Gross Primary Productivity of Four European Ecosystems Constrained by Joint CO2 and COS Flux Measurements.

Gross primary productivity (GPP), the gross uptake of carbon dioxide (CO2) by plant photosynthesis, is the primary driver of the land carbon sink, which presently removes around one quarter of the anthropogenic CO2 emissions each year. GPP, however, cannot be measured directly and the resulting uncertainty undermines our ability to project the magnitude of the future land carbon sink. Carbonyl sulfide (COS) has been proposed as an independent proxy for GPP as it diffuses into leaves in a fashion very similar to CO2, but in contrast to the latter is generally not emitted. Here we use concurrent ecosystem-scale flux measurements of CO2 and COS at four European biomes for a joint constraint on CO2 flux partitioning. The resulting GPP estimates generally agree with classical approaches relying exclusively on CO2 fluxes but indicate a systematic underestimation under low light conditions, demonstrating the importance of using multiple approaches for constraining present-day GPP.

Sun-induced fluorescence and gross primary productivity during a heat wave.

Remote sensing of sun-induced chlorophyll fluorescence (SIF) has been suggested as a promising approach for probing changes in global terrestrial gross primary productivity (GPP). To date, however, most studies were conducted in situations when/where changes in both SIF and GPP were driven by large changes in the absorbed photosynthetically active radiation (APAR) and phenology. Here we quantified SIF and GPP during a short-term intense heat wave at a Mediterranean pine forest, during which changes in APAR were negligible. GPP decreased linearly during the course of the heat wave, while SIF declined slightly initially and then dropped dramatically during the peak of the heat wave, temporally coinciding with a biochemical impairment of photosynthesis inferred from the increase in the uptake ratio of carbonyl sulfide to carbon dioxide. SIF thus accounted for less than 35% of the variability in GPP and, even though it responded to the impairment of photosynthesis, appears to offer limited potential for quantitatively monitoring GPP during heat waves in the absence of large changes in APAR.

Urban flux measurements reveal a large pool of oxygenated volatile organic compound emissions.

Atmospheric chemistry is fueled by a large annual influx of nonmethane volatile organic compounds (NMVOC). These compounds influence ozone formation, lead to secondary organic aerosol production, and play a significant role for the oxidizing capacity of the atmosphere. The anthropogenic NMVOC budget is considerably uncertain due to the diversity of urban emission sources. Here, we present comprehensive observations of urban NMVOC eddy covariance fluxes using a newly designed proton-transfer-reaction quadrupole interface time-of-flight mass spectrometer. We found emission fluxes of a surprisingly large pool of oxygenated NMVOCs (OVOCs) with an appreciable fraction of higher oxidized OVOCs that cannot be explained by known fast photochemical turnaround or current primary emission estimates. Measured OVOC/NMVOC bulk flux ratios are two to four times higher than inferred from aggregated anthropogenic emission inventories. Extrapolating these results would double the global anthropogenic NMVOC flux. In view of globally accelerating urbanization, our study highlights the need to reevaluate the influence of anthropogenic NMVOC on atmospheric chemistry, human health, and the climate system.

Urban eddy covariance measurements reveal significant missing NOx emissions in Central Europe.

Nitrogen oxide (NOx) pollution is emerging as a primary environmental concern across Europe. While some large European metropolitan areas are already in breach of EU safety limits for NO2, this phenomenon does not seem to be only restricted to large industrialized areas anymore. Many smaller scale populated agglomerations including their surrounding rural areas are seeing frequent NO2 concentration violations. The question of a quantitative understanding of different NOx emission sources is therefore of immanent relevance for climate and air chemistry models as well as air pollution management and health. Here we report simultaneous eddy covariance flux measurements of NOx, CO2, CO and non methane volatile organic compound tracers in a city that might be considered representative for Central Europe and the greater Alpine region. Our data show that NOx fluxes are largely at variance with modelled emission projections, suggesting an appreciable underestimation of the traffic related atmospheric NOx input in Europe, comparable to the weekend-weekday effect, which locally changes ozone production rates by 40%.

Estimating carbon dioxide fluxes from temperate mountain grasslands using broad-band vegetation indices.

The broad-band normalised difference vegetation index (NDVI) and the simple ratio (SR) were calculated from measurements of reflectance of photosynthetically active and short-wave radiation at two temperate mountain grasslands in Austria and related to the net ecosystem CO2 exchange (NEE) measured concurrently by means of the eddy covariance method. There was no significant statistical difference between the relationships of midday mean NEE with narrow- and broad-band NDVI and SR, measured during and calculated for that same time window, respectively. The skill of broad-band NDVI and SR in predicting CO2 fluxes was higher for metrics dominated by gross photosynthesis and lowest for ecosystem respiration, with NEE in between. A method based on a simple light response model whose parameters were parameterised based on broad-band NDVI allowed to improve predictions of daily NEE and is suggested to hold promise for filling gaps in the NEE time series. Relationships of CO2 flux metrics with broad-band NDVI and SR however generally differed between the two studied grassland sites indicting an influence of additional factors not yet accounted for.

Summertime elemental mercury exchange of temperate grasslands on an ecosystem-scale.

In order to estimate the air-surface mercury exchange of grasslands in temperate climate regions, fluxes of gaseous elemental mercury (GEM) were measured at two sites in Switzerland and one in Austria during summer 2006. Two classic micrometeorological methods (aerodynamic and modified Bowen ratio) have been applied to estimate net GEM exchange rates and to determine the response of the GEM flux to changes in environmental conditions (e.g. heavy rain, summer ozone) on an ecosystem-scale. Both methods proved to be appropriate to estimate fluxes on time scales of a few hours and longer. Average dry deposition rates up to 4.3 ng m-2 h-1 and mean deposition velocities up to 0.10 cm s-1 were measured, which indicates that during the active vegetation period temperate grasslands are a small net sink for atmospheric mercury. With increasing ozone concentrations depletion of GEM was observed, but could not be quantified from the flux signal. Night-time deposition fluxes of GEM were measured and seem to be the result of mercury co-deposition with condensing water. Effects of grass cuts could also be observed, but were of minor magnitude.

Leaf area controls on energy partitioning of a temperate mountain grassland.

Using a six year data set of eddy covariance flux measurements of sensible and latent heat, soil heat flux, net radiation, above-ground phytomass and meteorological driving forces energy partitioning was investigated at a temperate mountain grassland managed as a hay meadow in the Stubai Valley (Austria). The main findings of the study were: (i) Energy partitioning was dominated by latent heat, followed by sensible heat and the soil heat flux; (ii) When compared to standard environmental forcings, the amount of green plant matter, which due to three cuts varied considerably during the vegetation period, explained similar, and partially larger, fractions of the variability in energy partitioning; (iii) There were little, if any, indications of water stress effects on energy partitioning, despite reductions in soil water availability in combination with high evaporative demand, e.g. during the summer drought of 2003.

Sevoflurane and mivacurium in a patient with Huntington's chorea.

There is little experience of anaesthesia for patients with Huntington's chorea. These patients have an increased risk of intraoperative complications such as pulmonary aspiration. We present the successful anaesthetic management of a 17-yr-old patient suffering from Huntington's chorea requiring urgent appendectomy. After rapid-sequence induction with thiopental 400 mg and succinylcholine 100 mg, anaesthesia was maintained with sevoflurane. For maintenance of neuromuscular blockade mivacurium 10 mg was administered and repeated 15 min later. Except for a short episode of postoperative shivering, the perioperative course was uneventful. Sevoflurane and mivacurium were used safely and effectively in this patient.

[Knowledge-based diagnosis and therapeutic recommendations with fuzzy-set theory methods in patients with acute lung failure (ARDS)]. / Wissensbasierte Diagnostik und Therapieempfehlung mit Methoden der Fuzzy-Set-Theorie bei Patienten mit akutem Lungenversagen (ARDS).

OBJECTIVE: Since the treatment of patients with severe ARDS using the extracorporal lung assist (ECLA) methods remains a cost intensive and speculative procedure, a knowledge based computer system should be created and evaluated in order to support clinical decisions. METHODS: The model was based on the fuzzy set theory and therefore able to give decisions between yes and no, that means that a criterion could also be fulfilled to 35% or 80% for example. The development of this computer program consists of two steps: first, the entry criteria for the ECLA therapy were established within a framework of an international evaluation of clinical data from 3 centres (Berlin, Marburg, Vienna). Here, inherent vagueness, uncertainty of the occurrence and limited availability of medical data are to be considered to establish a useful tool. Secondly, this was done by grouping and weighting of parameters by the system and the status of each patient or patient group was assigned by the percentage of fulfillment of the criterion. RESULTS: By using a mixed sample of patients from these three centres, the fulfillment of entry criteria according either to definitions of Berlin or to definition of Marburg was different (68% versus 36%). Other differences (36% vs. 22% and 68% vs. 60%) were found between the fuzzy based score and the crisp score which represents the usually performed method. CONCLUSIONS: This now preevaluated minimal data set to describe severe ARDS patients based on the fuzzy set theory may be useful to evaluate patients for ECLA therapy or for another controlled ARDS-therapy.

Effects of pentoxifylline on hemodynamics and oxygenation in septic and nonseptic patients.

OBJECTIVE: To evaluate the effects of pentoxifylline on hemodynamics and systemic oxygenation in septic and nonseptic critically ill patients. DESIGN: Prospective clinical investigation. SETTING: Intensive care unit (ICU) of a university hospital. PATIENTS: Nineteen critically ill patients were included in the study 1 to 4 days after their admission to the ICU. A systemic inflammatory response syndrome was present in 12 patients, fulfilling at least two of the American College of Chest Physicians/ Society of Critical Care Medicine Consensus Conference criteria. The other seven patients did not fulfill these criteria and were classified as nonseptic. INTERVENTIONS: All patients were mechanically ventilated. The dosage of catecholamines was kept constant during the entire study period and at least during 15 mins before the start of the study. In both study groups, pulmonary and radial artery catheters were inserted and 5 mg/kg of pentoxifylline (diluted in 300 mL of physiologic saline) was intravenously administered over a period of 180 mins at a rate of 100 mL/hr. MEASUREMENTS AND MAIN RESULTS: Hemodynamic variables, oxygen transport (DO2), oxygen uptake (VO2), and oxygen extraction ratio were determined before pentoxifylline, after 2.5 mg/kg of pentoxifylline, after 5 mg/kg of pentoxifylline, and 60 mins after the termination of pentoxifylline. Repeated-measures analysis of variance and Mann-Whitney test were used for statistical analysis. At baseline, there were significant differences between the septic and the nonseptic groups in mean pulmonary arterial pressure (septic: 31 +/- 5 mm Hg; nonseptic: 26 +/- 7 mm Hg, p < .05), and pulmonary vascular resistance index (PVRI) (septic: 344 +/- 121 dyne.sec/ cm5.m2; nonseptic: 233 +/- 100 dyne.sec/cm5.m2, p < .05). In the septic group, significant increases in heart rate and cardiac index were observed. Systemic vascular resistance index and PVRI decreased. No significant changes in hemodynamic variables occurred in the nonseptic group. In both groups, DO2 and VO2 increased significantly, while oxygen extraction ratio remained unchanged. CONCLUSIONS: The administration of pentoxifylline to septic patients results in a significant improvement in hemodynamic performance compared with critically ill nonseptic patients. The better hemodynamic state is accompanied by an increase in DO2 and VO2 with unchanged oxygen extraction ratio.

The acute respiratory distress syndrome: definitions, severity and clinical outcome. An analysis of 101 clinical investigations.

OBJECTIVE: To determine possible changes in outcome from acute respiratory distress syndrome (ARDS) and to compare severity of lung injury and methods of treatment from 1967 to 1994. DATA SOURCES: Computerized (Medline, Current Contents) and manual (Cumulated Index Medicus) literature search using the key word and/or title ARDS. STUDY SELECTION: Only clinical studies published as full papers reporting data on both patient mortality (survival) and oxygenation index (PaO2/FIO2) were included. Single case reports, abstracts, reviews and editorials were excluded from evaluation. DATA EXTRACTION: Relevant data were extracted in duplicate, followed by quality checks on approximately 80% of data extracted. DATA SYNTHESIS: 101 papers reporting on 3264 patients were included: 48 studies (2207 patients) were performed in the USA, 43 studies (742 patients) in Europe and 10 studies (315 patients) elsewhere. Mortality reported in these studies was 53 +/- 22% (mean +/- SD), with no apparent trend towards a higher survival (1994: 22 studies, mortality 51 +/- 19%). The mean PaO2/FIO2 ratio remained unchanged throughout the observation period (118 +/- 47 mmHg). No correlation could be established between outcome and PaO2/FIO2 or lung injury score. Patients who underwent pressure-limited ventilation had a significantly lower mortality (35 +/- 20%) than patients on volume-cycled ventilation (54 +/- 22%) or patients for whom there was no precise information on ventilatory support (59 +/- 19%). Significantly lower PaO2/FIO2 ratios (61 +/- 17 mmHg) were observed in patients prior to extracorporeal lung assist, together with mortality rates in the range of those for conventionally treated patients (55 +/- 22%). CONCLUSIONS: The mortality of ARDS patients remained constant throughout the period studied. Therefore, the standard for outcome in ARDS should be a mortality in the 50% range. Neither PaO2/FIO2 ratio nor lung injury score was a reliable predictor for outcome in ARDS. Patients might benefit from pressure-limited ventilatory support, as well as extracorporeal lung assist. Since crucial data were missing in most clinical studies, thus preventing direct comparison, we emphasize the importance of using standardized definitions and study entry criteria.

The clinical application of two newly developed lipid emulsions (Solipid 20% S&E) in critically ill patients.

OBJECTIVE: The clinical compatibility of two newly developed lipid emulsions based on soy oil (20%) emulsified with egg lecithin (12 g/l) or soy lecithin (15 g/l) (Solipid 20% E&S) has been compared. DESIGN: Double-blind prospective randomized study. SETTING: Intensive care unit of a university hospital. PATIENTS: 20 patients (16 men, 4 women, age 20-59 years) were entered into the study. INTERVENTIONS: One g of lipids/kg body weight per day was administered on day 1 and subsequently 2 g/kg/day on days 2-5. Blood was drawn once a day, lipids, lipoproteins, apoproteins and other routine clinical chemistry parameters were determined. RESULTS: No significant increase of total triglycerides could be observed. Total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, apolipoproteins A I and B usually remained below the reference ranges. Electrolytes, uric acid and glucose, blood cells, parameters of liver and kidney function, coagulation and protein metabolism did not show relevant changes; only the activity of gamma-GT in both groups--independent of the sort of lecithin--increased significantly. CONCLUSION: The results indicate adequate elimination of both tested lipid emulsions from the plasma at usual clinical conditions. Therefore Solipid 20% S&E can be used in critically ill patients.

Severity and outcome of ARDS: the present place of extracorporeal lung assist (ECLA).

Within the last decade extracorporeal lung assist has been recommended for the treatment of acute respiratory distress syndrome. However, this recommendation was challenged by several recent clinical studies and reviews. The goal of our analysis was therefore to investigate data on outcome and severity of gas exchange disturbance published from patients treated with ECLA. These data were compared to a historical control group consisting of ARDS patients treated conventionally. Computerized (MEDLINE 1967-95) literature search using the keywords ARDS, ECLA, ECMO, ECCO2R and HUMAN was performed. Only clinical studies published as full papers reporting data on both, patients mortality and oxygenation index (PaO2/FiO2) were included. Overall mean mortality reported was 53 +/- 22% in 17 studies (419 patients), with no apparent trend towards a higher survival within the last decade with a mean PaO2/FIO2 (14 papers; 61 +/- 17 mmHg). However, mean mortality rates of ARDS patients requiring ECLA was 52.3% and 44.9% if patients undergoing ECMO were excluded (3 papers). Therefore the mortality of these patients with severe lung injury was in the range of patients treated conventionally. Patient outcome observed in our analysis is in accordance with the mortality rates from the European ECLA centres published recently (49% in 1993). Therefore, we conclude that the mean mortality rate of patients suffering from severe ARDS treated with ECLA is in the 50% range and does not differ significantly from those of patients treated conventionally, despite significantly poorer pulmonary function.

In vivo modulation of human neutrophil function by pentoxifylline in patients with septic syndrome.

The influence of pentoxifylline on human polymorphonuclear granulocyte (PMN) respiratory burst activity (RBA) was studied in 23 patients fulfilling the established criteria of sepsis and in 10 healthy donors. Pentoxifylline (PTX) was administered (5 mg/kg) by intravenous infusion in 13 septic patients over a period of 180 min. The control group consisted of 10 patients with septic syndrome who received an infusion of physiological saline. For determination of RBA, 10 mL of blood was drawn at respective time intervals before, during, and after treatment with PTX or a placebo. RBA measurements were performed using a chemiluminescence assay after stimulation of PMN with formyl-methionyl-leucyl-phenylalanine (FMLP), phorbol-myristate-acetate, and opsonized zymosan, respectively. RBA measurements of each patient were performed in replicate samples. CL was measured for 1 h at respective time intervals (1, 3, 5, 8, 10, 15 min etc). RBA of PMN of septic patients was compared with RBA of PMN of healthy donors and patients receiving PTX were compared with controls. Our results demonstrate that PMN of patients with sepsis had an increased oxidative response compared with healthy donors. We found that PTX administered intravenously was able to reduce this reactivity. RBA was significantly decreased during PTX infusion when PMN were stimulated with FMLP and phorbol-myristate-acetate, compared with the control group. No significant decrease was observed when PMN were stimulated with opsonized zymosan. These data suggest that PTX may be a valuable drug in septic state.

Resistance of nitrogen metabolism to growth hormone treatment in the early phase after injury of patients with multiple injuries.

OBJECTIVES AND DESIGN: Several studies have shown an anticatabolic effect of recombinant human growth hormone (rhGH) in surgical patients. We investigated, in a prospective, randomized, double blind, and placebo-controlled study, the effect of r-hGH on hormone and nitrogen metabolism in 14 patients with multiple injuries in the early phase of injury. MATERIALS AND METHODS: All patients were treated in the intensive care unit, had mechanical ventilation, and were highly catabolic, with a mean daily nitrogen loss of 13.2 +/- 1.8 g. r-hGH was given subcutaneously (once a day, at 8 PM) in a dosage of 0.2 IU/kg.d for seven days, starting on the second day after injury. RESULTS: Administration of r-hGH evoked a significant increase in plasma concentrations of GH, insulin-like growth factor-I (IGF-I), and insulin-like growth factor binding-protein-3 (IGFBP-3). No significant differences were found for either daily or cumulative nitrogen balances (-103.1 +/- 14 g for patients receiving r-hGH and -92.1 +/- 18.1 for those with placebo). r-hGH therapy did not affect skeletal muscle extracellular water, nor did it affect plasma or muscle concentrations of total free amino acids or glutamine. Plasma albumin, prealbumin, and retinol-binding protein concentrations were also unchanged by r-hGH therapy, as were the urinary excretion of potassium and urea. CONCLUSIONS: We conclude that elevated plasma levels of GH, insulin, and IGF-I are unable to effect a protein anabolic drive in patients with multiple injuries during the early postinjury phase and assume that this r-hGH resistance to nitrogen metabolism takes place at the level distal to IGF-I.