Urban, Matthew W.

Arterial stiffness predicts cardiovascular disease, the leading cause of death worldwide. Ultrasound elastography methods that measure wave velocity have promise for evaluating the stiffness of blood vessels in vivo. However, vessel geometry modulates wave velocity by inducing geometric dispersion. Here, we compare Young's modulus E estimates obtained using in vivo wave velocity measurements and techniques that either do or do not consider geometry to ex vivo reference E values from mechanical testing . An acoustic radiation force was applied to generate propagating waves in the right common carotid artery (N = 9) and external jugular vein (N = 10) of anesthetized pigs. Vessels were imaged with ultrafast ultrasound to measure wave motion. Group velocity cg was estimated from wave motion using a Radon transform. E was estimated from cg using a bulk media assumption which neglects geometry, as well as the Moens–Korteweg equation and a semi-analytical finite element model, which consider geometry. Pigs were euthanized and vessels were excised. Ring-shaped samples were extracted and tested in a uniaxial tension setup to obtain reference E values for comparison with E values obtained from wave-based techniques. Techniques considering geometry exhibited higher correlation with reference E values, underscoring the need to incorporate geometry for accurate vascular elastography assessments.

Background Esophageal pathology such as perforation or malignancy often necessitates esophageal reconstruction. However, the optimal method of esophageal primary repair and anastomosis are unclear. We aim to determine stress to failure of esophageal anastomosis for full thickness and mucosal‐submucosal anastomotic techniques. Methods Six esophagi from freshly sacrificed 60 kilogram swine were transected at the mid thoracic portion of the esophagus. Esophageal anastomoses were created and subsequently primarily anastomosed using 2‐0 running continuous polyglactin (Vicryl, Ethicon, Somerville, NJ) suture either as full thickness or partial thickness (mucosa‐submucosa alone). The sutured specimens were then mounted on cannulae. Using a syringe pump system, the esophagi were infused with colored saline while monitoring pressure continuously with optical tracking for detection of fluid leak. Data acquisition software was used to collect stress‐to‐failure data. Synchronized video and pressure data were analyzed post hoc for visualization of the leak and concurrent pressure to determine failure pressure. Results The full‐thickness anastomosis failed at a mean ± (SEM) pressure of 15.33 ± (1.45) mmHg while the mucosal‐submucosal anastomosis failed at a mean ± (SEM) pressure of 36.33 ± (3.76) mmHg, ( P = 0.02, unpaired t ‐test with Welch's correction). MATLAB (MathWorks, Natick, MA) was used calculate the statistical results. Conclusion While the optimal in vivo method for esophageal anastomosis is unclear, we present evidence that an anastomosis incorporating only the mucosa and submucosa may be superior to full thickness. Additional research is needed to further clarify optimal technique and post‐operative outcomes. Support or Funding Information Dr. Aho reports funding from a Grant from the National Heart, Lung, and Blood Institute T32 HL105355, a component of the National Institutes of Health (NIH).

The diaphragm muscle is important in both sustaining ventilation and performing higher-force behaviors necessary for maintaining airway patency. Ventilatory behaviors (i.e., eupnea and response to hypoxia-hypercapnia) require only ~20% of maximal force generation, whereas coughing requires forces ~60% of maximal. Existing techniques to measure the full range of forces generated by respiratory muscles are limited by their invasiveness (e.g., balloon manometry for transdiaphragmatic pressure (Pdi) measurements), requirements for training, supervision and subjectivity (e.g., maximal inspiratory and expiratory pressures). Ultrasound-based shear-wave elastography (SWE) assesses muscle stiffness and has shown promising results in being used as a surrogate for Pdi to evaluate diaphragm muscle force. Previous literature has demonstrated a correlation between diaphragm SWE and Pdi at lower force behaviors and the goal of the present study was to evaluate the efficacy of SWE-based measurements of the diaphragm in correlating with Pdi measurements across the range of forces generated by the diaphragm. In this pilot study, we recruited 6 male and 5 female healthy volunteers. Subjects were positioned in a seated position with their torso unsupported. Pdi was measured during graded inspiratory threshold loading trials using a POWERbreathe Plus commercial inspiratory loading device, as well as during maximal inspiratory pressure (MIP). Simultaneously, SWE was performed at the zone of apposition in the right anterior axillary line, and diaphragm Young’s modulus and shear wave speed were subsequently measured. The average Pdi during MIP testing was 149 ± 66 cm H2O. Pdi during inspiratory loading at a low resistance was 39 ± 14 cm H2O and at a high resistance was 78 ± 29 cm H2O. Subjects were able to generate an average Pdi range of 39 ± 19 cm H2O across the graded resistance levels, and the average percent of MIP obtained was 54 ± 13%. Average Young’s modulus as measured with SWE during inspiratory loading at a low resistance was 46 ± 19 kPa and at a high resistance was 104 ± 19 kPa. From low to high resistance, Pdi, Young’s modulus, and shear wave speed increased by an average of 100%, 126%, and 59%, respectively. Taken together, SWE is a promising method of non-invasive assessment of diaphragm muscle forces across a range of voluntary behaviors. Support from NIH grant R21 DA055848 and the Mayo Clinic. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The color Doppler twinkling artifact has been attributed to existing microbubbles or cavitation occurring on objects like kidney stones, some breast biopsy markers, and sandpaper. The grooves of helical constructs that twinkle may provide sufficient locations for bubble retention and/or cavitation. We developed six half-cylinders that replicate the geometry of twinkling helical constructs with a micro 3D-printing process to explore how their characteristics relate to twinkling. Four copies of each design including a control were created. The cylinders had pitch (groove-to-groove distance) of 87.5–343 μm and amplitude (groove depth) of 41.5–209 μm. The cylinders were submerged in degassed water and optically imaged before and after ultrasound to visualize bubbles on the cylinders. The cylinders remained submerged while scanning with color Doppler at frequencies from 3.1 to 6.3 MHz with a General Electric Logiq E9 scanner and 9L linear array transducer. Two designs that showed twinkling characteristics were further examined. The presence or absence of bubbles on these designs was confirmed with microscopy, and the resulting twinkling behavior was investigated. This work shows strong evidence that both existing visible bubbles and either cavitation or ultrasound wave interactions with patterned or rough surfaces are significant factors in producing the twinkling signature.