Improved coronary artery definition with T2-weighted, free-breathing, three-dimensional coronary MRA.

BACKGROUND: Three-dimensional (3D) navigator-gated and prospectively corrected free-breathing coronary magnetic resonance angiography (MRA) allows for submillimeter image resolution but suffers from poor contrast between coronary blood and myocardium. Data collected over >100 ms/heart beat are also susceptible to bulk cardiac and respiratory motion. To address these problems, we examined the effect of a T2 preparation prepulse (T2prep) for myocardial suppression and a shortened acquisition window on coronary definition. METHODS AND RESULTS: Eight healthy adult subjects and 5 patients with confirmed coronary artery disease (CAD) underwent free-breathing 3D MRA with and without T2prep and with 120- and 60-ms data-acquisition windows. The T2prep resulted in a 123% (P<0. 001) increase in contrast-to-noise ratio (CNR). Coronary edge definition was improved by 33% (P<0.001). Acquisition window shortening from 120 to 60 ms resulted in better vessel definition (11%; P<0.001). Among patients with CAD, there was a good correspondence with disease. CONCLUSIONS: Free-breathing, T2prep, 3D coronary MRA with a shorter acquisition window resulted in improved CNR and better coronary artery definition, allowing the assessment of coronary disease. This approach offers the potential for free-breathing, noninvasive assessment of the major coronary arteries.

Relationship between motion of coronary arteries and diaphragm during free breathing: lessons from real-time MR imaging.

OBJECTIVE: Diaphragmatic navigators are frequently used in free-breathing coronary MR angiography, either to gate or prospectively correct slice position or both. For such approaches, a constant relationship between coronary and diaphragmatic displacement throughout the respiratory cycle is assumed. The purpose of this study was to evaluate the relationship between diaphragmatic and coronary artery motion during free breathing. SUBJECTS AND METHODS: A real-time echoplanar MR imaging sequence was used in 12 healthy volunteers to obtain 30 successive images each (one per cardiac cycle) that included the left main coronary artery and the domes of both hemidiaphragms. The coronary artery and diaphragm positions (relative to isocenter) were determined and analyzed for effective diaphragmatic gating windows of 3, 5, and 7 mm (diaphragmatic excursions of 0-3, 0-5, and 0-7 mm from the end-expiratory position, respectively). RESULTS: Although the mean slope correlating the displacement of the right diaphragm and the left main coronary artery was approximately 0.6 for all diaphragmatic gating windows, we also found great variability among individual volunteers. Linear regression slopes varied from 0.17 to 0.93, and r2 values varied from .04 to .87. CONCLUSION: Wide individual variability exists in the relationship between coronary and diaphragmatic respiratory motion during free breathing. Accordingly, coronary MR angiographic approaches that use diaphragmatic navigator position for prospective slice correction may benefit from patient-specific correction factors. Alternatively, coronary MR angiography may benefit from a more direct assessment of the respiratory displacement of the heart and coronary arteries, using left ventricular navigators.

Efecto de los usos del suelo en la emisión de dióxido de carbono del suelo a la atmósfera en un agroecosistema semiárido del Valle del Ebro

Los cambios en los usos del suelo han contribuido de manera importante al incremento de gases de efecto invernadero en la atmósfera, especialmente de dióxido de carbono, aumentando sus emisiones desde 1970 en un 80%. Estos cambios causan la alteración de los suelos provocando un impacto sobre el ciclo del carbono, aumentando las tasas de descomposición de la fracción orgánica creando así un flujo de CO2 a la atmosfera. Entre las recomendaciones del Panel Intergubernamental de expertos sobre el Cambio Climático (IPCC, en inglés), y contemplado en el Protocolo de Kyoto, se encuentra el proceso de secuestro de carbono en suelos, que implica la eliminación del CO2 atmosférico por parte de las plantas y su almacenamiento como materia orgánica del suelo. Para poder favorecer dicho proceso, en un determinado tipo de ecosistema, es fundamental conocer cuáles son los factores que gobiernan la respiración del suelo y el impacto que tienen los diferentes usos en la emisión de CO2. En el presente trabajo se han estudiado 4 usos del suelo representativos del secano aragonés: un monocultivo de cebada en siembra directa (NT), un suelo abandonado labrado (AC), un suelo abandonado no alterado (AU) y un suelo forestal (FR) con el objetivo de conocer sus tasas de respiración, la influencia de diferentes parámetros edáficos en ellas, y proponer cambios en el uso del suelo que ayuden a mitigar estas emisiones. Además, se ha dedicado un apartado para conocer cómo influyen diferentes técnicas de fertilización nitrogenada (mineral y orgánica) en la respiración de un monocultivo de cebada en siembra directa. En cuanto a los usos, los resultados obtenidos tanto in situ como en laboratorio muestran una mayor respiración en AC, siendo los valores más bajos los de NT y FR. Una de las principales conclusiones es que la supresión del laboreo y del periodo de barbecho largo, así como la conversión de tierras abandonadas y marginales a cultivos y zonas forestales se presentan en este tipo de ecosistemas como prácticas de secuestro de carbono. En el estudio de aplicación de fertilizantes, no se observó ningún cambio en la respiración del suelo después de la aplicación de nitrógeno mineral. En cambio, el suelo fertilizado con purín sí que mostró picos de emisión durante las siguientes horas a la incorporación de éste, debido fundamentalmente a su alto contenido de carbono lábil.

Oedeme pulmonaire chez un jeune homme sportif [Acute pulmonary oedema in a young sportive man]

This article reports the case of a 31 years old man who suffered from an acute pulmonary oedema after laryngospasma following extubation. This pathology, better known by anesthesiologists than internists, results primarly from a rapid rise in negative intrapleural pressure. It is not associated with previous cardio-pulmonary illness and has a begnin course with resolution within 48 hours with oxygen and positive end expiratory pressure support.

Modifiable and nonmodifiable risk factors for postoperative delirium after cardiac surgery with cardiopulmonary bypass.

Postoperative delirium after cardiac surgery is associated with increased morbidity and mortality as well as prolonged stay in both the intensive care unit and the hospital. The authors sought to identify modifiable risk factors associated with the development of postoperative delirium in elderly patients after elective cardiac surgery in order to be able to design follow-up studies aimed at the prevention of delirium by optimizing perioperative management. A post hoc analysis of data from patients enrolled in a randomized controlled trial was performed. A single university hospital. One hundred thirteen patients aged 65 or older undergoing elective cardiac surgery with cardiopulmonary bypass. None. MEASUREMENTS AND MAINS RESULTS: Screening for delirium was performed using the Confusion Assessment Method (CAM) on the first 6 postoperative days. A multivariable logistic regression model was developed to identify significant risk factors and to control for confounders. Delirium developed in 35 of 113 patients (30%). The multivariable model showed the maximum value of C-reactive protein measured postoperatively, the dose of fentanyl per kilogram of body weight administered intraoperatively, and the duration of mechanical ventilation to be independently associated with delirium. In this post hoc analysis, larger doses of fentanyl administered intraoperatively and longer duration of mechanical ventilation were associated with postoperative delirium in the elderly after cardiac surgery. Prospective randomized trials should be performed to test the hypotheses that a reduced dose of fentanyl administered intraoperatively, the use of a different opioid, or weaning protocols aimed at early extubation prevent delirium in these patients.

Impact of bedside open lung biopsies on the management of mechanically ventilated immunocompromised patients with acute respiratory distress syndrome of unknown etiology.

BACKGROUND: Open lung biopsy (OLB) is helpful in the management of patients with acute respiratory distress syndrome (ARDS) of unknown etiology. We determine the impact of surgical lung biopsies performed at the bedside on the management of patients with ARDS. METHODS: We reviewed all consecutive cases of patients with ARDS who underwent a surgical OLB at the bedside in a medical intensive care unit between 1993 and 2005. RESULTS: Biopsies were performed in 19 patients mechanically ventilated for ARDS of unknown etiology despite extensive diagnostic process and empirical therapeutic trials. Among them, 17 (89%) were immunocompromised and 10 patients experienced hematological malignancies. Surgical biopsies were obtained after a median (25%-75%) mechanical ventilation of 5 (2-11) days; mean (+/-SD) Pao(2)/Fio(2) ratio was 119.3 (+/-34.2) mm Hg. Histologic diagnoses were obtained in all cases and were specific in 13 patients (68%), including 9 (47%) not previously suspected. Immediate complications (26%) were local (pneumothorax, minimal bleeding) without general or respiratory consequences. The biopsy resulted in major changes in management in 17 patients (89%). It contributed to a decision to limit care in 12 of 17 patients who died. CONCLUSION: Our data confirm that surgical OLB may have an important impact on the management of patients with ARDS of unknown etiology after extensive diagnostic process. The procedure can be performed at the bedside, is safe, and has a high diagnostic yield leading to major changes in management, including withdrawal of vital support, in the majority of patients.

Influence of the menstrual cycle on the sweating response measured by direct calorimetry in women exposed to warm environmental conditions.

The whole body sweating response was measured at rest in eight women during the follicular (F) and the luteal (L) phases of the menstrual cycle. Subjects were exposed for 30-min to neutral (N) environmental conditions [ambient temperature (Ta) 28 degrees C] and then for 90-min to warm (W) environmental conditions (Ta, 35 degrees C) in a direct calorimeter. At the end of the N exposure, tympanic temperature (Tty) was 0.18 (SEM 0.06) degrees C higher in the L than in the F phase (P less than 0.05), whereas mean skin temperature (Tsk) was unchanged. During W exposure, the time to the onset of sweating as well as the concomitant increase in body heat content were similar in both phases. At the onset of sweating, the tympanic threshold temperature (Tty,thresh) was higher in the L phase [37.18 (SEM 0.08) degrees C] than in the F phase [36.95 (SEM 0.07) degrees C; P less than 0.01]. The magnitude of the shift in Tty,thresh [0.23 (SEM 0.07) degrees C] was similar to the L-F difference in Tty observed at the end of the N exposure. The mean skin threshold temperature was not statistically different between the two phases. The slope of the relationship between sweating rate and Tty was similar in F and L. It was concluded that the internal set point temperature of resting women exposed to warm environmental conditions shifted to a higher value during the L phase compared to the F phase of the menstrual cycle; and that the magnitude of the shift corresponded to the difference in internal temperature observed in neutral environmental conditions between the two phases.

Reproducibility of 3D free-breathing magnetic resonance coronary vessel wall imaging.

AIMS: Although the coronary artery vessel wall can be imaged non-invasively using magnetic resonance imaging (MRI), the in vivo reproducibility of wall thickness measures has not been previously investigated. Using a refined magnetization preparation scheme, we sought to assess the reproducibility of three-dimensional (3D) free-breathing black-blood coronary MRI in vivo. METHODS AND RESULTS: MRI vessel wall scans parallel to the right coronary artery (RCA) were obtained in 18 healthy individuals (age range 25-43, six women), with no known history of coronary artery disease, using a 3D dual-inversion navigator-gated black-blood spiral imaging sequence. Vessel wall scans were repeated 1 month later in eight subjects. The visible vessel wall segment and the wall thickness were quantitatively assessed using a semi-automatic tool and the intra-observer, inter-observer, and inter-scan reproducibilities were determined. The average imaged length of the RCA vessel wall was 44.5+/-7 mm. The average wall thickness was 1.6+/-0.2 mm. There was a highly significant intra-observer (r=0.97), inter-observer (r=0.94), and inter-scan (r=0.90) correlation for wall thickness (all P<0.001). There was also a significant agreement for intra-observer, inter-observer, and inter-scan measurements on Bland-Altman analysis. The intra-class correlation coefficients for intra-observer (r=0.97), inter-observer (r=0.92), and inter-scan (r=0.86) analyses were also excellent. CONCLUSION: The use of black-blood free-breathing 3D MRI in conjunction with semi-automated analysis software allows for reproducible measurements of right coronary arterial vessel-wall thickness. This technique may be well-suited for non-invasive longitudinal studies of coronary atherosclerosis.

Potential impact of climate change on vegetation in the European Alps: a review

Based on conclusions drawn from general climatic impact assessment in mountain regions, the review synthesizes results relevant to the European Alps published mainly from 1994 onward in the fields of population genetics, ecophysiology, phenology, phytogeography, modeling, paleoecology and vegetation dynamics. Other important factors of global change interacting synergistically with climatic factors are also mentioned, such as atmospheric CO2 concentration, eutrophication, ozone or changes in land-use. Topics addressed are general species distribution and populations (persistence, acclimation, genetic variability, dispersal, fragmentation, plant/animal interaction, species richness, conservation), potential response of vegetation (ecotonal shift - area, physiography - changes in the composition, structural changes), phenology, growth and productivity, and landscape. In conclusion, the European Alps appear to have a natural inertia and thus to tolerate an increase of 1-2 K of mean air temperature as far as plant species and ecosystems are concerned in general. However, the impact of land-use is very likely to negate this buffer in many areas. For a change of the order of 3 K or more, profound changes may be expected.

Oxidative phosphorylation flexibility in the liver of mice resistant to high-fat diet-induced hepatic steatosis.

OBJECTIVE To identify metabolic pathways that may underlie susceptibility or resistance to high-fat diet-induced hepatic steatosis. RESEARCH DESIGN AND METHODS We performed comparative transcriptomic analysis of the livers of A/J and C57Bl/6 mice, which are, respectively, resistant and susceptible to high-fat diet-induced hepatosteatosis and obesity. Mice from both strains were fed a normal chow or a high-fat diet for 2, 10, and 30 days, and transcriptomic data were analyzed by time-dependent gene set enrichment analysis. Biochemical analysis of mitochondrial respiration was performed to confirm the transcriptomic analysis. RESULTS Time-dependent gene set enrichment analysis revealed a rapid, transient, and coordinate upregulation of 13 oxidative phosphorylation genes after initiation of high-fat diet feeding in the A/J, but not in the C57Bl/6, mouse livers. Biochemical analysis using liver mitochondria from both strains of mice confirmed a rapid increase by high-fat diet feeding of the respiration rate in A/J but not C57Bl/6 mice. Importantly, ATP production was the same in both types of mitochondria, indicating increased uncoupling of the A/J mitochondria. CONCLUSIONS Together with previous data showing increased expression of mitochondrial β-oxidation genes in C57Bl/6 but not A/J mouse livers, our present study suggests that an important aspect of the adaptation of livers to high-fat diet feeding is to increase the activity of the oxidative phosphorylation chain and its uncoupling to dissipate the excess of incoming metabolic energy and to reduce the production of reactive oxygen species. The flexibility in oxidative phosphorylation activity may thus participate in the protection of A/J mouse livers against the initial damages induced by high-fat diet feeding that may lead to hepatosteatosis.

PCAF regulates the stability of the transcriptional regulator and cyclin-dependent kinase inhibitor p27Kip1

P27(Kip1) (p27) is a member of the Cip/Kip family of cyclin-dependent kinase inhibitors. Recently, a new function of p27 as transcriptional regulator has been reported. It has been shown that p27 regulates the expression of target genes mostly involved in splicing, cell cycle, respiration and translation. We report here that p27 directly binds to the transcriptional coactivator PCAF by a region including amino acids 91-120. PCAF associates with p27 through its catalytic domain and acetylates p27 at lysine 100. Our data showed that overexpression of PCAF induces the degradation of p27 whereas in contrast, the knockdown of PCAF stabilizes the protein. A p27 mutant in which K100 was substituted by arginine (p27-K100R) cannot be acetylated by PCAF and has a half-life much higher than that of p27WT. Moreover, p27-K100R remains stable along cell-cycle progression. Ubiquitylation assays and the use of proteasome inhibitors indicate that PCAF induces p27 degradation via proteasome. We also observed that knockdown of skp2 did not affect the PCAF induced degradation of p27. In conclusion, our data suggest that the p27 acetylation by PCAF regulates its stability.

Forced oscillation assessment of respiratory mechanics in ventilated patients

The forced oscillation technique (FOT) is a method for non-invasively assessing respiratory mechanics that is applicable both in paralysed and non-paralysed patients. As the FOT requires a minimal modification of the conventional ventilation setting and does not interfere with the ventilation protocol, the technique is potentially useful to monitor patient mechanics during invasive and noninvasive ventilation. FOT allows the assessment of the respiratory system linearity by measuring resistance and reactance at different lung volumes or end-expiratory pressures. Moreover, FOT allows the physician to track the changes in patient mechanics along the ventilation cycle. Applying FOT at different frequencies may allow the physician to interpret patient mechanics in terms of models with pathophysiological interest. The current methodological and technical experience make possible the implementation of portable and compact computerised FOT systems specifically addressed to its application in the mechanical ventilation setting.

Performance of mechanical ventilators at the patient's home: a multicentric quality control study

Background: Quality control procedures vary considerably among the providers of equipment for home mechanical ventilation (HMV). Methods: A multicentre quality control survey of HMV was performed at the home of 300 patients included in the HMV programmes of four hospitals in Barcelona. It consisted of three steps: (1) the prescribed ventilation settings, the actual settings in the ventilator control panel, and the actual performance of the ventilator measured at home were compared; (2) the different ventilator alarms were tested; and (3) the effect of differences between the prescribed settings and the actual performance of the ventilator on non-programmed readmissions of the patient was determined. Results: Considerable differences were found between actual, set, and prescribed values of ventilator variables; these differences were similar in volume and pressure preset ventilators. The percentage of patients with a discrepancy between the prescribed and actual measured main ventilator variable (minute ventilation or inspiratory pressure) of more than 20% and 30% was 13% and 4%, respectively. The number of ventilators with built in alarms for power off, disconnection, or obstruction was 225, 280 and 157, respectively. These alarms did not work in two (0.9%), 52 (18.6%) and eight (5.1%) ventilators, respectively. The number of non-programmed hospital readmissions in the year before the study did not correlate with the index of ventilator error. Conclusions: This study illustrates the current limitations of the quality control of HMV and suggests that improvements should be made to ensure adequate ventilator settings and correct ventilator performance and ventilator alarm operation.

Effect of expiratory flow limitation on respiratory mechanical impedance: a model study

Large phasic variations of respiratory mechanical impedance (Zrs) have been observed during induced expiratory flow limitation (EFL) (M. Vassiliou, R. Peslin, C. Saunier, and C. Duvivier. Eur. Respir. J. 9: 779-786, 1996). To clarify the meaning of Zrs during EFL, we have measured from 5 to 30 Hz the input impedance (Zin) of mechanical analogues of the respiratory system, including flow-limiting elements (FLE) made of easily collapsible rubber tubing. The pressures upstream (Pus) and downstream (Pds) from the FLE were controlled and systematically varied. Maximal flow (Vmax) increased linearly with Pus, was close to the value predicted from wave-speed theory, and was obtained for Pus-Pds of 4-6 hPa. The real part of Zin started increasing abruptly with flow (V) >85%Vmax and either further increased or suddenly decreased in the vicinity of V¿max. The imaginary part of Zin decreased markedly and suddenly above 95%Vmax. Similar variations of Zin during EFL were seen with an analogue that mimicked the changes of airway transmural pressure during breathing. After pressure andV measurements upstream and downstream from the FLE were combined, the latter was analyzed in terms of a serial (Zs) and a shunt (Zp) compartment. Zs was consistent with a large resistance and inertance, and Zp with a mainly elastic element having an elastance close to that of the tube walls. We conclude that Zrs data during EFL mainly reflect the properties of the FLE.

Mechanical properties of cultured human airway smooth muscle cells from 0.05 to 0.4 Hz.

We investigated the rheological properties of living human airway smooth muscle cells in culture and monitored the changes in rheological properties induced by exogenous stimuli. We oscillated small magnetic microbeads bound specifically to integrin receptors and computed the storage modulus (G') and loss modulus (G") from the applied torque and the resulting rotational motion of the beads as determined from their remanent magnetic field. Under baseline conditions, G' increased weakly with frequency, whereas G" was independent of the frequency. The cell was predominantly elastic, with the ratio of G" to G' (defined as eta) being ~0.35 at all frequencies. G' and G" increased together after contractile activation and decreased together after deactivation, whereas eta remained unaltered in each case. Thus elastic and dissipative stresses were coupled during changes in contractile activation. G' and G" decreased with disruption of the actin fibers by cytochalasin D, but eta increased. These results imply that the mechanisms for frictional energy loss and elastic energy storage in the living cell are coupled and reside within the cytoskeleton.