Gas Exchange Efficiency Research Articles

Fourteen Days Of Hypoxia And Apnea Training Does Not Modify Pulmonary Gas Exchange Efficiency

Fourteen Days Of Hypoxia And Apnea Training Does Not Modify Pulmonary Gas Exchange Efficiency

Evaluation of PTFPMS membrane towards application in artificial oxygenation

The tradeoff between efficient gas exchange and blood leakage as well as thrombosis caused by contact between blood and membrane are existing challenges in extracorporeal membrane oxygenation (ECMO). Herein, poly (3,3,3-trifluoropropyl) methylsiloxane/polyetherimide (PTFPMS/PEI) composite membranes, with a thin PTFPMS dense layer for functional CO2 and O2 exchange coated on microporous PEI substrate membrane for mechanical support, were synthesized, characterized and evaluated for potential application as oxygenation membrane. Characterization data from scanning electron microscopy with energy dispersive spectroscopy, thermogravimetric analysis, contact angle and zeta potential measurements confirmed that PTFPMS/PEI composite membrane with different coating concentrations were successfully prepared, and the composite membranes obtained exhibited thermal stability, surface hydrophobicity as well as surface electronegativity. Analysis on gas permeance and hemocompatibility performance demonstrated that the composite membranes displayed effective gas transfer and good blood compatibility in terms of hemolysis rate, protein adsorption, platelet adhesion as well as plasma recalcification time. More notably, the membrane also displayed excellent long term anti-fouling performance. In summary, the PTFPMS/PEI composite membrane showed impressive application potential for use as oxygenation membrane in ECMO.

Device updates in pediatric and neonatal ECMO

Since the early use of extracorporeal life support (ECLS), new innovations and technological advancements have augmented the ability to use this technology in children and neonates. Cannulae have been re-designed to maintain structure and allow for single cannula venovenous (VV) ECLS in smaller patients. Circuit technology, including pumps and tubing, has evolved to permit smaller priming volumes and lower flow rates with fewer thrombotic or hemolytic complications. New oxygenator developments also improve efficiency of gas exchange. This paper serves as an overview of recent device developments in ECLS delivery to pediatric and neonatal patients.

The combined effect of branch position, temperature, and VPD on gas exchange and water-use efficiency of Norway spruce

The combined effect of branch position, temperature, and VPD on gas exchange and water-use efficiency of Norway spruce

Exploring key physiological attributes of grapevine cultivars under the influence of seasonal environmental variability

Seasonal climatic variability is a key challenge in many grape-growing regions across the globe, affecting phenology, growth, physiological responses, and yield at harvest. Unfavourable climatic conditions impair the plant's physiological processes, such as chlorophyll accumulation, gas exchange and photosynthesis in grapevine leaves. It is critical to unlock the complex physiological behaviour of grapevine cultivars at key phenological stages and under varying environmental conditions. The present study was designed to evaluate the key physiological processes, such as gas exchange, chlorophyll contents and water use efficiency (WUE), of four table grape cultivars at key growth stages under varying environmental conditions of the Pothwar region, in a factorial experimental set up (Location× Year × Cultivar × Phenological stage). The physiological responses of the table grape cultivars were recorded at the 5-leaf stage, full bloom, berry set, veraison and harvest during two consecutive vintages (2019 and 2020) in two locations (Islamabad and Chakwal). The results show that the mean photosynthetic activity in colder Islamabad was 30.7 % higher than in Chakwal, and the transpiration rate and WUE were 10.4 % and 28.6 % higher. Similarly, 12 % higher photosynthetic activity, with 13 % more WUE, was observed in the colder vintage of 2020 compared to that of 2019. The vine physiological activity also varied among cultivars; for example, cv. Sugraone was found to have 12 % more chlorophyll and 30 % higher photosynthetic activity than cv. Kings Ruby. Similarly, higher photosynthetic activity and transpiration rates were recorded at the berry set stage, while WUE peaked near blooming. The biplot analysis for the first two principal components also showed cv. Sugraone to be a highly responsive and physiologically efficient cultivar. The findings of the present research will help to better assess the effect of seasonal variability on vine physiological performance and to identify genotypes with higher photosynthetic potential and WUE. It could also assist in devising vineyard management strategies to better adapt to varying environmental conditions.

PULM2: Combining Extracorporeal Lung and Kidney Support: Evaluation of Fibre Configurations on Gas Exchange Preservation for the Development of a Novel Highly Integrated Device (RenOx)

Background: Combined lung and kidney dysfunction are frequent in extracorporeal membrane oxygenation (ECMO) patients affecting up to 70% of them. Current treatment relies on the use of two separate circuits combining ECMO and renal replacement therapy, increasing infection risks and the use of artificial surfaces. Therefore, we aim to develop a novel artificial lung that integrates lung and kidney support in a single device combining oxygenation and hemodialysis fibers. Thus, we analyzed how many oxygenation fibers could be substituted by hemodialysis fibers while still maintaining 90% of the oxygenator’s gas exchange capacity and the effect fiber configuration has on oxygen (O2) and carbon dioxide (CO2) transfer. Methods: Fiber bundles were composed of oxygenation fiber mats (Oxyplus™ 90/200, 3M) stacked perpendicularly at a 90° angle and/or crossed at a 24° angle on top of each other. We manufactured bundles with all oxygenation fibers open and bundles with oxygenation fibers closed in a way that they could not contribute to gas exchange, simulating hemodialysis fibers. Bundles in perpendicular configuration had 100% of fibers open (Oxy100P), 50% of fibers closed (Oxy50P), or 25% of fibers closed (Oxy75P), Figure 1. Bundles in crossed configuration had all fibers open (Oxy100C) or 33% of fibers closed (Oxy67C). Bundles were tested for gas exchange performance following in-vitro blood tests according to ISO 7199:2016. Results: Our results show that bundles with 25% of oxygenation fibers closed in perpendicular configuration were able to still maintain 90% of the O2 exchange and 80% of the CO2 exchange capacity of our oxygenator. Bundles with 25% oxygenation fibers closed had no statistically significant difference in O2 or CO2 transfer compared to a fully open oxygenator with the same fiber configuration, Figure 2. Additionally, Oxy75P bundles were able to keep O2 delivery above 55 mL/LBlood flow and CO2 removal above 52 mL/LBlood flow up to 140 mL/min. Fiber configuration did not affect gas exchange for fully open bundles, however, configuration significantly influenced O2 and CO2 exchange for bundles with closed fiber layers. Closing fibers in perpendicular configuration resulted in a lower decrease in gas transfer. Below 140 mL/min, this was demonstrated by a similar decrease in O2 transfer of 20% when 50% of perpendicular fibers or 33% of crossed fibers were closed Conclusions: We analyzed the effect of replacing oxygenation fibers with hemodialysis fibers on gas exchange efficiency. Our results demonstrate that 25% of oxygenation fibers in a perpendicular configuration could be replaced by hemodialysis fibers while still maintaining 90% of the O2 exchange of our oxygenator. Moreover, this type of bundle kept O2 delivery above 55 mL/LBlood flow up to 140 mL/min. This shows that gas exchange can be preserved to a desirable extent when oxygenation fiber layers are replaced. This is a step towards combining lung and kidney support in a single device.Figure 1. Illustration of a device combining extracorporeal lung and kidney support. Oxygen flows through the lumen of oxygenation fibers and dialysate flows inside hemodialysis fibers. In this work, fiber bundles were manufactured with a perpendicular and/or crossed configuration having a varying number of oxygenation fiber layers closed, simulating hemodialysis fibers (open fibers in white and closed fibers in blue). Perpendicular bundles had 50% of fibers closed (Oxy50P), 25% of fibers closed (Oxy75P), or 100% of fibers open (Oxy100P), while crossed bundles had 33% of fibers closed (Oxy67C), or all fibers open (Oxy100C).Figure 2. Oxygen exchange performance mL/LBlood flow ± standard deviation from the mean (n = 10) for bundles with different fiber configurations. We found no statistically significant difference in mean oxygen exchange between Oxy75P and the fully open oxygenator Oxy100P (ANOVA p > 0.38).

PULM3: The Effects of a Two-step Coating Process and Flow on Artificial Lung Fiber Fouling.

The densely packed fiber bundle design of the artificial lung increases the gas exchange efficiency of the device by dramatically increasing its surface area to volume ratio. However, the close arrangement of the lung’s fibers is a significant source for blood coagulation, and therefore the effectiveness of their in-situ coating for effective protein antifouling activity requires a process that uniformly applies the coating across the bundle thickness. In this study, polydopamine/polysulfobetaine methacrylate (pDOPA/pSBMA) was grafted onto the artificial lung circuit using a two-step surface modification process consisting of an ultraviolet-oxygen plasma surface activation followed by surface grating in pDOPA/pSBMA dissolved in tris(hydroxymethyl)aminomethane (TRIS, pH 8.5) buffer. The antifouling activities of coating on fiber mats at the surface or buried in the bundle, on fiber bundle exposed to 24hr phosphate buffered saline (pH 7.34, temp. ~37C) flow (1.22L/min), and uncoated controls were analyzed. Fibrinogen (Fg) and platelet (plt) fouling on fibers were used as metrics of antifouling activity. Ultimately, the utility of fully priming the lung circuit with pDOPA/pSBMA coating solution with a side-to-side positioning of the primed device every 10 minutes for 2 hrs was evaluated for coating uniformity across bundle thickness. Fg and plt fouling on uncoated controls, coated bundle surface fibers, coated bundle buried fibers, coated bundle surface fibers after 24hr flow, and coated bundle buried fibers after 24hr flow were respectively (0.83±0.01, 0.20±0.003) (0.36±0.01 pval=0.026, 0.36±0.01 pval=8.740E-11), (0.38±0.004 pval=0.026, 0.01±0.02 pval=8.740E-11), (2.64±0.53 pval=0.077, 0.02±0.003 pval=0.218), and (2.70±0.72 pval= 0.077, 0.03±0.01 pval=0.218). The data indicated that while the pDOPA/pSBMA coating significantly reduced fouling, not only did its appearance vary across the bundle thickness but so did its antifouling activity. This warrants the optimization of the coating process.

BIO27: Automated PDMS Engraving and Assembly of a Prototype Microfluidic Artificial Lung

Purpose: The ability to cost-effectively produce high-surface area microfluidic devices would bring many small-scale technologies from the realm of research to clinical and commercial applications. In particular microfluidic artificial lungs (µALs) promise improved gas exchange efficiency through micron-scale feature sizes. However, most µALs have only a single layer which limits their rated flows. Efforts to scale up these devices, such as by stacking multiple flat µALs have been labor intensive and resulted in bulky devices. Here, we present an automated roll-to-roll (R2R) manufacturing system and a cylindrical multi-layer µAL. Methods: The R2R system (Fig 1A) begins with a roll of biocompatible silicone rubber (Silpuran 2030). A heavily-modified CO2 laser engraver (Omtech K40 with custom vacuum engraving bed, N2 purge, and custom motherboard) creates patterns in the silicone sheet (Fig 1B). The sheet is then plasma-activated using two CeraPlas F-series cold-plasma wands to bond the PDMS to itself in an irreversible bond. Finally, it is rerolled into a processed device around a 30 mm PDMS core. This entire process from unrolling to rerolling is performed simultaneously and synchronously, allowing the creation of very large area microfluidic devices. Further, it is automated (Arduino Mega 1680), eliminating human error over this repetitive process. Results: Using our automated manufacturing system, we fabricated a 27-layer cylindrical prototype µAL, consisting of 1) an 8-layer base, 2) 11 layers of alternating blood and gas channels, and 3) an 8-layer protective cover. Laser-engraved fluidic channels were triangular, 60 µm deep and 180 µm wide (Fig 1B). If unrolled, the microfluidic part of this system would stretch 1.1 m, and the total length would stretch 2.7 m. This was placed into a custom 3D printed housing which routes blood and gas to their respective microfluidic channels (Fig 2A,B; filled with dyed water for visualization). Empirical pressure drop data were gathered for flows from 1 mL/min to 10 mL/min, which were similar to theoretical values (Fig 3). While the R2R manufacturing system successfully created the prototype 27-layer µAL, the device exhibited some internal fluid pooling and layer-to-layer leaks during fluidic testing. Both issues are believed to be caused by inadequate localized layer-to-layer adhesion. We plan to remedy these issues in the coming months. Conclusion: This roll-to-roll manufacturing system is designed to manufacture the first large surface-area microfluidic devices that are impractical to manufacture by conventional means. This can be employed for large-scale membrane gas exchange such as human-scale µALs.Figure 1. (A) An automated roll to roll manufacturing system for silicone. The path of the silicone is shown in green. The silicone comes on a protective PET backing, which is removed and highlighted in cyan. (B) Confocal scan of engraved Silpuran 2030. Channels were 60 µm deep, and 180 µm wide.Figure 2. (A) Finished device, with custom housing (B) Device with colored water being routed through. Red arrows depict blood connections, and blue arrows depict gas connections. Two of the blood outlets filled with blue dye, and there is a dark blue region indicating imperfect layer-to-layer bonding resulting in leaking.Figure 3. Experimental vs theoretical pressure drop across the μAL (water)

P44: Toward 3D-Printed Microfluidic Artificial Lungs with Complex, Biomimetic Geometries

Purpose: Current hollow-fiber oxygenators used in Extracorporeal Membrane Oxygenation have suboptimal gas exchange performance and hemocompatibility. Microfluidic artificial lungs (µALs) promise smaller feature sizes, improving gas exchange efficiency, and biomimetic flow paths, improving blood compatibility. For the first time, we leverage the geometric freedom of 3D-printing technology to demonstrate µALs with truly 3D, biomimetic branching capillaries and gas-side designs to increase gas exchange surface area. Methods: Two µAL designs were generated in Solidworks and printed on an Asiga MAX X27 UV printer. The first was a “simple branching” µAL (Fig 1A) with quadfurcating, biomimetic branching for blood distribution. The second was a “hatched” µAL (Fig 1B) employing a gas phase with strategically placed supports to maximize gas exchange surface area while maintaining structural stability. These changes are only to the gas, and so the blood-phase is unchanged. Dyed water was used to visualize internal structures (Fig 1D). Geometric analysis and proven models were used to calculate theoretical shear rate and rated flow. Computational Fluid Dynamics (CFD) was used to visualize flow (Fig 1E,F). Experimental pressure drop vs water flow rates were measured (Fig 2). Results: Through geometric analysis (Table 1), branching distribution technique provides more uniform shear stress (0.95-1.34 dyn/cm2) compared to a non-branching “open-plenum” control (0.09-1.27 dyn/cm2). The hatched µAL has a 3.18 mL/min rated flow, 1.7x greater than the 1.84 mL/min rated flow of the non-hatched branching µAL. As a result of the higher rated flow, it also has higher theoretical shear of 1.64-2.31 dyn/cm2 (at rated flow) despite identical blood-side geometry. The branching lung demonstrated a pressure drop up to 12 mmHg at flows up to 5 mL/min (Fig 2). These are significantly larger than analytically predicted values (extrapolated 7 mmHg vs 0.233 mmHg at 3.2 mL/min), prompting investigation into resolution of internal capillaries and effects of surface roughness on pressure drop. Conclusion: We have demonstrated the first 3D-printed branching biomimetic µAL formed from a gas permeable material, with gas-side geometries to improve gas exchange efficiency. These geometries are expected to translate to greater blood flows enabling creation of future animal and human-scale µALs. Table 1. Theoretical calculations. All uALs have 256 8.5mm long 216x324 µm blood and gas channels, with 54 µm-thick membranes. They differ in their effective gas exchange area, and blood distribution method, resulting in differing rated flows, shears, and pressure drops. The Branching uAL employs a branching distribution, resulting in a much tighter shear stress range. The GasHatch uAL employs both a branching distribution, and a blood-gas geometric-synchronization, with 100% rather than 58% of the gas-exchange capillary face being used for gas exchange. Values for a theoretical “control” lung (not fabricated; contains an open plenum/ non-branching distribution region) are displayed for comparison. Flow velocity and shear stresses are calculated separately for capillary and distribution areas.Figure 1. Blood flows are indicated using red arrows, and gas flows are indicated using blue arrows. (A) Design of simple (non-hatched) branched μAL. (B) Close-up of the hatched μAL capillaries and gas channels, showing how gas-side supports are only in regions not adjacent to capillaries and therefore not reducing gas exchange surface area. (C) Hatched μAL with the gas phase filled with blue dye for visualization. (D) Non-hatched branching μAL with blood phase filled with blue dye, and gas phase filled with red dye. (E) CFD visualization of flow velocities in the branching blood distribution network; (F) CFD analysis of pressure drop in the biomimetic blood distribution channels.Figure 2. Pressure drop of branching µALs (water; n=3)

BIO13: Effect of Artificial Lung Fiber Bundle Geometric Design on Micro- and Macro-scale Clot Formation

Purpose of Study: The hollow fiber membrane bundle is the functional component of artificial lungs, transferring oxygen and carbon dioxide to and from the blood. It is also the primary location of blood clot formation and propagation in these devices. The geometric design of fiber bundles is defined by a narrow range of parameters that determine gas exchange efficiency and blood flow resistance, such as fiber packing density, path length, and frontal area. However, these parameters also affect thrombosis. Methodology: This study investigated the effect of these parameters on clot formation using 3-D printed flow chambers that mimic the geometry and blood flow patterns of fiber bundles. Hollow fibers were represented by an array of vertical micro-rods (380 micron diameter) arranged with varying packing densities (40, 50, and 60%) and path lengths (2 and 4 cm), all of which are fiber bundle parameters in commercially available artificial lung devices. Blood was pumped through the device corresponding to three mean blood flow velocities (16, 20, and 25 cm/min), which were scaled from 4 L/min flowrates in an Adult Quadrox oxygenator. Results: Results showed that (1) clot formation decreases dramatically with decreasing packing density and increasing blood flow velocity, (2) clot formation at the outlet of fiber bundle enhances deposition upstream, and consequently (3) greater path length provides more clot-free fiber surface area for gas exchange than a shorter path length. Summary: These results can be used to create less thrombogenic, more efficient artificial lung designs.Figure 1. a) The experimental flow chamber was designed to be 2 or 4 cm and with a packing density of 60%, 50% or 40% rods to simulate the flow path of blood through an artificial lung hollow fiber bundle. (b) The flow circuit involved one-way flow from a syringe pump, connected to the flow chamber and then to a waste container. A manometer measured the pressure drop across each experimental device. (c) The averaged clot volumes from the microCT scans show more clot (red) at the outlets of all devices. There was also less clot in the chambers with a longer path length device, faster flow rate, and less density.

Absence of aluminium compromises root integrity, reduces leaf hydration and Rubisco performance in Qualea grandiflora, an Al-accumulating species.

Aluminium (Al) is toxic to most plants. Nevertheless, some species accumulate Al without showing toxicity symptoms. Previous studies have evidenced Al in chloroplasts of Al-accumulating species from the Cerrado vegetation in South America. We ask whether Al increases carbon assimilation through enhanced apparent efficiency of Rubisco. Seedlings of the Al-accumulator Qualea grandiflora (Vochysiaceae) were grown in nutrient solution with 0, 740, and 1480 μm Al. Growth parameters, relative leaf water content, Al concentration in organs, gas exchange and apparent carboxylation efficiency (measured from A/Ci curves) were evaluated for 60 days. Plants without Al showed no root growth, necrotic roots, low gas exchange rates, and decreased apparent carboxylation efficiency. Al-treated plants, however, showed new white roots and increased root biomass leading to higher leaf hydration, and apparent carboxylation efficiency was higher in these plants. Increased Al available in the nutrient solution increased Al accumulation in plant organs. Absence of Al compromised root integrity in Q. grandiflora, thus limiting leaf hydration. No positive direct effect of Al on Rubisco was evidenced in Al-treated plants.

Ecophysiology of Mentha piperita under saline stress and biostimulant in the Brazilian semiarid region

Brazilian semiarid region has water with high levels of salts that limit its use in agriculture, necessitating the adoption of strategies to reduce the impact of salinity. The objective of this study was to assess the effect of a biostimulant as a attenuating of mitigate saline stress on the growth, gas exchange, chlorophyll indices, and chlorophyll a fluorescence of Mentha piperita. The experiment was performed using a randomized block design, employing a 5 × 5 incomplete factorial schemes. This involved five different electrical conductivities of the irrigation water (ECw = 0.5, 1.01, 2.25, 3.49, and 4.00 dS m-1) and five doses of the biostimulant (Stimulate® = 0.0, 1.45, 5.00, 8.55, and 10.0 mL L-1). In total, nine combinations were generated using the Central Composite Design. Growth, gas exchange, chlorophyll indices, and chlorophyll a fluorescence were evaluated 45 days after irrigation with saline water. The results indicated that saline stress hindered the growth, gas exchange, chlorophyll indices, and photochemical efficiency of M. piperita. However, the biostimulant mitigated the adverse effects of salinity on the growth, gas exchange, and photochemical efficiency of M. piperita.

Tension controlled hollow-fiber winding machine for blood oxygenator prototypes

Blood oxygenators involve a complex network of hollow fibers for efficient gas exchange with blood. The optimal microstructural arrangement of these fibers is an ongoing research interest. While the fiber systems of commercial oxygenators are manufactured to address mass production, the research oxygenator prototypes demand more flexibility so that different design parameters can be tested. Here a hollow-fiber assembly system is designed and built for winding research grade extracorporeal blood oxygenator mandrels at different layout dimensions so that these different configurations can be evaluated for mass transfer capacity and blood damage. The hardware design and manufacturing details of this system presented together with its impact on the prototype oxygenator device assembly process. This in-house built system can wind thin fibers, having outer diameters ranging from 100 μm to 1 mm, at any specified winding angle continuously. A control system for fiber stress is also incorporated to eliminate fiber damage. Our system consists of three main units: (1) unwinding, (2) accumulator, and (3) winding systems, integrated together via the control software. The unwinding unit has a PID controller to maintain the position of the accumulator motor on the reference point by tuning the velocity of feeding fibers to the accumulator unit. Another PID controller preserves the desired tension value of the fibers by adjusting the position of the accumulator motor. Desired tension value is defined by the user and typically obtained through uniaxial testing of fibers. The control unit employs a “cascaded” PID controller since the PID controller in the accumulator unit maintains the tension and the PID controller in the unwinding unit controls the position of the accumulator motor. Finally, the winding unit utilizes two motors to wind the fibers over the outer diameter of a mandrel at the desired winding angle. The first motor drives the translational movement, and the second one provides mandrel rotation. The desired angles are achieved by tuning the synchronous movement of the winding motors. While the system is designed to produce assembled blood oxygenator mandrel prototypes, this concept is also applicable for producing cylindrical fiber-reinforced composite materials with specified fiber angles and stents winded on jigs.

GO nanoparticles mitigate the negative effects of salt and alkalinity stress by enhancing gas exchange and photosynthetic efficiency of strawberry plants

Considering the potential use of nanomaterials, particularly carbon-based nanostructures, in agriculture, we conducted a study to investigate the effect of graphene oxide (GO) on strawberry plants under salinity and alkalinity stress conditions. We used GO concentrations of 0, 2.5, 5, 10, and 50 mg/L, and applied stress treatments at three levels: without stress, salinity (80 mM NaCl), and alkalinity (40 mM NaHCO3). Our results indicate that both salinity and alkalinity stress negatively impacted the gas exchange parameters of the strawberry plants. However, the application of GO significantly improved these parameters. Specifically, GO increased PI, Fv, Fm, and RE0/RC parameters, as well as chlorophyll and carotenoid contents in the plants. Moreover, the use of GO significantly increased the early yield and dry weight of leaves and roots. Therefore, it can be concluded that the application of GO can enhance the photosynthetic performance of strawberry plants, and improve their resistance to stress conditions.

Short and long-term acclimation to water status at leaf and plant level of fungus-tolerant genotypes

Today’s viticulture faces the double challenge of reducing chemical input while adapting plant material to future climate conditions. Adopting fungus disease-tolerant varieties appears to be a long-term solution as long as they are performant under abiotic constraints, such as drought. This study aimed to study the effects of water deficit (WD) and characterise the different strategies adopted to cope with drought in six new fungus disease-tolerant varieties selected by INRAE compared to Syrah. During five consecutive seasons (2018 to 2022), a gradient of WD was applied in field conditions and monitored through vine predawn water potential measurements. Grape development was non-destructively tracked by imaging to determine the arrest of berry phloem unloading. All variables were collected at the single plant level. The impacts of WD on leaf gas exchange and intrinsic water use efficiency (WUEi), vegetative development and yield components were assessed, as well as the genotypic sensitivity to WD at the leaf, vegetative and reproductive levels. All variables were negatively impacted by WD, except for intrinsic water use efficiency and total non-structural carbohydrate concentrations. Genotypes were differently impacted by WD at the physiological and vegetative levels, while no genotype-dependent response was observed for most reproductive variables. Generally, genotypes with the highest potential (highest intercept) in a certain variable were also the most sensitive to water deficit (higher slope). The most sensitive genotype regarding physiological and reproductive variables was G5, which showed higher reductions in berry weight, photosynthesis and WUEi, contrasting with Syrah, 3159B and Floreal. In this study, we observed a diversity of strategies to cope with WD in the long term, where some genotypes opted to reduce most variables (G5 and Artaban) or to maintain functioning at higher levels (Syrah and 3176N). Others displayed mixed responses: either reducing vegetative growth more than yield (3159B) or vice-versa (G14).

Improved ventilation efficiency due to continuous gas flow compared to decelerating gas flow in mechanical ventilation: results of a porcine trial.

In pressure-controlled ventilation (PCV), a decelerating gas flow pattern occurs during inspiration and expiration. In contrast, flow-controlled ventilation (FCV) guarantees a continuous gas flow throughout the entire ventilation cycle where the inspiration and expiration phases are simply performed by a change of gas flow direction. The aim of this trial was to highlight the effects of different flow patterns on respiratory variables and gas exchange. Anesthetized pigs were ventilated with either FCV or PCV for 1 h and thereafter for 30 min each in a crossover comparison. Both ventilation modes were set with a peak pressure of 15 cmH2O, positive end-expiratory pressure of 5 cmH2O, a respiratory rate of 20/min, and a fraction of inspired oxygen at 0.3. All respiratory variables were collected every 15 min. Tidal volume and respiratory minute volume were significantly lower in FCV (n = 5) compared with PCV (n = 5) animals [4.6 vs. 6.6, MD -2.0 (95% CI -2.6 to -1.4) mL/kg; P < 0.001 and 7.3 vs. 9.5, MD -2.2 (95% CI -3.3 to -1.0) L/min; P = 0.006]. Notwithstanding these differences, CO2-removal as well as oxygenation was not inferior in FCV compared with PCV. Mechanical ventilation with identical ventilator settings resulted in lower tidal volumes and consecutive minute volume in FCV compared with PCV. This finding can be explained physically by the continuous gas flow pattern in FCV that necessitates a lower alveolar pressure amplitude. Interestingly, gas exchange was comparable in both groups, which is suggestive of improved ventilation efficiency at a continuous gas flow pattern.NEW & NOTEWORTHY This study examined the effects of a continuous (flow-controlled ventilation, FCV) vs. decelerating (pressure-controlled ventilation, PCV) gas flow pattern during mechanical ventilation. It was shown that FCV necessitates a lower alveolar pressure amplitude leading to reduced applied tidal volumes and consequently minute volume. Notwithstanding these differences, CO2-removal as well as oxygenation was not inferior in FCV compared with PCV, which is suggestive of improved gas exchange efficiency at a continuous gas flow pattern.

Effect of hollow fiber configuration and replacement on the gas exchange performance of artificial membrane lungs

Artificial membrane lungs are composed of hollow fiber membranes. Blood flows with low velocities in the membrane bundle, forming a laminar boundary layer near the membrane surfaces that limits gas transfer. Passive blood mixing within the fiber array is utilized to overcome this limitation. Nevertheless, it is unclear to which extent blood mixing and fiber configuration contribute to the performance of membrane oxygenators.This study aims to evaluate the effect of fiber configuration and replacement on the gas exchange performance of membrane oxygenators to contribute to a better understanding of the influence of blood mixing to gas transfer and the mechanisms of gas exchange in blood. Furthermore, designs in which hollow fibers of different functions could be combined in highly integrated membrane lungs are provided.We analyzed the gas transfer performance of membrane oxygenators in a perpendicular configuration with 100%, 75%, or 50% of fibers open, and in a crossed configuration with 100% or 67% of fibers open. 95%–100% of the oxygen transfer of a fully open oxygenator could be maintained in our prototypes with 25% of gas exchange fibers closed in a perpendicular configuration, indicating that several fibers contributed to gas exchange by mixing the blood flow. Closing fibers in a perpendicular configuration resulted in a lower decrease in oxygen transfer. This study contributes to the development of novel membrane oxygenators integrating fibers of different functionalities (e.g. oxygenation and dialysis) maintaining high gas exchange efficiency.

Airway allergy causes alveolar macrophage death, profound alveolar disorganization and surfactant dysfunction.

Respiratory disorders caused by allergy have been associated to bronchiolar inflammation leading to life-threatening airway narrowing. However, whether airway allergy causes alveolar dysfunction contributing to the pathology of allergic asthma remains unaddressed. To explore whether airway allergy causes alveolar dysfunction that might contribute to the pathology of allergic asthma, alveolar structural and functional alterations were analyzed during house dust mite (HDM)-induced airway allergy in mice, by flow cytometry, light and electron microscopy, monocyte transfer experiments, assessment of intra-alveolarly-located cells, analysis of alveolar macrophage regeneration in Cx3cr1 cre:R26-yfp chimeras, analysis of surfactant-associated proteins, and study of lung surfactant biophysical properties by captive bubble surfactometry. Our results demonstrate that HDM-induced airway allergic reactions caused severe alveolar dysfunction, leading to alveolar macrophage death, pneumocyte hypertrophy and surfactant dysfunction. SP-B/C proteins were reduced in allergic lung surfactant, that displayed a reduced efficiency to form surface-active films, increasing the risk of atelectasis. Original alveolar macrophages were replaced by monocyte-derived alveolar macrophages, that persisted at least two months after the resolution of allergy. Monocyte to alveolar macrophage transition occurred through an intermediate stage of pre-alveolar macrophage and was paralleled with translocation into the alveolar space, Siglec-F upregulation, and downregulation of CX3CR1. These data support that the severe respiratory disorders caused by asthmatic reactions not only result from bronchiolar inflammation, but additionally from alveolar dysfunction compromising an efficient gas exchange.

On the significance of group III/IV muscle afferent feedback for the control of breathing and gas exchange efficiency during prolonged locomotor exercise

Introduction: By projecting to medullary respiratory center, group III/IV muscle afferents determine the ventilatory response during short (~3 min) bouts of locomotor exercise. However, their significance for the hyperpneic response, gas exchange efficiency, and arterial oxygenation during exercise of longer durations (&gt;15min) remains unknown. Methods: On 2 separate days, 8 healthy subjects (22±3yrs, 4 f) performed two 20-min bicycling bouts at 30% (~50% V̇O2max) and 50% (~75% V̇O2max) of peak power (Wpeak) under a) control condition (intact leg muscle afferent feedback; CTRL), and b) lumbar intrathecal fentanyl (attenuated group III/IV leg muscle afferent feedback; FENT). Ventilation (V̇E) and gas exchange were continuously recorded, data averaged over the last min of each bout. Arterial blood samples (radial catheter) were used to determine O2 and CO2 partial pressures (PaO2 and PaCO2) and O2 saturation (HbO2). Alveolar O2 pressure (PAO2) was calculated, pulmonary gas exchange efficiency was evaluated using the alveolar-to-arterial O2 difference (A-aDO2) and the arterial-to-end-tidal PCO2 difference (PaCO2-PETCO2). Results: Fentanyl had no effect at rest. There was no difference in V̇O2, V̇CO2, and VT between CTRL and FENT. However, during FENT vs CTRL, V̇E (30 % Wpeak: 42±9 vs 46±8 L/min; 50 %Wpeak: 75±12 vs 71±12), f R (30 %: 25±3 vs 28±4b/min; 50%: 33±5 vs 35±5), V̇E/V̇O2 (30%: 25±3 vs 28±3; 50 %: 29±5 vs 32±4), V̇E/V̇CO2 (30 %: 31±4 vs 34±4; 50 %: 34±5 vs 37±5), PAO2 (30 %: 94±3 vs 97±5 mmHg; 50 %: 98±3 vs 100±4), PaO2 (30%: 84±5 vs 90±3 mmHg; 50%: 84±7 vs 88±4), HbO2 (30 %: 95±1 vs 96±1 %; 50 %: 95±2 vs 96±1 %), VD/VT (30 %: 0.18±0.04 vs 0.22±0.08; 50 %: 0.16±0.05 vs 0.21±0.07), and the PaCO2-PETCO2 difference (30 %: -2.6±1.6 vs -1.4±2.1 mmHg; 50 %: -2.8±2.4 vs -1.0±2.1) were lower ( P&lt;0.05), while PaCO2 (30 %: 33±3 vs 31±3 mmHg; 50 %: 30±3 vs 29±3) and A-aDO2 (30 %: 9±3 vs 5±5 mmHg; 50 %: 14±5 vs 10±5) were greater ( P&lt;0.05). Conclusions: In addition to regulating the initial ventilatory response, tonic feedback from group III/IV muscle afferents remains a key determinant of the pulmonary response during prolonged locomotor exercise. The relative importance of these sensory neurons for optimizing exercise hyperpnea is emphasized by the fact that the pulmonary response to bicycling with attenuated sensory feedback remains inadequate despite concomitant increases in potent ventilatory stimuli (↑PaCO2, ↓PaO2). We conclude that group III/IV muscle afferent feedback is critical for matching the pulmonary response to the metabolic cost of locomotion and for perpetually optimizing gas exchange efficiency and arterial oxygenation during longer exercise. National Heart, Lung, and Blood Institute (HL-116579), U.S. Veterans Affairs Rehabilitation Research and Development (E3343-R) 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.

Advanced hemocompatible polyethersulfone composite artificial lung membrane with efficient CO2/O2 exchange channel constructed by modified carbon nanotubes network

Artificial lung membranes as the core module of the extracorporeal membrane oxygenation technology (ECMO) execute the function of extracorporeal blood-gas barrier accomplishing CO2/O2 exchange with blood. However, the unsatisfactory hemocompatibility and difficulty in functionalization are the prominent challenges faced by current artificial lung membrane materials. In this study, polyethersulfone (PES) composite membranes with self-anticoagulant property and high gas exchange efficient are fabricated by blending PES matrix with poly(vinylamine) (PVAm) modified carboxylic carbon nanotubes (mCNTs) and citrate-based poly(octamethylene-citrate) (POC) pre-polymers. The mCNTs construct specific gas transfer channels within the composite membranes to enhance the gas permeability, while the POC pre-polymers provide anticoagulant property based on the chelation to blood Ca2+ and the inactivation effect to intrinsic coagulation factors. Importantly, directed by the actual ECMO gas exchange mode, we design a gas-liquid convectional circulation device that could evaluate gas exchange efficiency for the composite membranes under mimetic ECMO state. Therefore, this strategy not only proposes a new design method of advanced artificial lung membranes to solve the practical challenges in the current ECMO technology, but also establishes a scientific testing method to evaluate the gas exchange performance for new-type artificial lung membrane materials in the future.