Bench-top testing of suction forces generated through endoscopic ultrasound-guided aspiration needles.

Background: Adequate needle size and tissue acquisition techniques for endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) need further elucidation. Moreover, the actual negative pressure and suction forces of FNA needles remain unknown. We evaluated the suction forces of 19-gauge, 22-gauge, and 25-gauge conventional FNA needles and side hole aspiration needles using conventional negative pressure and the slow pull technique.

Methods: Using a manometer, we determined the mean (SD) negative pressure and suction force for needle gauge, aspiration volume, and aspiration technique. We also evaluated the time to reach the maximum negative pressure.

Results: Suction force was comparatively higher in the 19-gauge needle when 50 ml of negative pressure was applied. Suction force using the slow pull method was very weak at 5% of pressure found with conventional methods. With the use of a 20-ml syringe, the time to reach the maximum negative pressure was 4 s in the 19-gauge needle, 11 s in the 22-gauge needle, and 80 s in the 25-gauge needle.

Conclusions: Bench-top testing showed that suction force increases with a larger gauge needle and larger aspiration volume. The slow pull method produces a very weak suction force. The time to reach the maximum negative pressure was longest in the 25-gauge needle.