Background and objectives Our previous work found that needle visibility could be improved by introducing microbubbles into needles. The primary aim of this study was to test the hypothesis that the negative pressure method is superior to two other methods for enhancing needle visibility by introducing microbubbles into needles. The secondary aim was to evaluate the impacts of three factors on the visibility of microbubble-filled needles.

Methods In the first phase, three methods, including the negative pressure method, the mixing method and commercialized microbubbles, were applied to generate microbubbles inside needles for comparison of visibility in a porcine meat model. In the second phase, three factors were tested with a 2×5×5 factorial design to explore their influence on the visibility of microbubble-filled needles. The three factors included types of needles, insertion angles and types of contents inside needles. Needles filled with saline without microbubbles were used as the control in both phases. Insertion videos were recorded, and ultrasound images of needles were captured for the objective visibility analysis.

Results Needle visibility was highest in the negative pressure method group (p<0.001). Needle visibility was mainly determined by insertion angles (p<0.001). Microbubble-filled needles were more visible than control needles at 40°, 50° and 60° (p<0.001, p<0.001 and p<0.001, respectively).

Conclusions Needle visibility can be significantly improved by microbubbles generated with the negative pressure method when insertion angles are 40°, 50° and 60° in porcine meat.