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

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.

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.

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.

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.