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.

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 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%.

Respiratory burst capability of polymorphonuclear neutrophils and TNF-alpha serum levels in relationship to the development of septic syndrome in critically ill patients.

Activated polymorphonuclear neutrophils (PMN) and neutrophil activating mediators such as tumor necrosis factor-alpha (TNF-alpha) are thought to be involved in the pathophysiology of sepsis and multiple organ failure syndrome (MOFS). In critically ill patients at high risk for the development of septic syndrome (n = 17) peripheral blood PMN were assayed for O2- and H2O2 production after stimulation with phorbol myristate acetate (PMA, 40 nM). Serum TNF-alpha levels were determined by ELISA. At the time of admission to the intensive care unit we found significant higher levels of TNF-alpha (P = 0.0001) in the serum of patients finally developing sepsis correlating to higher respiratory burst capability in comparison to nonseptic patients. Additionally we were able to demonstrate a significant (P = 0.0016) lower dismutation rate of O2- to H2O2 in deceased patients in comparison to survivors. These results give further evidence that elevated levels of circulating TNF-alpha and activated PMN play a significant role in the pathogenesis of septic syndrome in critically ill patients.

Role of beta-endorphins in silent myocardial ischemia.

The reason for the absence of pain perception in silent myocardial ischemia is unknown. A role of increased endorphinic activity in patients with silent ischemia has been postulated. To further investigate this hypothesis, 10 men with documented coronary artery disease and previous positive electrocardiographic findings during exercise without anginal pain were studied. Six healthy volunteers served as control subjects. The protocol included 2 bicycle exercise tests, the first test serving as baseline and the second performed after administration of naloxone, a specific opiate antagonist. Plasma beta-endorphin levels were measured by radioimmunoassay in both tests at rest, at peak exercise level and after recovery. All patients underwent thallium-201 scintigraphy after coronary vasodilation to provide an additional independent marker of ischemia. All patients showed stress-induced reversible perfusion abnormalities. No patient reported pain after naloxone application. Exercise duration, blood pressure and heart rate were not significantly altered by naloxone. Plasma beta-endorphin levels ranged from 18 +/- 6 pg/100 microliters (mean +/- standard deviation) at rest to 22 +/- 6 pg/100 microliters during exercise in the patient group and from 20 +/- 5 to 27 +/- 9 pg/100 microliters in the control subjects. Thus, there was no significant increase of plasma beta-endorphins during exercise or after naloxone administration, nor was there any difference observed between patients and control group. These data support the view that endorphinic activity does not play an essential role in the pathophysiology of silent myocardial ischemia.

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.

Mixed venous oxygen saturation in critically ill septic shock patients. The role of defined events.

STUDY OBJECTIVE: To investigate the frequency and extent of spontaneous changes ("events") in continuously measured mixed venous oxygen saturation (SvO2) in septic patients and to determine whether attention to individual event-frequency offers additional information for patient management. DESIGN: Nonrandomized prospective study. SETTING: General intensive care unit at a university hospital. PATIENTS: Fifteen patients suffering from septic shock and multiple organ dysfunction syndrome. MEASUREMENTS: For the continuous assessment of SvO2 a fiberoptic pulmonary artery catheter (Baxter Edwards) was inserted in all patients. A certain event was defined as a sudden change in SvO2 of > or = 5 percent lasting for > 10 min. All events were grouped as either moderate (< or = 10 percent changes in SvO2) or severe events (> 10 percent changes). Hemodynamics and inotropic support, oxygenation and ventilatory support, hemoglobin levels and body temperature were determined at the event and compared with the ultimate values registered before the event. RESULTS: We evaluated 377 events during an observation period of 1,575 h. Patients' mean SvO2 levels ranged between 72 +/- 7 and 82 +/- 4. Desaturations below 65 percent (39 out of 377 events) occurred in 11 patients. Overall, 74 percent of all events were moderate and 26 percent were severe. The incidence of events was 5.6 +/- 1.5 during 24 h in survivors (n = 10) and 6.3 +/- 1.6 during 24 h in nonsurvivors (n = 5). While in survivors only 20 percent of all events were severe events, this portion was significantly higher in nonsurvivors (34 percent; p = 0.03). In 67 percent of all events we observed changes in the registered physiologic parameters or therapeutic interventions probably causing the event. The cause of the remaining 33 percent of all events could not be elucidated. CONCLUSIONS: The SvO2 of septic shock patients is mainly normal or even supranormal. However, short-term changes in SvO2 do occur frequently in these patients. Nonsurvivors exhibit a higher frequency as well as a significantly greater severity of events, which may point toward a concealed mismatch of oxygen supply and demand. A high incidence of short-term SvO2 changes in a septic shock patient may be of diagnostic and prognostic significance. Therefore, we recommend the installation of a computerized alarm-function for the automatic detection and indication of frequent events.

Right ventricular function in early septic shock states.

OBJECTIVES: To define a variable which could reliably predict when fluid resuscitation as monotherapy is not expected to improve organ perfusion pressure, owing to limitations in cardiac output responsiveness in patients with severe sepsis. DESIGN: Prospective controlled trial. SETTING: Anesthesiological ICU in a university hospital. PATIENTS: Twenty seven patients in early septic shock states (MAP < 60 mmHg). INTERVENTIONS: Infusion therapy was titrated until no further increase in cardiac index and mean arterial pressure could be achieved. Fluid resuscitation as monotherapy was deemed unsuccessful at the end of 2 h if inotropic or vasoactive pharmacologic support was required to maintain a mean arterial pressure > 60 mmHg. MEASUREMENTS AND RESULTS: We investigated the hemodynamic course during fluid resuscitation (2850 +/- 210 ml crystalloids) with special emphasis on right heart function using the thermodilution technique. Eleven patients (group A) had a right ventricular (RV) ejection fraction below 45%. In this group positive inotropic and/or vasoactive drugs were obligatory to achieve and maintain a sufficient perfusion pressure (MAP > 60 mmHg) after fluid challenge. CONCLUSIONS: In 27 septic shock patients investigated, we diagnosed right ventricular dysfunction in 41%. In this specific patient population fluid replacement alone did not succeed in stabilizing hemodynamic variables, therefore necessitating catecholamine therapy.

The activity of the sympathetic nervous system following severe head injury.

The activity of the sympathetic nervous system during the course of severe closed head injury has been evaluated in 15 patients by measuring plasma levels of epinephrine and norepinephrine. With the onset of the transition stage from midbrain syndrome to the apallic syndrome the plasma levels mainly of norepinephrine started to increase and remained high during the further course of the disease. During the remission from the apallic syndrome the elevated norepinephrine levels started to decline. The data indicate that a longlasting overactivity of the sympathetic nervous system is a characteristic feature in the course of severe head injury. As a rational therapy to protect the peripheral tissues against the consequences of a longlasting sympathetic overactivity we suggest the use of beta-adrenergic blocking agents and adrenergic neuron blocking drugs.

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.

Neuroleptanalgesia in acute myocardial infarction: effects of hemodynamic parameters and plasma catecholamines.

The use of neuroleptanalgesia in acute myocardial infarction offers the possibility of reducing pain and emotional stress. The influence of such treatment on hemodynamic parameters (heart rate, cardiac output, stroke volume, peripheral resistance, systemic blood pressure, and pulmonary pressure) and on the plasma level of adrenaline and noradrenaline has been studied in 6 patients with acute myocardial infarction. This results demonstrate that during neuroleptanalgesia the already elevated levels of noradrenaline and adrenaline further increase. This increase was most pronounced in the patients with the highest initial levels of catecholamines. Since the peripheral resistance and systolic and diastolic blood pressures decrease concomitantly, it is concluded that the increase in levels of noradrenaline and adrenaline further increase. This increase was most pronounced in the plasma catecholamines is due to a reaction of the sympathetic nervous system to the alpha-adrenergic receptor blocking activity of droperidol causing vasodilation. The data indicate that pain, emotional stress, and anxiety in the acute phase of myocardial infarction do not play the expected essential role for the activation of the sympathetic nervous system generally observed in acute myocardial infarction. Additionally, the data demonstrate that drugs producing a vasodilation can have a deteriorating effect on the hemodynamic situation and that a reduction of the afterload by vasodilating drugs can result in a further increase in the release of catecholamines.

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.

Haemodynamic evaluation during small volume resuscitation in patients with acute respiratory failure.

In addition to the invasive haemodynamic monitoring procedures, an on-line assessment of cardiac performance by means of transoesophageal echocardiography might have a certain role in small volume resuscitation of patients with acute respiratory failure or Adult Respiratory Distress Syndrome (ARDS). The goal of this investigation was therefore to determine the effects of a hypertonic hyperoncotic solution, hypertonic hydoxyethl-starch (HHES), (HHES = HES [200.000/0.6-0.66; 60 g l-1; Leopold, Graz; Austria] combined with NaCl [75 g l-1) on haemodynamics and cardiac performance using the transoesophageal echocardiography. After institutional approval we investigated 23 patients suffering from septic ARDS after trauma or major surgery during four periods of resuscitation. Phase I = control values after infusion of 20 ml kg-1 crystalloid solution, phase II = 50% hypertonic hydroxyethyl-starch solution (2 ml kg-1), phase III = at the end of HHES (4 ml kg-1), IV = 30 min after the end of HHES. Before HHES-infusion, all patients showed arterial hypotension with mean arterial pressures of 64 +/- 2 mmHg. The infusion of 2 ml kg-1 HHES resulted in a significant increase of systemic and pulmonary arterial pressures over the study period. A significant improvement in cardiac output was associated with increasing stroke volumes, oxygen delivery and oxygen consumption (see Tables 1 and 2). Small volume resuscitation also resulted in significant increases of endsystolic and endiastolic left ventricular areas and the corresponding calculated wall stress (Figs 1-3). We conclude from our preliminary data that when using HHES, only modest fluid resuscitation was sufficient to restore adequate preload and oxygen delivery in patients with sepsis-related acute respiratory failure.

Scanning electron microscopy of circulating platelets reveals new aspects of platelet alteration during cardiopulmonary bypass operations.

Seventeen male patients undergoing cardiopulmonary bypass (CPBP) surgery for aorto-coronary bypass grafting were investigated by scanning electron microscopy (SEM) for alterations of the surface morphology of circulating platelets. An initial decline in the percentage of unactivated smooth discocytes (SD) to 87 +/- 12% was found after thoracotomy. Three minutes after the onset of CPBP, the percentage of SD had dropped drastically to 59 +/- 13%, and by the 8th minute of CPBP it had dropped to its lowest point (49 +/- 19%). On the other hand, the percentage of shape-changed platelets (SC) increased to 17 +/- 9% after 3 minutes, and the percentage of pseudopod discocytes (PD) to 25 +/- 13% after 8 minutes. Surprisingly, a remarkable recovery of platelet morphology could be observed after even 15 minutes of CPBP, and by the end of bypass 78 +/- 15% of the circulating platelets had regained the smooth discoid (SD) appearance of unactivated platelets. We conclude that this recovery of platelet morphology is due to an increasing insensitivity of the platelets to activating stimuli during the course of CPBP. Our study provides evidence that the only major platelet activation occurs during the first minutes of CPBP, and that CPBP-caused platelet activation is much less pronounced than generally believed.

[Plasma catecholamines in accidental hypothermia (author's transl)]. / Das Verhalten der Plasmakatecholamine bei akzidenteller Hypothermie.

The plasma levels of adrenaline and noradrenaline were measured by a radioenzymatic method in 3 patients with accidental hypothermia and followed up until normal body temperature was achieved. In all 3 patients the hypothermia was accompanied by markedly elevated levels of noradrenaline, whereas adrenaline increased considerably only in one of the 3 patients. During normalization of body temperature the elevated catecholamine levels started to decrease. In 2 of the 3 patients nearly normal catecholamine levels were measured, when body temperature had normalized. In spite of the high levels of catecholamines in plasma the heart rate was strikingly low at the lowest temperature. During the increase of the lowered body temperature the heart rate increased in contrast to the decreasing catecholamine levels. The increase of the catecholamine levels in plasma in patients with accidental hypothermia can be explained either by an augmented stimulation of the sympathetic nervous system or by a decreased metabolism. On the basis of the high endogeneous catecholamine levels the use of beta-sympathomimetics appears contraindicated in case a haemodynamic insufficiency develops during the course of accidental hypothermia.

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.

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.

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.