Development and assessment of novel assist device for cardiac cannulation.

PURPOSE: Congenital heart defects are the most common birth defects in the USA and in 25% of cases need to be treated with cardiovascular interventions. One of such interventions is the postoperative use of an extracorporeal membrane oxygenation (ECMO) machine for the treatment of cardiorespiratory failure. The process of placing the patient on the ECMO is extremely time-critical and requires the use of cardiac cannulation. For the first time, our team developed and evaluated a new quick-connect cannulation system that allows for rapid, easy, and safe ECMO cannulation in the pediatric population. The design should eliminate the need for purse-string sutures that are currently used to secure cannulas, as the cannulas will be inserted through a port that is glued to the cardiovascular tissue. METHODS: The rapid cannulation assistance device was designed on the SolidWorks computer-aided design software using the dimensions of the commercially available arterial and venous catheters. These designs were then 3D printed, and tensile testing was performed. Then, a flow loop was developed, and cannulation was performed and analyzed on both 3D-printed hearts and porcine hearts. RESULTS: The rapid cannulation assistance device was designed and 3D printed. Tensile testing found that the parts were strong enough to withstand forces that may be introduced in studies. 3D-printed and porcine heart tests with a flow loop found no leakage with the 3D-printed hearts but minimal leaking with the porcine hearts. However, this leakage was observed at the junction between the device and the heart, leading us to believe that a glue better suited to attach the device to the heart would prevent leakage in the future. CONCLUSIONS: This project successfully demonstrated how a rapid cannulation assistance device could be developed and tested. Future studies will be conducted that address device adhesion to the cardiovascular tissue so that accurate pressure and flow rates can be measured. Future studies will also include testing the device in a fluid environment to more effectively analyze the device success and comparing the time required to cannulate using our device compared to the standard of care.

A novel pneumatic drill for bone biopsy under MRI imaging.

PURPOSE: Bone biopsies are currently conducted under computed tomography (CT) guidance using a battery-powered drill to obtain tissue samples for diagnosis of suspicious bone lesions. However, this procedure is suboptimal as images produced under CT lack soft tissue discrimination and involve ionizing radiation. Therefore, our team developed an MRI-safe pneumatic drill to translate this clinical workflow into the MR environment, which can improve target visualization and eliminate radiation exposure. We compare drill times and quality of samples between the 2 drills using animal bones. METHODS: Five porcine spare rib bones were obtained from a butcher shop. Each bone was drilled twice using the Arrow OnControl battery-powered drill and twice using our pneumatically actuated drill. For this study, we used an 11-gauge bone biopsy needle set with an internal core capturing thread. A stopwatch recorded the overall time of drilling for each specimen obtained. RESULTS: All 20 samples collected contained a high-quality inner core and cortex. The total average time for drilling with the pneumatic drill was 8.5 s (+ / - 2.5 s) and 7.1 s (+ / - 1.4 s) with the standard battery-powered drill. CONCLUSION: Both drills worked well and were able to obtain comparable specimens. The pneumatic drill took slightly longer, 1.39 s on average, but this extra time would not be significant in clinical practice. We plan to use the pneumatic drill to enable MRI-safe bone biopsy for musculoskeletal lesions. Biopsy under MRI would provide excellent lesion visualization with no ionizing radiation.

Quantification of manipulation forces needed for robot-assisted reduction of the ankle syndesmosis: an initial cadaveric study.

PURPOSE: Manual surgical manipulation of the tibia and fibula is necessary to properly align and reduce the space in ankle fractures involving sprain of the distal tibiofibular syndesmosis. However, manual reduction is highly variable and can result in malreduction in about half of the cases. Therefore, we are developing an image-guided robotic assistant to improve reduction accuracy. The purpose of this study is to quantify the forces associated with reduction of the ankle syndesmosis to define the requirements for our robot design. METHODS: Using a cadaveric specimen, we designed a fixture jig to fix the tibia securely on the operating table. We also designed a custom fibula grasping plate to which a force-torque measuring device is attached. The surgeon manually reduced the fibula utilizing this construct while translational and rotational forces along with displacement were being measured. This was first performed on an intact ankle without ligament injury and after the syndesmosis ligaments were cut. RESULTS: Six manipulation techniques were performed on the three principal directions of reduction at the cadaveric ankle. The results demonstrated the maximum force applied to the lateral direction to be 96.0 N with maximum displacement of 8.5 mm, applied to the anterior-posterior direction to be 71.6 N with maximum displacement of 10.7 mm, and the maximum torque applied to external-internal rotation to be 2.5 Nm with maximum rotation of 24.6°. CONCLUSIONS: The specific forces needed to perform the distal tibiofibular syndesmosis manipulation are not well understood. This study quantified these manipulation forces needed along with their displacement for accurate reduction of ankle syndesmosis. This is a necessary first step to help us define the design requirements of our robotic assistance from the aspects of forces and displacements.

Quantitative serology for SARS-CoV-2 using self-collected saliva and finger-stick blood.

Convenient and widespread serology testing may alter the trajectory of the COVID-19 pandemic. This study seeks to leverage high-throughput, multiplexed serologic assays, which have been adopted as benchmarks for vaccine efficacy, to support large-scale surveys of SARS-CoV-2 immunity using finger-stick blood and/or saliva. Specifically, we optimized MSD's serology assays, which were analytically validated for serum, to test self-collected finger-stick blood and saliva samples to identify prior infection. We show that these assays can be used with FDA-registered specimen collection devices to obtain quantitative measurements for self-collected samples. First, we show that salivary antibodies are stable without refrigeration or preservatives for at least 5 days. We selected classification thresholds for antibodies against SARS-CoV-2 N, RBD and Spike in finger-stick blood and saliva that provided 98% specificity in a set of individuals without known COVID-19 exposure. Using matched samples, we show that testing of saliva and finger-stick blood equivalently identified individuals with humoral responses to CoV-2 antigens. Moreover, we piloted a simple saliva collection kit that can be used to safely send samples through the mail using written instructions only. This work establishes key parameters to robustly assay self-collected finger-stick blood and saliva using quantitative immunoassays that could support large-scale serology testing.