O2 Exchange Research Articles

Effects of Temperature, Dissolved Oxygen Concentration, and Photosynthetic Photon Flux Density on the Growth of the Sea Bivalve Tridacna crocea in Combination with the Symbiotic Alga Zooxanthella

The sea bivalve clam Tridacna crocea inhabiting the shallow sea of tropical and subtropical zones lives with the symbiotic alga zooxanthella in its mantle. Zooxanthellae algae perform photosynthesis and supply nutrients to T. crocea. Recently, the abundance of T. crocea has decreased rapidly due to overfishing in coastal areas in Okinawa, Japan. T. crocea culture systems for mass production will contribute to the conservation of T. crocea and thus marine ecosystems. Environmental control methods for T. crocea culture have not been established because of a lack of knowledge about the appropriate environmental conditions for T. crocea growth. The present study was initiated to obtain basic data for developing environmental control methods for T. crocea land-based aquaculture. The effects of water temperature, dissolved oxygen concentration, and photosynthetic photon flux density (PPFD) on the O2 exchange rates of the symbiotic system of T. crocea and zooxanthella, which are indicators of photosynthesis and respiration in the system, and the effect of daily integrated PPFD on T. crocea growth were investigated. Basic knowledge was obtained for the development of optimal environmental control technology for T. crocea clam culture. The optimum water temperature and dissolved oxygen concentration for photosynthesis in this symbiotic system were 28 °C, 5–6 mgO2 L−1 and 500 μmol m−2 d−1, respectively. The optimum daily integrated PPFD for clam growth was 20 mol m−2 d−1.

Various Cultivars of Citrus Fruits: Effects of Construction on Gas Diffusion Resistance and Internal Gas Concentration of Oxygen and Carbon Dioxide

Various cultivars of citrus fruits have unique constructions, such as thick outer skin. These constructions generate gas diffusion resistance between the atmosphere and the fruit, which can limit the gas exchange of O2 and CO2.This has not been sufficiently investigated. This study on seven cultivars of citrus fruit firstly aimed to investigate gas diffusion resistance utilizing the ethane efflux method; secondly, this study aimed to investigate the internal gas concentration of O2 and CO2. As a result, a cultivar of citrus fruit with slimmer outer skin thickness had lower resistance. For the internal gas, a high CO2 concentration in comparison with the atmosphere was observed even in the fruits with the minimum resistance, and no considerable difference was observed among all cultivars, regardless of the gas diffusion resistance value. However, when the fruits were stored at 25 °C for 2 weeks, CO2 gas concentration tended to increase and O2 gas concentration tended to decrease, with an increase in the resistance value. Therefore, when the respiration of citrus fruits is activated at ambient temperature, the self-control system of internal gas concentration can be driven to suppress the respiration which was induced by gas diffusion resistance generated from their construction.

Polypropylene membrane with gradient-distributed covalent organic framework for highly efficient blood oxygenation

Hollow fiber membrane (HFM) is widely used for extracorporeal membrane oxygenator (ECMO) because of large membrane area, high packing density, self-supporting structure and good flexibility. However, polymeric HFMs often suffer from a trade-off between gas permeability and anti-plasma leakage performance. In this study, HFMs with gradient structure were prepared by introducing COF-42 as fillers into the polypropylene (PP) matrix through surface segregation. The enriched COF-42 near the upper surface endowed the membrane a gradient structure to reduce the plasma leakage and improve gas permeability. Compared with PP membranes, PP/COF-42 oxygenation membranes retained good blood compatibility and higher mechanical properties. The PP/COF-42–0.5 HFMs exhibited O2 exchange rate of ∼ 342.6 ml min−1 m−2 and CO2 exchange rate of ∼ 989.6 ml min−1 m−2, which was about 218.7 % and 15.4 % larger than that of the PP HFMs, respectively. Moreover, the simulated plasma leakage time could reach 124 h, which was about 21 times longer than that of PP HFMs. The membranes exhibited excellent blood oxygenation performance and anti-plasma leakage performance, which had great potential in ECMO.

A Reduced Resistance, Concentric-Gated Artificial Membrane Lung for Pediatric End-Stage Lung Failure.

The goal of the low-resistance pediatric artificial lung (PAL-LR) is to serve as a pumpless bridge-to-transplant device for children with end-stage lung failure. The PAL-LR doubles the exposed fiber length of the previous PAL design. In vitro and in vivo studies tested hemocompatibility, device flow, gas exchange and pressure drop performance. For in vitro tests, average rated blood flow (outlet SO2 of 95%) was 2.56 ± 0.93 L/min with a pressure drop of 25.88 ± 0.90 mm Hg. At the targeted pediatric flow rate of 1 L/min, the pressure drop was 8.6 mm Hg compared with 25 mm Hg of the PAL. At rated flow, the average O2 and CO2 transfer rates were 101.75 ± 10.81 and 77.93 ± 8.40 mL/min, respectively. The average maximum O2 and CO2 exchange efficiencies were 215.75 ± 22.93 and 176.99 ± 8.40 mL/(min m2), respectively. In vivo tests revealed an average outlet SO2 of 100%, and average pressure drop of 2 ± 0 mm Hg for a blood flow of 1.07 ± 0.02 L/min. Having a lower resistance, the PAL-LR is a promising step closer to a pumpless artificial membrane lung that alleviates right ventricular strain associated with idiopathic pulmonary hypertension.

Biomimetic nanoporous oxygenation membranes with high hemocompatibility and fast gas transport property

Membrane technology holds great potential for separation applications and also finds critical needs in biomedical fields, such as blood oxygenation. However, the bottlenecks in gas permeation, plasma leakage, and especially hemocompatibility hamper the development of membrane oxygenation. It remains extremely challenging to design efficient membranes and elucidate underlying principles. In this study, we report biomimetic decoration of asymmetric nanoporous membranes by ultrathin FeIII-tannic acid metal–ligand networks to realize fast gas exchange with on plasma leakage and substantially enhance hemocompatibility. Because the intrinsic nanopores facilitate gas permeability and the FeIII-catechol layers enable superior hydrophilicity and electronegativity to original surfaces, the modified membranes exhibit high transport properties for gases and great resistances to protein adsorption, platelet activation, coagulation, thrombosis, and hemolysis. Molecular docking and density functional theory simulations indicate that more preferential adsorption of metal–ligand networks with water molecules than proteins is critical to anticoagulation. Moreover, benefiting from the better antiaging property gave by biomimetic decoration, the membranes after four-month aging present gas permeances similar to or even larger than those of pristine ones, despite the initial permeation decline. Importantly, for blood oxygenation, the designed membranes after aging show fast O2 and CO2 exchange processes with rates up to 28–17 and 97–47 mL m−2 min−1, respectively, accompanied with no detectable thrombus and plasma leakage. We envisage that the biomimetic decoration of nanoporous membranes provide a feasible route to achieve great biocompatibility and transport capability for various applications.

Net O2 exchange rates under dark and light conditions across different stem compartments.

Woody plants display some photosynthetic activity in stems, but the biological role of stem photosynthesis and the specific contributions of bark and wood to carbon uptake and oxygen evolution remain poorly understood. We aimed to elucidate the functional characteristics of chloroplasts in stems of different ages in Fraxinus ornus. Our investigation employed diverse experimental approaches, including microsensor technology to assess oxygen production rates in whole stem, bark, and wood separately. Additionally, we utilized fluorescence lifetime imaging microscopy (FLIM) to characterize the relative abundance of photosystems I and II (PSI : PSII chlorophyll ratio) in bark and wood. Our findings revealed light-induced increases in O2 production in whole stem, bark, and wood. We present the radial profile of O2 production in F. ornus stems, demonstrating the capability of stem chloroplasts to perform light-dependent electron transport. Younger stems exhibited higher light-induced O2 production and dark respiration rates than older ones. While bark emerged as the primary contributor to net O2 production under light conditions, our data underscored that wood chloroplasts are also photosynthetically active. The FLIM analysis unveiled a lower PSI abundance in wood than in bark, suggesting stem chloroplasts are not only active but also acclimate to the spectral composition of light reaching inner compartments.

Red Blood Cell Hemoglobin Oxygen Transfer in Deep-Diving Marine Mammals

Objective: Some marine mammals of the order pinniped and cetacean can dive for long durations to forage for food and travel over distances. During these extended dives both pinnipeds and cetaceans experience extreme tissue hypoxia. Numerous adaptations have evolved to allow these species to effciently deliver and utilize oxygen (O2). One genetic difference, which our laboratory has proposed to play an important role in O2 transport effciency in modern hominids, is the inactivation of the CMP-Neu5AC hydroxylase (CMAH) gene. Pinnipeds inactivated Cmah ~ 40 million years ago but, cetaceans still express this N-glycan modifying enzyme. CMAH converts the sialic acid, N-acetylneuraminic acid (Neu5Ac), to its hydroxylated form, N-glycolylneuraminic acid (Neu5Gc). These sialic acids are located at the end of branched sugar chains on the surface of cell membranes. As a result, a change in composition could affect cell membrane charge and hydrophobicity, as well as potentially alter O2 diffusion laterally or across cell membranes. Hypothesis: In this study we hypothesized that O2 transfer from hemoglobin (Hb) in red blood cells (RBCs) to myoglobin (Mb) would differ between cetaceans (CMAH+) and pinnipeds (CMAH-). Methods: This hypothesis was tested using optical absorption spectroscopy to measure O2 exchange between oxygenated Hb in RBC and deoxygenated Mb collected in several species of mustelids and pinniped (CA sea otter, CA sea lion, and walrus) and cetaceans (Bottlenose Dolphin, Beluga, and Orca). Measurements of cell diameters (diffusion length) were also measured. Results: The mean oxygen transfer (O2D/A410) was 47% lower in pinnipeds than cetaceans (p<0.01). The amount of O2 transferred in cetaceans increased with longer reported maximal dive durations. There was a trend for overall RBC diameters to be larger in cetaceans than pinnipeds (p=0.054). Summary: The RBC O2 transfer data in these hypoxia tolerant marine mammals suggest a transfer mechanism that is more effcient in cetaceans in a normoxic environment. Conclusions: More effcient oxygen transfer in cetaceans, who retained the Cmah gene, compared to pinnipeds and mustelids, who did not retain the Cmah gene, suggests that the gene knockout may not be the only factor that facilitates delivery of O2 in these marine mammals. A trend for larger RBC diameters in cetaceans than pinnipeds also suggests that diffusion length is not a main contributing factor. Future experiments to measure oxygen transfer from RBC O2-Hb to Mb under different O2 environments are needed to more closely model what may occur during long duration dives. NSF1929325. This is the full abstract presented at the American Physiology Summit 2024 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.

Contrasting effects of increasing dissolved iron on photosynthesis and O2 availability in the gastric cavity of two Mediterranean corals.

Iron (Fe) plays a fundamental role in coral symbiosis, supporting photosynthesis, respiration, and many important enzymatic reactions. However, the extent to which corals are limited by Fe and their metabolic responses to inorganic Fe enrichment remains to be understood. We used respirometry, variable chlorophyll fluorescence, and O2 microsensors to investigate the impact of increasing Fe(III) concentrations (20, 50, and 100 nM) on the photosynthetic capacity of two Mediterranean coral species, Cladocora caespitosa and Oculina patagonica. While the bioavailability of inorganic Fe can rapidly decrease, we nevertheless observed significant physiological effects at all Fe concentrations. In C. caespitosa, exposure to 50 nM Fe(III) increased rates of respiration and photosynthesis, while the relative electron transport rate (rETR(II)) decreased at higher Fe(III) exposure (100 nM). In contrast, O. patagonica reduced respiration, photosynthesis rates, and maximum PSII quantum yield (Fv/Fm) across all iron enrichments. Both corals exhibited increased hypoxia (<50µmol O2 L-1) within their gastric cavity at night when exposed to 50 and 100 nM Fe(III), leading to increased polyp contraction time and reduced O2 exchange with the surrounding water. Our results indicate that C. caespitosa, but not O.patagonica, might be limited in Fe for achieving maximal photosynthetic efficiency. Understanding the multifaceted role of iron in corals' health and their response to environmental change is crucial for effective coral conservation.

Investigating trees as an interdisciplinary phenomenon in climate regulation: an intervention study on iSTEM education and scientific literacy in secondary schools

ABSTRACT Climate change and CO2-emissions are key-issues of the 21st century. As a complex interdisciplinary phenomenon, educational systems appear to be forced to expand their curricula beyond disciplines or school subjects. Thus, cross-disciplinary concepts in science, such as iSTEM (integrated science, technology, engineering, and mathematics) address this demand. Also, the Organisation for Economic Co-operation and Development (OECD) stresses the need for interdisciplinarity in compulsory education. The present intervention study ‘CO2BS - Coole Bäume und Sensoren [Cool(ing) Trees and Sensors]’ focuses on the tree as a key-factor in the understanding of gas-exchange for which a proper scientific understanding demands thinking across disciplines. In accordance with a OECD competence framework, Scientific Literacy, the intervention aimed to foster secondary school students’ interdisciplinary conceptual knowledge (ICK) of how a tree’s exchange of O2 and CO2 can be investigated scientifically. Students’ changes in self-concept in science as well as their interest in climate and science along with epistemic emotions associated with scientific procedures were also investigated. The results showed positive changes in students’ self-concept and epistemic emotions. Though ICK increased significantly too, the results indicate that future interventions will need to focus more on how to establish interdisciplinarity within secondary education more effectively.

83 Automated PDMS Engraving and Assembly of a Prototype Microfluidic Artificial Lung

OBJECTIVES/GOALS: We report an automated manufacturing system, and a series of cylindrical multi-layer microfluidic artificial lungs manufactured with the system and tested for fluidic fidelity and function. METHODS/STUDY POPULATION: A Roll-to-Roll (R2R) system to engrave multiple-layer devices was assembled. A 100 um-thick silicone sheet passes through an embedded CO2 laser engraver, which creates patterns of any geometry on the surface. The sheet is plasma-activated to create an irreversible bond, and rerolled into a processed device. Unlike typical applications of R2R, this process is synchronized to achieve consistent radial positioning. This allows the fluidics in the device to be accessed without being unwrapped. The result is a cylindrical core surrounded by many layers of microfluidic channels that can be accessed through the side of the device or through fluidic vias. This core is cut to expose the microfluidic layers, and then installed into a housing which routes the fluids into their respective microfluidic flow paths. RESULTS/ANTICIPATED RESULTS: To demonstrate the capabilities of the R2R manufacturing system, this method was used to manufacture multi-layer microfluidic artificial lungs (µALs). Gas and blood flow channels are engraved in alternating layers and routed orthogonally. The close proximity of gas and blood separated by gas-permeable PDMS permits CO2 and O2 exchange. Three µALs were successfully manufactured. Their flow paths were visualized using dyed water and checked for leaks. Then they were evaluated using water for pressure drop and CO2 gas-exchange. The top performing device had 15 alternating blood and gas layers. Test with whole blood demonstrated oxygenation from venous (70%) saturation levels to arterial (95%) saturation levels at a flow rate of 3 ml/min. DISCUSSION/SIGNIFICANCE: 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, most microfluidic artificial lungs only have small rated flows due to a lack of manufacturing processes able to create high surface area devices.

Probing the exchange of CO2 and O2 in the shallow critical zone during weathering of marl and black shale

Abstract. Chemical weathering of sedimentary rocks can release carbon dioxide (CO2) and consume oxygen (O2) via the oxidation of petrogenic organic carbon and sulfide minerals. These pathways govern Earth's surface system and climate over geological timescales, but the present-day weathering fluxes and their environmental controls are only partly constrained due to a lack of in situ measurements. Here, we investigate the gaseous exchange of CO2 and O2 during the oxidative weathering of black shales and marls exposed in the French southern Alps. On six field trips over 1 year, we use drilled headspace chambers to measure the CO2 concentrations in the shallow critical zone and quantify CO2 fluxes in real time. Importantly, we develop a new approach to estimate the volume of rock that contributes CO2 to a chamber, and assess effective diffusive gas exchange, by first quantifying the mass of CO2 that is stored in a chamber and connected rock pores. Both rock types are characterized by similar contributing rock volumes and diffusive movement of CO2. However, CO2 emissions differed between the rock types, with yields over rock outcrop surfaces (inferred from the contributing rock volume and the local weathering depths) ranging on average between 73 and 1108 tCkm-2yr-1 for black shales and between 43 and 873 tCkm-2yr-1 for marls over the study period. Having quantified diffusive processes, chamber-based O2 concentration measurements are used to calculate O2 fluxes. The rate of O2 consumption increased with production of CO2, and with increased temperature, with an average O2:CO2 molar ratio of 10:1. If O2 consumption occurs by both rock organic carbon oxidation and carbonate dissolution coupled to sulfide oxidation, either an additional O2 sink needs to be identified or significant export of dissolved inorganic carbon occurs from the weathering zone. Together, our findings refine the tools we have to probe CO2 and O2 exchange in rocks at Earth's surface and shed new light on CO2 and O2 fluxes, their drivers, and the fate of rock-derived carbon.

Roll-to-roll manufacturing of large surface area PDMS devices, and application to a microfluidic artificial lung.

The ability to cost-effectively produce large surface area microfluidic devices would bring many small-scale technologies such as microfluidic artificial lungs (μALs) from the realm of research to clinical and commercial applications. However, efforts to scale up these devices, such as by stacking multiple flat μALs have been labor intensive and resulted in bulky devices. Here, we report an automated manufacturing system, and a series of cylindrical multi-layer lungs manufactured with the system and tested for fluidic fidelity and function. A roll-to-roll (R2R) system to engrave multiple-layer devices was assembled. Unlike typical applications of R2R, the rolling process is synchronized to achieve consistent radial positioning. This allows the fluidics in the final device to be accessed without being unwrapped. To demonstrate the capabilities of the R2R manufacturing system, this method was used to manufacture multi-layer μALs. Gas and blood are engraved in alternating layers and routed orthogonally to each other. The proximity of gas and blood separated by gas permeable PDMS permits CO2 and O2 exchange via diffusion. After manufacturing, they were evaluated using water for pressure drop and CO2 gas exchange. The best performing device was tested with fresh whole bovine blood for O2 exchange. Three μALs were successfully manufactured and passed leak testing. The top performing device had 15 alternating blood and gas layers. It oxygenated blood from 70% saturation to 95% saturation at a blood flow of 3 mL min-1 and blood side pressure drop of 234 mmHg. This new roll-to-roll manufacturing system is suitable for the automated construction of multi-layer microfluidic devices that are difficult to manufacture by conventional means. With some upgrades and improvements, this technology should allow for the automatic creation of large surface area microfluidic devices that can be employed for various applications including large-scale membrane gas exchange such as clinical-scale microfluidic artificial lungs.

12 years of continuous atmospheric O2, CO2 and APO data from Weybourne Atmospheric Observatory in the United Kingdom

Abstract. We present a 12-year time series of continuous atmospheric measurements of O2 and CO2 at the Weybourne Atmospheric Observatory in the United Kingdom. These measurements are combined into the term atmospheric potential oxygen (APO), a tracer that is invariant to terrestrial biosphere fluxes. The CO2, O2 and APO datasets discussed are hourly averages between May 2010 and December 2021. We include details of our measurement system and calibration procedures, and describe the main long-term and seasonal features of the time series. The 2 min repeatability of the measurement system is approximately ±3 per meg for O2 and approximately ±0.005 ppm for CO2. The time series shows average long-term trends of 2.40 ppm yr−1 (2.38 to 2.42) for CO2, −24.0 per meg yr−1 for O2 (−24.3 to −23.8) and −11.4 per meg yr−1 (−11.7 to −11.3) for APO, over the 12-year period. The average seasonal cycle peak-to-peak amplitudes are 16 ppm for CO2, 134 per meg for O2 and 68 per meg for APO. The diurnal cycles of CO2 and O2 vary considerably between seasons. The datasets are publicly available at https://doi.org/10.18160/Z0GF-MCWH (Adcock et al., 2023) and have many current and potential scientific applications in constraining carbon cycle processes, such as investigating air–sea exchange of CO2 and O2 and top-down quantification of fossil fuel CO2.

A modeling approach to investigate drivers, variability and uncertainties in O2 fluxes and O2 : CO2 exchange ratios in a temperate forest

Abstract. The O2 : CO2 exchange ratio (ER) between terrestrial ecosystems and the atmosphere is a key parameter for partitioning global ocean and land carbon fluxes. The long-term terrestrial ER is considered to be close to 1.10 mol of O2 consumed per mole of CO2 produced. Due to the technical challenge in measuring directly the ER of entire terrestrial ecosystems (EReco), little is known about variations in ER at hourly and seasonal scales, as well as how different components contribute to EReco. In this modeling study, we explored the variability in and drivers of EReco and evaluated the hypothetical uncertainty in determining ecosystem O2 fluxes based on current instrument precision. We adapted the one-dimensional, multilayer atmosphere–biosphere gas exchange model “CANVEG” to simulate hourly EReco from modeled O2 and CO2 fluxes in a temperate beech forest in Germany. We found that the modeled annual mean EReco ranged from 1.06 to 1.12 mol mol−1 within the 5-year study period. Hourly EReco showed strong variations over diel and seasonal cycles and within the vertical canopy profile. The determination of ER from O2 and CO2 mole fractions in air above and within the canopy (ERconc) varied between 1.115 and 1.15 mol mol−1. CANVEG simulations also indicated that ecosystem O2 fluxes could be derived with the flux-gradient method using measured vertical gradients in scalar properties, as well as fluxes of CO2, sensible heat and latent energy derived from eddy covariance measurements. Owing to measurement uncertainties, however, the uncertainty in estimated O2 fluxes derived with the flux-gradient approach could be as high as 15 µmol m−2 s−1, which represented the 90 % quantile of the uncertainty in hourly data with a high-accuracy instrument. We also demonstrated that O2 fluxes can be used to partition net CO2 exchange fluxes into their component fluxes of photosynthesis and respiration if EReco is known. The uncertainty of the partitioned gross assimilation ranged from 1.43 to 4.88 µmol m−2 s−1 assuming a measurement uncertainty of 0.1 or 2.5 µmol m−2 s−1 for net ecosystem CO2 exchange and from 0.1 to 15 µmol m−2 s−1 for net ecosystem O2 exchange, respectively. Our analysis suggests that O2 measurements at ecosystem scale have the potential to partition net CO2 fluxes into their component fluxes, but further improvement in instrument precision is needed.

Seasonal Tropospheric Distribution and Air‐Sea Fluxes of Atmospheric Potential Oxygen From Global Airborne Observations

AbstractSeasonal change of atmospheric potential oxygen (APO ∼ O2 + CO2) is a tracer for air‐sea O2 flux with little sensitivity to the terrestrial exchange of O2 and CO2. In this study, we present the tropospheric distribution and inventory of APO in each hemisphere with seasonal resolution, using O2 and CO2 measurements from discrete airborne campaigns between 2009 and 2018. The airborne data are represented on a mass‐weighted isentropic coordinate (Mθe) as an alternative to latitude, which reduces the noise from synoptic variability in the APO cycles. We find a larger seasonal amplitude of APO inventory in the Southern Hemisphere relative to the Northern Hemisphere, and a larger amplitude in high latitudes (low Mθe) relative to low latitudes (high Mθe) within each hemisphere. With a box model, we invert the seasonal changes in APO inventory to yield estimates of air‐sea flux cycles at the hemispheric scale. We found a larger seasonal net outgassing of APO in the Southern Hemisphere (518 ± 52.6 Tmol) than in the Northern Hemisphere (342 ± 52.1 Tmol). Differences in APO phasing and amplitude between the hemispheres suggest distinct physical and biogeochemical mechanisms driving the air‐sea O2 fluxes, such as fall outgassing of photosynthetic O2 in the Northern Hemisphere, possibly associated with the formation of the seasonal subsurface shallow oxygen maximum. We compare our estimates with four model‐ and observation‐based products, identifying key limitations in these products or in the tools used to create them.

Engineering metal-covalent organic framework-based hybrid oxygenation membranes for facilitated blood-gas exchange

Oxygenation membranes operate as indirectly contacting barriers between blood and gas in extracorporeal membrane oxygenation (ECMO), improving oxygenation and removing carbon dioxide from blood. However, the low gas exchange efficiency of the current poly (4-methyl-1-pentene) (PMP) artificial lung membrane results in a high prime volume. Facilitated transport membrane is a fascinating strategy to construct high-performance membranes for blood-gas exchange. This study put forward hybrid strategy by using metal-covalent organic frameworks (MCOFs) to construct facilitated transport membrane of PMP flat membranes and hollow fiber membranes (HFMs) via thermally induced phase separation (TIPS) to achieve facilitated blood-gas exchange. Cu-TAPB-COF nanosheets (CuCON) with framework structure and abundant active metal sites were synthetized and introduced into PMP to construct hybrid oxygenation membranes, reducing the resistance of gas exchange channels and ensuring the high affinity toward CO2 and O2. Cu+ and benzene rings existed in aromatic skeleton as well as the tunable structure, that could ensure the stability of MCOF and the uniform distribution of facilitated transport sites. The prepared PMP-CuCON-1 HFMs exhibited O2 and CO2 exchange rate of ∼467.5 ml min−1 m−2 and ∼309.1 ml min−1 m−2 in blood gas exchange process, which was 143.1% and 261.3% higher than the commercial PMP HFM, respectively. Asymmetric structure ensured resistance to plasma leakage for more than two weeks, and Cu+ kept stable in CuCON and hybrid membranes. The hybrid membrane exhibited superior blood-gas exchange performance and good hemocompatibility, possessing great potential for application.

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.

Blood Gas Transport: Implications for O2 and CO2 Exchange in Lungs and Tissues.

The well-known ways in which O2 and CO2 (and other gases) are carried in the blood were presented in the preceding chapter. However, what the many available texts about O2 and CO2 transport do not emphasize is why knowing how gases are carried in blood matters, and this second, companion, article specifically addresses that critical aspect of gas exchange physiology. During gas exchange, both at the lungs and in the peripheral tissues, it is the shapes and the slopes of the O2 and CO2 binding curves that explain almost all of the behaviors of each gas and the quantitative differences observed between them. This conclusion is derived from first principle considerations of the gas exchange processes. Dissociation curve shape and slope differences explain most of the differences between O2 and CO2 in both diffusive exchange in the lungs and tissues and convective exchange/transport in, and between, the lungs and tissues. In fact, each of the chapters in this volume describes physiological behavior that depends more or less directly on the dissociation curves of O2 and CO2.

Ventilation Mechanics.

A fundamental task of the respiratory system is to operate as a mechanical gas pump ensuring that fresh air gets in close contact with the blood circulating through the lung capillaries to achieve O2 and CO2 exchange. To ventilate the lungs, the respiratory muscles provide the pressure required to overcome the viscoelastic mechanical load of the respiratory system. From a mechanical viewpoint, the most relevant respiratory system properties are the resistance of the airways (R aw), and the compliance of the lung tissue (C L) and chest wall (C CW). Both airflow and lung volume changes in spontaneous breathing and mechanical ventilation are determined by applying the fundamental mechanical laws to the relationships between the pressures inside the respiratory system (at the airway opening, alveolar, pleural, and muscular) and R aw, C L, and C CW. These relationships also are the basis of the different methods available to measure respiratory mechanics during spontaneous and artificial ventilation. Whereas a simple mechanical model (R aw, C L, and C CW) describes the basic understanding of ventilation mechanics, more complex concepts (nonlinearity, inhomogeneous ventilation, or viscoelasticity) should be employed to better describe and measure ventilation mechanics in patients.

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).