Use of a Novel Three-Dimensional Model to Teach Ultrasound-guided Subclavian Vein Cannulation.

Background: Central venous cannulation is an essential skill in perioperative and critical care medicine. Ultrasound guidance is the standard of care for femoral and internal jugular vein access, with the subclavian vein being perceived to be less amenable to ultrasound-guided (UG) insertion, resulting in a lack of procedural competency and low cannulation rate. There is a paucity of resources and a lack of experience among staff physicians to effectively instruct trainees. Simulation-based medical education has the potential to help maintain high-stakes, infrequently performed skills and counteract possible unrecognized skill decline. We aimed to create a novel, low-cost, high-fidelity three-dimensional (3D) model for UG subclavian vein (UG-SCV) access with an accompanying curriculum to improve this important skill. Methods: A curriculum was created consisting of preparatory material reviewing UG-SCV access, followed by an in-person didactic lecture focusing on ultrasound use and management of complications and a deliberate practice session scanning volunteers and practicing UG vascular puncture on a 3D model. A qualitative usability test design was used to assess the validity of the curriculum in trainees with advanced vascular access skills (anesthesiologists). Participants were second-year anesthesia residents, anesthesia fellows, and staff physicians. Focus groups conducted after each session explored the face validity of the model and curriculum. By applying a usability design, the curriculum was optimized and finalized. Results: Between September 2020 and February 2021, 28 participants tested the curriculum. The focus groups ensured that the curriculum achieved its objective, with iterative changes made after each session in a quality improvement framework Plan-Do-Study-Act approach. After the third cycle, minimal changes were suggested, and the curriculum and 3D model were finalized. An additional group of participants was used to ensure that no new input would help improve the curriculum further. Conclusions: A focused curriculum for enhancing skills in UG-SCV cannulation using a novel 3D model was successfully implemented and validated through a usability test design. This curriculum is better targeted for practitioners experienced in central venous access to master a subclavian approach and maintain their skill level.

Precontouring Plates for MIS Bilateral Femur Osteosynthesis Using a Patient-Specific 3D Printed Model: A Case Report.

CASE: A 27-year-old woman with increasing bilateral thigh pain and underlying diagnosis of dysosteosclerosis was diagnosed with bilateral impending pathological femur fractures. Both femurs exhibited abnormal morphology with bowing, thickened cortices, and narrow intramedullary canals. We planned minimally invasive prophylactic plate osteosynthesis. Computed tomography scans of both femora were obtained and used to generate 3-dimensional (3D) printed models. Osteosynthesis plates were precontoured to fit the 3D models and sterilized, and prophylactic fixation was performed using a minimally invasive submuscular technique. CONCLUSION: 3D printed models aided in precontouring fixation plates in a case with challenging bony anatomy, enabling minimally invasive surgery.

Development, manufacturing, and preliminary validation of a reusable half-face respirator during the COVID-19 pandemic.

INTRODUCTION: The COVID-19 pandemic has led to widespread shortages of N95 respirators and other personal protective equipment (PPE). An effective, reusable, locally-manufactured respirator can mitigate this problem. We describe the development, manufacture, and preliminary testing of an open-hardware-licensed device, the "simple silicone mask" (SSM). METHODS: A multidisciplinary team developed a reusable silicone half facepiece respirator over 9 prototype iterations. The manufacturing process consisted of 3D printing and silicone casting. Prototypes were assessed for comfort and breathability. Filtration was assessed by user seal checks and quantitative fit-testing according to CSA Z94.4-18. RESULTS: The respirator originally included a cartridge for holding filter material; this was modified to connect to standard heat-moisture exchange (HME) filters (N95 or greater) after the cartridge showed poor filtration performance due to flow acceleration around the filter edges, which was exacerbated by high filter resistance. All 8 HME-based iterations provided an adequate seal by user seal checks and achieved a pass rate of 87.5% (N = 8) on quantitative testing, with all failures occurring in the first iteration. The overall median fit-factor was 1662 (100 = pass). Estimated unit cost for a production run of 1000 using distributed manufacturing techniques is CAD $15 in materials and 20 minutes of labor. CONCLUSION: Small-scale manufacturing of an effective, reusable N95 respirator during a pandemic is feasible and cost-effective. Required quantities of reusables are more predictable and less vulnerable to supply chain disruption than disposables. With further evaluation, such devices may be an alternative to disposable respirators during public health emergencies. The respirator described above is an investigational device and requires further evaluation and regulatory requirements before clinical deployment. The authors and affiliates do not endorse the use of this device at present.

Echocardiographic assessment of left ventricular function in ex situ heart perfusion using pump-supported and passive afterload working mode: a pilot study.

Ex situ heart perfusion (ESHP) has been developed to decrease cold ischemia time and allow metabolic assessment of donor hearts prior to transplantation. Current clinical ESHP systems preserve the heart in an unloaded condition and only evaluate the cardiac metabolic profile. In this pilot study we performed echocardiographic functional assessment using two alternative systems for left ventricular (LV) loading: pump supported afterload working mode (SAM) and passive afterload working modes (PAM). Six hearts were procured from male Yorkshire pigs. During cold ischemia, hearts were mounted on our custom made ESHP circuit and a 3D-printed enclosure for the performance of echocardiography with a standard TEE probe. Following perfusion with Langherdorf mode of the unloaded heart, the system was switched into different working modes to allow LV loading and functional assessment: pump supported (SAM) and passive (PAM). Echocardiographic assessment of left ventricular function in the donor hearts was performed in vivo and at 1 h of ESHP with SAM, after 4.5 h with PAM and after 5.5 h with SAM. We obtained good quality epicardial echocardiographic images at all time points allowing a comprehensive LV systolic assessment. All indices showed a decrease in LV systolic function throughout the trial with the biggest drop after heart harvesting. We demonstrated the feasibility of echocardiographic functional assessment during ESHP and two different working modes. The expected LV systolic dysfunction consisted of a reduction in EF, FAC, FS, and strain throughout the experiment with the most significant decrease after harvesting.

Evaluation of a Patient-Specific, Low-Cost, 3-Dimensional-Printed Transesophageal Echocardiography Human Heart Phantom.

OBJECTIVE: Currently available 3-dimensional (3D) modeling and printing techniques allow for the creation of patient-specific models based on 3D medical imaging data. The authors hypothesized that a low-cost, patient-specific, cardiac computed tomography-based phantom, created using desktop 3D printing and casting, would have comparable image quality, accuracy, and usability to an existing commercially available echocardiographic phantom. DESIGN: Blinded comparative study. SETTING: Simulation laboratory at a single academic institution. PARTICIPANTS: Voluntary cardiac anesthesiologists at a single academic institution. INTERVENTIONS: Stage 1 of the study consisted of an online questionnaire in which a set of basic transesophageal echocardiography (TEE) views obtained from the 3D printed phantom and commercial phantom were presented to participants, who had to identify the views and evaluate their fidelity to clinical images on a Likert scale. In stage 2, participants performed an unblinded basic TEE examination on both phantoms. MEASUREMENTS AND MAIN RESULTS: The time needed to acquire each basic view was recorded. Overall usability of the phantoms was assessed through a questionnaire. The participants could recognize most of the views. Fidelity ratings for both phantoms were similar (p < 0.05), with the exception of a midesophageal 2-chamber view that was observed better on the 3D printed phantom. The time required to obtain the views was shorter for the 3D printed phantom, although not statistically significant for most views. The overall user experience was better for the 3D phantom for all categories examined (p < 0.05). CONCLUSIONS: The study suggested that a 3D-printed TEE phantom is comparable with the commercially available one with good usability.

Validation of Quantitative 3-Dimensional Transesophageal Echocardiography Mitral Valve Analysis Using Stereoscopic Display.

OBJECTIVE: The use of 3-dimensional (3D) transesophageal echocardiography (TEE) in perioperative evaluation of the mitral valve (MV) is increasing progressively, including the use of 3D MV models for quantitative analysis. However, the use of 3D MV models in clinical practice still is limited by the need for specific training and the long time required for analysis. A new stereoscopic visualization tool (EchoPixel True 3D) allows virtual examination of anatomic structures in the clinical setting, but its accuracy and feasibility for intraoperative use is unknown. The aim of this study was to assess the feasibility of 3D holographic display and evaluate 3D quantitative measurements on a volumetric MV image using the EchoPixel system compared with the 3D MV model generated by QLAB Mitral Valve Navigation (MVN) software. DESIGN: This was a retrospective comparative study. SETTING: The study took place in a tertiary care center. PARTICIPANTS: A total of 40 patients, 20 with severe mitral regurgitation who underwent mitral valve repair and 20 controls with normal MV, were enrolled retrospectively. INTERVENTIONS: The 3D-TEE datasets of the MV were analyzed using a 3D MV model and stereoscopic display. The agreement of measurements, intraobserver and interobserver variability, and time for analysis were assessed. MEASUREMENTS AND MAIN RESULTS: Fair agreement between the 2 software systems was found for annular circumference and area in pathologic valves, but good agreement was reported for prolapse height and linear annular diameters. A higher agreement for all annular parameters and prolapse height was seen in normal valves. Excellent intraobserver and interobserver reliability was proved for the same parameters; time for analysis between the 2 methods in pathologic valves was substantially equivalent, although longer in pathologic valves when compared with normal MV using both tools. CONCLUSION: EchoPixel proved to be reliable to display 3D TEE datasets and accurate for direct linear measurement of both MV annular sizes and prolapse height compared to QLAB MVN software; it also carries a low interobserver and intraobserver variability for most measurements.

Low-cost three-dimensional printed phantom for neuraxial anesthesia training: Development and comparison to a commercial model.

METHODS: Anonymized CT DICOM data was segmented to create a 3D model of the lumbar spine. The 3D model was modified, placed inside a digitally designed housing unit and fabricated on a desktop 3D printer using polylactic acid (PLA) filament. The model was filled with an echogenic solution of gelatin with psyllium fiber. Twenty-two staff anesthesiologists performed a spinal and epidural on the 3D printed simulator and a commercially available Simulab phantom. Participants evaluated the tactile and ultrasound imaging fidelity of both phantoms via Likert-scale questionnaire. RESULTS: The 3D printed neuraxial phantom cost $13 to print and required 25 hours of non-supervised printing and 2 hours of assembly time. The 3D printed phantom was found to be less realistic to surface palpation than the Simulab phantom due to fragility of the silicone but had significantly better fidelity for loss of resistance, dural puncture and ultrasound imaging than the Simulab phantom. CONCLUSION: Low-cost neuraxial phantoms with fidelity comparable to commercial models can be produced using CT data and low-cost infrastructure consisting of FLOS software and desktop 3D printers.

Description of a Novel Set-up for Functional Echocardiographic Assessment of Left Ventricular Performance During Ex Vivo Heart Perfusion.

Ex vivo heart perfusion (EVHP) is a new technology aimed at decreasing cold ischemia time and evaluating cardiac function before transplanting a donor heart. In an experimental EVHP swine model, we tested a 3D-printed custom-made set-up to perform surface echocardiography on an isolated beating heart during left ventricular loading. The views obtained at any time point were equivalent to standard transesophageal and transthoracic views. A decrease in left ventricular function during EVHP was observed in all experiments.

Effects of statins on plaque rupture assessed by optical coherence tomography in patients presenting with acute coronary syndromes: insights from the optical coherence tomography (OCT)-FORMIDABLE registry.

Aims: Chronic pre-treatment with statins may reduce mortality and morbidity in patients experiencing acute coronary syndromes (ACS), but mechanisms accounting for these findings are not completely understood. Methods and results: The optical coherence tomography (OCT)-Formidable registry retrospectively enrolled 285 consecutive patients with ACS undergoing OCT in 9 European centres. Mean age was 60.4 ± 12.8 years, 148 (51.9%) patients had hyperlipemia, 45 (15.8%) diabetes mellitus and 142 (49.8%) presented with ST Segment Elevation Myocardial Infarction (STEMI). Patients were stratified according to statin prescription: 150 (52.6%) were on chronic pre-treatment with statins before ACS and were more likely to present with non-ST segment elevation acute coronary syndromes (NSTE-ACS) at admission (111, 74%) rather than STEMI, while the opposite was observed for patients not on statins. The primary end-point of ruptured plaque at OCT occurred significantly less frequently in the patients on chronic pre-treatment with statins [odds ratio (OR) 0.375, 95% confidence interval (CI) 0.185-0.759, P = 0.006]. The secondary end-point of thin-cap fibro-atheroma (TCFA) at any site was significantly less frequent in the statin group (OR 0.423, 95%CI 0.213-0.840, P = 0.014). No differences were observed for the secondary end-point of not-ruptured TCFA as the culprit lesion. Pre-specified sensitivity analysis was conducted according to the pattern of ACS: the reported differences were confirmed for NSTE-ACS patients, with a trend towards less plaque rupture and a significant reduction of TCFA at any site with statins, but not for STEMI. Conclusions: Chronic pre-treatment with statins is associated with a reduced prevalence of ruptured plaques in patients presenting with ACS, particularly in those with NSTE-ACS. Statins bear hence the potential to reduce morbidity during the acute phase of ACS.

The effect of diet-induced serum hypercholesterolemia on the surfactant system and the development of lung injury.

Acute respiratory distress syndrome (ARDS) is a pulmonary disorder associated with alterations to the pulmonary surfactant system. Recent studies showed that supra-physiological levels of cholesterol in surfactant contribute to impaired function. Since cholesterol is incorporated into surfactant within the alveolar type II cells which derives its cholesterol from serum, it was hypothesized that serum hypercholesterolemia would predispose the host to the development of lung injury due to alterations of cholesterol content in the surfactant system. Wistar rats were randomized to a standard lab diet or a high cholesterol diet for 17-20 days. Animals were then exposed to one of three models of lung injury: i) acid aspiration ii) ventilation induced lung injury, and iii) surfactant depletion. Following physiological monitoring, lungs were lavaged to obtain and analyze the surfactant system. The physiological results showed there was no effect of the high cholesterol diet on the severity of lung injury in any of the three models of injury. There was also no effect of the diet on surfactant cholesterol composition. Rats fed a high cholesterol diet had a significant impairment in surface tension reducing capabilities of isolated surfactant compared to those fed a standard diet exposed to the surfactant depletion injury. In addition, only rats that were exposed to ventilation induced lung injury had elevated levels of surfactant associated cholesterol compared to non-injured rats. It is concluded that serum hypercholesterolemia does not predispose rats to altered surfactant cholesterol composition or to lung injury. Elevated cholesterol within surfactant may be a marker for ventilation induced lung damage.

Cholesterol-mediated surfactant dysfunction is mitigated by surfactant protein A.

The ability of pulmonary surfactant to reduce surface tension at the alveolar surface is impaired in various lung diseases. Recent animal studies indicate that elevated levels of cholesterol within surfactant may contribute to its inhibition. It was hypothesized that elevated cholesterol levels within surfactant inhibit human surfactant biophysical function and that these effects can be reversed by surfactant protein A (SP-A). The initial experiment examined the function of surfactant from mechanically ventilated trauma patients in the presence and absence of a cholesterol sequestering agent, methyl-ß-cyclodextrin. The results demonstrated improved surface activity when cholesterol was sequestered in vitro using a captive bubble surfactometer (CBS). These results were explored further by reconstitution of surfactant with various concentrations of cholesterol with and without SP-A, and testing of the functionality of these samples in vitro with the CBS and in vivo using surfactant depleted rats. Overall, the results consistently demonstrated that surfactant function was inhibited by levels of cholesterol of 10% (w/w phospholipid) but this inhibition was mitigated by the presence of SP-A. It is concluded that cholesterol-induced surfactant inhibition can actively contribute to physiological impairment of the lungs in mechanically ventilated patients and that SP-A levels may be important to maintain surfactant function in the presence of high cholesterol within surfactant.