BME.08 – Procedural Mannequin for Ultrasound Guided Thoracentesis

• Saba Ali
• Alaa Mohamed
• Mahanoor Murtaza
• Quetzalli Rodriguez
• Edah Tumuti
• Leslie Villanueva

The project aims to manufacture a procedural mannequin for ultrasound-guided thoracentesis. Thoracentesis is a procedure where a needle is inserted along with a catheter into the pleural cavity to remove excess fluid. The fluid is located in the pleural cavity, which is a space between two pleura and surrounds the lungs. Ultrasound imaging can help identify fluid location and reduce errors while increasing the precision of the needle insertion. Our needs statement is “physicians and residents who perform ultrasound-guided thoracentesis need an effective and accessible training tool to minimize procedural errors in thoracentesis.” Although there are existing commercial solutions with ultrasound compatibility, they are high in cost. With a budget of $500, one of the main aspects our solution entails is its cost-effectiveness. The outer shell of the mannequin was 3D printed using Polylactic Acid (PLA). Silicone-molded lungs were attached to the inner portion of the shell using a silicone adhesive. An opening in the back of the shell comprises an insert containing ultrasound-compatible silicone, ballistic gel, and 3D-printed ribs cured together. The insert represents skin, fascia, and muscle, cured in a cohesive assembly. Ballistic gel was melted in a 3D-printed mold to represent the pleural cavity. The needle punctures both the insert and the pleural cavity placed directly behind. The pleural cavity is supported by a base placed underneath. Some requirements we took into consideration were ultrasound-compatibility, a minimum of 20 punctures before the pleural cavity leaks, and ensuring a 20 gauge needle penetrates the insert and pleural cavity when a force of 2.75 N – 4.53 N is applied. We tested the force required to penetrate the insert for verification testing. We built a testing apparatus that allowed us to apply forces across a range of 2 N to 6 N by increasing the mass and relying on force induced by gravity. The passing criteria of our protocol was for the length of the needle that fully passes through the insert, to be greater than or equal to 0.005 cm and this served as our null hypothesis. We followed the same procedure for a commercial insert to compare the depth of penetration and performed a two-factor ANOVA analysis. The ANOVA results indicated that at 2 N, a p-value of .8300 was observed, which shows there is not enough evidence to reject the null hypothesis. An inconclusive p-value was observed for trials at 4 N and 6 N due to uniform result of complete puncture for all the trials. The passing result at 4 N and 6 N provided no variance that could be used to find the corresponding p-values. Our mannequin has shown its effectiveness and will allow users to practice thoracentesis before performing it on a patient, thereby reducing errors and increasing precision.