Twenty-four-hour Normothermic Ex Vivo Heart Perfusion With Low Flow Functional Assessment in an Adult Porcine Model.

BACKGROUND: Cold static storage and normothermic ex vivo heart perfusion are routinely limited to 6 h. This report describes intermittent left atrial (LA) perfusion that allows cardiac functional assessment in a working heart mode. METHODS: Using our adult porcine model, general anesthesia was induced and a complete cardiectomy was performed following cardioplegic arrest. Back-table instrumentation was completed and normothermic ex vivo heart perfusion (NEHP) was initiated in a nonworking heart mode (Langendorff). After 1 h of resuscitation and recovery, LA perfusion was initiated and the heart was transitioned to a coronary flow-only working heart mode for 30 min. Baseline working heart parameters were documented and the heart was returned to nonworking mode. Working heart assessments were performed for 30 min every 6 h for 24 h. RESULTS: Twenty-four-hour NEHP on 9 consecutive hearts (280 ±â€…42.1 g) was successful and no significant differences were found between working heart parameters at baseline and after 24 h of perfusion. There was no difference between initial and final measurements of LA mean pressures (5.0 ±â€…3.1 versus 9.0 ±â€…6.5 mm Hg, P  = 0.22), left ventricular systolic pressures (44.3 ±â€…7.2 versus 39.1 ±â€…9.0 mm Hg, P  = 0.13), mean aortic pressures (30.9 ±â€…5.8 versus 28.1 ±â€…8.1 mm Hg, P  = 0.37), and coronary resistance (0.174 ±â€…0.046 versus 0.173 ±â€…0.066 mL/min/g, P  = 0.90). There were also no significant differences between lactate (2.4 ±â€…0.5 versus 2.6 ±â€…0.4 mmol/L, P  = 0.17) and glucose (173 ±â€…75 versus 156 ±â€…70 mg/dL, P  = 0.37). CONCLUSIONS: A novel model using intermittent LA perfusion to create a coronary flow-only working heart mode for assessment of ex vivo cardiac function has been successfully developed.

Optical beam scanner with reconfigurable non-mechanical control of beam position, angle, and focus for low-cost whole-eye OCT imaging.

Whole-eye optical coherence tomography (OCT) imaging is a promising tool in ocular biometry for cataract surgery planning, glaucoma diagnostics and myopia progression studies. However, conventional OCT systems are set up to perform either anterior or posterior eye segment scans and cannot easily switch between the two scan configurations without adding or exchanging optical components to account for the refraction of the eye's optics. Even in state-of-the-art whole-eye OCT systems, the scan configurations are pre-selected and cannot be dynamically reconfigured. In this work, we present the design, optimization and experimental validation of a reconfigurable and low-cost optical beam scanner based on three electro-tunable lenses, capable of non-mechanically controlling the beam position, angle and focus. We derive the analytical theory behind its control. We demonstrate its use in performing alternate anterior and posterior segment imaging by seamlessly switching between a telecentric focused beam scan to an angular collimated beam scan. We characterize the corresponding beam profiles and record whole-eye OCT images in a model eye and in an ex vivo rabbit eye, observing features comparable to those obtained with conventional anterior and posterior OCT scanners. The proposed beam scanner reduces the complexity and cost of other whole-eye scanners and is well suited for 2-D ocular biometry. Additionally, with the added versatility of seamless scan reconfiguration, its use can be easily expanded to other ophthalmic applications and beyond.

Long-range frequency-domain optical delay line based on a spinning tilted mirror for low-cost ocular biometry.

Optical biometers are routinely used to measure intraocular distances in ophthalmic applications such as cataract surgery planning or myopia monitoring. However, due to their high cost and reduced transportability, access to them for screening and surgical planning is still limited in low-resource and remote settings. To increase patients' access to optical biometry we propose a novel low-cost frequency-domain optical delay line (FD-ODL) based on an inexpensive stepper motor spinning a tilted mirror, for integration into a time-domain (TD)-biometer, amenable to a compact footprint. In the proposed FD-ODL, the axial scan range and the A-scan rate are decoupled from one another, as the former only depends on the spinning mirror tilt angle, while the A-scan rate only depends on the motor shaft rotational speed. We characterized the scanning performance and specifications for two spinning mirror tilt angles, and compared them to those of the standard, more expensive FD-ODL implementation, employing a galvanometric scanner for group delay generation. A prototype of the low-cost FD-ODL with a 1.5 deg tilt angle, resulting in an axial scan range of 6.61 mm and an A-scan rate of 10 Hz was experimentally implemented and integrated in a dual sample beam optical low-coherence reflectometry (OLCR) setup with a detour unit to replicate the measurement window around the anterior segment and the retina. The intraocular distances of a model eye were measured with the proposed low-cost biometer and found to be in good agreement with those acquired by a custom swept-source optical coherence tomography (SS-OCT) system and two commercial biometers, validating our novel design.

Energetic and environmental assessment of thermochemical and biochemical ways for producing energy from agricultural solid residues: Coffee Cut-Stems case.

Forest residues are an important source of biomass. Among these, Coffee Cut-Stems (CCS) are an abundant wood waste in Colombia obtained from coffee crops renovation. However, only low quantities of these residues are used directly in combustion processes for heating and cooking in coffee farms where their energy efficiency is very low. In the present work, an energy and environmental assessment of two bioenergy production processes (ethanol fermentation and gasification) using CCS as raw material was performed. Biomass gasification seems to be the most promising thermochemical method for bioenergy production whereas, ethanol fermentation is a widely studied biochemical method to produce biofuels. Experimental runs of the CCS gasification were carried out and the synthesis gas composition was monitored. Prior to the fermentation process, a treatment of the CCS is required from which sugar content was determined and then, in the fermentation process, the ethanol yield was calculated. Both processes were simulated in order to obtain the mass and energy balance that are used to assess the energy efficiency and the potential environmental impact (PEI). Moderate high energy efficiency and low environmental impacts were obtained from the CCS gasification. In contrast, high environmental impacts in different categories and low energy efficiencies were calculated from the ethanolic fermentation. Biomass gasification seems to be the most promising technology for the use of Coffee Cut-Stems with high energy yields and low environmental issues.