Effective Gas Exchange Research Articles

There is no limitation for CO2 excretion across the lung in exercising American alligators (Alligator mississippiensis).

Vertebrates utilize various respiratory organs like gills, lungs, and skin in combination with diverse cardiovascular structures, including single, three, and four-chambered hearts, to enable oxygen delivery and carbon dioxide removal. They also exhibit differences in aerobic and anaerobic metabolism during exertion, but the cardiorespiratory gas transport of all vertebrates follow is a similar a four-step process governed by Fick's Principle and Fick's Law of Diffusion over the entire range of metabolic rates. Hillman et al. (2013) suggested that previous exercise studies have focused too narrowly on mammals and proposed that the cardiorespiratory system's excess capacity serves an evolutionary role in enhancing CO2 excretion in non-mammalian vertebrates. In contrast, an analysis by Hicks and Wang (2021) concluded that vertebrates maintain effective gas exchange even at peak activity, finding no evidence of arterial hypercapnia at maximal oxygen consumption and thus challenging the proposal of significant limitations to pulmonary or branchial CO2 efflux. In the present study, we investigate the limits for CO2 exchange in exercising American alligators (Alligator mississippiensis) and provide evidence that the cardiorespiratory system is adequately built to sustain CO2 excretion during strenuous exercise and maintain arterial PCO2 , with no evidence of diffusion limitation for pulmonary CO2 excretion.

Exposure to fine particulate matter 2.5 from wood combustion smoke causes vascular changes in placenta and reduce fetal size

During gestation, maternal blood flow to the umbilical cord and placenta increases, facilitating efficient nutrient absorption, waste elimination, and effective gas exchange for the developing fetus. However, the effects of exposure to wood smoke during this period on these processes are unknown. We hypothesize that exposure to PM2.5, primarily sourced from wood combustion for home heating, affects placental vascular morphophysiology and fetal size. We used exposure chambers that received either filtered or unfiltered air. Female rats were exposed to PM2.5 during pre-gestational and/or gestational stages. Twenty-one days post-fertilization, placentas were collected via cesarean section. In these placentas, oxygen diffusion capacity was measured, and the expression of angiogenic factors was analyzed using qPCR and immunohistochemistry. In groups exposed to PM2.5 during pre-gestational and/or gestational stages, a decrease in fetal weight, crown-rump length, theoretical and specific diffusion capacity, and an increase in HIF-1α expression were observed. In groups exposed exclusively to PM2.5 during the pre-gestational stage, there was an increase in the expression of placental genes Flt-1, Kdr, and PIGF. Additionally, in the placental labyrinth region, the expression of angiogenic factors was elevated. Changes in angiogenesis and angiogenic factors reflect adaptations to hypoxia, impacting fetal growth and oxygen supply. In conclusion, this study demonstrates that exposure to PM2.5, emitted from wood smoke, in both pre-gestational and gestational stages, affects fetal development and placental health. This underscores the importance of addressing air pollution in areas with high levels of wood smoke, which poses a significant health risk to pregnant women and their fetuses.

Improving the storage quality and suppressing off-flavor generation of winter jujube by precise micro-perforated MAP.

Traditional modified atmosphere packaging (MAP) cannot meet the preservation requirements of winter jujube, and the high respiration rate characteristics of winter jujube will produce an atmosphere component with high CO2 concentration in traditional MAP. Micro-perforated MAP is suitable for the preservation of winter jujube due to its high permeability, which can effectively remove excess CO2 and supply O2. In this study, a microporous film preservation system that can be quickly applied to winter jujube was developed, namely PMP-MAP (precise micro-perforated modified atmosphere packaging). An experiment was designed to store winter jujube in PMP-MAP at 20°C and 2°C, respectively. The quality, aroma and antioxidant capacity, etc. of winter jujube at the storage time were determined. In this study, the optimal micropore area required for microporous film packaging at different temperatures is first determined. To ensure the best perforation effect, the effects of various factors on perforation efficiency were studied. The gas composition within the package was predicted using the gas prediction equation to ensure that the gas composition of the perforated package achieved the desired target. Finally, storage experiments were designed to determine the quality index of winter jujube, including firmness, total soluble solids, titratable acid, reddening, and decay incidence. In addition, sensory evaluation, aroma and antioxidant capacity were also determined. Finally, the preservation effect of PMP-MAP for winter jujube was evaluated by combining the above indicators. At the end of storage, PMP-MAP reduced the respiration rate of winter jujube, which contributed to the preservation of high total soluble solids and titratable acid levels, and delayed the reddening and decay rate of winter jujube. In addition, PMP-MAP maintained the antioxidant capacity and flavor of winter jujube while inhibiting the occurrence of alcoholic fermentation and off-flavors. This can be attributed to the effective gas exchange facilitated by PMP-MAP, thereby preventing anaerobic stress and quality degradation. Therefore, the PMP-MAP approach is an efficient method for the storage of winter jujube.

Human alveolar macrophages display marked hypo-responsiveness to IFN-γ in both proteomic and gene expression analysis.

Alveolar macrophages (AM) perform a primary defense mechanism in the lung through phagocytosis of inhaled particles and microorganisms. AM are known to be relatively immunosuppressive consistent with the aim to limit alveolar inflammation and maintain effective gas exchange in the face of these constant challenges. How AM respond to T cell derived cytokine signals, which are critical to the defense against inhaled pathogens, is less well understood. For example, successful containment of Mycobacterium tuberculosis (Mtb) in lung macrophages is highly dependent on IFN-γ secreted by Th-1 lymphocytes, however, the proteomic IFN-γ response profile in AM remains mostly unknown. In this study, we measured IFN-γ induced protein abundance changes in human AM and autologous blood monocytes (MN). AM cells were activated by IFN-γ stimulation resulting in STAT1 phosphorylation and production of MIG/CXCL9 chemokine. However, the global proteomic response to IFN-γ in AM was dramatically limited in comparison to that of MN (9 AM vs 89 MN differentially abundant proteins). AM hypo-responsiveness was not explained by reduced JAK-STAT1 signaling nor increased SOCS1 expression. These findings suggest that AM have a tightly regulated response to IFN-γ which may prevent excessive pulmonary inflammation but may also provide a niche for the initial survival and growth of Mtb and other intracellular pathogens in the lung.

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.

A Pumpless Pediatric Artificial Lung Maintains Function for 72 h Without Systemic Anticoagulation Using the Nitric Oxide Surface Anticoagulation System

BackgroundChildren with end-stage lung disease are commonly managed with extracorporeal life support (ECLS) as a bridge to lung transplantation. A pumpless artificial lung (MLung) is a portable alternative to ECLS and it allows for ambulation. Both ECLS and pumpless artificial lungs require systemic anticoagulation which is associated with hemorrhagic complications. We tested the MLung with a novel Nitric Oxide (NO) Surface Anticoagulation (NOSA) system, to provide local anticoagulation for 72 h of support in a pediatric-size ovine model. MethodsFour mini sheep underwent thoracotomy and cannulation of the pulmonary artery (inflow) and left atrium (outflow), recovered and were monitored for 72hr. The circuit tubing and connectors were coated with the combination of an NO donor (diazeniumdiolated dibutylhexanediamine; DBHD-N2O2) and argatroban. The animals were connected to the MLung and 100 ppm of NO was added to the sweep gas. Systemic hemodynamics, blood chemistry, blood gases, and methemoglobin were collected. ResultsMean device flow was 836 ± 121 mL/min. Device outlet saturation was 97 ± 4%. Pressure drop across the lung was 3.5 ± 1.5 mmHg and resistance was 4.3 ± 1.7 mmHg/L/min. Activated clotting time averaged 170 ± 45s. Methemoglobin was 2.9 ± 0.8%. Platelets declined from 590 ± 101 at baseline to 160 ± 90 at 72 h. NO flux (x10-10 mol/min/cm2) of the NOSA circuit averaged 2.8 ± 0.6 (before study) and 1.9 ± 0.1 (72 h) and across the MLung 18 ± 3 NO flux was delivered. ConclusionThe MLung is a more portable form of ECLS that demonstrates effective gas exchange for 72 h without hemodynamic changes. Additionally, the NOSA system successfully maintained local anticoagulation without evidence of systemic effects.

The Tritube: Facilitating Upper Airway Surgery With an Ultrathin Cuffed Airway Device.

The Tritube is a narrow-bore cuffed tracheal tube (outer diameter 4.4 mm and inner diameter ~2.4 mm) that permits effective alveolar gas exchange using flow-controlled ventilation. Constant gas flow delivers physiological minute volumes, within preset pressure limits, and applies suction to the airway during expiration. The technique has attracted interest for laryngotracheal microsurgery as it provides superior surgical exposure and avoids many of the complications associated with high-frequency jet ventilation. Cuff inflation protects the lower airway and produces a motionless operating field. We describe the structure of the device, discuss its benefits, and suggest how it should be used clinically.

Effect of external dead space removal on CO2 homeostasis in mechanically ventilated adult Covid-19 patients.

Patients with Covid-19 respiratory failure present with hypoxemia, often in combination with hypercapnia. In this prospective, observational study we examined the effect of removing external dead space (DS) on CO2 -homeostasis in mechanically ventilated Covid-19 patients. In addition, volumetric capnography was validated for its ability to estimate external DS volume using in vitro measured DS volumes as reference. In total, 10 patients with acute respiratory distress syndrome from Covid-19 were included. Volumetric capnography, mechanical ventilation, and arterial blood gas data were analyzed before and after removal of external DS and analyzed for potentially significant changes in response to DS removal. Measurements of external DS were obtained in circuit using volumetric capnography and compared to actual measured DS volumes off the circuit. After the removal of external DS, the alveolar minute ventilation and CO2 elimination improved, notwithstanding unchanged respiratory rate and tidal volumes. The increase in CO2 elimination was associated with a decrease in arterial CO2 partial pressure (PaCO2 ). The volumetric capnography method for assessment of external DS showed a low bias of -9 mL (lower limit of agreement -40, 95% CI -60 to -20 mL, upper limit of agreement 21 mL, 95% CI: 1-40 mL) and a percentage error of 48% compared to absolute values measured in vitro. Removal of external DS increased alveolar minute ventilation and CO2 elimination in Covid-19 patients with respiratory failure in the current study. This was associated with a decrease in PaCO2 . This may indicate a decreased CO2 production due to decreased work of breathing and more effective gas-exchange in response to DS removal. In addition, volumetric capnography appears to be a clinically feasible method for continuous measurement of external DS in the current study and may be of value in optimizing ventilator treatment.

Allometric scaling of metabolic rate and cardiorespiratory variables in aquatic and terrestrial mammals.

While basal metabolic rate (BMR) scales proportionally with body mass (Mb ), it remains unclear whether the relationship differs between mammals from aquatic and terrestrial habitats. We hypothesized that differences in BMR allometry would be reflected in similar differences in scaling of O2 delivery pathways through the cardiorespiratory system. We performed a comparative analysis of BMR across 63 mammalian species (20 aquatic, 43 terrestrial) with a Mb range from 10 kg to 5318 kg. Our results revealed elevated BMRs in small (>10 kg and <100 kg) aquatic mammals compared to small terrestrial mammals. The results demonstrated that minute ventilation, that is, tidal volume (VT )·breathing frequency (fR ), as well as cardiac output, that is, stroke volume·heart rate, do not differ between the two habitats. We found that the "aquatic breathing strategy", characterized by higher VT and lower fR resulting in a more effective gas exchange, and by elevated blood hemoglobin concentrations resulting in a higher volume of O2 for the same volume of blood, supported elevated metabolic requirements in aquatic mammals. The results from this study provide a possible explanation of how differences in gas exchange may serve energy demands in aquatic versus terrestrial mammals.

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)

Adverse neonatal outcome and veno-arterial differences in umbilical cord blood pH (ΔpH) at birth: a population-based study of 108,629 newborns

BackgroundUmbilical cord blood gases are routinely used by midwives and obstetricians for quality assurance of birth management and in clinical research. They can form the basis for solving medicolegal issues in the identification of severe intrapartum hypoxia at birth. However, the scientific value of veno-arterial differences in cord blood pH, also known as ΔpH, is largely unknown. By tradition, the Apgar score is frequently used to predict perinatal morbidity and mortality, however significant inter-observer and regional variations decrease its reliability and there is a need to identify more accurate markers of perinatal asphyxia. The aim of our study was to investigate the association of small and large veno-arterial differences in umbilical cord pH, ΔpH, with adverse neonatal outcome.MethodsThis retrospective, population-based study collected obstetric and neonatal data from women giving birth in nine maternity units from Southern Sweden from 1995 to 2015. Data was extracted from the Perinatal South Revision Register, a quality regional health database. Newborns at ≥37 gestational weeks with a complete and validated set of umbilical cord blood samples from both cord artery and vein were included. Outcome measures included: ΔpH percentiles, ‘Small ΔpH’ (10th percentile), ‘Large ΔpH’ (90th percentile), Apgar score (0–6), need for continuous positive airway pressure (CPAP) and admission to neonatal intensive care unit (NICU). Relative risks (RR) were calculated with modified Poisson regression model.ResultsThe study population comprised of 108,629 newborns with complete and validated data. Mean and median ΔpH was 0.08 ± 0.05. Analyses of RR showed that ‘Large ΔpH’ was associated with a decreased RR of adverse perinatal outcome with increasing UApH (at UApH ≥7.20: RR for low Apgar 0.29, P = 0.01; CPAP 0.55, P = 0.02; NICU admission 0.81, P = 0.01). ‘Small ΔpH’ was associated with an increased RR for low Apgar score and NICU admission only at higher UApH values (at UApH 7.15–7.199: RR for low Apgar 1.96, P = 0.01; at UApH ≥7.20: RR for low Apgar 1.65, P = 0.00, RR for NICU admission 1.13, P = 0.01).ConclusionLarge differences between cord venous and arterial pH (ΔpH) at birth were associated with a lower risk for perinatal morbidity including low 5-minute Apgar Score, the need for continuous positive airway pressure and NICU admission when UApH was above 7.15. Clinically, ΔpH may be a useful tool in the assessment of the newborn’s metabolic condition at birth. Our findings may stem from the ability of the placenta to adequately replenish acid-base balance in fetal blood. ‘Large ΔpH’ may therefore be a marker of effective gas exchange in the placenta during birth.

Pulmonary surfactant function and molecular architecture is disrupted in the presence of vaping additives

Inhalation of harmful vaping additives has led to a series of lung illnesses. Some of the selected additives such as vitamin E acetate, and related molecules like vitamin E and cannabidiol, may interfere with the function of the lung surfactant. Proper lipid organization in lung surfactant is key to maintaining low surface tensions, which provides alveolar stability and effective gas exchange throughout respiration. Physiological surfactants, such as bovine lipid extract surfactant used to treat neonatal respiratory distress syndrome, serve as a good model for examining the potential effects of vape additives on proper function. We have found that all additives impede the surfactants’ ability to efficiently reach high surface pressures as these systems displayed numerous shoulders throughout compression with accompanying defects to lipid organization. Moreover, the formation of lipid bilayer stacks in the film are hindered by the additives, most notably with vitamin e acetate. Loss of these stacks leave the film prone to buckling and collapse under high compression that occurs at the end of expiration. The data suggest that the additives may interfere with both proper lipid organization and the surfactant protein function.

Thiol-Ene Click Synthesis of Alginate Hydrogels Loaded with Silver Nanoparticles and Cefepime

Hydrogels used in biomedical applications, particularly for soft tissue treatment and regeneration, should have favorable mechanical properties and biocompatibility. Alginate hydrogels are suitable for developing wound dressings with desirable porosity, facilitating effective gas and vapor exchange necessary for wound healing. In this study, we present the synthesis and characterization of photocrosslinked hydrogels based on sodium alginate allyl glycidyl ether (SA-AGE). The composition and structure of the synthesized macromers were confirmed using nuclear magnetic resonance spectroscopy (1H-NMR), while scanning electron microscopy (SEM) revealed the presence of pores ranging in size from 5–32 μm. The UV light polymerization of SA-AGE hydrogel using the photoinitiator I295 was achieved within 60 minutes. The absorption of silver particles and the drug cefepime was determined through titration and UV-spectroscopy, indicating that the optimal concentration was 1 %. The antibacterial activity of the hydrogels loaded with silver nanoparticles and cefepime was evaluated against gram-negative (Pseudomonas aeruginosa) and gram-positive (Staphylococcus aureus) strains. Cytotoxicity of the hydrogels was assessed using the MTT assay with rat ADMSC cells, and the cell survival rate in the presence of the hydrogels was above 80 %, indicating their noncytotoxic nature.

The role of surfactant proteins SP-A and SP-D in viral infection: a focus on COVID-19

An immune response to invasion of viral pathogens is an integral part of maintaining the physiological functioning of the bronchopulmonary system and effective gas exchange. Collagen-containing C-type lectins (lung collectins) are some of the key proteins in the identification of viral particles. They have image-recognizing receptors that identify pathogen-associated molecular patterns, particularly viral glycoproteins. The surfactant proteins SP-A and SP-D, which are composed of trimerized units, belong to pulmonary collectins and oligomerize into higher-order structures. These proteins play an essential role in recognition and elimination of microbial pathogens (viruses, bacteria, fungi, parasites, nanoparticles, allergens) through a variety of mechanisms. Taking into account the burden of the novel coronavirus infection caused by the SARS-CoV-2 virus, it is important to consider the role of the surfactant proteins SP-A and SP-D in the pathogenesis of the immune response to viral invasion. Currently, there are data on the direct relationship between surfactant proteins and viruses belonging to the Coronaviridae family. The SP-A and SP-D proteins modulate inflammatory responses and cytokine synthesis, but prevent an excessive inflammatory response (cytokine storm). There is also an assumption that SARSCoV-2 directly suppresses and alters the production of surfactant proteins. Thus, the key pathogenetic role of the surfactant proteins SP-A and SP-D in the response to the viral pathogen SARS-CoV-2 is evident. Today, this is a promising area of translational medicine, which will contribute to a profound understanding of the pathogenesis of coronavirus infection for assessing the diagnostic and prognostic potentials of the surfactant proteins SP-A and SP-D in COVID-19. Additionally, it will help evaluate the therapeutic potential of recombinant fragments of human SP-A and SP-D.

0544 Polysomnography characteristics of children with obesity: A single center retrospective study

Abstract Introduction The constellations of symptoms known as obstructive sleep apnea (OSA) results from either partial or complete airway obstruction during sleep. This affects effective gas exchange and disrupts sleep architecture resulting in sleep fragmentation with downstream immediate and long-term adverse effects. Obesity is a significant risk factor in childhood OSA, especially in post-pubertal children. Obese/overweight children have been found to have significantly higher rates of OSA than their normal-weight counterparts, independent of tonsillar size. Polysomnography characteristics (PSG) comparing children with obesity with and without comorbidities (Hypertension, Diabetes or Pre-diabetes) has not been previously described. Methods Retrospective analysis of 190 obese children (BMI&amp;gt;95th centile), age between 7-18 years with AHI ≥5/hour met the criteria for the data analysis. Clinical, demographic and PSG parameters of children with obesity with and without co-morbidities were compared using Wilcoxon rank sum test. Correlation (Spearman non-parametric) and regression model was employed to explore associations between demographic and PSG characteristics. Results Majority of the obese children (mean BMI 33.2) had mild OSA, with no significant difference in AHI between the two groups. Children with obesity and comorbidities were older with higher BMI. There was no difference in BMI between the two groups after adjusting for BMI z scores. AHI increased with increasing BMI centiles. In our regression model, peak ETCO2 was associated with Black race, AHI, rhinitis and inversely associated with asthma. Peak ETCO2 increased with BMI. Oxygen at baseline, nadir and desaturation duration inversely correlated with BMI-centiles. Older children had lower O2 nadir. Black race was associated with higher desaturation, supine AHI, and arousal index. Supine AHI was higher with rhinitis. Average heart rate when awake, NREM and REM increased with higher BMI. Conclusion In our study, majority of the children had mild OSA with no significant difference in AHI between obese children with and without comorbidities. AHI, average heart rate and peak ETCO2 increased with BMI. O2 nadir was lower in older children and with higher BMI. Black race was associated with higher peak ETCO2, higher desaturation and supine AHI. Children with obesity and comorbidities were older with higher BMI suggesting synergistic effect of BMI and duration of obesity. Support (If Any)

Heart position and pulmonary vasculature in snakes with different lung morphologies

Abstract The respiratory system of snakes, composed of a trachea and one or two lungs, shows considerable variation in terms of size and complexity, especially in terms of length and distribution of the respiratory epithelium. The importance of heart position within snakes has previously been investigated concerning gravitational stress. The relationship between respiratory gas exchange epithelium and heart position, however, has not been addressed in detail, which seems necessary, since the heart needs to pump blood through the pulmonary circulation for effective gas exchange. Herein, we analyze the morphology of the respiratory epithelium in Boa constrictor and Crotalus durissus stereologically regarding the composition of the gas exchange tissue and the distribution of blood vessels within the vascularized parts of the respiratory system. The gas exchange epithelium is composed of blood capillaries, larger vessels, trabeculae, and septa, forming an overall faveolar-type epithelium in both species. Pulmonary capillaries and respiratory surface area showed a tendency to be more concentrated in the anterior and middle portions of each lung’s respiratory epithelium, suggesting a tendency toward greater parenchymal development in these regions. Therefore, there seems to be no conclusive relationship between the position of the heart and pulmonary circulation, since in C. durissus the anterior and middle parenchymal regions are distant from the heart, whereas in B. constrictor the anterior and middle parenchymal regions are close to the heart, facilitating blood transport between the heart and the gas exchange epithelium.

Development of a reverse-loop scavenged poppet-valve 2-stroke diesel engine for down speed and performance comparisons with its 4-stroke baseline

In the present study, a reverse-loop scavenged poppet-valve 2-stroke (PV2S) diesel engine was developed and compared with its 4-stroke baseline experimentally. Firstly, the valve cam profiles and the valve timings for the PV2S engine was optimized using 1D simulations. Results show that, the present intake and exhaust cam profiles meet the design requirements under a series of designing allowances. The nonlinear relationship between the gas exchange performance and the power output for the PV2S engine is due to the fact that the expansion work loss increases more than the volume efficiency improvement with the exhaust valve closure timing changes from 95 °CA to 85 °CA. Then, the in-cylinder flow of the new designed upright-strait ports and masked head was simulated using 3D simulations in comparison with the original horizontal head. It is found that the upright-strait intake port can induce intense reverse tumble in-cylinder flow to make an effective gas exchange than the under 2-stroke mode. Finally, the performances of the new developed PV2S engine and the its 4-stroke baseline are compared on the single-cylinder engine test bench. Experimental results show that the brake specific fuel consumption of the PV2S engine is higher than that of the 4-stroke engine under same engine speed and same power output conditions because of the decreased thermal efficiency and the increased friction loss proportions. However, the PV2S engine shows a better economic performance than the 4-stroke engine at rated conditions due to the reduced friction losses from down-speeding.

Intravascular Gas Exchange: Physiology, Literature Review, and Current Efforts.

Acute respiratory failure with inadequate oxygenation and/or ventilation is a common reason for ICU admission in children and adults. Despite the morbidity and mortality associated with acute respiratory failure, few proven treatment options exist beyond invasive ventilation. Attempts to develop intravascular respiratory assist catheters capable of providing clinically important gas exchange have had limited success. Only one device, the IVOX catheter, was tested in human clinical trials before development was halted without FDA approval. Overcoming the technical challenges associated with providing safe and effective gas exchange within the confines of the intravascular space remains a daunting task for physicians and engineers. It requires a detailed understanding of the fundamentals of gas transport and respiratory physiology to optimize the design for a successful device. This article reviews the potential benefits of such respiratory assist catheters, considerations for device design, previous attempts at intravascular gas exchange, and the motivation for continued development efforts.

Single-Cell RNA Sequencing-Based Characterization of Resident Lung Mesenchymal Stromal Cells in Bronchopulmonary Dysplasia.

Late lung development is a period of alveolar and microvascular formation, which is pivotal in ensuring sufficient and effective gas exchange. Defects in late lung development manifest in premature infants as a chronic lung disease named bronchopulmonary dysplasia (BPD). Numerous studies demonstrated the therapeutic properties of exogenous bone marrow and umbilical cord-derived mesenchymal stromal cells (MSCs) in experimental BPD. However, very little is known regarding the regenerative capacity of resident lung MSCs (L-MSCs) during normal development and in BPD. In this study we aimed to characterize the L-MSC population in homeostasis and upon injury. We used single-cell RNA sequencing (scRNA-seq) to profile in situ Ly6a+ L-MSCs in the lungs of normal and O2-exposed neonatal mice (a well-established model to mimic BPD) at 3 developmental timepoints (postnatal days 3, 7, and 14). Hyperoxia exposure increased the number and altered the expression profile of L-MSCs, particularly by increasing the expression of multiple pro-inflammatory, pro-fibrotic, and anti-angiogenic genes. In order to identify potential changes induced in the L-MSCs transcriptome by storage and culture, we profiled 15 000 Ly6a+ L-MSCs after in vitro culture. We observed great differences in expression profiles of in situ and cultured L-MSCs, particularly those derived from healthy lungs. Additionally, we have identified the location of Ly6a+/Col14a1+ L-MSCs in the developing lung and propose Serpinf1 as a novel, culture-stable marker of L-MSCs. Finally, cell communication analysis suggests inflammatory signals from immune and endothelial cells as main drivers of hyperoxia-induced changes in L-MSCs transcriptome.

Lung Injury and Repair in Coronavirus Disease 2019–Related Acute Lung Injury

The alveolar epithelium is the largest surface area of the body in continuous contact with the outside environment and is critical for effective gas exchange to support metabolism. The alveolar walls consist of three distinct layers: the alveolar epithelium, comprising type I and type II alveolar epithelial cells; a matrix scaffold; and the microvascular endothelium. Most of the alveolar surface is covered by thin type I epithelial cells that cover the matrix framework and are closely opposed to microvascular endothelial cells.