A Left-Side Channel Design Improves Gastric Tube Insertion Through Supraglottic Airway Devices
Supraglottic airway devices (SADs) are vital tools in anesthesia, helping maintain breathing during surgery—especially for procedures like laparoscopic cholecystectomy or cesarean delivery, where draining stomach contents (gastric decompression) is critical. Second-generation SADs, which include a gastric drainage channel, are designed for this purpose—but there’s a catch: Most of these devices have the gastric channel centered at the tip. This can make inserting a gastric tube difficult if the device isn’t perfectly positioned at the upper esophageal aperture (the opening where the esophagus meets the throat).
Here’s the anatomical twist: The upper esophageal aperture naturally sits to the left of the trachea (windpipe). So researchers at Beijing Friendship Hospital asked a simple question: Could moving the gastric channel to the left side of the SAD tip make tube insertion easier?
To find out, they modified an existing SAD called the Oro-Pharyngo-Laryngeal Airway Cap (OPLAC) by gluing a 5mm silicone tube to the left side of its expandable silicone cap. This tube acted as a guide for gastric tube insertion. They then compared this modified OPLAC to the LMA Supreme—a widely used second-generation SAD with a central gastric channel—in 60 patients undergoing elective laparoscopic cholecystectomy.
How the Study Worked
Patients were randomly assigned to either the modified OPLAC group or the LMA Supreme group. An experienced anesthesiologist inserted the devices following manufacturer guidelines, and the team measured:
- Device insertion time: From picking up the device to establishing adequate ventilation.
- Ease of gastric tube insertion: Scored 1 (easy), 2 (difficult—required force), or 3 (very difficult—needed device adjustments).
- Airway performance: Airway sealing pressure (how well the device kept air from leaking) and peak airway pressure (pressure during breathing).
- Gastric insuflation: Whether air entered the stomach (a potential complication).
Correct device placement was confirmed by chest movement and capnography (measuring exhaled carbon dioxide). Gastric tube placement was verified by aspirating stomach fluid or listening for air over the abdomen.
The Results: Left-Side Channel Wins for Ease
The modified OPLAC outperformed the LMA Supreme in one key area: gastric tube insertion. Every patient in the OPLAC group had easy insertion (score 1)—100% success with no struggles. For the LMA Supreme? Only 22 of 30 patients had easy insertion; 1 had difficulty, and 7 needed device adjustments to get the tube in.
The modified OPLAC also saved time: It took just 5.5 seconds on average to insert, compared to 8.5 seconds for the LMA Supreme. And crucially, the left-side channel didn’t hurt the device’s ability to maintain a secure airway. Airway sealing pressure and peak airway pressure were nearly identical between the two groups—even during pneumoperitoneum (abdominal inflation for surgery) or when the patient was in a head-up position.
Why the Left Side Matters
The researchers attribute the success to anatomical alignment. By placing the gastric channel on the left, the tube follows the natural path of the upper esophagus—eliminating the resistance caused by a central channel that may misalign with the aperture. This isn’t just about the device itself: Similar SADs like the I-gel (which has a central channel) have performed worse than the LMA Supreme for gastric tube insertion in past studies. The difference here is the position of the channel, not the device’s basic design.
Small Trade-offs, Big Benefits
While the modified OPLAC had fewer cases of gastric insuflation (5 vs. 11 in the LMA Supreme group), the difference wasn’t statistically significant. The team notes that adding the left-side tube might slightly affect the device’s seal—but not enough to impact clinical safety.
What This Means for Surgery
This study offers a simple, effective upgrade for second-generation SADs: A left-side gastric channel makes inserting a gastric tube easier without compromising airway performance. For patients, this could mean faster, smoother procedures with fewer complications. For anesthesiologists, it’s a more reliable tool for managing patients who need gastric decompression.
This research was conducted by Jing-Dong Ke, Hai-Jun Hou, Min Wang, and Fu-Shan Xue from the Department of Anesthesiology at Beijing Friendship Hospital, Capital Medical University (Beijing, China). It was published in the Chinese Medical Journal in 2019.
doi.org/10.1097/CM9.0000000000000222
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