Biology subjects

Dayton, P. A.

Publications and source records attributed to Dayton, P. A..

5 recordsLinked to original sources

bioRxiv2026

Human decompression in real time: programmable ultrasound imaging during hyperbaric exposure

The formation of inert gas bubbles during decompression can lead to decompression sickness (DCS), a major operational risk for divers, compressed-gas workers, astronauts, and high-altitude aviators. In diving, DCS risk is typically inferred from post-dive ultrasound detection of venous gas emboli (VGE), precluding modification of decompression schedules based on real-time physiological feedback. Two-dimensional ultrasound imaging could provide additional insight into decompression-related physiological changes; however, its use in hyperbaric environments has been largely precluded by fire risk associated with elevated oxygen partial pressures (ppO2) in enclosed spaces. Here, we developed a workflow for operating a programmable ultrasound system under hyperbaric conditions and acquiring ultrasound data from the subclavian vein and calf muscle during decompression. A total of 42 dives were conducted by 26 individuals using a previously characterized dive profile to 132 feet seawater (FSW) for 20 min with 9 min of decompression. Three exposure conditions were evaluated: non-exercising, exercising, and a brief pause at 20 FSW during compression. Twelve dives included programmable ultrasound imaging during decompression. Post-dive VGE responses were consistent with prior reports while demonstrating substantial inter-individual variability and sensitivity to modest profile modifications. VGE were detected in the subclavian vein during decompression in two participants and subsequently confirmed by post-dive echocardiography. Calf muscle ultrasound brightness typically increased from pre-dive to decompression measurements, before decreasing below baseline in the 120 min post dive measurement period. These findings demonstrate the feasibility of programmable ultrasound imaging during human decompression and establish a practical framework for ultrasound operation under hyperbaric conditions. This approach may support future physiological studies and development of automated decompression monitoring technologies. New and NoteworthyThis study demonstrates the first use of a programmable ultrasound system to acquire and quantitatively analyze ultrasound data during human decompression. The approach enabled direct visualization of venous gas emboli during decompression and revealed calf muscle ultrasound signal changes, providing a new tool for investigating physiological responses during decompression that are not accessible through conventional post-dive monitoring.

physiology↗

bioRxiv2022

A Model of High-Speed Endovascular Sonothrombolysis with Vortex Ultrasound-Induced Shear Stress to Treat Cerebral Venous Sinus Thrombosis

This research aims to demonstrate a novel vortex ultrasound enabled endovascular thrombolysis method designed for treating cerebral venous sinus thrombosis (CVST). This is a topic of significant importance since current treatment modalities for CVST still fail in as many as 20-40% of the cases and the incidence of CVST has increased since the outbreak of the COVID-19 pandemic. Compared with conventional anticoagulant or thrombolytic drugs, sonothrombolysis has the potential to remarkably shorten the required treatment time owing to the direct clot targeting with acoustic waves. However, previously reported strategies for sonothrombolysis have not demonstrated clinically meaningful outcomes (e.g., recanalization within 30 minutes) in treating large, completely occluded veins or arteries. In this paper, we demonstrated a new vortex ultrasound technique for endovascular sonothrombolysis utilizing wave-matter interaction-induced shear stress to enhance the lytic rate substantially. Our in vitro experiment showed that the lytic rate was increased by at least 64.3 % compared with the nonvortex endovascular ultrasound treatment. A 3.1 g, 7.5 cm long, completely occluded in vitro 3D model of acute CVST was fully recanalized within 8 minutes with a record-high lytic rate of 237.5 mg/min for acute bovine clot in vitro. Furthermore, we confirmed that the vortex ultrasound causes no vessel wall damage over ex vivo bovine veins. This vortex ultrasound thrombolysis technique potentially presents a new life-saving tool for severe CVST cases that cannot be efficaciously treated using existing therapies.

bioengineering↗

bioRxiv2021

Feasibility of an Inhalable Ultrasound Contrast Agent to Enhance Airway Imaging

IntroductionUltrasound is a relatively inexpensive and non-ionizing imaging modality, but is under-utilized in large airway assessments due to poor image quality. No commercially available contrast agents currently exist for sonographic evaluation of the respiratory system, nor has a respiratory route of microbubble contrast agent (MCA) administration been previously described for the enhancement of airway imaging. MethodsWe conducted a feasibility study to assess proof-of-concept for an inhalable ultrasound MCA composed of lipid-encapsulated decaflourobutane gas. The MCA was nebulized and administered as an aerosol through the lumen of an ex vivo porcine trachea, with image enhancement evaluated by comparing images pre- and post-exposure. Additionally, primary human bronchial epithelial (hBE) cells from three donors were differentiated at an air-liquid interface and exposed apically to 25 L of undiluted MCA or vehicle control to assess contrast agent-induced cytotoxicity and inflammation. Basolateral medium was collected 24-hours post-exposure and lactate dehydrogenase (LDH) and interleukin-8 (IL-8) concentrations were measured as biomarkers of cytotoxicity and inflammation, respectively. ResultsContrast microbubbles remained intact following nebulization and enhanced sonographic delineation of ex vivo porcine tracheal walls, indicating adherence of the nebulized MCA to the lumenal mucosa. No significant cytotoxic or inflammatory effects were observed in cultured hBE cells following exposure to MCA. ConclusionsWe present proof-of-concept for an inhaled MCA for the enhancement of sonographic evaluations of the large airways. Pending further evaluations for safety and effectiveness, inhaled MCA may be feasible for clinical ultrasound applications, such as enhancing ultrasound-guided tracheal intubation, detecting airway bleeds, or monitoring large airway diseases in pediatric populations.

bioengineering↗

bioRxiv2020

Harnessing Ultrasound-Stimulated Phase Change Contrast Agents to Improve Antibiotic Efficacy Against Methicillin-Resistant Staphylococcus aureus Biofilms

Bacterial biofilms, often associated with chronic infections, respond poorly to antibiotic therapy and frequently require surgical intervention. Biofilms harbor persister cells, metabolically indolent cells, which are tolerant to most conventional antibiotics. In addition, the biofilm matrix can act as a physical barrier, impeding diffusion of antibiotics. Novel therapeutic approaches frequently improve biofilm killing, but usually fail to achieve eradication. Failure to eradicate the biofilm leads to chronic and relapsing infection, associated with major financial healthcare costs and significant morbidity and mortality. We address this problem with a two-pronged strategy using 1) antibiotics that target persister cells and 2) ultrasound-stimulated phase-change contrast agents (US-PCCA), which improve antibiotic penetration. We previously demonstrated that rhamnolipids, produced by Pseudomonas aeruginosa, could induce aminoglycoside uptake in gram-positive organisms, leading to persister cell death. We have also shown that US-PCCA can transiently disrupt biological barriers to improve penetration of therapeutic macromolecules. We hypothesized that combining antibiotics which target persister cells with US-PCCA to improve drug penetration could eradicate methicillin resistant S. aureus (MRSA) biofilms. Aminoglycosides alone or in combination with US-PCCA displayed limited efficacy against MRSA biofilms. In contrast, the anti-persister combination of rhamnolipids and aminoglycosides combined with US-PCCA dramatically reduced biofilm viability, frequently culminating in complete eradication of the biofilm. These data demonstrate that biofilm eradication can be achieved using a combined approach of improving drug penetration of therapeutics that target persister cells.

microbiology↗

bioRxiv2020

Conventional dose rate spatially-fractionated radiation therapy (SFRT) treatment response and its association with dosimetric parameters - A preclinical study in a Fisher 344 rat model

PurposeTo identify key dosimetric parameters that have close associations with tumor treatment response and body weight change in SFRT treatments with a large range of spatial-fractionation scale at dose rates of several Gy/min. MethodsSix study arms using uniform tumor radiation, half-tumor radiation, 2mm beam array radiation, 0.3mm minibeam radiation, and an untreated arm were used. All treatments were delivered on a 320kV x-ray irradiator. Forty-two female Fischer 344 rats with fibrosarcoma tumor allografts were used. Dosimetric parameters studied are peak dose and width, valley dose and width, peak-to-valley-dose-ratio, volumetric average dose, percentage volume directly irradiated, and tumor- and normal-tissue EUD. Animal survival, tumor volume change, and body weight change (indicative of treatment toxicity) are tested for association with the dosimetric parameters using linear regression and Cox Proportional Hazards models. ResultsThe dosimetric parameters most closely associated with tumor response are tumor EUD (R2=0.7923, F-stat=15.26*; z-test=-4.07***), valley/minimum dose (R2=0.7636, F-stat=12.92*; z-test=-4.338***), and percentage tumor directly irradiated (R2=0.7153, F-stat=10.05*; z-test=-3.837***) per the linear regression and Cox Proportional Hazards models, respectively. Tumor response is linearly proportional to valley/minimum doses and tumor EUD. Average dose (R2=0.2745, F-stat=1.514 (no sig.); z-test=-2.811**) and peak dose (R2=0.04472, F-stat=0.6874 (not sig.); z-test=-0.786 (not sig.)) show the weakest associations to tumor response. Only the uniform radiation arm did not gain body weight post-radiation, indicative of treatment toxicity; however, body weight change in general shows weak association with all dosimetric parameters except for valley/min dose (R2=0.3814, F-stat=13.56**), valley width (R2=0.2853, F-stat=8.783**), and peak width (R2=0.2759, F-stat=8.382**). ConclusionsFor a single-fraction SFRT at conventional dose rates, valley, not peak, dose is closely associated with tumor treatment response and thus should be used for treatment prescription. Tumor EUD, valley/min dose, and percentage tumor directly irradiated are the top three dosimetric parameters that exhibited close associations with tumor response.

cancer biology↗