Smart Drain for Post-Cardiac Surgery Left Ventricular Volumes Evaluated in Large Animal Models.

BACKGROUND: Open heart surgeries for coronary arterial bypass graft and valve replacements are performed on 400,000 Americans each year. Unexplained hypotension during recovery causes morbidity and mortality through cerebral, kidney, and coronary hypoperfusion. An early detection method that distinguishes between hypovolemia and decreased myocardial function before onset of hypotension is desirable. We hypothesized that admittance measured from a modified pericardial drain can detect changes in left ventricular end-systolic, end-diastolic, and stroke volumes. METHODS: Admittance was measured from 2 modified pericardial drains placed in 7 adult female dogs using an open chest preparation, each with 8 electrodes. The resistive and capacitive components of the measured admittance signal were used to distinguish blood and muscle components. Admittance measurements were taken from 12 electrode configurations in each experiment. Left ventricular preload was reduced by inferior vena cava occlusion. Physiologic response to vena cava occlusion was measured by aortic pressure, aortic flow, left ventricle diameter, left ventricular wall thickness, and electrocardiogram. RESULTS: Admittance successfully detected a drop in left ventricular end-diastolic volume (P < .001), end-systolic volume (P < .001), and stroke volume (P < .001). Measured left ventricular muscle resistance correlated with crystal-derived left ventricular wall thickness (R2 = 0.96), validating the method's ability to distinguish blood from muscle components. CONCLUSIONS: Admittance measured from chest tubes can detect changes in left ventricular end-systolic, end-diastolic, and stroke volumes and may therefore have diagnostic value for unexplained hypotension.

Data automated bag breathing unit for COVID-19 ventilator shortages.

BACKGROUND: The COVID-19 pandemic has caused a global mechanical ventilator shortage for treatment of severe acute respiratory failure. Development of novel breathing devices has been proposed as a low cost, rapid solution when full-featured ventilators are unavailable. Here we report the design, bench testing and preclinical results for an 'Automated Bag Breathing Unit' (ABBU). Output parameters were validated with mechanical test lungs followed by animal model testing. RESULTS: The ABBU design uses a programmable motor-driven wheel assembled for adult resuscitation bag-valve compression. ABBU can control tidal volume (200-800 ml), respiratory rate (10-40 bpm), inspiratory time (0.5-1.5 s), assist pressure sensing (- 1 to - 20 cm H2O), manual PEEP valve (0-20 cm H2O). All set values are displayed on an LCD screen. Bench testing with lung simulators (Michigan 1600, SmartLung 2000) yielded consistent tidal volume delivery at compliances of 20, 40 and 70 (mL/cm H2O). The delivered fraction of inspired oxygen (FiO2) decreased with increasing minute ventilation (VE), from 98 to 47% when VE was increased from 4 to 16 L/min using a fixed oxygen flow source of 5 L/min. ABBU was tested in Berkshire pigs (n = 6, weight of 50.8 ± 2.6 kg) utilizing normal lung model and saline lavage induced lung injury. Arterial blood gases were measured following changes in tidal volume (200-800 ml), respiratory rate (10-40 bpm), and PEEP (5-20 cm H2O) at baseline and after lung lavage. Physiological levels of PaCO2 (≤ 40 mm Hg [5.3 kPa]) were achieved in all animals at baseline and following lavage injury. PaO2 increased in lavage injured lungs in response to incremental PEEP (5-20 cm H2O) (p < 0.01). At fixed low oxygen flow rates (5 L/min), delivered FiO2 decreased with increased VE. CONCLUSIONS: ABBU provides oxygenation and ventilation across a range of parameter settings that may potentially provide a low-cost solution to ventilator shortages. A clinical trial is necessary to establish safety and efficacy in adult patients with diverse etiologies of respiratory failure.

Implantable Cardiac Kirigami-Inspired Lead-Based Energy Harvester Fabricated by Enhanced Piezoelectric Composite Film.

Harvesting biomechanical energy to power implantable electronics such as pacemakers has been attracting great attention in recent years because it replaces conventional batteries and provides a sustainable energy solution. However, current energy harvesting technologies that directly interact with internal organs often lack flexibility and conformability, and they usually require additional implantation surgeries that impose extra burden to patients. To address this issue, here a Kirigami inspired energy harvester, seamlessly incorporated into the pacemaker lead using piezoelectric composite films is reported, which not only possesses great flexibility but also requires no additional implantation surgeries. This lead-based device allows for harvesting energy from the complex motion of the lead caused by the expansion-contraction of the heart. The device's Kirigami pattern has been designed and optimized to attain greatly improved flexibility which is validated via finite element method (FEM) simulations, mechanical tensile tests, and energy output tests where the device shows a power output of 2.4 µW. Finally, an in vivo test using a porcine model reveals that the device can be implanted into the heart straightforwardly and generates voltages up to ≈0.7 V. This work offers a new strategy for designing flexible energy harvesters that power implantable electronics.

Flexible Energy Harvester on a Pacemaker Lead Using Multibeam Piezoelectric Composite Thin Films.

Implantable medical devices, such as cardiac pacemakers and defibrillators, rely on batteries for operation. However, conventional batteries only last for a few years, and additional surgeries are needed for replacement. Harvesting energy directly from the human body enables a new paradigm of self-sustainable power sources for implantable medical devices without being constrained by the battery's limited lifetime. Here, we report the design of a multibeam cardiac energy harvester using polydimethylsiloxane (PDMS)-infilled microporous P(VDF-TrFE) composite films. We first added ZnO nanoparticles and multiwall carbon nanotubes into microporous P(VDF-TrFE) films to increase the energy output. The mixing ratios of 30% ZnO and 0.1% MWCNTs yielded 3.22 ± 0.24 V output, which resulted in a voltage output 46 times higher than that of pure P(VDF-TrFE) films. Next, we discovered that the voltage generated by the composite film with PDMS is approximately 105% higher than that of the one without PDMS. For the application in cardiac pacemakers, we developed a facile fabrication method by building a cylindrical multibeam device that resides on the pacemaker lead to harvest energy from the complex motion of the lead driven by the heartbeat. Since the energy harvesting component is integrated into the pacemaker, it significantly reduces the risks and expenses associated with pacemaker-related surgeries. This work paves the way toward the new generation of energy harvesters that will benefit patients with a variety of implantable biomedical devices.

Multifunctional Pacemaker Lead for Cardiac Energy Harvesting and Pressure Sensing.

Biomedical self-sustainable energy generation represents a new frontier of power solution for implantable biomedical devices (IMDs), such as cardiac pacemakers. However, almost all reported cardiac energy harvesting designs have not yet reached the stage of clinical translation. A major bottleneck has been the need of additional surgeries for the placements of these devices. Here, integrated piezoelectric-based energy harvesting and sensing designs are reported, which can be seamlessly incorporated into existing IMDs for ease of clinical translation. In vitro experiments validate the energy harvesting process by simulating the bending and twisting motion during heart cycle. Clinical translation is demonstrated in four porcine hearts in vivo under various conditions. Energy harvesting strategy utilizes pacemaker leads as a means of reducing the reliance on batteries and demonstrates the charging ability for extending the lifetime of a pacemaker battery by 20%, which provides a promising self-sustainable energy solution for IMDs. The additional self-powered blood pressure sensing is discussed, and the reported results demonstrate the potential in alerting arrhythmias by monitoring the right ventricular pressure variations. This combined cardiac energy harvesting and blood pressure sensing strategy provides a multifunctional, transformative while practical power and diagnosis solution for cardiac pacemakers and next generation of IMDs.

Laser brain cancer surgery in a xenograft model guided by optical coherence tomography.

Higher precision surgical devices are needed for tumor resections near critical brain structures. The goal of this study is to demonstrate feasibility of a system capable of precise and bloodless tumor ablation. An image-guided laser surgical system is presented for excision of brain tumors in vivo in a murine xenograft model. The system combines optical coherence tomography (OCT) guidance with surgical lasers for high-precision tumor ablation (Er:YAG) and microcirculation coagulation (Thulium (Tm) fiber laser). Methods: A fluorescent human glioblastoma cell line was injected into mice and allowed to grow four weeks. Craniotomies were performed and tumors were imaged with confocal fluorescence microscopy. The mice were subsequently OCT imaged prior, during and after laser coagulation and/or ablation. The prior OCT images were used to compute three-dimensional tumor margin and angiography images, which guided the coagulation and ablation steps. Histology of the treated regions was then compared to post-treatment OCT images. Results: Tumor sizing based on OCT margin detection matched histology to within experimental error. Although fluorescence microscopy imaging showed the tumors were collocated with OCT imaging, margin assessment using confocal microscopy failed to see the extent of the tumor beyond ~ 250 µm in depth, as verified by OCT and histology. The two-laser approach to surgery utilizing Tm wavelength for coagulation and Er:YAG for ablation yielded bloodless resection of tumor regions with minimal residual damage as seen in histology. Conclusion: Precise and bloodless tumor resection under OCT image guidance is demonstrated in the murine xenograft brain cancer model. Tumor margins and vasculature are accurately made visible without need for exogenous contrast agents.