Single-blinded randomized controlled trial comparing the effect of underwater versus carbon dioxide insufflation...

Underwater endoscopic techniques have gained traction given their potential advantages. The aim of this multicenter randomized trial was to compare the effect of saline solution-immersion "underwater" peroral endoscopic myotomy (U-POEM) versus carbon dioxide insufflation during peroral endoscopic myotomy (CO₂-POEM) on postprocedural pain.

Consecutive patients with achalasia subtype I and II were randomized in a 1:1 ratio to U-POEM or CO₂-POEM during the study period between February 2025 and November 2025. Pain was assessed using the validated Numeric Pain Rating Scale (NPRS) on a scale of 0 (none) to 10 (most severe). The primary outcome was immediate postprocedural pain. Secondary outcomes included postprocedural pain at different times, requirement of analgesics, and clinical response (defined as a post-POEM Eckardt score <3).

Thirty-six patients were randomized to U-POEM (n = 18) and CO₂-POEM (n = 18). Technical and clinical success rates were 100% in both groups with no immediate or delayed adverse events. There were no differences in dissection speed or procedural time between the 2 groups. The immediate post-POEM mean NPRS score was significantly lower in the U-POEM versus CO₂-POEM group (1.6 ± 1.6 vs 3.3 ± 2.6; 95% CI, 0.23-3.16; P = .02). Compared with CO₂-POEM, patients who underwent U-POEM reported less moderate-to-severe pain (16.7% vs 55.5%; 95% CI, 0.04-0.64; P = .04) and a lower number required opioids for postoperative pain management (5.5% vs 50%; 95% CI, 0.11-0.68; P = .007). Mean NPRS score remained lower in the U-POEM versus CO₂-POEM group at 72 hours after the procedure (1.13 ± 1.36 vs 2.26 ± 1.78; 95% CI, 0.06-2.20; P = .04).

U-POEM was safe, effective, and associated with lower postprocedural pain scores than CO₂-POEM (U-POEM trial: NCT06918730).