube insertion channel on the left side of the ventilation mask can indeed facilitate gastric tube insertion via a second-generation SAD.
The airway sealing pressure and peak airway pressure were similar for both devices at all observed points, and the incidence of gastric insufflation was not significantly different between the two devices. However, the incidence of gastric insufflation was higher in this study than in previous studies with the original OPLAC device. This may be due to the addition of the gastric tube insertion channel on the left side of the expandable silicone membranous cap, which could have interfered with the mechanism of airway sealing. This suggests that any additional structure for the gastric tube insertion channel should be designed to avoid interfering with the fitness of the ventilation mask of the device.
In conclusion, this study demonstrates that both the LMA Supreme and modified OPLAC device can be successfully inserted by an experienced operator on the first attempt. However, the modified OPLAC device, with its gastric tube insertion channel placed on the left side, provides an easier and more reliable method for gastric tube insertion compared to the LMA Supreme, which has a gastric tube channel opening at the center of the distal tip. This design improvement could enhance the clinical utility of second-generation SADs, particularly in procedures requiring gastric decompression.
doi.org/10.1097/CM9.0000000000000222
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