Carbon Monoxide Uptake Research Articles

The emission of CO from tropical rainforest soils

Abstract. Soil carbon monoxide (CO) fluxes represent a net balance between biological soil CO uptake and abiotic soil and (senescent) plant CO production. Studies largely from temperate and boreal forests indicate that soils serve as a net sink for CO, but uncertainty remains about the role of tropical rainforest soils to date. Here we report the first direct measurements of soil CO fluxes in a tropical rainforest and compare them with estimates of net ecosystem CO fluxes derived from accumulation of CO at night under stable atmospheric conditions. Furthermore, we used laboratory experiments to demonstrate the importance of temperature on net soil CO fluxes. Net soil surface CO fluxes ranged from −0.19 to 3.36 nmol m−2 s−1, averaging ∼1 nmol CO m−2 s−1. Fluxes varied with season and topographic location, with the highest fluxes measured in the dry season in a seasonally inundated valley. Ecosystem CO fluxes estimated from nocturnal canopy air profiles, which showed CO mixing ratios that consistently decreased with height, ranged between 0.3 and 2.0 nmol CO m−2 s−1. A canopy layer budget method, using the nocturnal increase in CO, estimated similar flux magnitudes (1.1 to 2.3 nmol CO m−2 s−1). In the wet season, a greater valley ecosystem CO production was observed in comparison to measured soil valley CO fluxes, suggesting a contribution of the valley stream to overall CO emissions. Laboratory incubations demonstrated a clear increase in CO production with temperature that was also observed in field fluxes, though high correlations between soil temperature and moisture limit our ability to interpret the field relationship. At a common temperature (25 °C), expected plateau and valley senescent-leaf CO production was small (0.012 and 0.002 nmol CO m−2 s−1) in comparison to expected soil material CO emissions (∼ 0.9 nmol CO m−2 s−1). Based on our field and laboratory observations, we expect that tropical rainforest ecosystems are a net source of CO, with thermal-degradation-induced soil emissions likely being the main contributor to ecosystem CO emissions. Extrapolating our first observation-based tropical rainforest soil emission estimate of ∼ 1 nmol m−2 s−1, global tropical rainforest soil emissions of ∼ 16.0 Tg CO yr−1 are estimated. Nevertheless, total ecosystem CO emissions might be higher, since valley streams and inundated areas might represent local CO emission hot spots. To further improve tropical forest ecosystem CO emission estimates, more in situ tropical forest soil and ecosystem CO flux measurements are essential.

Prevalence of trace gas-oxidizing soil bacteria increases with radial distance from Polloquere hot spring within a high-elevation Andean cold desert.

High-elevation arid regions harbor microbial communities reliant on metabolic niches and flexibility to survive under biologically stressful conditions, including nutrient limitation that necessitates the utilization of atmospheric trace gases as electron donors. Geothermal springs present "oases" of microbial activity, diversity, and abundance by delivering water and substrates, including reduced gases. However, it is unknown whether these springs exhibit a gradient of effects, increasing their impact on trace gas-oxidizers in the surrounding soils. We assessed whether proximity to Polloquere, a high-altitude geothermal spring in an Andean salt flat, alters the diversity and metabolic structure of nearby soil bacterial populations compared to the surrounding cold desert. Recovered DNA and metagenomic analyses indicate that the spring represents an oasis for microbes in this challenging environment, supporting greater biomass with more diverse metabolic functions in proximal soils that declines sharply with radial distance from the spring. Despite the sharp decrease in biomass, potential rates of atmospheric hydrogen (H2) and carbon monoxide (CO) uptake increase away from the spring. Kinetic estimates suggest this activity is due to high-affinity trace gas consumption, likely as a survival strategy for energy/carbon acquisition. These results demonstrate that Polloquere regulates a gradient of diverse microbial communities and metabolisms, culminating in increased activity of trace gas-oxidizers as the influence of the spring yields to that of the regional salt flat environment. This suggests the spring holds local importance within the context of the broader salt flat and potentially represents a model ecosystem for other geothermal systems in high-altitude desert environments.

MRI and Pulmonary Function Tests' Results as Ventilation Inhomogeneity Markers in Children and Adolescents with Cystic Fibrosis.

Magnetic resonance imaging (MRI) of the chest is becoming more available in the detection and monitoring of early changes in lung function and structure in patients with cystic fibrosis (CF). The aim of this study was to assess the relationship between pulmonary function tests (PFT) and perfusion deficits in CF children measured by MRI. We performed a retrospective analysis of the perfusion lung MRI scans and the results of spirometry, oscillometry, body plethysmography, single-breath carbon monoxide uptake, and multiple-breath washout technique (MBW). There were statistically significant correlations between the MRI perfusion scores and MBW parameters (2.5% LCI, M1/M0, M2/M0), spirometry parameters (FEV1, FVC, FEF25/75), reactance indices in impulse oscillometry (X5Hz, X10Hz), total lung capacity (TLC) measured in single breath carbon monoxide uptake, markers of air-trapping in body plethysmography (RV, RV/TLC), and the diffusing capacity of the lungs for carbon monoxide. We also observed significant differences in the aforementioned PFT variables between the patient groups divided based on perfusion scores. We noted a correlation between markers of functional lung deficits measured by the MRI and PFTs in CF children. MRI perfusion abnormalities were reflected sooner in the course of the disease than PFT abnormalities.

Surfactant-assisted synthesis of defective UiO-67(Zr) framework and its application for CO adsorption and CO/N2 separation

The Cu+-based π-complex adsorbent is a promising material for storing and separating carbon monoxide (CO) from various industrial gas emission sources. Herein, defective Cu+@UiO-67(Zr) materials were developed and exploited for the adsorptive separation of CO. First, a defective UiO-67(Zr) framework was prepared using cetyltrimethylammonium bromide (CTAB) as a modulator (UiO-67-CT). Then, Cu2+ was reduced to defective UiO-67(Zr)-CT at 150 °C to obtain Cu+@UiO-67-CT adsorbents. Results indicated that CTAB-created UiO-67 contained defects with the ligand deficiency of ca. ∼ 2.05 per Zr6 unit, enhancing their porosity and giving beneficiation for loading Cu+. The gas adsorption experiments showed that the Cu+@UiO-67-CT adsorbents exhibited enhanced CO adsorption compared to the parent MOF, and their adsorption ability depends on the Cu+ load. The optimal 25Cu+@UiO-67-CT had CO uptake capacity and CO/N2 selectivity of ca. ∼ 2.91 mmol g−1 and ∼ 318 at 100 kPa and 27 °C, respectively, exceeding many reported adsorbents, such as CuCl/Al2O3, CuCl/MCM-41, CuZSM-5, and Cu(I)/polymer. Furthermore, the prepared defective Cu+@UiO-67-CT showed good CO/N2 separation under dynamic flow mixture conditions. The study provides a strategy for developing efficient π-complex adsorbents for CO recovery and separation.

Carbon monoxide (CO) cycling in the Fram Strait, Arctic Ocean

Abstract. Carbon monoxide (CO) influences the radiative budget and oxidative capacity of the atmosphere over the Arctic Ocean, which is a source of atmospheric CO. Yet, oceanic CO cycling is understudied in this area, particularly in light of the ongoing rapid environmental changes. We present results from incubation experiments conducted in the Fram Strait in August–September 2019 under different environmental conditions: while lower pH did not affect CO production (GPCO) or consumption (kCO) rates, enhanced GPCO and kCO were positively correlated with coloured dissolved organic matter (CDOM) and dissolved nitrate concentrations, respectively, suggesting microbial CO uptake under oligotrophic conditions to be a driving factor for variability in CO surface concentrations. Both production and consumption of CO will likely increase in the future, but it is unknown which process will dominate. Our results will help to improve models predicting future CO concentrations and emissions and their effects on the radiative budget and the oxidative capacity of the Arctic atmosphere.

Perchlorate-Coupled Carbon Monoxide (CO) Oxidation by Moorella glycerini, an Obligately Anaerobic, Thermophilic, Nickel-Dependent Carboxydotroph.

Many facultative and obligate anaerobes reduce perchlorate. Likewise, carbon monoxide (CO) oxidation has been documented in many aerobes, facultative anaerobes, and obligate anaerobes. A molybdenum-dependent CO dehydrogenase (Mo-CODH) and a nickel-dependent CO dehydrogenase (Ni-CODH) distinguish the former from the latter. Some Mo-dependent CO oxidizers (Mo-COX) couple CO oxidation to perchlorate reduction, but only at low concentrations of both under conditions that do not support growth in cultures. In contrast, CO-coupled perchlorate reduction has not been documented in Ni-dependent CO oxidizers (Ni-COX). To assess the potential for Ni-COX to reduce perchlorate, a model, obligately anaerobic homoacetogen, Moorella glycerini DSM 11254T, was cultivated with or without perchlorate, usiing CO or glycerol as its sole carbon and energy source. It grew with glycerol with or without perchlorate, and its maximum cell densities were only weakly affected by the perchlorate. However, when CO (at a 30% headspace concentration) was used as a carbon and energy source, perchlorate reduction supported greater cell densities and more rapid growth rates. The stoichiometry of CO uptake, perchlorate reduction, and chloride production were consistent with the cryptic pathway for perchlorate reduction with chlorite as an end product. Chloride production occurred abiologically in the medium due to a reaction between chlorite and the sulfide used as a reducing agent. These results provide the first demonstration of CO-coupled perchlorate reduction supporting growth in Ni-COX, and they provide constraints on the potential for perchlorate-coupled, anaerobic CO oxidation in engineered systems as well as terrestrial systems and hypothetical, sub-surface, serpentinite-hosted systems on Mars.

Real-world diffusing capacity simulation data: how well do they fit current European Respiratory Society/American Thoracic Society acceptability criteria?

ERS/ATS D LCO standards recommend acceptability ranges for weekly D LCO simulation testing performed with a 3-L syringe. On some devices, the ERS/ATS limits may exceed or not fit a 3-sd range, in which case, simulation ranges based on 3 sd may be appropriate. https://bit.ly/3Z0YoZL.

A semi-automated device rapidly determine circulating blood volume in healthy males and carbon monoxide uptake kinetics of arterial and venous blood.

We examined whether a semi-automated carbon monoxide (CO) rebreathing method accurately detect changes in blood volume (BV) and total hemoglobin mass (tHb). Furthermore, we investigated whether a supine position with legs raised reduced systemic CO dilution time, potentially allowing a shorter rebreathing period. Nineteen young healthy males participated. BV and tHb was quantified by a 10-min CO-rebreathing period in a supine position with legs raised before and immediately after a 900ml phlebotomy and before and after a 900ml autologous blood reinfusion on the same day in 16 subjects. During the first CO-rebreathing, arterial and venous blood samples were drawn every 2 min during the procedure to determine systemic CO equilibrium in all subjects. Phlebotomy decreased (P < 0.001) tHb and BV by 166 ± 24g and 931 ± 247ml, respectively, while reinfusion increased (P < 0.001) tHb and BV by 143 ± 21g and 862 ± 250ml compared to before reinfusion. After reinfusion BV did not differ from baseline levels while tHb was decreased (P < 0.001) by 36 ± 21g. Complete CO mixing was achieved within 6 min in venous and arterial blood, respectively, when compared to the 10-min sample. On an individual level, the relative accuracy after donation for tHb and BV was 102-169% and 55-165%, respectively. The applied CO-rebreathing procedure precisely detect acute BV changes with a clinically insignificant margin of error. The 10-min CO-procedure may be reduced to 6min with no clinical effects on BV and tHb calculation.Notwithstanding, individual differences may be of concern and should be investigated further.

Enhancing of CO Uptake in Metal-Organic Frameworks by Linker Functionalization: A Multi-Scale Theoretical Study

In the present work, the interaction strength of Carbon Monoxide (CO) with a set of forty-two, strategically selected, functionalized benzenes was calculated. Our ab initio calculations at the MP2/6-311++G** level of theory reveal that phenyl hydrogen sulfate (-OSO3H) showed the highest interaction with CO (−19.5 kJ/mol), which was approximately three times stronger compared with the unfunctionalized benzene (−5.3 kJ/mol). Moreover, the three top-performing functional groups (-OSO3H, -OPO3H2, -SO3H) were selected to modify the organic linker of IRMOF-8 and test their ability to capture CO at 298 K for a wide pressure range. Our Grand Canonical Monte Carlo (GCMC) simulations showed a significant increase in the CO uptake in the functionalized MOFs compared with the parent IRMOF-8. It is distinctive that for the volumetric uptake, a 60× increase was observed at 1 bar and 2× was observed at 100 bar. The proposed functionalization strategy can be applied for improving the CO uptake performance not only in MOFs but also in various other porous materials.

Bioreactor modelling for syngas fermentation: Kinetic characterization

A dynamic-kinetic model for gas fermentation of C. carboxidivorans is presented. The model described the acid/alcohol production in gas-fed stirred tank reactors (GFSTR) and in batch pressurized reactors. The model took into account gas–liquid mass transfer rate, carbon monoxide uptake rate and three conversion paths: cell growth associated with acid/alcohol production, alcohol production by acid conversion and direct alcohol production not associated to cell growth. The assessment of kinetic parameters/yields was carried out by regression of experimental data retrieved from the literature. The model was then used to study the effects of several process conditions on the fermentation performances. The sensitivity was analysed with respect to three operating variables (agitation speed, gas feeding flow-rate and bioreactor filling ratio) and also to the kinetic parameters/yields. The proposed model successfully reproduced the experimental data: the R2 of the investigated variable concentrations ranged between 0.769 and 0.885. Sensitivity analysis pointed out that: i) the model was significantly affected by parameters related to the growth kinetic whereas it was not impacted by parameters related to direct alcohol production; ii) fermentation performances could be improved tuning the operating conditions, in particular, the decrease of the mass transfer rate could increase the cell/metabolite production.

Putative Nickel-Dependent Anaerobic Carbon Monoxide Uptake Occurs Commonly in Soils and Sediments at Ambient Temperature and Might Contribute to Atmospheric and Sub-Atmospheric Carbon Monoxide Uptake During Anoxic Conditions

Carbon monoxide (CO) occurs naturally in the atmosphere where it plays a critical role in tropospheric chemistry. Atmospheric CO uptake by soils has been well documented as an important CO sink and has been attributed to a group of aerobic bacteria that possess a molybdenum-dependent CO dehydrogenase (Mo-CODH). CO can also be oxidized by obligate Ni-dependent anaerobes (Ni-COX) that possess nickel-dependent CODHs (Ni-CODH) but relatively little is known about their ecology or their potential to contribute to CO dynamics within soils and sediments or to soil-atmosphere CO exchanges. Results from a series of assays undertaken with diverse soils and sediments and CO concentrations of 10 ppm and 25% with incubation temperatures of 10, 25, and 60°C revealed anaerobic uptake rates with 10 ppm CO that were comparable to those measured under oxic conditions; further, anaerobic CO uptake occurred without a lag and at atmospheric and sub-atmospheric CO concentrations. Assays with 25% CO revealed previously undocumented activity at 10°C and showed extensive activity at 25°C. Results from prior studies with isolates and soils suggest that anaerobic uptake at both 10 ppm and 25% CO concentrations might be attributed to Ni-COX. Collectively the results considerably expand the ecological range for Ni-COX and indicate that they could play previously unsuspected roles in soil CO dynamics.

Lower transfer factor of the lung for carbon monoxide in women with a patent foramen ovale.

What is the central question of this study? Do individuals with a patent foramen ovale (PFO+ ) have a lower lung transfer factor for carbon monoxide than those without (PFO- )? What is the main finding and its importance? We found a lower rate constant for carbon monoxide uptake in PFO+ compared with PFO- women, which was physiologically relevant (≥0.5 z-score difference), but not for PFO+ versus PFO- men. This suggests that factors independent of the PFO are responsible for our findings, possibly inherent structural differences in the lung. The transfer factor of the lung for carbon monoxide (TLCO ) measure assumes that all cardiac output flows through the pulmonary circuit. However, right-to-left blood flow through a shunt can result in a lower transfer factor than predicted. A patent foramen ovale (PFO) is a potential source of right-to-left shunt that is present in ∼35% of the population, but the effect of PFO on TLCO is unknown. We sought to determine the effect of PFO on the TLCO . We conducted a retrospective analysis of TLCO data from 239 (101 women) participants. Anthropometrics and lung function, including spirometry, plethysmography and TLCO , were compiled from our previously published work. Women, but not men, with a PFO had a significantly lower TLCO and rate constant for carbon monoxide uptake (KCO ) (percentage of predicted and z-score) than women without a PFO. Women and men with a PFO had normal alveolar volumes that did not differ from those without a PFO. Correcting the data for haemoglobin in a subset of subjects did not change the results (n=58; 25 women). The lower KCO in women with versus without a PFO was physiologically relevant (≥0.5 z-score difference). There was no effect of PFO in men. This suggests that factors independent of the PFO are responsible for our findings, possibly inherent structural differences in the lung.

Tree phyllospheres are a habitat for diverse populations of CO-oxidizing bacteria.

Carbon monoxide (CO) is both a ubiquitous atmospheric trace gas and an air pollutant. While aerobic CO-degrading microorganisms in soils and oceans are estimated to remove ~370 Tg of CO per year, the presence of CO-degrading microorganisms in above-ground habitats, such as the phyllosphere, and their potential role in CO cycling remains unknown. CO-degradation by leaf washes of two common British trees, Ilex aquifolium and Crataegus monogyna, demonstrated CO uptake in all samples investigated. Based on the analyses of taxonomic and functional genes, diverse communities of candidate CO-oxidizing taxa were identified, including members of Rhizobiales and Burkholderiales which were abundant in the phyllosphere at the time of sampling. Based on predicted genomes of phyllosphere community members, an estimated 21% of phyllosphere bacteria contained CoxL, the large subunit of CO-dehydrogenase. In support of this, data mining of publicly available phyllosphere metagenomes for genes encoding CO-dehydrogenase subunits demonstrated that, on average, 25% of phyllosphere bacteria contained CO-dehydrogenase gene homologues. A CO-oxidizing Phyllobacteriaceae strain was also isolated from phyllosphere samples which contains genes encoding both CO-dehydrogenase as well as a ribulose-1,5-bisphosphate carboxylase-oxygenase. These results suggest that the phyllosphere supports diverse and potentially abundant CO-oxidizing bacteria, which are a potential sink for atmospheric CO.

Late effects in pediatric Hodgkin lymphoma survivors after uniform treatment with ABVD with or without radiotherapy.

ABVD (doxorubicin, bleomycin,vinblastine, and dacarbazine) is not a standard regimen in children due to concerns regarding late effects. However, no studies have evaluated long-term toxicities of ABVD in children. Total 154 pediatric Hodgkin lymphoma (HL) survivors uniformly treated with ABVD were clinically followed up as per institutional protocol. All participants were evaluated for cardiac, pulmonary, and thyroid function abnormalities by multigated acquisition scan (MUGA) scan, spirometry with diffusion capacity of lung for the uptake of carbon monoxide (DLCO), and thyroid profile test, respectively, at a single time point. Predictors of toxicity were also analyzed. The median duration of follow-up of the cohort was 10.3years (6.04-16.8). No secondary malignant neoplasm (SMN) or symptomatic cardiac/pulmonary toxicities were detected. Nine patients (5.9%) had left ventricular ejection fraction (LVEF) <55%. Subclinical and overt hypothyroidism were observed in 78 (50.6%) and 16 (10.4%) survivors, respectively. Abnormal spirometry and reduced DLCO was observed in 43.2% and 42.0% survivors, respectively. Receiving neck radiation was significantly associated with thyroid dysfunction (odds ratio [OR] 16.04, p<.001); age ≥10years predicted reduced DLCO (OR 4.12, p=.001). Sixty-three and 33 patients had one and two late adverse effects, respectively; receiving neck radiation predicted development of multiple late effects (proportional OR 4.72, p<0.001). Cumulative dose of chemotherapy did not predict toxicity. Overall, ABVD appears safe in children at a relatively short follow-up. Long-term safety data are required before it can be adopted for treating pediatric HL patients. Children receiving neck radiation require close follow-up.

Empirical validation and simulation of existing CO exposure models with hospital pulmonary function datasets

BACKGROUND AND AIM: Carbon monoxide (CO) poisoning is a critical global public health issue. Several CO exposure models were built to predict the kinetics of CO uptake and elimination in CO poisoning but based on a limited data set. Therefore, the aim of the study is to extend the CO exposure models to people with a wider range of several characteristic, such as age, sex, height, weight, smoking status. To address this, we tested relationships between these demographic factors, pulmonary function (DLCO), and the rate of CO uptake and CO elimination. METHODS: We collected pulmonary function datasets from Tri-Service General Hospital in Taiwan (N=1,943 Asian patients), and Royal Berkshire Hospital in the UK (N=691 Caucasian patients). In these data we obtained the DLCO by demographics. Then we used the observed DLCO values within existing CO models (Coburn-Forster-Kane (CFK) models) to predict the rate of CO uptake and elimination for different individuals in different scenarios. RESULTS:We found that males had a higher value of DLCO than females, and DLCO was positively associated with height (β=0.122, p0.05) and weight (β=0.104, p0.05), and negatively associated with age (β=-0.186, p0.05). Then, we used estimated DLCO from data gathered from pulmonary function datasets to update established CFK models. The results showed that for example: when exposed to 10,000 ppm for 5 min, there is a higher peak of CO ppm in a younger male compared to an older male (COHb (%): 20.8 vs. 19.5). CONCLUSIONS:In conclusion, the updated model has the advantage of being able to predict CO uptake and elimination for a wider range of individuals compared to previous CFK models, factoring in their age, sex, height, weight, ethnic group, and smoking status. This could help estimate past CO exposure, and help medical staff recognize CO exposure and design optimal treatments for CO exposure victims. KEYWORDS: Air pollution, Biomarkers of exposure, Epidemiology, Exposures, Exposure assessment, Toxicology

DFT Approach on Characterizing Various Configurations of Carbon Monoxide Uptake by a Single-Standing Iron-Doped Carbon Layer Surface

Density functional theory (DFT) calculations were carried out to characterize various configurations of carbon monoxide (CO) uptake by a single-standing iron-doped (Fe-doped) carbon (FC) layer surface. Different starting positions of CO were examined towards Fe of FC layer leading to C-Head, O-Head, and P-Head models of interacting CO@FC complex formations. Optimization processes and properties evaluations all indicated that the FC layer surface could work as a diagnosis sensor in addition to its role of CO uptake for deathful gas removal purposes. All results indicated that the C-Head model could be the most suitable configuration for CO uptake by FC layer surface. All other two models were also suitable for the purpose. The evaluated infrared (IR) spectra demonstrated variations of locations of peaks in the models in agreement with changes of bond distances after CO uptake. Molecular orbitals features also indicated that the FC layer models were suitable for CO uptake, in which such representations of orbitals distribution patterns approved the effects of the formation of interacting CO@FC complexes. Consequently, the dual role of diagnosis sensor and gas removal could be proposed for FC layer surface during CO uptake processes to further investigate the important issues of this deathful gas.

Species diversity and composition, and above-ground carbon of mangrove vegetation in Jor Bay, East Lombok, Indonesia

Abstract. Zulhalifah, Syukur A, Santoso D, Karnan. 2021. Species diversity and composition, and above-ground carbon of mangrove vegetation in Jor Bay, East Lombok, Indonesia. Biodiversitas 22: 2066-2071. Mangroves play a very important role to mitigate global warming. This study aimed to assess the species diversity and composition as well as the above-ground biomass and carbon content of mangroves in Jor Bay (Teluk Jor), Lombok Island, Indonesia. A purposive sampling method was implemented using transects and square plots as data collection techniques. The data was analyzed to reveal the frequency, density, dominance, above-ground biomass, and carbon content. The results of this study found seven mangrove species, namely Avicennia marina, Ceriops tagal, Rhizophora apiculata, Rhizophora stylosa, Sonneratia alba, Sonneratia caseolaris, and Lumnitzera racemosa. In general, Sonneratia alba was the most important species in terms of frequency, density, and dominance followed by Rhizophora apiculata. In total, mangrove vegetation in Jor Bay stored 697.45 ton C/ha, or equivalent to carbon monoxide uptake of 2559.63 CO2/ ha. In accordance with species composition, Sonneratia alba had the largest contribution to total carbon content with 453.76 tons C/ha), followed by Rhizophora apiculata with 74.47 tons C/ha. These findings suggest that mangrove vegetation in Jor Bay stored large amount of carbon in the form of above-ground biomass, implying the importance to preserve this area for carbon conservation.

Assessment of Ventilatory Heterogeneity in Chronic Obstructive Pulmonary Disease Using the Inspired Sinewave Test.

BackgroundThere is marked variability in the symptoms and outcomes of patients with chronic obstructive pulmonary disease (COPD) which are poorly predicted by spirometry/FEV1%pred. Furthermore, as spirometry requires the performance of potentially distressing respiratory manoeuvres which are to some extent user-effort dependent, there is need for non-invasive and simple-to-perform techniques to identify subtypes of COPD which are more closely related to clinically relevant outcomes.Materials and MethodsThe inspired sinewave test (IST) sinusoidally modulates the inspired concentration of a tracer gas (N2O) over successive tidal breaths. A single-compartment tidal-ventilation lung model processes the amplitude/phase of the expired N2O sinewave and estimates cardiopulmonary variables including: effective lung volume and indices of ventilatory heterogeneity (VH; ELV180/FRCpleth and ELV180/ELVpred). 83 COPD patients and 53 healthy controls performed the IST test, standard pulmonary function tests (Spirometry, body plethysmography and the single breath test of carbon monoxide uptake), and symptom severity questionnaires (COPD assessment test, CAT; mMRC dyspnoea-scale, mMRC-DS; Cough+Mucus score; C+M score).ResultsELV180/FRCpleth and ELV180/ELVpred were significantly lower in patients with COPD vs healthy participants (0.34±0.11 vs 0.68±0.14 and 0.7±0.27 vs 0.98±0.15, respectively; P<0.05). Multivariable regression analysis demonstrated that ELV180/FRCpleth was a stronger and independent predictor of CAT, mMRC-DS and C+M score vs FEV1%pred. ELV180/ELVpred was a stronger and independent and better predictor of C+M score vs FEV1%pred. Phenotyping patients, based upon ELV180/ELVpred and FRC%pred, uncovered significant symptomatic differences between groups.ConclusionThe IST indices of VH were superior and independent predictors of symptom severity vs FEV1%pred and has potential as a non-invasive and simple-to-perform method to stratify patients into subgroups related to clinically relevant features of COPD.

Anaerobic Carbon Monoxide Uptake by Microbial Communities in Volcanic Deposits at Different Stages of Successional Development on O-yama Volcano, Miyake-jima, Japan.

Research on Kilauea and O-yama Volcanoes has shown that microbial communities and their activities undergo major shifts in response to plant colonization and that molybdenum-dependent CO oxidizers (Mo-COX) and their activities vary with vegetation and deposit age. Results reported here reveal that anaerobic CO oxidation attributed to nickel-dependent CO oxidizers (Ni-COX) also occurs in volcanic deposits that encompass different developmental stages. Ni-COX at three distinct sites responded rapidly to anoxia and oxidized CO from initial concentrations of about 10 ppm to sub-atmospheric levels. CO was also actively consumed at initial 25% concentrations and 25 °C, and during incubations at 60 °C; however, uptake under the latter conditions was largely confined to an 800-year-old forested site. Analyses of microbial communities based on 16S rRNA gene sequences in treatments with and without 25% CO incubated at 25 °C or 60 °C revealed distinct responses to temperature and CO among the sites and evidence for enrichment of known and potentially novel Ni-COX. The results collectively show that CO uptake by volcanic deposits occurs under a wide range of conditions; that CO oxidizers in volcanic deposits may be more diverse than previously imagined; and that Ni-dependent CO oxidizers might play previously unsuspected roles in microbial succession.

Endogenous Carbon Monoxide Production and Diffusing Capacity of the Lung for Carbon Monoxide in Sepsis-Induced Acute Respiratory Distress Syndrome.

Low-dose inhaled carbon monoxide is a novel therapeutic under investigation in acute respiratory distress syndrome. The Coburn-Forster-Kane equation is a well-validated model of carbon monoxide uptake that can accurately predict carboxyhemoglobin levels to ensure safe administration of low-dose inhaled carbon monoxide in patients with acute respiratory distress syndrome. Using data from a Phase I trial of low-dose inhaled carbon monoxide, we performed a post hoc analysis to determine if the Coburn-Forster-Kane equation could be used to assess the diffusing capacity of the lung for carbon monoxide and endogenous carbon monoxide production in patients with sepsis-induced acute respiratory distress syndrome. Diffusing capacity of the lung for carbon monoxide was substantially reduced and correlated with Pao2/Fio2 and Sequential Organ Failure Assessment score. Endogenous carbon monoxide production was markedly elevated and was significantly associated with Lung Injury Score in sepsis-induced acute respiratory distress syndrome patients. Our data suggest that the Coburn-Forster-Kane equation can be used to estimate diffusing capacity of the lung for carbon monoxide and endogenous carbon monoxide production in mechanically ventilated patients. We found that increased endogenous carbon monoxide production and reduced diffusing capacity of the lung for carbon monoxide correlate with clinical endpoints associated with outcomes in patients with sepsis-induced acute respiratory distress syndrome.